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Abstract

A comprehensive study on fungus assisted bioleaching of manganese (Mn) was carried out to demonstrate Mn solubilization of collected low grade ore from mining deposits of Sanindipur, Odisha, India. A native fungal strain MSF 5 was isolated and identified as Aspergillus sp. by Inter Transcribed Spacer (ITS) sequencing. The identified strain revealed an elevated tolerance ability to Mn under varying optimizing conditions like initial pH (2, 3, 4, 5, 6, 7), carbon sources (dextrose, sucrose, fructose and glucose) and pulp density (2%, 3%, 4%, 5% and 6%). Bioleaching studies carried out under optimized conditions of 2% pulp density of Mn ore at pH 6, temperature 37 °C and carbon dosage (dextrose) resulted with 79% Mn recovery from the ore sample within 20 days. SEM-EDX characterization of the ore sample and leach residue was carried out and the micrographs demonstrated porous and coagulated precipitates scattered across the matrix. The corresponding approach of FTIR analysis regulating the Mn oxide formation shows a distinctive peak of mycelium cells with and without treated Mn, resulting with generalized vibrations like MnOx stretching and CH2 stretch. Thus, our investigation endeavors’ the considerate possible mechanism involved in fungal surface cells onto Mn ore illustrating an alteration in cellular Mn interaction.

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... Bioleaching studies reported to date employed diverse techniques for the production of relevant metabolites related to these processes, including OA. These analyses, performed under different conditions, assessed how this metabolite production affects the recovery of metals, in both one-step [4,5,58,65] and two-step [95] direct bioleaching processes (microorganisms and matrix together); and in indirect methodologies (produced metabolites and matrix) [4,5,58,65]. ...
... Bioleaching studies reported to date employed diverse techniques for the production of relevant metabolites related to these processes, including OA. These analyses, performed under different conditions, assessed how this metabolite production affects the recovery of metals, in both one-step [4,5,58,65] and two-step [95] direct bioleaching processes (microorganisms and matrix together); and in indirect methodologies (produced metabolites and matrix) [4,5,58,65]. ...
Article
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Minerals have been important throughout history, but nowadays, their use has increased, as well as their extraction needs. Therefore, due to the growing demand for metals, and both the depletion of high-grade ores and their related environmental concerns, the mining industry has been forced to leave behind the past traditional techniques of metal recovery (use of inorganic acids), and adopt eco-friendlier alternatives, such as the utilization of weaker leaching agents, such as organic acids. Thus, the present review is focused on the use of microbially-produced organic acids as a promising alternative to conventional techniques in the mining industry, with emphasis on the following topics: a) the advantages and disadvantages of the use of organic acids for leaching purposes, b) the main microorganisms studied for the production of these organic acids, c) a summary of the latest reports on bioleaching as well as a comparison of the existent techniques; d) the explanation of leaching mechanisms where organic acids may be involved, to fulfill metal recovery; and, e) interactions between metallic ions and organic acids. The review of the current knowledge regarding the use of organic acids for leaching purposes seeks the visualization of relevant strategies that may be improved for metal-recovery processes, intending to develop circular economy practices that may have the potential to be implemented at an industrial scale.
... For example, metal leaching from nodules in the Indian Ocean was performed using Aspergillus niger [17], manganese leaching from manganese ore using Penicillium citrinum and Aspergillus sp. [20] and the leaching of heavy metals from tailings with Aspergillus fumigatus [21]. The formation of oxalates in the Me 2+ C2O4·2H2O (Me 2+ -Fe, Mn, Mg) system is important for study, primarily due to the interest in biotechnologies using a variety of microbes that leach manganese and other metals from ores, including poor ones. ...
... For example, metal leaching from nodules in the Indian Ocean was performed using Aspergillus niger [17], manganese leaching from manganese ore using Penicillium citrinum and Aspergillus sp. [20] and the leaching of heavy metals from tailings with Aspergillus fumigatus [21]. ...
Article
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To clarify the crystal chemical features of natural and synthetic oxalates Me2+(C2O4)∙2H2O (Me2+ = Fe, Mn, Mg, Zn), including minerals of the humboldtine group, solid solutions of lindbergite Mn(C2O4)∙2H2O–glushinskite Mg(C2O4)∙2H2O were precipitated under various conditions, close to those characteristic of mineralization in biofilms: at the stoichiometric ratios ((Mn + Mg)/C2O4 = 1) and non-stochiometric ratios ((Mn + Mg)/C2O4 < 1), in the presence and absence of citrate ions. Investigation of precipitates was carried out by powder X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray spectroscopy. Thermodynamic modelling was performed in order to evaluate the lindbergite–glushinskite equilibrium. It was shown that glushinskite belongs to the orthorhombic β-modification (sp. Gr. Fddd), while lindbergite has a monoclinic α-modification (sp. gr. C2/c). Mg ions incorporate lindbergite in much higher quantities than Mn ions incorporate glushinskite; moreover, Mn glushinskites are characterized by violations of long-range order in their crystal structure. Lindbergite–glushinskite transition occurs abruptly and can be classified as a first-order isodimorphic transition. The Me2+/C2O4 ratio and the presence of citric acid in the solution affect the isomorphic capacity of lindbergite and glushinskite, the width of the transition and the equilibrium Mg/Mn ratio. The transition is accompanied by continuous morphological changes in crystals and crystal intergrowths. Given the obtained results, it is necessary to take into account in biotechnologies aimed at the bioremediation/bioleaching of metals from media containing mixtures of cations (Mg, Mn, Fe, Zn).
... The results showed that, despite A. thiooxidans displays the best oxidizing efficiency onto Sº, A. niger promotes better micronutrient availability from the low reactive mineral sources. This is due to the kind of acidity produced by A. niger, e.g., organic acids that dissolve heavy metals by forming soluble metal complexes and chelates [32,33]. Moreover, other compounds that have at least two hydrophilic reactive groups (such as phenol derivatives) may also have been excreted into the culture medium during microbial cultivation and helped solubilize the mineral oxides [31]. ...
... Moreover, other compounds that have at least two hydrophilic reactive groups (such as phenol derivatives) may also have been excreted into the culture medium during microbial cultivation and helped solubilize the mineral oxides [31]. Other mechanisms, such as enzymatic reduction of highly oxidized metal compounds may also play a role in the oxide solubilization process, although the enzymatic effect is low in comparison with the acidification due to organic acids [33]. Finally, about the release in soil, given that P release profiles were similar among the treatments, the bioactive coating did not interfere with phosphorus release, as well as the bioactive coating from maize starch did not impose a physical barrier to the phosphate solubilization. ...
Article
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Fertilization is essential to provide suitable conditions for plant development and crop productivity, but the environmental cost of fertilizers is a drawback for achieving a sustainable agriculture. A potential alternative is the use of unprocessed (raw) nutrient sources such as elemental sulfur (S⁰) and mineral oxides (ZnO, MnO, CuO) as fertilizers. However, these low reactive sources are not readily available to plants. Here, we developed a bioactive coating material containing microorganisms that allowed different nutrients to be made available from unprocessed nutrient sources. For that, the coating material composed of maize starch, elemental sulfur (S⁰), mineral oxides (ZnO, MnO, CuO), and a microbial source (Aspergillus niger or Acidithiobacillus thiooxidans) was applied on monoammonium phosphate (MAP) granules, as a model fertilizer. Our results revealed that the bioactive coating did not affect the phosphorus (P) release, since it did not impose a physical barrier. However, the acidifying capacity of both microorganisms significantly enhanced the oxide solubilization and elemental sulfur oxidation. The presence of Aspergillus niger or Acidithiobacillus thiooxidans promoted local acidification, achieving sulfate release of up to 76.4 and 83.8% in 42 days of soil incubation. Furthermore, the bioactive coating material with Aspergillus niger reached Cu, Zn and Mn solubilization up to 10.9, 14.6 and 34.3% in 42 days of soil incubation. This phenomenon suggested that the organic acids produced by Aspergillus niger chelate the cations, reducing precipitation and, therefore, increasing their solubilization. This innovative system can effectively supply nutrients to plants using cheap and low reactivity nutrient sources with the advantage that it can be co-applied on currently used fertilizer granules in a single delivery, making easier the adoption by producers. Graphical Abstract
... Scores of researchers have investigated the extraction of manganese from its ores with the help of bacteria and have found various microorganisms that can be employed in such processes [7,8,9,10]. Recent research has also shown the potential with which bioleaching can be applied to extract manganese either from low grade ores or mine wastes [11,12,13], but the mechanism involved in these studies varies vastly. The process of extraction of manganese from ores using bacteria can be aerobic or anaerobic. ...
... We have talked about fungal species that can dissolve manganese from their ores to an appreciable extent [13,31,36]. These fungal species, however, reduce manganese indirectly by the production of acids. ...
Article
The increasing demand of manganese in the industries and various hindrances in its production from low grade ores by conventional method has made it imperative for researchers around the world to develop a method of manganese extraction from low grade ores that is both environment-friendly and economical. Bioleaching has shown significant potential in manganese extraction and efficiencies of extraction have been found to be 70–98% with the help of various bacteria and fungi. This study focuses on extraction of manganese with the help of mixed bacterial strains that have been collected from their natural anaerobic environment where manganese reducing activity was evident. The extraction of manganese from reagent grade manganese dioxide and high grade manganese ore has been studied over 180 days in an anaerobic environment at room temperature and pH around 5, without the addition of any mineral acids. Highest concentrations of dissolved manganese have been found to be 928.58 mg Mn/L for reagent grade manganese dioxide and 864.54 mg Mn/L for ore grade manganese, corresponding to 650 mg and 400 mg of cumulative manganese, respectively.
... Oxalic acid biosynthesis from glucose occurs when oxaloacetate is hydrolyzed to oxalate and acetate, catalyzed by cytosolic oxaloacetase, while citric acid is formed as an intermediate in a cycle of tricarboxylic acids involving a polysaccharide such as sucrose [29]. Therefore, sucrose present in the medium during the bioleaching experiment was used as a substrate by the strain for oxalic acid and citric acid biosynthesis. ...
... Compared to previous studies, both fungi were about 54% lower in extracting manganese than Aspergillus niger PTCC 5210 isolated from mining deposits in India [29]. Those fungi were also 22% lower in extracting metals than Penicillium chrysogenum Y5 isolated from heavy metal contaminated areas [33]. ...
Article
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The unique characteristics of sulfurous river sediment located in Ungaran, Indonesia, are a reservoir of novel fungi with manganese bioleaching properties. Fungi are known to produce metabolic organic acids that have a potential for the industrial application of leaching metal from the ores. This application has high advantages, including low cost, low energy, and creates minimal environmental damage. Therefore, this research was performed to analyze the manganese bioleaching activities of two fungal isolates (KA2B2 and KB4B) from Indonesian sulfurous river sediment on pyrolusite and determine their phenotypic characters. These activities were investigated in terms of changes in fungal biomass, soluble manganese concentration, pH reduction, and organic acid production during 16 days of leaching. Soluble manganese concentrations were measured by atomic absorption spectrometry (AAS), whereas organic acid concentrations were analyzed by high-performance liquid chromatography (HPLC). According to bioleaching investigations, KA2B2 strain was more efficient than KB4B1 strain in extracting manganese from 0.02 g/cm3 pyrolusite. It also produced higher levels of organic acids, such as oxalic acid and citric acid, than KB4B1 strain, proving that strain of KA2B2 could be used to extract manganese from pyrolusite. Based on the phenotypic characters, both strains were identified as genus Penicillium.
... For example, the leaching of metals from Indian ocean nodules was produced with Aspergillus niger (Mehta et al. 2010), the leaching of manganese from manganese ore with Penicillium citrinum (Acharya et al., 2001) and Aspergillus sp. (Mohanty et al. 2017), the leaching of heavy metals from mine tailings with Aspergillus fumigatus (Seh-Bardan et al. 2012). The biotechnologies for bioremediation of the environment from Mn and other toxic metals are also developed (Mota et al. 2020, Tsekova et al. 2010, Ren et. ...
Article
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Microscopic fungi (micromycetes) play an important role in rock alteration, often leading to the formation of insoluble biogenic oxalates on their surface. Oxalate crystallization under the influence of fungus Aspergillus niger (one of the most active stone destructors) was studied in vitro conditions on following Mn,Ca-bearing minerals of manganese ores: todorokite (Na0.36,Ca0.09,K0.06,Sr0.03, Ba0.02)0.56(Mn5.53,Mg0.47)O12∙3–4H2O and kutnohorite (Ca0.77,Mn0.23)(Mn0.74,Fe0.14,Mg0.11)(CO3)2. The underlying minerals and the products of their alteration were investigated via powder and single-crystal X-ray diffraction, optical microscopy, SEM and EDX methods. It was shown that more intense leaching of Ca-ions (compared to Mn-ions) from todorokite and kutnohorite leads to an earlier crystallization of calcium oxalates (predominantly whewellite) compared to manganese (lindbergite, falottaite). Crystallization of manganese oxalates on the surface of kutnohorite occurs in a more acidic (compared to todorokite) medium through the formation of mycogenic Mn,Ca-bearing oxides, which are close in composition and structure to todorokite. The possibility of structural evolution within the manganese oxalate crystalline phases caused by hydration and dehydration processes, which are responsible for changes in proportions of lindbergite and falottaite, derives from the similarities of falottaite and lindbergite crystal structures. The amorphization of falottaite in the temperature range of 70–80 °C suggests that formation of linbergite by falottaite dehydration occurs via amorphous precursor. The result can be used for developing efficient biotechnologies using fungi for industrial enrichment of poor manganese ores and environmental bioremediation.
... Among these sources, the increasing evidence of the presence of MPs in commercially important seafoods (such as fishes, shrimps and mussels) in are reported which indicating a possible risk to human health through biomagnification and become a potential route of exposure to human via diet (Walkinshaw et al., 2020;Devriese et al. 2015;Cauwenberghe and Janssen 2014). In a recent scientific study on the commercially important fish from Western Arabian Gulf, about 58.58% of synthetic textile fibers (most prominently polyethylene and polypropylene) were recovered from the gastrointestinal tracts of the fish (Baalkhuyur et al., 2020;Kumar et al.,2016b;Mohanty et al., 2017Mohanty et al., , 2018. Similarly, in case of mussels, approximately 2.6-5.1 microfibers per 10 g of commercial mussel sample ranging from 200-1500 mm were reported from Belgium stores (De Witte et al., 2014). ...
Chapter
Microplastics (MPs) pollutants are produced from macro plastic products and have harmful effects on our ecosystem. It can be generated as any form or shape such as chip, thread, and beads. Synthetic textiles materials such as polyester, nylon, rayon, and acrylic are used in used in clothing industry, which contribute about 70% of the clothing raw material globally. Synthetic microplastics are washed off from these products and contribute about 30–35% of primary microplastics polluting our environment and oceans. In a single laundry, approximately of 8 million microfibers are discharged into wastewater treatment plants, which cannot recover them and enter the marine environment. Microplastic pollution of the aquatic environment is most important distress in view of the devastating effect on the ecosystem. The application of highly developed wastewater treatment technologies is compulsory to avoid further spread of the emerging micro pollutants in the environment. MBR (membrane bioreactor) technology, as one of the modern wastewater treatment technologies, has many advantages over classical activated sludge treatment (CAS), with higher sludge ages, and higher sludge densities, thus giving enhanced properties to remove pollutants. MBR process facilitates to reach a more efficient elimination of microplastic particle contaminants from wastewaters. Treatment of waste waters through conventional method cannot able to eliminate microplastics (MPs) from the wastewater efficiently and final effluents can act as entrance path of MPs into the aquatic environments. Scientific reports concluded that almost 99% of MF particles can be retained by the activated sludge process and mainly through membrane bioreactors. The average concentrations decrease of microplastics from the primary to the final effluent 96.2% using MBR technique, indicating the importance of tertiary step to remove this emerging pollutant. In this present review, the present method of the detection, incidence and elimination of these microplastics pollutants in WWTPs were broadly appraised. Exclusively, the methods employed for sampling of microplastics from both wastewater and sewage sludge, and their pretreatment and characterization methods were analyzed. The key points concerning treatment microplastic pollutants trough MBR, total discharges, materials, and dimensions are discussed.
... Currently, bioleaching is more and more frequently applied to extract, recover and remove heavy metals from solid waste as well, including mine tailings and sediments [106,107]. In most cases, acidophilic chemolithotrophic microorganisms are the major microbes for bioleaching. ...
Article
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Tungsten is recognized as a critical metal due to its unique properties, economic importance, and limited sources of supply. It has wide applications where hardness, high density, high wear, and high-temperature resistance are required, such as in mining, construction, energy generation, electronics, aerospace, and defense sectors. The two primary tungsten minerals, and the only minerals of economic importance, are wolframite and scheelite. Secondary tungsten minerals are rare and generated by hydrothermal or supergene alteration rather than by atmospheric weathering. There are no reported concerns for tungsten toxicity. However, tungsten tailings and other residues may represent severe risks to human health and the environment. Tungsten metal scrap is the only secondary source for this metal but reprocessing of tungsten tailings may also become important in the future. Enhanced gravity separation, wet high-intensity magnetic separation, and flotation have been reported to be successful in reprocessing tungsten tailings, while bioleaching can assist with removing some toxic elements. In 2020, the world’s tungsten mine production was estimated at 84 kt of tungsten (106 kt WO3), with known tungsten reserves of 3400 kt. In addition, old tungsten tailings deposits may have great potential for exploration. The incomplete statistics indicate about 96 kt of tungsten content in those deposits, with an average grade of 0.1% WO3 (versus typical grades of 0.3–1% in primary deposits). This paper aims to provide an overview of tungsten minerals, tungsten primary and secondary resources, and tungsten mine waste, including its environmental risks and potential for reprocessing.
... Bands around 1380.78 cm −1 were due to C O stretching vibrations (Wei et al., 2017). Bands at and 1249.65 cm −1 was assigned to O-H or -C-O bending vibrations (Mohanty et al., 2017). The weak signals at 877.45 and 809.95 cm −1 were suggestive of the presence of D-mannopyranose and mannose residues (Liao et al., 2019), respectively. ...
Article
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The aim of this study was to evaluate the therapeutic effects of Bletilla striata polysaccharide (BSP) on wound healing in diabetes mellitus (DM) and to explore the underlying mechanisms. DM mouse models were induced by high fat-diet feeding combined with low-dose streptozocin injection. To establish diabetic foot ulcer (DFU) models, DM mice were wounded on the dorsal surface. Subsequently, mice were treated with vehicle or BSP for 12 days and wound healing was monitored. The effects of BSP on the production of interleukin-1β (IL-1β), tumor necrosis factor-α, macrophages infiltration, angiogenesis, the activation of nucleotide-binding and oligomerization (NACHT) domain, leucine-rich repeat (LRR), and pyrin domain (PYD)-containing protein 3 (NLRP3) inflammasome, and insulin sensitivity in wound tissues were subsequently evaluated. Separated- and cultured- bone marrow-derived macrophages (BMDMs) and cardiac microvascular endothelial cells (CMECs) were isolated from mice and used to investigate the effects of BSP on cell viability, reactive oxygen species (ROS) generation, NLRP3 inflammasome activation and insulin sensitivity in vitro following exposure to high glucose (HG). BSP administration accelerated diabetic wound healing, suppressed macrophage infiltration, promoted angiogenesis, suppressed NLRP3 inflammasome activation, decreased IL-1β secretion, and improved insulin sensitivity in wound tissues in DM mice. In vitro, co-treatment with BSP protected against HG-induced ROS generation, NLRP3 inflammasome activation, and IL-1β secretion in BMDMs, and improved cell viability and decreased ROS levels in CMECs. Moreover, in HG exposed BMDMs-CMECs cultures, BSP treatment suppressed NLRP3 inflammasome activation and IL-1β secretion in BMDMs, and improved cell viability and insulin sensitivity in CMECs. Furthermore, treatment with IL-1β almost completely suppressed the beneficial effects of BSP on the NLRP3 inflammasome, IL-1β secretion, and insulin sensitivity in HG-treated BMDMs-CMECs. BSP promotes DFU healing through inhibition of the HG-activated NLRP3 inflammasome.
... culture medium during microbial cultivation and have a solubilizing action on mineral oxides. Specifically for manganese, solubilization of the metal could also occur due to the enzymatic reduction of highly oxidized metal compounds, although the enzymatic effect is low in comparison to acidification by organic acids [31,32]. ...
Article
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Intensive fertilization has been required to provide nutrients for plant growth under the current agricultural practices being applied to meet the global food demands. Micronutrients such as zinc, manganese, and copper are required in small quantities when compared to macronutrients (such as nitrogen, phosphorus and potassium), but they are essential for the plant growth cycle and consequently for increasing productivity. Mineral oxides such as ZnO, MnO, and CuO are used in agriculture as micronutrient sources, but their low solubility limits practical applications in plant nutrition. Similarly, elemental sulfur (S⁰) can provide a high-concentration source of sulfate, but its availability is limited by the ability of the soil to promote S⁰ oxidation. We propose here the integration of these nutrients in a composite based on a biodegradable starch matrix containing mineral oxides and S⁰ in a dispersion that allowed encapsulation of the acidifying agent Aspergillus niger, a native soil fungus. This strategy effectively improved the final nutrient solubility, with the composite starch/S⁰/oxidemixture multi-nutrient fertilizer showing remarkable results for solubilization of the oxides, hence confirming a synergic effect of S⁰ oxidation and microbial solubilization. This composite exhibited an extended shelf life and soil–plant experiments with Italian ryegrass (Lolium multiflorum Lam.) confirmed high efficiencies for dry matter production, nutrient uptake, and recovery. These findings can contribute to the development of environmentally friendly fertilizers towards a more sustainable agriculture and could open up new applications for formulations containing poorly soluble oxide sources.
... In the case of common-occurring manganese oxide mineral (e.g., MnO2), Mn of higher oxidation state, i.e., Mn (IV), must first be reduced to MnO, which then can be leached in a dilute acid solution . Two methods have been suggested for this purpose: 749 1) Hydro reduction in the presence of various chemical reducing agents (Lin et al., 2016;Mohanty et al., 2017;Reuter et al., 2004) 2) Pyro-reduction at high temperature (Wasserstein and Lazar, 2016) Slags are generated in various pyrometallurgical processes, including pretreatments in metals extraction, refining and alloying, which usually consist of a combination of oxides, sulfides, elemental metals and silicate minerals. During these processes, huge amounts of slags are generally produced and disposed of to process tailings. ...
Article
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Using a software-based experiment design, the application of the leaching process for the extraction of manganese from Zinc Plant Slag (ZPS) was investigated. In this study, the effect of different parameters, i.e., H2SO4 concentration, pulp density, agitation rate, temperature and reaction time, was investigated. Response Surface Methodology (RSM) based on the Central Composite Design (CCD) has been implemented to consider the main parameters. A hydrometallurgical route to manganese silicate from spent zinc plant residue has been proposed in this investigation. Based on the investigation, Mn can be extracted from ZPS in sulfuric acid without any oxidant agents. The results showed that the optimum conditions of this study are an H2SO4 concentration of 2 mol/L and a solid/liquid ratio of 0.07 g/mL at 50°C for 150 min and an agitation speed of 1000 rpm. A manganese leaching efficiency higher than 83% is reached under these conditions, with a corresponding 22% iron, 23% lead, 68% zinc and 65% aluminum.
... The alignment of the present research focus on newer methods of metal extraction from secondary sources is rooted to the ever-growing global demand for metals (Mohanty et al., 2016a). Due to the limitation of natural mineral sources and also the huge wastage of minerals in form of mining wastes, the industries are in the pursuit of embracing newer, efficient and eco friendly alternatives for resource recycling (Das & Mishra, 2010). ...
Article
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The rapid decrease of natural resources and generation of huge amount of metallic wastes from mining industries has led to the focus of researchers to shift to alternative methods of waste benefaction and resource recycling. This study aims at the development of an eco friendly technique to recover Manganese (Mn) from mining waste residues using Acinetobacter sp. Bioleaching experiments were conducted in shake flasks at initial pH 6.5, 5% w/v inoculums and 2% pulp density at 30 °C with agitation speed 200 RPM and Acinetobacter sp. as inoculum. Mn recovery of 76% was recorded in 20 days. The analysis of the changes in cellular protein expression and conformation was carried out through sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS PAGE) and fourier transform infrared spectroscopy. The results reveal that bioleaching can alter protein expression and also result in conformational changes in protein structure. The present study sheds light on the greener alternative to recover and recycle manganese from wastes native bacteria. Exciting prospects for the utilization of mining wastes are in store in the near future; providing an economic and ecologically sound alternative to pyrometallurgical processes.
... Especially in case of bisolubilization by fungal strains, release of organic acids is highly observed which eventually accelerates the process of metal dissolution. However, their prevalence in case of bacterial dissolution of metals is not as recognized (Mohanty et al. 2017(Mohanty et al. , 2018. The dissolution of metals is due to a complex interaction among mineral surfaces, leaching lixiviants, and microbial cells resulting in both the induction of some proteins involved in the process of metal solubilization and the downregulation of some other proteins Das 2015, 2017). ...
Article
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There has been alarming depletion of manganese (Mn) reserves owing to the ongoing extensive mining operations for catering the massive industrial demand of this element. Moreover, the mining operations have been leading to the generation of Mn-rich waste, thereby contaminating both terrestrial and aquatic bodies. The current scenario necessitates the development of alternative processes for bioremediation as well as economic recovery of Mn from mining wastes. The present investigation aims to report the bioleaching of Mn by Lysinibacillus sp. from mining waste residues in the context of mine waste remediation. Results confirmed that the native isolate had a high Mn biosolubilization potential with a solubilizing efficiency of 84% at the end of a 21-day study under optimized conditions of pulp density 2% (< 150-μm particle size), pH 6.5, and temperature 30 °C. Fourier transform infrared spectroscopy (FTIR) studies followed by liquid chromatography mass spectrometry (LC-MS) analysis were used to ascertain the change in microbial protein conformation, configuration, and protein identification. The results revealed the expression of heat shock proteins (HSP) from the family HSP which is predominantly expressed in bacteria during stress conditions. This study represents the application of native bacterial strain in Mn biosolubilization. We foresee the utility of proteomics-based studies to provide a methodological framework to the underlying mechanism of metal solubilization, thereby facilitating the two-tier benefit of recovery of Mn from alternative sources as well as bioremediation of waste having high manganese content.
... Many filamentous fungi are able to live in environmental burdens conditions in extreme stress with the presence of toxic elements (Šimonovičová et al. 2013;Qayyum et al. 2016; Mohammadian et al. 2017). These fungal strains may have often enormous biotechnological potential and can be considered as a source of useful organic acids to be exploited in the mycoremediation of contaminated sites through the bioleaching of Cd, Cu, Zn, Pb, Mn, Al from red mud (Ren et al. 2009;Zeng et al. 2015;Urík et al. 2015Urík et al. , 2017Mohanty et al. 2017), and the bioaccumulation of Cr, Ni (Shivakumar et al. 2014;Remenárová et al. 2020) or As (Singh et al. 2015). Organic acids play a key role in the bioavailability of selenium (Dinh et al. 2017) and can also utilize Fe(III) citrate as an iron source (Odoni et al. 2017). ...
Article
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This paper investigates the differences in some metabolites using Biolog FF Microplate™ system and the production of organic acids such as β-hydroxybutyric, p-hydroxyphenylacetic, and others. Another group of organic acids such as gluconic, oxalic and citric acid were studied during cultivation in a liquid medium. Four different Aspergillus niger (An) wild type strains were used as a model organism. Three strains, from the Banská Štiavnica – Šobov (An – Š), Pezinok (An – P) and Slovinky (An – Sl) localities were isolated from contaminated old mining areas with soil with ultra acidic to strong alkaline reactions. The fourth strain isolated from the Gabčíkovovo (An – G) locality was used for comparative purposes. According to the RAMP analysis, the strains are clustered into two groups, An – Š and An – P (similarity 82%), An – G and An – Sl (similarity 64%) which correlates with the pH values of the original environment. However, significant differences were found in metabolic processes in the reaction with a wide range of organic acids. In general, the reactions with D-lactic acid and D-malic acid correlate with the results of the RAMP analysis of fungal genotype similarities, the An – Š and An – P strains had an identical negative reaction, and an identical positive reaction was found in the An – Sl and An – G strains. During incubation the wild-type strains produced substantial amounts of gluconic acid, oxalic acid and small amounts of citric acid. The appearance and accumulation of organic acids was found to be highly pH dependent with the most active strain isolated from an ultra-acidic environment. The comparative strain differs entirely in the production of oxalic acid.
... The amounts of these tiny fibers are increasingly released in to the environment from a variety of industrial and domestic effluents, due to the rapid urbanisation and industrialization. This is believed to be the most pervasive and long lasting anthropogenic pollutant in the earth atmosphere as compared to other pollutants (Mohanty et al., 2017(Mohanty et al., , 2018. Scientific attention has been increased immensely towards this in recent years due to their lethal effects on aquatic and terrestrial ecosystem. ...
Article
The ever-increasing use of domestic washing machine by urban population is playing a major role in synthetic microfibers (SMFs) pollution via entering the ecosystem. Although many of the sources of fragmented plastic pollution in oceanic environments have been well known, urban areas are playing a major contributor due to huge populations. Thousands of scientific investigations are now reporting the adverse effect of these micro pollutants on aquatic and terrestrial environment, food chain and human health. Microfiber particles along with washing machine grey waters are emitted into urban drainage adjoining the lakes and river which ultimately mix in ocean water and after emission these tiny particles dispersed though out the ocean water by currents due to their low density. Environmental pollution cause by domestic laundering processes of synthetic clothes has been reported as the major cause of primary microplastics in the marine system. While community awareness and improved education will be successful in making public conscious of this problem, there needs to be more research on global scale to mitigate the ecological consequences of microfiber pollution by urban habitats through environmental friendly approach. This paper focuses to improve the understanding of urban population influence on microfiber pollution, their ecological toxicity to aquatic organism and humans, detection and characterization techniques with an emphasis on future research for prevention and control of microfiber pollution.
... The surface of the lyophilized mycelia samples was coated by a carbon layer and SEM investigation was performed by a Hitachi S 4300 scanning electron microscope (Hitachi, Schaumburg, USA) equipped with a RÖNTEC energy dispersive X-ray spectrometer (Röntec, Berlin, Germany). Pictures were recorded at 15 kV accelerating voltage in secondary electron mode (46)(47). ...
Article
The fungus Aspergillus oryzae could be shown to be a viable alternative for biosorption of valuable metals from solution. Fungal biomass can be obtained easily in high quantities as a waste of biofermentation processes, and used in a complex, multi-phase solution mimicking naturally occurring, mining-affected water samples. With test solution formulated after natural conditions, formation of secondary Al and Fe phases co-precipitating Ce was recorded in addition to specific biosorption of rare earth elements. Remarkably, the latter were removed from the solution despite the presence of high concentrations of interfering Fe and Al. The biomass was viable even after prolonged incubation in the metal solution, and minimal inhibitory concentrations for single metals were higher than those in the test solution. While precipitation/biosorption of Ce (maximal biosorption efficiency was 58.0 ± 22.3% after 6 h of incubation) coincided with the gross removal of Fe from the metal solution, Y (81.5 ± 11.3% efficiency, 24 h incubation) and Nd (87.4 ± 9.1% efficiency, 24 h incubation) were sequestered later, similarly to Ni and Zn. The biphasic binding pattern specific to single metals could be connected to dynamically changing pH and NH4⁺ concentrations, which were attributed to the physiological changes taking place in starving A. oryzae biomass. The metals were found extracellularly in minerals associated with the cell wall, and intracellularly precipitated in the vacuoles. The latter process was explained with intracellular metal detoxification resulting in metal resistance. Aspergillus oryzae mycelia captured Y and Nd from a complex, multi-phase test solution concomitantly with increasing pH and NH4⁺ ion concentrations. Changing fungal cell physiology in starving mycelia may help to develop new technologies to sequester precious rare earth elements including Y effectively, even in the presence of high concentrations of interfering metals like Fe and Al.
... This process uses the ability of microorganisms which are capable of extracting metal minerals from their ores (Chen et al. 2011;Das et al. 2015). Mohanty et al. (2017) observed the role of fungi during the bioleaching process by producing organic acids, which can solubilize the manganese. The other group of microorganisms, such as sulfur-oxidizing bacteria also has capabilities for extracting metals from their deposits. ...
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Prasidya DA, Wilopo W, Warmada IW, Retnaningrum E. 2019. Optimization of manganese bioleaching activity and molecular characterization of indigenous heterotrophic bacteria isolated from the sulfuric area. Biodiversitas 20: 1904-1909. The present research evaluated the manganese bioleaching potency of a heterotrophic bacteria KB3B1. This bacterial strain has been isolated from sulfuric area located at Ungaran, Middle of Java, Indonesia using modified 9K medium by adding of several organic nutrients. The manganese bioleaching activities of the strain was analysed by applying of varying glycine concentrations (0, 5, 10, 15 mg mL-1) with pyrolusite pulp densities of 0.02 g cm-3 on a rotary shaker at 180 rpm for 18 days incubation. Several parameters, including the growth of bacteria, pH values, the concentration of soluble manganese and cyanide, were investigated at the interval of 3 days. Molecular characteristics of the strain were further analyzed based on 16S rDNA gene sequences. After 15 days, the maximum yield of manganese 16.6% was achieved under the addition of 10 mg mL-1 glycine. This maximum extract obtained was followed by the maximum bacterial growth, pH, and cyanide product of the strain. Phylogenetic analysis showed that the strain was closely related with Bacillus niacini EP89. Besides, the average frequencies of guanine and cytosine (G+C) of the strain was in same range as that of the reference bacteria in the GenBank and Bergey's Manual Systematics of Bacteria.
... They have been used for metal recovery or mineral beneficiation such as refractory gold and silver ores, copper oxides and carbonates, manganese oxides, spodumene, cobalt and zinc ores, oxidic ores of nickel, zircon, removal of unwanted minerals from bauxites, silicate ores containing chromium, iron, titanium and quartz sands and silicates [127]. Several fungal strains were used for metals extraction from black shale [9,8], incineration fly [157], waste material [65], power plant residues [110], and mining deposits [82]. Fungal strains were examined for tolerability towards these metals and it was discovered that several metals are crucial for cellular activity [150]. ...
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Nowadays, due to fast global industrial progress and near diminution of high-grade ore reserves, there has been massive call to cost-effectively process the resources of low-grade ores and industrial effluents for metal extraction. However, conventional approaches cannot be used to process such resources due to high capital cost and energy, also causing environmental pollution. Alternatively, bioleaching is highly environmental friendly and economic method to process such resources. Metal recovery from metal sulfide ore is carried out by chemolithotrophic bacteria like Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans. The same is done by heterotrophic microorganisms in non-sulfide ores. Additionally, for gold and copper extractions, bioleaching is used to extract cobalt, zinc, nickel, and uranium from low-grade ores and industrial effluents. In this review, the fundamental process of bioleaching from low-grade metal sulfide ores are discussed with emphasis on mechanism, types, pathways, techniques, and bioleaching development.
... Manganese is found in several ecological environs on the earth's surface in both terrestrial (Abdulsalam et al. 2011) and aquatic system. Besides naturally occurring manganese waste from mine quarries, water deposits are also contaminated with manganese ions that are frequently discharged into nearby environment devoid of pre-treatment (Mohanty et al. 2017). When manganese compounds accumulate in the soil in an elevated level, it may cause modification in microbe biological organization or changes in their behavioral actions (Krujatz et al. 2011), consequently resulting in degradation of soil. ...
... Manganese is found in several ecological environs on the earth's surface in both terrestrial (Abdulsalam et al. 2011) and aquatic system. Besides naturally occurring manganese waste from mine quarries, water deposits are also contaminated with manganese ions that are frequently discharged into nearby environment devoid of pre-treatment (Mohanty et al. 2017). When manganese compounds accumulate in the soil in an elevated level, it may cause modification in microbe biological organization or changes in their behavioral actions (Krujatz et al. 2011), consequently resulting in degradation of soil. ...
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The global consumption of manganese is rising due to its growing industrial requirement while the natural reserves of manganese are diminishing at an alarming rate. Consequently, recovery of manganese from metal containing wastes has become highly crucial. Bioleaching of metal from wastes using microbes provides an adequate advantage over the traditional method of recovery. A molecular level understanding of microbial catalyzed manganese recovery is essential for the exploitation of novel microorganisms for similar applications. In current scenario, the application of bioleaching concentrates on cost effective and eco-friendly recovery of precious metals from mining and industrial wastes. This review encompasses the modern improvements in biomining, highlights the comprehensive factors that emphasize the selection of manganese recovery technique, shed insights into spectacular progress in developing molecular based technologies and also identifies the applicability of different models in metal bioremediation which will not only aid in pollution abatement but also in the prevention of occupational health disorder.
... Manganese has various metallurgical applications in steel manufacturing and alloy making (;Freitas et al. 2007). Non-metallurgical applications of Mn includes glass, batteries, and different types of chemical production (Freitas et al. 2007;Mohanty et al. 2017) with various applications in organic synthesis (Figueroa-Esp ı et al. 2011), electrochemical, food, and pharmaceutical applications. Globally, more than 90% of Mn is utilized in desulfurization and reinforcement of steel and cast iron to improve its strength, toughness, hardness, and workability. ...
Research
Mineral resources have been counted as public assets with economic benefit since time immemor-ial. Due to the rising issue of decreasing mineral deposits, recovery of metals from several waste residues has become progressively more essential. Novel and efficient recycling processes have been on the rise globally. Manganese (Mn) as the fourth most industrially applicable metal generates an extensive quantity of metallic waste which not only leads to loss of precious metal but also results in environmental toxicity. Globally, around 7 million tons of high-grade ores are produced , whereas 8 million tons of Mn alloys are produced yearly. Therefore, it is of greater significance to recover and recycle Mn from various waste residues. Various physical and biological techniques have been developed for recycling Mn from waste residues. Traditional Mn extraction processes are costly and labor intensive in nature, on the contrary, bioleaching techniques using diverse microorganism's, form the basis of an efficient, eco-friendly, and economically sustainable process of metal recovery. The quick progress in current methodologies to counteract the fast consumption of innate mineral resources involves the proper utilization of unused waste residues containing industrially important metals like Mn. This review focuses to enumerate diverse features of Mn recovery, efficient methodologies, bioleaching of Mn, merits of Mn bioleaching, and applications of recycled Mn along with the futuristic applications. Manganese recovery by means of biol-eaching will play a major role in changing the present situation where innate assets are quickly diminishing and substitute for metal recovery methodologies are the demand of this time. ARTICLE HISTORY
... Integration of the biotic and abiotic influences on biodiversity of a community is essential for correct evaluation of a microbial ecosystem. While soil moisture influences Verrucomicrobia abundance 33 , the pH of oil controls the abundance of acidobacteria. Several factors such as Ca 2+ /Mg 2+ ratio, altitude, Aluminium and phosphorus content also influences the microbial biodiversity of site 2 . ...
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To extend the knowledge on the microbial diversity of manganese rich environments, we performed a clone library based study using metagenomic approach. Pyrosequencing based analysis of 16S rRNA genes were carried out on an Illumina platform to gain insights into the bacterial community inhabiting in a manganese mining site and the taxonomic profiles were correlated with the inherent capacities of these strains to solubilise manganese. The application of shot gun sequencing in this study yielded results which revealed the highest prevalence of Proteobacteria (42.47%), followed by Actinobacteria (23.99%) in the area of study. Cluster of orthologous group (COG) functional category has 85,066 predicted functions. Out of which 11% are involved in metabolism of amino acid, 9% are involved in production and conversion of energy while Keto Encyclopedia of Gene and Genomes (KEGG) functional category has 107,388 predicted functions, out of which 55% are involved in cellular metabolism, 15% are environmental and information processing and 12% are genetic information processing in nature. The isolated microbial consortia demonstrated visible growth in presence of high concentrations of Mn. Solubilisation studies resulted in 86% of manganese recovery after 20 days. The result presented in this study has important implications in understanding the microbial diversity in manganese contaminated mine tailings and their role in natural geochemical cycling of Mn.
... Bioleaching has been increasingly used to extract and recover heavy metals from solid waste. Target materials include concentrates, ore, mine tailings, electronic waste, and sediments (Zhu et al., 2011;Seidel et al., 2006;Ghassa et al., 2014;Cheng et al., 2009;Mohanty et al., 2017). Bioleaching is based on the ability of acidophilic chemolithotrophic microorganisms, using elemental sulfur or Fe 2þ as energy sources, to dissolve sulfide minerals in the form of extractable metals, these metals can then be recovered or removed. ...
Article
Mine tailings often contain significant amounts of metals and sulfide, many traditional operations used to minerals was not as good as those currently available. This study investigated metals removal from lead-zinc mine tailings using bioleaching and followed by sulfide precipitation. Metals were dissolved from the tailings by the bacteria in a bioleaching reactor. During a 10% pulp density bioleaching experiment, approximately 0.82% Pb, 97.38% Zn, and 71.37% Fe were extracted after 50 days. With the pulp density of 10% and 20%, the dissolution of metals followed shrinking core kinetic model. Metals (Pb, Zn, and Fe) present in the pregnant bioleaching leachate. Metals were next precipitated as a sulfide phase using sodium sulfide (Na2S). Metal precipitations were selectively and quantitatively produced from the bioleaching leachate by adding Na2S. More than 99% of the zinc and 75% of the iron was precipitated using 25 g/L Na2S in the bioleaching leachate. The results in the study were to provide useful information for recovering or removing metals from lead-zinc mine tailings.
... Bioleaching has been increasingly used to extract and recover heavy metals from solid waste. Target materials include concentrates, ore, mine tailings, electronic waste, and sediments (Zhu et al., 2011;Seidel et al., 2006;Ghassa et al., 2014;Cheng et al., 2009;Mohanty et al., 2017). Bioleaching is based on the ability of acidophilic chemolithotrophic microorganisms, using elemental sulfur or Fe 2þ as energy sources, to dissolve sulfide minerals in the form of extractable metals, these metals can then be recovered or removed. ...
Article
Wastewater containing EDTA-Ni (ethylenediaminetetraacetic acid nickel salt) must be treated due to its high toxicity, accumulation of nickel and non-degradability. In the present study, effect of carbon chain length of dithiocarbamate on the removal efficiency of Ni2+ from an EDTA-Ni solution has been analyzed. Sodium dimethyl dithiocarbamate, sodium diethyl dithiocarbamate and sodium dibutyl dithiocarbamate were used to study their Ni2+ removal performances from various types of EDTA-Ni solutions. Mechanisms of reactions between different dithiocarbamates and Ni2+ were also studied. The results indicate that the rate of Ni2+ increased with an increase in the carbon chain length of dithiocarbamate. Infrared spectral analysis inferred that the three dithiocarbamates had similar removal mechanisms despite having different carbon chain lengths: all showing Ni2+ chelation. The thiol of dithiocarbamate captures Ni2+ and tends to produce an insoluble chelate. The results from scanning electron microscope show that for longer carbon chain, the chelate product is more closely packed. Therefore, removed efficiency by sodium dibutyl dithiocarbamate was higher. Meanwhile coexistence of Cr6+, Cu2+ and Fe3+ inhibited the removal of Ni2+, but Zn2+ promoted it. Metal ion impact became clearer as carbon chain length increased. The chelation capability of the three dithiocarbamates with metal ions was: Cr6+<Fe3+<Ni2+<Cu2+and Cu2+>Zn2+. Finally, these dithiocarbamates were tested in actual electroplating wastewater to validate our conclusions. After sodium dibutyl dithiocarbamate treatment, all residual metals’concentrations met the new tougher requirements announced by the Department of Environmental Protection of Guangdong province in Document No.25.
A wide range of plastic debris dumped into the ocean has recently gained concern of the marine ecosystems. Discarded and abandoned fishing nets, also known as ghost nets, are lost in the marine water and has no commercial significance. Additionally these fishing gear left out in the aquatic environment pose a severe risk to marine environment. Fishing nets, made up of synthetic plastic materials, are a major source of marine pollutants and act as a vector for transporting other toxic chemical pollutants. Approximately 10% of total marine plastic pollutants come from commercial fishing nets, and each year up to 1 million tons of fishing gear are discarded into the marine ecosystem. It can be estimated that by 2050 the amount will be doubled, adding 15–20 million metric tons of discarded lost fishing gears into ocean. The gradual and increased deposition of plastic pollutants in aquatic habitat also affects the whole food chain. Recently, microbial degradation of marine plastics has focussed the eyes of researchers and a lot of investigations on potential microbial degraders are under process. Microorganisms have developed the ability to grow under plastic stress condition and adapt to alter metabolic pathways by which they can directly feed upon marine plastic pollutants as sole carbon source. The present review compiles information on marine plastic pollution from discarded and abandoned fishing nets, their effect on aquatic ecosystems, marine animals and food chain and discusses microbial remediation strategies to control this pollution, especially and their implications in the marine ecosystems.
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A robust environmental monitoring system is highly essential for the instant detection of environmental microfiber pollutants for the sustainable management of the environment and human health. The extent of microfiber pollution is growing exponentially across the globe in both terrestrial and marine environments. An immediate and accurate environmental monitoring system is crucial to investigate the composition and distribution of these micropollutants. Fourier Transform Infrared Spectroscopy and Raman Spectroscopy are vibrational spectroscopic techniques that have the novel ability to detect microfibers within a minute concentration from diverse environmental samples. The major micropollutants which have been analyzed are polyethylene, polypropylene, nylon 6, polystyrene, and polyethylene terephthalate. After a detailed and critical study of the various aspects of spectroscopic analysis, the review is concluded with a comprehensive discussion of the significance of these robust methods and their application in future aspects for further preventing microfiber pollution in the marine environment. This study highlights the utilities and significance of vibrational spectroscopic detection techniques for the immediate and accurate identification of synthetic microfibers. This review also evaluated the implementation of spectroscopic methods as a precise tool for the characterization and monitoring of microfiber pollutants in the environment.
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Synthetic microfibers are universally recognized as an emerging pollutant in all ecosystems. The present investigation focuses on the evaluation and quantification of synthetic microfiber released from domestic laundering wastewater from different regions of Bhubaneswar city of Odisha state of India. The estimated number of microfibers collected from 500 ml of sample varied from 200 to 500 in numbers with an average amount of biomass in the range of 0.4-4 g. The surface morphology of the samples was assessed by Scanning Electron Microscopic analysis which revealed that the fibers were having a length of approximately 10-30 mm and diameter of 10-20 μm. Carbonyl (C-O) stretching band at 1711 cm − 1 and Aldehyde (-C-H) Weak bond at 2917.38 cm − 1 absorption were recorded from Fourier transform infrared spectroscopic analysis. As microfibers released from synthetic apparels are major source of environmental microplastic pollution their precise detection could help in controlling this problem.
Article
Background Enormous amounts of gold mine tailings (GMT) are produced as a result of mineral activities, but these mine tailings produced from previous ore processing still contain significant amounts of elements (e.g. strontium (Sr)) and rare earth elements (REEs) such as cerium (Ce). In this study, extraction of Ce and Sr from GMT using an adapted sulfur oxidizers acidophilic strain for developing a one-step bioleaching was performed for the first time. Methods Determination of the optimal conditions by response surface methodology (RSM), for maximizing Ce and Sr recovery, was carried out using influential factors of initial sulfur concentration, pH and pulp density. Significant findings The optimal values of pH, pulp density and initial sulfur concentration were 1.8, 2% (w v⁻¹) and 0.55% (w v⁻¹), respectively. The highest sulfate production was obtained in initial sulfur concentration of 0.5% (w v⁻¹). In addition, among the various inhibition kinetic models, Tessier inhibition kinetic model was the most suitable based on the experimental data. In conclusion, the kinetic study of the process indicated that a high recovery of 75.8% of Ce and 86.4% of Sr was achieved from GMT under optimal conditions, where the chemical reaction was revealed to be the rate controlling step. Bioleaching of GMT by A. thiooxidans is a promising technology to reduce the environmental hazards of these wastes. The results showed that GMT can be a source of supply of Ce and Sr.
Chapter
Microfiber (MFs), are classified as secondary microplastic pollutants with diameter less than 10 µm, mainly released from the laundering of synthetic fabric. Investigations confirmed the universal presence of these fragments throughout the atmosphere including air water and soil. Tiny plastic fibers are the major source of this type of pollutant. Microfiber released by domestic laundering processes of synthetic fabric has recently been detected as the prime source of microfiber pollution in the aquatic environment. However, it is vital to understand the contribution of the synthetic clothes laundering to this environmental problem. Current study mainly focuses on the quantification of data about the release of microplastics, and to identify possible influences of textile characteristics on the release. Washing trials were performed using daily use synthetic garments in the household washing machine in order to record the influence of the washing parameters on the quantity of micro fleeces released. These tiny particles are discharged into the marine environment each year from a variety of sources, of which approximately 700,000 micro fragments are released and 1900 particles from one piece of garment. It can be predicted that, till date, 1.5 million trillion of MF pollutants are currently gathered in the ocean discharged by principal microfiber contributing countries. Domestic washing machines, unable to filter tiny fibers; hence, they can be easily escaped through the outlet to the river and oceans via domestic drainage. Synthetic microfibers are harmful as they are polluting the whole food chain when these pollutants are ingested by smaller aquatic organisms inadvertently. Advancement in the microscopic and spectroscopic techniques is employed for the quick detection of microfleece pollutant in various aquatic systems. Although few and technology with advanced density separation and centrifugation were developed to combat this pollution. However it was scientifically investigated that none of this method and product can filter MFs so competently. Meticulous research in this field is necessary and pre requisite for developing a technique for recycling of these pollutants and sustainable management, which may diminish the pollution level of the water bodies. Future research should primarily aim at developing novel techniques as a solution to this problem. In this present work, primarily the washing machine effluents samples were collected from 5 different house hold regions of Bhubaneswar city, from Odisha state of India. Physiochemical parameters such as pH, Total dissolved solid, Total suspended solid of the collected grey water samples were measured to observe the variation. Morphological feature of the collected microfiber particles such as texture, colour, number and weight were measured. Around 500–520 numbers of visible fiber fleeces were present in 1 L of effluent sample, having biomass 3 mg/L approximately. Dominant presence of deep-red, black and blue coloured microfibers having fiber length 1–2.5 cm was observed. Abundant presence of polyester fiber groups is confirmed through hit description image and peaks 1240.03–2917.38 obtained from FTIR (Fourier transform infrared spectroscopy) analysis.
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This article reviews the effect of fungus filaments on the solubility of harmful elements, such as Zn, Cd, Hg, Cr, and As, released from sphalerite, greenockite, cinnabar, chromite, and arsenopyrite minerals, respectively, which are associated with gold mine tailings. Thus, gold mine sites liberate the hazardous elements in different parts of the environment. The fungi’s ability to bioleach Zn, Cd, Hg, Cr, and As elements was investigated, and the method was based on the capacity of microorganisms to extract these harmful elements from solid compounds, such as ZnS, CdS, HgS, FeCr2O4, and FeAsS, which are mostly insoluble. The investigation showed that the filaments of fungi cultivated along gold mine tailing dumps increased the solubility of the harmful elements. Maximum removal of 53% and 62% was observed for As and Zn, respectively, in a leachate of oxalic acid; 100%, 83.2%, and 57% of Cr(VI), Hg(II), and Cd(II) were removed, respectively.
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In order to treat the typical waste (acidic wastewater) from the production process of titanium dioxide, a collaborative utilization process of wastewater and pyrolusite was studied, which recovered both Ti, Fe from the wastewater and saved the amount of sulfuric acid used in the leaching process of pyrolusite. Acidic titanium dioxide wastewater was used to react with phosphoric acid to prepare titanium phosphate, and the recovery of titanium reached 95%. After the extraction of titanium, a portion of ferrous sulfate heptahydrate was separated using the freezing crystallization method. Then the pyrolusite was leached with a leaching efficiency of 93% for manganese. Finally, the pH was neutralized to 4 using manganese carbonate. Fe²⁺ was oxidized to Fe³⁺ and separated by precipitation. Compared with the neutralization and concentration methods, although the process is longer, it has higher resource utilization, less pollution, simple operation and wide application prospect.
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Extensive use of these harmful dyes has resulted in the surplus presence of these emerging pollutants in the environment, thus demanding an instant and sensitive detection method. Various synthetic dyes are illegitimately mixed into food and other consuming items for displaying bright colours that attracts consumers. The synthetic dyes cause a number of environmental health hazards and promote toxicity, mutagenicity and carcinogenicity in humans. Despite these serious health glitches, synthetic dyes are widely used due to their much lower cost. As a result, a faster, more selective and extremely sensitive technology for detecting and quantifying hazardous dyes in trace amount is urgently needed. This topic is currently in its initial phases of development and needs continuous refinements, such as explaining various sensing methods and potential future uses linked with dye detection technologies. The present review encompasses a comprehensive literature survey on detection of dyes and latest progress in developing sensors for dye detection and summarizes different detection mechanisms, including biosensor-, optical- and electrochemical-based sensors. Detection methodologies are examined with a focus on biosensor-based recent advancements in dye detection and the growing demand for more appropriate systems in terms of accuracy and efficiency.
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The increased amount of heavy metal pollution, due to rapid urbanization is one of the main reasons for ecosystem degradation. The sewer systems of industries, as well as the mining grounds, are the potential sources of toxic heavy metals. Broad application of mutagenic metals in different industrial processes results in their bioaccumulation in the soil ecosystem. The primary metal wastes are mercury, arsenic, lead, cadmium, cyanide, chromium, etc. Long-term exposure to even the low concentration of metals induces multiple health hazards and organ failure. The safe removal or treatment of wastes is crucial as many approaches might lead to the generation of harmful by-products or incomplete transformation of toxic metals. Therefore, eco-friendly biodegradation of toxic metals administrating efficient bioleachers is generally preferred. However, the activity of the microbes depends on their ability to tolerate large content of metals, and the use of metal-tolerant microbes found in nature is the simplest and biogenic way of degrading the metal contaminants of industries such as mining, manufacturing, textile, petroleum, plastics, etc. Microbial remediation includes the following mechanisms; surface absorption, bioleaching, transformation to less toxic products, biomineralization, and bioaccumulation. The objective of this review is to describe the industrial production and environmental occurrence of carcinogenic metals, highlight the role of the bioleachers in the decontamination process, harmful effects of toxic metals, and microbial bioleaching mechanism.
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A major apprehension is over microplastic pollution in the aquatic environment. These microplastics particles represent a novel medium in the aquatic environment, providing a substratum for various organic contaminants and for colonization of microorganisms. Microorganisms form a biofilm on the exterior of pollutants, consequential in a region known as a plastisphere, in which they interrelate and generate acid and different enzymes for microplastic degradation. The use of microbes for microplastic degradation has become a contentious exit indication as society focuses more on environmentally friendly pollution reduction methods. After both substantial and elemental degradation, biodegradation occurs, weakening the arrangement of polymers. Natural resource microbes have a significant effect on the reduction of plastic waste in the environment. The current review article discusses microbial colonization and degradation of microplastics present in aquatic ecosystems and the processes involved. While studying and considering how these microplastic particles have now turn out to be a recent environmental position within various aquatic environments, we emphasized the significance of colonization and microbial-assisted degradation of aquatic microplastics in this article.
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Biomining through bioleaching and bio-oxidation aims at recovering desired metals at the required specifications with lower environmental impact and costs from ores and waste streams. Research and developments related to the process technology and efficient implementation of this approach are advanced worldwide. Small particles of gold, a metal of higher interest, are mostly found in a matrix of sulfide-based minerals and not affordably recovered with conventional approaches encompassing cyanidation, pyrometallurgy, extreme heating (roasting), oxidation of ore samples at high pressure. Recently, advances in bio-oxidation have been made in addressing scientific and technical challenges that arise during the pilot and demonstration scales in the operations units in bioreactors and heaps. Through including high-throughput bacterial growth data and better process knowledge of the extraction and recovery approaches, bio-oxidation becomes more economically feasible and efficient. More advancements are necessary to evaluate the wide range of mineralogical structure of ores being processed, microbiological, and physicochemical that can significantly influence the bio-oxidation reaction within the different types of reactors (heap and continuously stirred tank reactors), the microbial interactions between metal and microbes, geographical localizations of the mining sector, economic as well as data interpretation by using advanced artificial intelligence methods toward obtaining optimized operation and efficiency. This review covers important advances and developments and associated industrial and academic research and challenges from the past few years for gold bio-oxidation.
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In this research, Zn, Ni, and Cu recovery from mobile phone printed circuit boards was investigated. The initial pH and pulp density using Aspergillus niger or Penicillium simplicissimum fungi were optimized to improve the recovery of Zn, Ni, and Cu using a central composite design. Fungi were able to recover 97% of Cu. Often for Ni recovery, A. niger was more effective, but in low pulp densities and low pH, P. simplicissimum was preferred. For recovery of Zn, A. niger is more appropriate at pH lower than 6, but P. simplicissimum outperforms at pH higher than 6. Under the optimum conditions (pulp density of 4 gL−1 and initial pH 10), the respective recovery of Cu, Ni, and Zn was determined as 94%, 100%, and 100% using A. niger as well as 100%, 95%, and 87% using P. simplicissimum. At alkaline conditions, oxalic acid, citric acid, and gluconic acid are the main acids produced by A. niger; the main acid produced by P. simplicissimum is oxalic acid. Similarly, FTIR and chemical characteristics of the metabolites (the organic acid produced) were analyzed under optimal conditions using HPLC. A. niger in alkaline and acidic conditions produces more acids which lead to higher recovery.Graphic abstract
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Probiotics are potential health-promoting microorganisms representing a significant health aid with diverse pharmaceutical applications. But its role in modulating the human gut microbiome necessities a profound analysis. Undoubtedly, the human gut is a reservoir of infinite species such as bacteria, viruses, fungi, etc. But host with chronic illness bids enrichment of the pathogenic strain which may alter the composition gut microbiome. Culture-based techniques are providing unclear taxonomic data where the possibility of the discrepancy is very high. Therefore the use of next-generation sequencing (NGS) analysis helps to explore depth understanding of the curd microbiome and can generate big genomic data. The present investigation aims to explore the microbial diversity of curd samples from different local dairy farms of Odisha, India using a metagenomic approach. The data read comprising 304,725 sequences totaling 148,546,295 base pairs were interpreted. Taxonomical distribution at different levels unfolded the absolute abundance of phylum, class, order, family, genus, and species within each microbial community. The most dominant species found to be Lactobacillus at order level is 49%, whereas phyla proteobacteria and firmicutes have shown taxonomic percentage abundance of 50.01% and 48.77%, respectively. However, nearly 26.41% of unclassified species from the Lactococcus genus were identified in the sample at different taxonomic levels. The metagenomics sequence data has been deposited to sequence read archive (SRA) of NCBI database under Bioproject PRJNA383620. The present study has vital implications in understanding the microbial diversity in curd samples with their role in human health and application in future pharmaceutical probiotic research.
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This article has reviewed the progress that has been made in bioleaching research of metals using filamentous fungi. This review has focused on fungal bioleaching from various metal sources, including mine tailings, electronic waste, solid mine wastes, spent catalysts, and low-grade ores. Filamentous fungi are used in bioleaching due to their ability to secrete organic acids and facilitate the solubilization of metal ions from the solution phase. The information provided in this review shows that fungal species under different specific operating parameters (pH, temperature, substrate, incubation time) can be used in the recovery of essential metals. Several drawbacks that lie in fungal bioleaching have been listed in this review. However, we have put forward suggestions that might help counter these challenges and invigorate interest in this research line. The present review examines the gaps and summarizes the fundamental mechanisms of fungal bioleaching. Furthermore, fungal species' practical potentiality for the future development of enhanced bioleaching technology applications is underlined.
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Low-grade metal resources generated during different mineral processing activities are increasing while there are not many economic and environmentally friendly techniques to manage them. There is no viable technique for the manganese extraction from low-grade ores as the conventional procedures are costly and environmentally unfriendly. In this research, the D-optimal response surface methodology has been used to optimize the bioleaching parameters. Varied contact methods (one-step, two-step, and spent medium), nutrition sources (sucrose and glucose), and pulp densities (1 g.L⁻¹ to 10 g.L⁻¹) were used in different experiments having been done in 30 days using Aspergillus niger. A maximum recovery of over 80% of Mn was achieved based on the acidolysis, complexolysis, and redoxolysis leaching of the organic acids produced by the fungi under the optimum condition; a two-step approach, in a glucose medium, and with a pulp density of 1 g.L⁻¹. A kinetic study was also performed and revealed that the leaching mechanism was a mixed one which consisted of two stages (diffusion through the liquid film and a chemical reaction) for the first 12 day period, and a mechanism of diffusion through the product layer for the rest of the experiment.
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Industrial processes and mining of coal and metal ores are generating a number of threats by polluting natural water bodies. Contamination of heavy metals (HMs) in water and soil is the most serious problem caused by industrial and mining processes and other anthropogenic activities. The available literature suggests that existing conventional technologies are costly and generated hazardous waste that necessitates disposal. So, there is a need for cheap and green approaches for the treatment of such contaminated wastewater. Bioremediation is considered a sustainable way where fungi seem to be good bioremediation agents to treat HM-polluted wastewater. Fungi have high adsorption and accumulation capacity of HMs and can be potentially utilized. The most important biomechanisms which are involved in HM tolerance and removal by fungi are bioaccumulation, bioadsorption, biosynthesis, biomineralisation, bioreduction, bio-oxidation, extracellular precipitation, intracellular precipitation, surface sorption, etc. which vary from species to species. However, the time, pH, temperature, concentration of HMs, the dose of fungal biomass, and shaking rate are the most influencing factors that affect the bioremediation of HMs and vary with characteristics of the fungi and nature of the HMs. In this review, we have discussed the application of fungi, involved tolerance and removal strategies in fungi, and factors affecting the removal of HMs.
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Several geoactive fungi were investigated for their biocorrosion impact on metallic copper, to further understanding of the potential roles that fungi may have in the biotransformation of such substrate, and the mechanisms involved. Copper metal showed little toxicity and test fungi were able to grow in direct or indirect contact with copper and to colonize copper sheet. A. niger was able to biodeteriorate copper metal through proton- and ligand-mediated dissolution mechanisms, leading to significant mass loss and surface etching. The formation of a secondary copper oxalate (moolooite) biomineral crust together with cuprite deposition lead to alteration of surface topography and visual appearance, highlighting the significance of oxalate excretion in effecting fungal metal biotransformations. The metal transforming influence of fungal colonization may have some implications for biodeterioration, protection and preservation of cultural relics and artefacts as well as certain components of the built environment.
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Currently, bioleaching of manganese (Mn) from Mn-poor ore (e.g. pyrolusite) is facing the challenges of low leaching efficiency and high cost of leachant and process operation. In this study, a new process was developed that uses Microbacterium trichothecenolyticum Y1 (bacteria Y1) and waste molasses to bioleach Mn from pyrolusite or pure MnO2 (for comparison). Results indicate that the innovative process can be operated at normal temperature/pressure and a weak acidic condition (pH = 3.5) with a much improved Mn bioleaching efficiency (about 98% in 6–8 days) as compared with the previously-reported efficiencies (only 60–80%). The optimal conditions were found as the solid-liquid ratio of 1 kg of mineral powder to 20 L of leaching liquid, pH 3.5, anaerobic, stirring speed of 80 rpm, temperature 45 °C and waster molasses dose of 2.5 g L⁻¹. The associated mechanism was elucidated with the help of different equipment and methods. The leaching process first reduced Mn(IV) in MnO2 to Mn(II) as MnO in the solid phase and then dissolved Mn(II) into the liquid phase. Bacteria Y1 could produce a large number of tyrosine-like substances in the system, which promoted the decomposition of sugar and Mn(IV) reduction. Weak acid (pH = 3.5) could destroy biofilm and manganese oxides (e.g., MnO) on mineral surfaces to promote the leaching process. Kinetic studies show that the pyrolusite leaching process belongs to mixed control by solid film diffusion control and chemical reaction control. The innovative process may be cost-effective and green, with a great potential for future applications.
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End of life waste Lead (Pb) acid batteries are one of the largest sources of secondary lead production globally. Recycling lead by melting down used batteries is a commercial trade all over the world; but, regrettably, reprocessing lead from end of life batteries is reported for anthropogenic lead exposures causing harsh human health consequence and environmental pollution. The current research intends to isolate and identify Lead (Pb) solubilizing bacteria from automobile waste deposits from Agartala city in Tripura state of India. Scanning Electron Microscope equipped with energy-dispersive X-ray characterization of the grounded lead sample was carried out, and the micrographs demonstrated scattered structures across the matrix. The X-ray diffraction (XRD) spectrum indicates the presence of Lead Oxide (PbO), Lead dioxide (PbO2), and Lead sulfate (PbSO4) in the collected samples. A single bacterium viewing observable growth on Pb supplemented plates was isolated and its Pb recovering capability was estimated through ICP AES analysis. Molecular characterization of the bacterium was investigated using 16S rRNA sequencing along with isolated culture was taxonomically grouped as Cupriavidus sp. The genomic DNA sequences were submitted in NCBI GenBank with the accession number MG171197. In the present case of inspection, the ability of the bacterial strain to recover Pb from end life battery waste was carried out in laboratory scale on a shake flask for 20 days. The experiment conducted under optimum bioleaching parameters with initial pH 6, 5% w/v of microbial culture, 2% pulp density and 2 g/100 mL dextrose concentration at 30 °C temperature with a speed of 200 RPM resulted in 67% Pb recovery from the battery sample. This investigation emphasizes the significance of Pb recycling ability of native bacterial isolate for efficient Pb bio-recovery from end of life waste batteries.
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The capability of oxalic acid produced by Aspergillus niger was investigated for bioleaching of platinum from a refinery reforming catalyst. The spent medium mode was selected for bioleaching because of its higher efficiency at favorable pH and temperature conditions. The effects of several important factors such as the pulp density, pH and temperature on platinum recovery were optimized using Box-Behnken design of response surface methodology. The results indicated that pH adjustment during the bioleaching process increases the final platinum recovery significantly. The obtained optimum conditions were 1% for the pulp density, 0.5 for the medium pH, and 70 °C for the temperature which led to 37% platinum recovery. The significance of oxalic acid as the leaching agent in platinum bioleaching was highlighted by investigating the recovery of a blank medium without oxalic acid at the optimum conditions which was just about 13%. The presented method can be utilized in an environmentally friendly process to recover platinum from industrial catalysts.
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The strategic situation of Sinai made it an urgent national target for the sustainable development. One of the important factors in such development is the exploration and the processing of uraniferous rock materials. Consequently, the Lower Carboniferous sedimentary rocks were chosen for the present study to test the uranium bioleaching capacity of fungal strains isolated from exposed sedimentary rocks in southwestern Sinai. Eight fungal species were isolated from three grades of uraniferous sedimentary rock samples in southwestern Sinai, Egypt and tested for their bioleaching activity. Aspergillus niger (A. niger) and Aspergillus terreus (A. terreus) were the only isolates which gave a high grade leaching efficiency of uranium from the studied uraniferous rocks. The most favorable factors for solubilization of uranium were 7 days incubation time, 3% ore concentration, solid/liquid ratio 1/3 and 30 °C incubation temperature. Both fungi produced organic acids (oxalic, citric, formic and ascorbic) in the culture filtrate which are the key compounds of bioleaching processes. Applying these conditions on one kilogram of Ag-3 sample (the lowest U grade), the A. niger strain gave high uranium leaching efficiency of 71.4%. The recovery test of U has been performed by proper precipitation to obtain a high quality uranium concentrate.
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The requirement for manganese (Mn) has augmented extensively owing to the intense production of steel and the mounting paucity of natural deposits. The widespread mining, mineral processing, and further human activities have faced a severe consequence in the generation of massive quantity of manganese mining waste residues. The inappropriate supervision and unprocessed liberation of these wastes have resulted in the spread of Mn to the contiguous atmosphere, soil and groundwater pollution, and loads of severe ecological tribulations. Chronic and acute exposure of this metal pollutant leads to lethal consequences and is clinically categorized by the multiple symptoms of neurotoxicity including cognitive and psychiatric symptoms, Parkinson’s disease, manganism, motor system dysfunction, and other neurodegenerative diseases. The advancement of bioremediation technology focuses on accomplishing successful removal of these metal pollutants by increasing the effectiveness of microbes related to metal-solubilizing activities. This chapter describes a complete advance in the research on manganese environmental pollution, manganese compound-induced toxicity, and recent approaches for the microbial remediation of manganese pollutants.
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Manufacturing of manganese (Mn) compounds, their industrial applications as well as mining overburden, has generated a potential environmental pollutant. Occupational exposure to elevated levels of Mn occurs during mining, welding, smelting and other industrial anthropogenic sources. Chronic and acute exposure of this metal pollutant leads to adverse consequences and is clinically categorized by various symptoms of neurotoxicity including cognitive, psychiatric symptoms, Parkinson's disease, extra pyramidal signs, manganism, dystonia, and motor system dysfunction. The aim of this review is to summarize the possible mechanism underlying Mn compounds-mediated neurotoxicity leading to neurodegenerative diseases. Our review endeavours to examine recent advances in research on Mn-related environmental pollution, Mn-induced poisoning, molecular mechanisms underlying Mn-induced neurotoxicity with case studies as well as current approaches employed for treatment and prevention of Mn exposure.
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Pyrolysis has been examined as an attractive alternative to incineration for municipal solid waste (MSW) disposal that allows energy and resource recovery; however, it has seldom been applied independently with the output of pyrolysis products as end products. This review addresses the state-of-the-art of MSW pyrolysis in regards to its technologies and reactors, products and environmental impacts. In this review, first, the influence of important operating parameters such as final temperature, heating rate (HR) and residence time in the reaction zone on the pyrolysis behaviours and products is reviewed; then the pyrolysis technologies and reactors adopted in literatures and scale-up plants are evaluated. Third, the yields and main properties of the pyrolytic products from individual MSW components, refuse-derived fuel (RDF) made from MSW, and MSW are summarised. In the fourth section, in addition to emissions from pyrolysis processes, such as HCl, SO2 and NH3, contaminants in the products, including PCDD/F and heavy metals, are also reviewed, and available measures for improving the environmental impacts of pyrolysis are surveyed. It can be concluded that the single pyrolysis process is an effective waste-to-energy convertor but is not a guaranteed clean solution for MSW disposal. Based on this information, the prospects of applying pyrolysis technologies to dealing with MSW are evaluated and suggested. Copyright © 2015 Elsevier Ltd. All rights reserved.
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Heavy metal tolerating bacterial isolates-AD1, AD2, AD3, AD4, AD5, AD6 and AD7 were isolated from garden soil, industrial waste water and textile effluent samples from the local area of Kalyan, Dist Thane, MS. The isolates were observed to tolerate high levels of mercury, cadmium, arsenic and lead and were seen to be resistant to a wide range of antibiotics. Plasmid isolation was carried out using Alkaline lysis method. The size of the isolated plasmid DNA was approximately 15-26 kb. Plasmid curing was carried out by Ethidium Bromide and 2 % Sodium Dodecyl Sulphate. Lead, cadmium and arsenic resistance gene was found to be present on the chromosomal DNA rather than the plasmid DNA whereas, mercury genes were found to be present on the plasmid. Curing result showed the loss of antibiotic and heavy metal resistance property from the isolated strain and confirms a relationship between antibiotic and heavy metal resistance with plasmid. The whole cell protein samples from the isolates treated with different concentrations of lead, cadmium, arsenic and mercury were isolated, electrophoresed on SDS-PAGE and the protein profile was studied. A significant change in the banding pattern was observed.
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Bacterial manganese (Mn) oxidation plays an important role in the global biogeochemical cycling of Mn and other compounds, and the diversity and prevalence of Mn oxidizers have been well established. Despite many hypotheses of why these bacteria may oxidize Mn, the physiological reasons remain elusive. Intracellular Mn levels were determined for Pseudomonas putida GB-1 grown in the presence or absence of Mn by inductively coupled plasma mass spectrometry (ICP-MS). Mn oxidizing wild type P. putida GB-1 had higher intracellular Mn than non Mn oxidizing mutants grown under the same conditions. P. putida GB-1 had a 5 fold increase in intracellular Mn compared to the non Mn oxidizing mutant P. putida GB-1-007 and a 59 fold increase in intracellular Mn compared to P. putida GB-1 ∆2665 ∆2447. The intracellular Mn is primarily associated with the less than 3 kDa fraction, suggesting it is not bound to protein. Protein oxidation levels in Mn oxidizing and non oxidizing cultures were relatively similar, yet Mn oxidation did increase survival of P. putida GB-1 when oxidatively stressed. This study is the first to link Mn oxidation to Mn homeostasis and oxidative stress protection.
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Bioleaching of metal sulfides is performed by a diverse group of microorganisms. The dissolution chemistry of metal sulfides follows two pathways, which are determined by the mineralogy and the acid solubility of the metal sulfides: the thiosulfate and the polysulfide pathways. Bacterial cells can effect this metal sulfide dissolution via iron(II) ion and sulfur compound oxidation. Thereby, iron(III) ions and protons, the metal sulfide-attacking agents, are available. Cells can be active either in planktonic state or in forming biofilms on the mineral surface; however, the latter is much more efficient in terms of bioleaching kinetics. In the case of Acidithiobacillus ferrooxidans, bacterial exopolymers contain iron(III) ions, each complexed by two uronic acid residues. The resulting positive charge allows an electrostatic attachment to the negatively charged pyrite. Thus, the first function of complexed iron(III) ions is the mediation of cell attachment, while their second function is oxidative dissolution of the metal sulfide, similar to the role of free iron(III) ions in non-contact leaching. In both cases, the electrons extracted from the metal sulfide reduce molecular oxygen via a redox chain forming a supercomplex spanning the periplasmic space and connecting both outer and inner membranes. In this review, we summarize some recent discoveries relevant to leaching bacteria which contribute to a better understanding of these fascinating microorganisms. These include surface science, biochemistry of iron and sulfur metabolism, anaerobic metabolism, and biofilm formation. The study of microbial interactions among multispecies leaching consortia, including cell-to-cell communication mechanisms, must be considered in order to reveal more insights into the biology of bioleaching microorganisms and their potential biotechnological use.
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Manganese oxide catalysts, both bulk and supported on gamma-Al2O3 and SiO2, have been studied by Raman and FTIR spectroscopies, their phase composition being determined by X-ray diffraction. The supported catalysts were prepared via pore volume impregnation from nitrate precursors, the atomic ratio of manganese to aluminium and silicon, respectively, being in the range from 0.5/100 to 18/100. The use of Raman analysis in the microscopic configuration allowed the spectra to be taken at different points of the surface and revealed the inhomogeneity of the catalyst. Besides the Raman features of the beta-MnO2 and alpha-Mn2O3 phases, other signals were assigned to isolated Mn2+ ions accommodated in tetrahedral vacancies on the support surface and to some epitaxial layers of gamma-Mn2O3 and manganese silicate, respectively. The FTIR spectra, though not as useful because of the strong bands of the support that overlap those of manganese oxides, support these findings.
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Bioleaching is technologically feasible for extraction of manganese from low grade ores (containing manganese less than 35% by weight). The principle involves the non-enzymatic reduction of pyrolusite [Mn(IV) oxides] to +2 oxidation state by fungi with the production of metabolites such as oxalic acid and citric acid. In the present investigation, a fungal strain, Penicillium citrinum was isolated from top soil of Joda East manganese mine area, Tata Iron and Steel Company(TISCO), Orissa. Growth of the fungus was determined in terms of the final pH of the growth medium, biomass dry weight and total acid produced by the fungus. These data were used to evaluate the growth kinetics. Finally, it was used for bioleaching of low grade manganese ore. Effect of various parameters on in-situ leaching of manganese ore with P. citrinum such as (a) particle size (b) pulp density (c) sucrose concentration (d) inoculum size and (e) duration of leaching were studied. The maximum solubilisation of manganese (64.6%) was obtained with particle size of -45μm of the ore at pulp density of 2% (w/v), sucrose concentration 10% (w/v) and inoculum size of 10% (v/v) in a period of 30 days.
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A fungi strain named Fusarium sp. was isolated from manganese-electrolysed slag by using a gradient dilution spread plate method, identified by 26S RNA sequence analysis and phylogenetic tree analysis, and explored for the bioleaching capacity to manganese (II) from manganese-electrolysed slag in liquid mineral medium under different environmental conditions, including system temperature, incubator rotation speed and initial pH value. DNA sequence and phylogenetic analysis indicated the name of this fungi strain, that is, Fusarium sp., and higher bioleaching efficiencies (71.6%) of manganese by this fungi were observed when the bioleaching was carried out under the optimized conditions as follows: contact time: 72 h; system temperature: 28 degrees C; inoculums concentration: 2% (v/v); incubator rotation speed: 150 rpm; pH 4.0. Because of its low cost, environment friendliness and better efficiency, the bioleaching technique will have a significant impact on manganese-electrolysed slag pollution mitigation.
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Manganese minerals are widely distributed throughout the globe. The most important industrial uses of Mn are in the manufacture of steel, non-ferrous alloys, carbon-zinc batteries and some chemical reagents. Microbial recovery of manganese from low grade manganese ores using bioleaching was investigated in this paper. A bacterial strain, Staphylococcus epidermidis (MTCC-435) was collected from microbial type culture collection, IMTECH Chandigarh and used for the experiment. The experimental results for bioleaching with S. epidermidis showed that under pH 5.5, particle size –150 μm, pulp density 10%, temperature 35℃ and agitation 200 rpm, about 80% of Mn was recovered within 20 days of incu
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Biomineralization in heterogeneous aqueous systems results from a complex association between pre-existing surfaces, bacterial cells, extracellular biomacromolecules, and neoformed precipitates. Fourier transform infrared (FTIR) spectroscopy was used in several complementary sample introduction modes ( attenuated total reflectance [ATR], diffuse reflectance [DRIFT], and transmission) to investigate the processes of cell adhesion, biofilm growth, and biological Mn-oxidation by Pseudomonas putida strain GB-1. Distinct differences in the adhesive properties of GB-1 were observed upon Mn oxidation. No adhesion to the ZnSe crystal surface was observed for planktonic GB-1 cells coated with biogenic MnOx, whereas cell adhesion was extensive and a GB-1 biofilm was readily grown on ZnSe, CdTe, and Ge crystals prior to Mn-oxidation. IR peak intensity ratios reveal changes in biomolecular (carbohydrate, phosphate, and protein) composition during biologically catalyzed Mn-oxidation. In situ monitoring via ATR-FTIR of an active GB-1 biofilm and DRIFT data revealed an increase in extracellular protein (amide I and II) during Mn( II) oxidation, whereas transmission mode measurements suggest an overall increase in carbohydrate and phosphate moieties. The FTIR spectrum of biogenic Mn oxide comprises Mn-O stretching vibrations characteristic of various known Mn oxides (e. g., "acid" birnessite, romanechite, todorokite), but it is not identical to known synthetic solids, possibly because of solid-phase incorporation of biomolecular constituents. The results suggest that, when biogenic MnOx accumulates on the surfaces of planktonic cells, adhesion of the bacteria to other negatively charged surfaces is hindered via blocking of surfaces proteins.
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The bioleaching of chalcopyrite in shake flasks was investigated by using pure Acidithiobacillus ferrooxidans and mixed culture isolated from the acid mine drainage in Yushui and Dabaoshan Copper Mine in China, marked as YS and DB, respectively. The mixed culture consisted mainly of Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans, and Leptospirillum spp. (Leptospirillum ferriphilum and Leptospirillum ferrooxians). The results show that the mixed culture is more efficient than the pure Acidithiobacillus ferrooxidans because of the presence of the sulfur-oxidizing cultures that positively increase the dissolution rate and the recovery of copper from chalcopyrite. The pH value decreases with the decrease of chalcopyrite leaching rate, because of the formation of jarosite as a passivation layer on the mineral surface during bioleaching. In the bioleaching using the mixed culture, low pH is got from the sulfur oxidizing inhibiting, the formation of jarosite. The copper extraction reaches 46.27% in mixed culture and 30.37% in pure Acidithiobacillus ferrooxidans after leaching for 75 d.
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Mature dormant spores of marine Bacillus sp. strain SG1 catalyze the oxidation of Mn(II) to MnO2. We report that vegetative cells of the same strain reduced MnO2 under low-oxygen conditions. The rate of reduction was a function of cell concentration. The process had a pH optimum of 7.5 to 8.0 and was inhibited by HgCl2, by preheating of the cells at 80 degrees C for 5 min, by antimycin A, and by N-heptyl-hydroxy-quinoline-N-oxide. At a nonlimiting O2 concentration, little MnO2 reduction was observed. Under these conditions, the process could be induced by the addition of NaN3. Spectrophotometric analysis of the Bacillus cells indicated the presence of type b and c cytochromes. Both types can be oxidized in situ by addition of MnO2 to the cells.
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Culture supernatants of the white-rot fungus Trametes versicolor were found to contain Mn(III)-complexing agents able to effectively promote manganese-dependent peroxidase (MnP)-mediated oxidation of phenol red. The high molecular weight fractions of these supernatants contained carbohydrate polymers that functioned as effective Mn(III)-complexing agents. Gluconic and glucuronic acids were also found to be effective Mn(III)-complexing ligands capable of supporting MnP-mediated phenol red oxidation, as was the cellobionic acid formed from cellobiose by cellobiose:quinone oxidoreductase (CBQase) (EC 1.1.5.1). The formation of cellulose-derived sugar acid manganese-complexing agents by CBQase increased in the presence of wood pulp and cellulolytic enzymes. CBQase, while oxidizing cellobiose, reduced insoluble Mn(IV)O2 to Mn(II) or Mn(III) by a reaction whose rate is determined by the nature of the manganese-complexing agents present. A model is proposed to explain how oxidation of carbohydrate and reduction of MnO2 and quinones by CBQase may complement oxidation by MnP, thus promoting lignin biodegradation.
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Manganese peroxidase (MnP) production in the white-rot basidiomycete Physisporinus rivulosus T241i was studied. Separate MnP isoforms were produced in carbon-limited liquid media supplemented with Mn(2+), veratryl alcohol, or sawdust. The isoforms had different pH ranges for the oxidation of Mn(2+) and 2,6-dimethoxyphenol. Although lignin degradation by white-rot fungi is often triggered by nitrogen depletion, MnPs of P. rivulosus were efficiently produced also in the presence of high-nutrient nitrogen, especially in cultures supplemented with veratryl alcohol. Two MnP encoding genes, mnpA and mnpB, were identified, and their corresponding cDNAs were characterized. Structurally, the genes showed marked dissimilarity, and the expression of the two genes implicated quantitative variation and differential regulation in response to manganese, veratryl alcohol, or sawdust. The variability in regulation and properties of the isoforms may widen the operating range for efficient lignin degradation by P. rivulosus.
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The present investigation reports the isolation, molecular identification and screening of Mn solubilizing fungal strains from low grade Mn mine tailings. Six morphologically distinct Mn solubilizing fungal strains were isolated on MnO2 supplemented agar plates with Mn concentration of 0.1 % (w/v).The biochemical characterization of the isolated fungal strains was carried out. The molecular identification by Internal Transcribed Spacer (ITS) sequencing identified the strains as Aspergillus terreus, Aspergillus oryzae, Penicillium species, Penicillium species, Penicillium dalea, and Penicillium species with GenBank accession numbers KP309809, KP309810, KP309811, KP309812, KP309813 and KP309814 respectively. The ability of the isolated fungal strains to tolerate and solubilize Mn was investigated by sub-culturing them on Mn supplemented plates with concentration ranging from 0.1-0.5% (w/v). Mn solubilizing ability of the fungal isolates is possibly due to the mycelia production of bio generated organic acids such as oxalic acid, citric acid, maleic acid and gluconic acid as revealed by ion chromatography. Our investigation signifies the role of fungi in biotransformation of insoluble Mn oxide.
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In view of unremitting diminution of mineral resources, rising energy economics along with increasing global consumption of Manganese (Mn), development of environment friendly technologies for tapping alternate sources of Mn has gained importance lately. Mn recovery from mining residues using conventional approaches is extremely expensive due to high capital and energy costs involved. However lean grade ores present in millions of tons awaits the development of competent and cost effective extractive process. Mn recovery by biomining with diverse microbes is thereby recommended as a superior and green alternative to the current pyro metallurgical techniques. The synergistic effects of different factors are known to influence microbial leaching of mineral ores which includes microbiological, mineralogical, physicochemical and process parameters. Bacterial bioleaching is mostly due to enzymatic influence, however fungal bioleaching is non enzymatic. Genomic studies on microbial diversity and an insight of its metabolic pathways provides unique dimension to the mechanism of biomining microorganisms. The extraction of Mn has a massive future prospective and will play a remarkable role in altering the situation of ever-decreasing grades of ore. This review aims to encompass the different aspects of Mn bioleaching, the plethora of organisms involved, the mechanisms driving the process and the recent trends and future prospects of this green technology.
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Most agricultural soils contain large reserves of phosphorus (P), a considerable part of which accumulates as a consequence of regular applications of P fertilizers. However, a greater part of soil phosphorus, approximately 95-99% is present in the form of insoluble phosphates and hence cannot be utilized by the plants. In the present study fungal strains isolated from agriculture soil, having potential to solubilize insoluble inorganic phosphates were characterized. Two fungal isolates were tested for their tricalcium phosphate (TCP) solubilization efficiency in both solid and liquid medium. Isolates were identified as Aspergillus sp. and Penicillium sp. depending upon their colony morphology and microscopic studies. Phosphate solubilization was related to pH decrease caused by growth of fungus in medium containing glucose as carbon source. Aspergillus sp. solubilized 480 μg/ml of phosphorus, while Penicillium sp. solubilized 275 μg/ml of phosphorus from 0.5% tricalcium phosphate after 4 and 3 days of growth respectively. Both the strains show diverse levels of phosphate solubilization activity in liquid broth culture in presence of various carbon and nitrogen sources. Drop in pH during growth was more prominent in absence of TCP in the liquid medium. This indicates that absence of soluble P in media induces the acid production. Phosphate solubilizing microorganisms convert insoluble phosphates into soluble forms generally through the process of acidification, chelation and exchange reactions. Thus such microorganisms may not only compensate for higher cost of manufacturing fertilizers in industry but also mobilizes the fertilizers added to soil.
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Manganese (Mn) ranks twelfth among the most exuberant metal present in the earth's crust and finds its imperative application in the manufacturing steel, chemical, tannery, glass, and battery industries. Solubilisation of Mn can be performed by several bacterial strains which are useful in developing environmental friendly solutions for mining activities. The present investigation aims to isolate and characterize Mn solubilising bacteria from low grade ores from Sanindipur Manganese mine of Sundargh district in Odisha state of India. Four morphologically distinct bacterial strains showing visible growth on Mn supplemented plates were isolated. Mn solubilising ability of the bacterial strains was assessed by visualizing the lightening of the medium appearing around the growing colonies. Three isolates were gram negative and rod shaped while the remaining one was gram positive, coccobacilli. Molecular identification of the isolates was carried out by 16S rRNA sequencing and the bacterial isolates were taxonomically classified as Bacillus anthrasis MSB 2, Acinetobacter sp. MSB 5, Lysinibacillus sp. MSB 11, and Bacillus sp. MMR-1 using BLAST algorithm. The sequences were deposited in NCBI GenBank with the accession number KP635223, KP635224, KP635225 and JQ936966, respectively. Manganese solubilisation efficiency of 40, 96, 97.5 and 48.5% were achieved by MMR-1, MSB 2, MSB 5 and MSB 11 respectively. The efficiency of Mn solubilisation is suggested with the help of a pH variation study. The results are discussed in relation to the possible mechanisms involved in Manganese solubilisation efficiency of bacterial isolates.
Chapter
The “manganese-oxidizing group” is a phylogenetically diverse assemblage, which is characterized by the ability to catalyze the oxidation of divalent, soluble Mn(II) to insoluble manganese oxides of the general formula MnOx (where X is some number between 1 and 2). This results in the accumulation of conspicuous and easily detectable extracellular deposits of insoluble brown or black manganese oxides. Many different organisms have the ability to catalyze Mn oxidation, including a diverse array of bacteria, fungi, algae, and even eukaryotes (Ghiorse, 1984b). Among the prokaryotes, the ability to oxidize Mn is also quite widespread (Ehrlich, 1981; Ghiorse, 1984b, 1988; Marshall, 1979; Nealson, 1983); included are members of many phylogenetic and physiological groups: e.g., cyanobacteria, a diversity of heterotrophic rods and cocci, the sheathed (Leptothrix-like) and budding (Hyphomicrobium-like) bacteria, some purported autotrophic strains related to Pseudomonas species and the still-controversial Metallogenium group. The anaerobic lactobacilli, which utilize the Mn oxidation reaction as a protection against oxygen toxicity (Archibald and Fridovich, 1981, 1982) are not included, as they do not precipitate extracellular Mn oxides, but rather accumulate millimolar levels of protein-associated Mn in the cytoplasm. This chapter focuses on the process of Mn oxidation and also considers why so many bacteria have been identified as Mn oxidizers. It also offers suggestions that may help to clarify this complex area. Since there is no evidence of any advantage that Mn oxidation confers on bacteria, one might well ask the reason for the widespread distribution of this trait. The answer may lie in the Mn oxidation reaction itself. Under the conditions characteristic of most of the environments in which microbes are abundant, Mn is a very active element. Some critical features of Mn chemistry are summarized in Fig. 1 and are also discussed in more detail elsewhere (Ghiorse, 1988; Mulder and Dienema, 1981; Nealson et al., 1988, 1989; Pankow and Morgan, 1981). The oxidation of Mn(II) to Mn(IV) is thermodynamically favored under aerobic conditions, with a negative free energy of approximately 16 kcal/mol (Stumm and Morgan, 1981; Ehrlich, 1981; Nealson et al., 1988). However, the large activation energy of Mn(II) oxidation renders Mn(II) very stable in most aquatic environments (Stumm and Morgan, 1981). The activation energy barrier can be overcome by raising the pH (see Fig. 1) or by the addition of Mn-binding components, including Mn oxides themselves, which are excellent chelators of Mn(II) (Stumm and Morgan, 1981). The catalysis of Mn(II) oxidation by Mn oxides (autooxidation) makes it difficult to distinguish between chemically and microbially catalyzed Mn oxidation, especially in natural environments where organic chelators and Mn oxide particles may be abundant. Mn is, therefore, an element whose distribution and chemical speciation is kinetically controlled, thus allowing for the intervention of microbes and microbial products into the system. Some of the ways in which microbes might oxidize Mn(II) are shown in Table 1. If the pH or Eh of the environment is raised, if oxidants are produced by cells, or if binding of Mn(II) occurs so as to lower the activation energy, Mn(II) oxidation can rapidly proceed. With this in mind, it is not surprising that so many different bacteria have been identified as Mn(II) oxidizers, since the mechanisms of Mn oxidation are quite diverse (Ghiorse, 1988; Nealson et al., 1988, 1989). A true understanding of the “Mn-oxidizing bacteria” will likely await the time when it is possible to identify those reactions that confer some advantage to the bacteria and to disregard those that occur simply because of the dynamic chemistry of Mn(II). With regard to this, some of the recent studies of the mechanism of Mn(II) oxidation by cells, which include the isolation of Mn(II)-binding proteins (both intra- and extracellular) and polysaccharides, are particularly encouraging (Ghiorse, 1988; Nealson et al., 1989).
Article
With the increase in environmental awareness, the disposal of any form of hazardous waste has become a great concern for the industrial sector. Spent catalysts contribute to a significant amount of the solid waste generated by the petrochemical and petroleum refining industry. Hydro-cracking and hydrodesulfurization (HDS) catalysts are extensively used in the petroleum refining and petrochemical industries. The catalysts used in the refining processes lose their effectiveness over time. When the activity of catalysts decline below the acceptable level, they are usually regenerated and reused but regeneration is not possible every time. Recycling of some industrial waste containing base metals (such as V, Ni, Co, Mo) is estimated as an economical opportunity in the exploitation of these wastes. Alkali roasted catalysts can be leached in water to get the Mo and V in solution (in which temperature plays an important role during leaching). Several techniques are possible to separate the different metals, among those selective precipitation and solvent extraction are the most used. Pyrometallurgical treatment and bio-hydrometallurgical leaching were also proposed in the scientific literature but up to now they did not have any industrial application. An overview on patented and commercial processes was also presented. Copyright © 2015 Elsevier Ltd. All rights reserved.
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Laccases (benzenediol: oxygen oxidoreductase; EC 1.10.3.2), a multicopper oxidase enzyme, widely distributed in plants, fungi and bacteria have ability to catalyze oxidation of various phenolic and non-phenolic compounds as well as many environmental pollutants. The diversified functions of laccases, including the antagonistic ones such as their involvement in lignin biosynthesis (in plants) as well as lignin degradation (in fungi and bacteria), make them an interesting enzyme for study from the point of view of their structure, function and application. Important applications of laccases include delignification, pulp bleaching and bioremediation. The ability of laccases to polymerize natural phenols helps to develop new cosmetic pigments, hair dyeing materials, deodorants, toothpastes, mouthwashes and other useful products.
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In iron and manganese-containing groundwater treatment for drinking water production, biological filter is an effective process to remove such pollutants. Until now the exact microbial mechanism of iron and manganese removal, especially coupled with other pollutants, such as ammonia, has not been clearly understood. To assess this issue, the performance of a full-scale biofilter located in Harbin, China was monitored over four months. Microbial populations in the biofilter were investigated using T-RFLP and clone library technique. Results suggested that Gallionella, Leptothrix, Nitrospira, Hyphomicrobium and Pseudomonas are dominant in the biofilter and play major roles in the removal of iron, manganese and ammonia. The spatial distribution of microbial populations along the depth of the biofilter demonstrated the stratification of the removal of iron, manganese and ammonia. Additionally, the absence of ammonia-oxidizing bacteria in the biofilter implicated that ammonia-oxidizing archaea might be responsible for the oxidation of ammonia to nitrite.
Article
The present study examines the biorecovery of heavy metals from a spent refinery catalyst obtained from one of the oil refineries in Iran using Aspergillus niger. Bioleaching experiments were carried out in batch cultures using A. niger in the one-step process to mobilize Co, Mo and Ni from hazardous spent catalysts. Response surface methodology (RSM) was applied for the design and analysis of experiments with the optimization of pH, temperature, inoculum percentage, pulp density and rotation speed during the bioleaching of the metals. Experiments were designed as per the central composite design (CCD) technique. Three cubic mathematical models were derived for prediction of the responses. In process optimization, maximal values of Co, Mo and Ni recoveries were achieved as 71%, 69% and 46%, respectively, with a pH of 5.0, a temperature of 31°C, a pulp density of 2g/L, a rotation speed of 115rpm, and using a 12% inoculum.
Article
The kinetics of Cr(VI) adsorption on granular activated carbon (GAC) Nobrac CG 700 was investigated in batch system, over the pH range of 1.10 - 4.05, at 24o C. The effect of pH was observed and experimental data has been interpreted in terms of zero-order, first-order, second-order, pseudo first-order and pseudo second-order integrated kinetic models. It was noticed that Cr(VI) adsorption rates decreased significantly with increasing pH. Moreover, at pH = 4.05 and higher, the adsorption process was found to be negligibly slow; therefore, all further kinetic interpretations were performed only for the pH range of 1.10 - 3.06. The adsorption process proceeds in two stages: high adsorption rates were observed within the first time interval, whereas a strong decrease in the Cr(VI) adsorption occurs in the second one. The results obtained indicate pseudo second-order kinetics for the first time interval, and zero-order kinetics for the second time interval. The rate coefficients were determined for both stages of the adsorption process.
Article
It was demonstrated that simultaneous removal of ammonia and manganese could be accomplished by biological aerated filter (BAF) with low-cost lava as media. Long-term operation performance and impact factors were systematically studied. DGGE analysis demonstrated that ammonia oxidizing bacteria (AOB), manganese oxidizing bacteria (MOB) and simultaneous ammonia and manganese oxidizing bacteria (SAMOB) co-existed in the bio-film. Ammonia and manganese concentration profiles along the height of BAF column, including that in the influent and effluent, were investigated with varying hydraulic loadings, aeration intensities and feed ammonia concentrations. It was inferred that AOB and MOB may have different spatial distribution in vertical direction, and AOB and MOB may compete for oxygen capture or be present on different layers of the bio-films. Further work should focus on the distribution of AOB, MOB and SAMOB in the reactor and optimize it for more efficient mass transfer and better system performance.
Article
We analyzed the soil microbial communities from one uncontaminated and two metal-impacted soils and found that while cadmium adversely affected the numbers of culturable bacteria in all soils, cadmium-resistant isolates were found from each of the soils. With exposure to 24 and 48 μg ml-1 soluble cadmium, the metal-contaminated soil communities were more resistant than the uncontaminated soil community. In addition, in one metal-stressed soil, the resistant population became more resistant with increased cadmium levels. Ribosomal 16S DNA sequencing identified the isolates as Arthrobacter, Bacillus, or Pseudomonas spp. Further characterization demonstrated that two of the isolates were highly resistant to soluble cadmium with maximum resistance at 275 μg ml-1 cadmium. These isolates were also resistant to a variety of antibiotics, namely ampicillin, gentamicin, penicillin, and streptomycin, but no overall correlation was found between enhanced antibiotic resistance and cadmium resistance. One Pseudomonas isolate H1 did become more resistant with increasing cadmium levels, suggesting a different resistance mechanism at high cadmium concentrations.
Article
The biological method has been considered as an efficient and cost-effective alternative to physicochemical treatment technologies for soil remediation. A bioleaching process was investigated for removal of heavy metals from metal-contaminated soil in this study. The optimal bioleaching operating parameters i.e., soil solid content and sulfur (substrate) dosage for this bioleaching process were studied using central composite design (CCD) and response surface methodology (RSM). Results showed that the rate of pH reduction was found decreasing with increasing of soil solid content because high soil solid content had high buffering capacity. Furthermore, the rate of pH reduction increased with an increase of sulfur dosage in the bioleaching. The maximum metal solubilization was obtained at 1% (w/v) soil solid content and 0.1% (w/v) sulfur dosage and the efficiency was higher than 80%, except Pb. In considering the application of bioleaching, the operating conditions were recommended to be selected in the range of 1–7% (w/v) solid content and 0.1–0.3% (w/v) sulfur dosage for high efficiency (>60%) of metal solubilization. After the bioleaching process, in the treated soil was stable and residual heavy metals were no longer harmful to the environment.
Article
Biomining comprises of processing and extraction of metal from their ores and concentrates using microbial techniques. Currently this is used by the mining industry to extract copper, uranium and gold from low grade ores but not for low grade manganese ore in industrial scale. The study of microbial genomes, metabolites and regulatory pathways provide novel insights to the metabolism of bioleaching microorganisms and their synergistic action during bioleaching operations. This will promote understanding of the universal regulatory responses that the biomining microbial community uses to adapt to their changing environment leading to high metal recovery. Possibility exists of findings ways to imitate the entire process during industrial manganese biomining endeavor. This paper reviews the current status of manganese biomining research operations around the world, identifies factors that drive the selection of biomining as a processing technology, describes challenges in exploiting these innovations, and concludes with a discussion of Mn biomining's future.
Article
Extraction of manganese from electrolytic manganese residues using bioleaching was investigated in this paper. The maximum extraction efficiency of Mn was 93% by sulfur-oxidizing bacteria at 4.0 g/l sulfur after bioleaching of 9days, while the maximum extraction efficiency of Mn was 81% by pyrite-leaching bacteria at 4.0 g/l pyrite. The series bioleaching first by sulfur-oxidizing bacteria and followed by pyrite-leaching bacteria evidently promoted the extraction of manganese, witnessing the maximum extraction efficiency of 98.1%. In the case of sulfur-oxidizing bacteria, the strong dissolution of bio-generated sulfuric acid resulted in extraction of soluble Mn2+, while both the Fe2+ catalyzed reduction of Mn4+ and weak acidic dissolution of Mn2+ accounted for the extraction of manganese with pyrite-leaching bacteria. The chemical simulation of bioleaching process further confirmed that the acid dissolution of Mn2+ and Fe2+ catalyzed reduction of Mn4+ were the bioleaching mechanisms involved for Mn extraction from electrolytic manganese residues.
Article
Hexavalent chromium [Cr(VI)], a potential mutagen and carcinogen, is regularly introduced into the environment through diverse anthropogenic activities, including electroplating, leather tanning, and pigment manufacturing. Human exposure to this toxic metal ion not only causes potential human health hazards but also affects other life forms. The World Health Organization, the International Agency for Research on Cancer, and the Environmental Protection Agency have determined that Cr(VI) compounds are known human carcinogens. The Sukinda valley in Jajpur District, Orissa, is known for its deposit of chromite ore, producing nearly 98% of the chromite ore in India and one of the prime open cast chromite ore mines in the world (CES, Orissa Newsletter). Our investigation involved microbial remediation of Cr(VI) without producing any byproduct. Bacterial cultures tolerating high concentrations of Cr were isolated from the soil sample collected from the chromite-contaminated sites of Sukinda, and their bioaccumulation properties were investigated. Strains capable of growing at 250 mg/L Cr(VI) were considered as Cr resistant. The experimental investigation showed the maximum specific Cr uptake at pH 7 and temperature 30°C. At about 50 mg/L initial Cr(VI) concentrations, uptake of the selected potential strain exceeded 98% within 12 h of incubation. The bacterial isolate was identified by 16S rRNA sequencing as Brevebacterium casei. Results indicated promising approach for microbial remediation of effluents containing elevated levels of Cr(VI).
Article
Microbes play key geoactive roles in the biosphere, particularly in the areas of element biotransformations and biogeochemical cycling, metal and mineral transformations, decomposition, bioweathering, and soil and sediment formation. All kinds of microbes, including prokaryotes and eukaryotes and their symbiotic associations with each other and 'higher organisms', can contribute actively to geological phenomena, and central to many such geomicrobial processes are transformations of metals and minerals. Microbes have a variety of properties that can effect changes in metal speciation, toxicity and mobility, as well as mineral formation or mineral dissolution or deterioration. Such mechanisms are important components of natural biogeochemical cycles for metals as well as associated elements in biomass, soil, rocks and minerals, e.g. sulfur and phosphorus, and metalloids, actinides and metal radionuclides. Apart from being important in natural biosphere processes, metal and mineral transformations can have beneficial or detrimental consequences in a human context. Bioremediation is the application of biological systems to the clean-up of organic and inorganic pollution, with bacteria and fungi being the most important organisms for reclamation, immobilization or detoxification of metallic and radionuclide pollutants. Some biominerals or metallic elements deposited by microbes have catalytic and other properties in nanoparticle, crystalline or colloidal forms, and these are relevant to the development of novel biomaterials for technological and antimicrobial purposes. On the negative side, metal and mineral transformations by microbes may result in spoilage and destruction of natural and synthetic materials, rock and mineral-based building materials (e.g. concrete), acid mine drainage and associated metal pollution, biocorrosion of metals, alloys and related substances, and adverse effects on radionuclide speciation, mobility and containment, all with immense social and economic consequences. The ubiquity and importance of microbes in biosphere processes make geomicrobiology one of the most important concepts within microbiology, and one requiring an interdisciplinary approach to define environmental and applied significance and underpin exploitation in biotechnology.
Article
A basic understanding related to the immobilization of chromium by bacteria is essential for chromate pollutant remediation in the environment. In this work, we studied the Cr(VI) uptake mechanism of living Ochrobactrum anthropi and the influence of a bacterial culture medium on the Cr-immobilization process. It was found that the Cr-immobilization ratio of bacteria in Tris-HCl buffer is higher than in LB medium. X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) analysis revealed that the chromium accumulated on bacteria were mostly in Cr(III) states. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) observations showed that noticeable Cr(III) precipitates were accumulated on bacterial surfaces. AFM roughness analysis revealed that the surface roughness of bacteria increased greatly when the bacteria-Cr(VI) interaction was in Tris-HCl buffer rather than in LB solution. Transmission electron microscopy (TEM) thin section analysis coupled with energy-dispersive X-ray spectroscopy showed that Cr(III) is also distributed in bacterial inner portions. A chromium-immobilization mechanism considering the participation of both bacterial inner portions and bacterial surfaces of living Ochrobactrum anthropi was proposed, whereas the bacterial surface was the dominant part of the immobilization of Cr(III). This work also proved that the control of Cr immobilization by living Ochrobactrum anthropi could be achieved via adjusting the bacterial culture medium.