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A review of biotechnology processes applied for manganese recovery from wastes

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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.
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A review of biotechnology processes applied for manganese
recovery from wastes
Sansuta Mohanty .Shreya Ghosh .Bhubaneswari Bal .Alok Prasad Das
Published online: 29 September 2018
ÓSpringer Nature B.V. 2018
Abstract 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 man-
ganese 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 bioremedi-
ation which will not only aid in pollution abatement
but also in the prevention of occupational health
Keywords Manganese Biodegradation
Recovery Recycling Recent trends
1 Introduction
Manganese is a naturally occurring element that
basically originates from rock crust, infertile soil,
mining deposits and deep marine nodules. Manganese
is an ubiquitous compound found in every possible
surrounding and comprises around 0.1% of the earth
crust. Chemical compounds of manganese are found in
3 different forms; first is oxides such as psilomelane,
birnessite, pyrolusite and carbonates, second is man-
ganite and third is silicates. They are deposited as a
chief constituent in more than 100 natural reserves of
mining effluent as described by Gadd (2010). Pyro-
lusite (MnO
) is the most widespread form in which
manganese is broadly scattered in the earth (Zhu et al.
2010). Predominantly, crustal rock and mining ore is
considered as the primary source of manganese
reserve in the biosphere (Barboza et al. 2016),
obtained due to volcanic action, woodland fires,
aquatic or terrestrial vegetation (Das et al. 2015a).
Developing countries like Australia, Russia, India,
Gabon, Brazil and South Africa possess the leading
S. Mohanty S. Ghosh
Bioengineering and Biomineral Processing Laboratory,
Centre of Biotechnology, Siksha O Anusandhan Deemed
to be University, Bhubaneswar, India
B. Bal A. P. Das (&)
Department of Chemical and Polymer Engineering,
Tripura University (A Central University),
Suryamaninagar, Tripura, India
Rev Environ Sci Biotechnol (2018) 17:791–811,-volV)(0123456789().,-volV)
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... Manganese is one of the most strategic metals. The metal and its compounds are used extensively in metallurgy, chemistry, batteries, fertilizers, feed additives, particularly in the ferroalloy industry, for 90 percent of consumption (Mohanty et al. 2018a;An et al. 2021). The production of manganese ore in 2020 was 58.8 million tons due to higher steel production (Rozhikhina et al. 2020). ...
... Manganese-containing secondary sources, such as LIBs and electrodes, have attracted researchers' attention due to declining primary manganese sources (Mohanty et al. 2018a). It is essential for the continued sustainability of the spent batteries to provide economic and environmental benefits (Razmjou et al. 2019). ...
... There has been increasing interest in efficient techniques for manganese extraction from secondary sources, such as e-waste (Niu et al. 2016;Mohanty et al. 2018a). However, despite the rapid development of the manganese industry, there is limited information on the secondary manganese resources Bal et al. 2019) and extraction methods. ...
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Manganese is extensively used in various advanced technologies. Due to high manganese demand and scarcity of primary manganese resources, extracting the metal from spent batteries is gaining increasing interest. The recycling of spent batteries for their critical metal content, is therefore environmentally and economically feasible. The conventional pyro- and hydrometallurgical extraction methods are energy-intensive or use hazardous chemicals. Bioleaching of manganese from spent batteries as secondary resource has been suggested to meet two objectives: reduce environmental footprint and turn waste into wealth. A bioleaching process can operate with less operating costs and consumption of energy and water, along with a simple process, which produces a reduced amount of hazardous by-products. Hence, this review discusses various approaches for bioleaching manganese from secondary resources using redoxolysis, acidolysis, and complexolysis. Candidate microbes for producing inorganic and organic biolixiviants are reviewed, along with the role of siderophores and extracellular polymeric substances as other effective agents in manganese extraction. The three main types of bioleaching are discussed, incorporating effective parameters with regard to temperature, pH, and pulp density, and future perspectives for manganese bioleaching and provided. Graphical abstract
... According to the general definition proposed by Liu et al. (2019), microfibers (MFs) are any natural or artificial fibrous materials of threadlike structure with a diameter less than 50 μm, length ranging from 1 μm to 5 mm, and length to diameter ratio greater than 100 [34]. Microplastics, especially MFs, contaminate and affect many aquatic organisms or species of birds or mammals that feed on aquatic species since they are often mistaken for food and ingested by prey species, which, in turn, are eaten by predators, allowing MPs to move up the trophic chain [35,36]. ...
... The separation of textile MFs from other MPs does not necessarily add complexity but, conversely, might bring consistency to the comparison across different investigations [38]. A recent study by Pedrotti et al., 2021, shows that fibers analyzed from Microplastics, especially MFs, contaminate and affect many aquatic organisms or species of birds or mammals that feed on aquatic species since they are often mistaken for food and ingested by prey species, which, in turn, are eaten by predators, allowing MPs to move up the trophic chain [35,36]. ...
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Among microplastics (MPs), fibers are one of the most abundant shapes encountered in the aquatic environment. Growing attention is being focused on this typology of particles since they are considered an important form of marine contamination. Information about microfibers distribution in the Mediterranean Sea is still limited and the increasing evidence of the high amount of fibers in the aquatic environment should lead to a different classification from MPs which, by definition, are composed only of synthetic materials and not natural. In the past, cellulosic fibers (natural and regenerated) have been likely included in the synthetic realm by hundreds of studies, inflating “micro-plastic” counts in both environmental matrices and organisms. Comparisons are often hampered because many of the available studies have explicitly excluded the micro-fibers (MFs) content due, for example, to methodological problems. Considering the abundance of micro-fibers in the environment, a chemical composition analysis is fundamental for toxicological assessments. Overall, the results of this review work provide the basis to monitor and mitigate the impacts of microfiber pollution on the sea ecosystems in the Mediterranean Sea, which can be used to investigate other basins of the world for future risk assessment.
... Natural aging of microfibers depends on several factors which includes environmental temperature, pH, Sun light and water quality that controls the rate of polymer biofragmentation . Bioremediation offers an better alternative to combat environmental pollutants as compared to traditional chemical and thermal methods (Mohanty et al., 2018;Bal et al., 2022). ...
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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.
... In mining areas, both microfibers and heavy metal ions are released substantially into the water streams due to anthropogenic and industrial activities [34,69], Das et al., 2011a, [75,84], which have detrimental impact on organisms present in each trophic levels as these particles get deposited in their tissues [94]. The mechanism of heavy metal ion adsorption on microfiber particles is depicted in Fig. 1. ...
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Synthetic microfbers (SMFs), tiny particles which gets fragmented from large fragments of large synthetic fbers having less than 10 µm in diameter, have gathered ubiquitously in each and every corner of the earth. After their release into the aquatic environment, they remain there without natural degradation. Furthermore, it can be anticipated that foating units are transported along the food chain leading to bioaccumulation. It has been esti- mated that approximately 10–20 Mt of large fabric products as garbage enter into aquatic system per annum. Recently, these synthetic fragments have been investigated as transport- ers of heavy metal ions (HMs) showing diferent types of interactions. Yet, the underlying mechanism of these types of interaction is not known, especially the factors stimulating this process and how badly they afect biotic communities. Through this article, a detailed sur- vey was carried out on the sources of microfbers and HMs into the aquatic environment, adsorption of diferent types of HMs on the SMF surface, mechanics favors these HM-MF interactions, particularly highlighting the signifcant roles of interaction on microbial bio- flm formation. Their collaborative efects which possess harmful efects on aquatic as well as terrestrial organisms was also discussed. Lastly, the future investigations should focus on rigorous research in this feld. This article to the best of our knowledge briefy describes the current research developments and emphasizes the vital function of the microorgan- isms on MFs-HMs interactions with the encouragement for rigorous research in this feld to reveal accurate mechanisms and decrease the hazards related with MF presence
... Arsenate reduction in prokaryotes is carried out by soluble arsenate reductases (ArsC) [65]. Several bacterial strains of Bacillus, Pseudomonas putida and Pedomicrobium reduces manganese-Mn (III and IV) to Mn (II) and further oxidize it to be used as terminal electron acceptor in electron transport chain [66]. ...
Heavy metals, a treasure of nature, turns to be toxic at high concentrations in water. Among several methods adopted to alleviate heavy metal pollution, bioremediation is considered to be a sustainable, cost-effective technology. Bioremediation largely relies on bacteria, apart from other microbes and plants. The inherent and adaptive mechanisms evolved in bacteria to defend the metal toxicity include bioadsorption/biosorption, bioaccumulation, bioprecipitation and bioleaching. Heavy metal resistant bacterial strains are easy to culture and maintain, and even dead cell biomass display high heavy metal remediation potential in solution. All the heavy metal remediation mechanisms exhibited by bacteria in water is comprehensively reviewed with recent research outputs and in-situ and ex-situ techniques. The cellular mechanisms of heavy metal remediation are discussed, considering efficient bacterial strains, physiochemical parameters, nutrient supplementation and design of novel microbial techniques. Research at omics level would effectuate further manipulation of the cellular process and increase its efficiency. Bacterial heavy metal remediation technique provides double benefit of metal recovery and water purification, along with reuse prospects for both water and metal resources. Technological intervention could meet the challenges of process acceleration, resist biofouling, compete with native wild bacterial species in wastewater, design for commercialization. Industrial translation of the technology is the pivotal avenue to be tackled. Ultimately, understanding of bacterial heavy metal remediation process is essential for the implementation of this promising technology to safeguard the environmental health.
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.
E-waste management has become a global concern because of the enormous rise in the rate of end-of-life electrical and electronic equipment's (EEEs). Disposal of waste EEE directly into the environment leads to adverse effects on the environment as well as on human health. For the management of E-waste, numerous studies have been carried out for extracting metals (base, precious, and rare earth) following pyrometallurgy, hydrometallurgy, and biometallurgy. Irrespective of the advantages of these processes, certain limitations still exist with each of these options in terms of their adoption as treatment techniques. Several journal publications regarding the different processes have been made which aids in future research in the field of E-waste management. This review provides a comprehensive summary of the various metal recovery processes (pyrometallurgy, hydrometallurgy, and biometallurgy) from E-waste, along with their advantages and limitations. A bibliometric study based on the published articles using different keywords in Scopus has been provided for a complete idea about E-waste with green technology perspective like bioleaching, biosorption, etc. The present study also focussed on the circular economic approach towards sustainable E-waste management along with its socio-economic aspects and the economic growth of the country. The present study would provide valuable knowledge in understanding E-waste and its different treatment processes to the students, researchers, industrialists, and policymakers of the country.
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.
Pollution of heavy metals is one of the risky contaminations that should be managed for all intents and purposes of general well-being concerns. The bioaccumulation of these heavy metals inside our bodies and pecking orders will influence our people in the future. Bioremediation is a bio-mechanism where residing organic entities use and reuse the squanders that are reused to one more form. This could be accomplished by taking advantage of the property of explicit biomolecules or biomass that is equipped for restricting by concentrating the necessary heavy metal particles. The microorganisms can't obliterate the metal yet can change it into a less harmful substance. In this unique circumstance, this review talks about the sources, poisonousness, impacts, and bioremediation strategies of five heavy metals: lead, mercury, arsenic, chromium, and manganese. The concentrations here are the ordinary strategies for bioremediation such as biosorption methods, the use of microbes, green growth, and organisms, etc. This review demonstrates the toxicity of heavy metal contamination degradation by biotransformation through bacterioremediation and biodegradation through mycoremediation.
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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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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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.
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
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.
In the natural environment, manganese is found as reduced soluble or adsorbed Mn(II) and insoluble Mn(lll) and Mn(IV) oxides. Mn oxidation has been reported in various microorganisms. Several possible pathways, indirect or direct, have been proposed. A wider variety of Mn‐reducing microorganisms, from highly aerobic to strictly anaerobic, has been described. The mechanisms of Mn reduction can be either an indirect process resulting from interactions with organic or inorganic compounds, or a direct enzymatic (electron‐transfer) reaction. The role of microorganisms in Mn cycle is now well demonstrated by various methods in superficial natural environments, and research has been initiated on subsurface sediments. Observations in vivo (Rh6ne valley) and under in vitro suggested that bacterial activities are the main processes that promote manganese evolution and migration in shallow aquifers. After the building of hydroelectric dams, the stream of the Rhône was modified, giving rise to mud deposition on the bank. In the mud, bacteria are stimulated by the high organic content and consume oxygen. The redox potential drops. The manganese oxides previously formed under aerobic conditions are reduced and soluble manganese (Mn(II)) migrates into the aquifer. If the subsurface sediments are coarse‐grained, the aquifer is well aerated, allowing the re‐oxidation of Mn(ll) by the oligotrophic attached bacteria in aquifer sediments. If the aquifer is confined, aeration is not sufficient for Mn‐reoxidafion. Mn(II) remains in a reduced state and migrates to the wells. Furthermore, the presence of organic matter in subsurface sediments results in the reduction of previously formed Mn oxides. Pseudo‐amorphous manganese oxides, which were probably recently formed by bacteria, are more readily reduced than old crystalline manganese oxides. Although the concentrations of soluble manganese found in groundwaters are not toxic, it still is a problem since its oxidation results in darkening of water and plugging of pipes in drinking or industrial water systems. Soluble manganese can be removed from water by biological processes involving manganese‐oxidizing bacteria, either in situ, or in sand filters after pumping. Various procedures are mentioned.
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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