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Bioremediation of lindane contaminated soil: Exploring the potential of Actinobacterial strains
Abstract
Lindane, an organochlorine pesticide, causes detrimental impacts on the environment and human health owing to its high toxicity, low degradation, and bioaccumulation. Its toxic nature can be overcome by biological and eco-friendly approaches involving its degradation and detoxification. The biodegradation of lindane was assessed using actinobacterial species Thermobifida cellulosilytica TB100 (T. cellulosilytica), Thermobifida halotolerans DSM 44931 (T. halotolerans) and Streptomyces coelicolor A3 (S. coelicolor). The degradation conditions of Lindane such as pH, temperature, inoculum volume, glucose concentration and number of days were optimized under broth conditions. Lindane degradation at different concentrations was studied in soil using reverse phase-high performance liquid chromatography over a 30 day period. A bioassay test was performed on seeds of Lactuca sativa (Lettuce) to assess the success of bioremediated soil. Maximum lindane degradation in soil was observed using T. cellulosilytica sp. The degradation trend for different concentrations of lindane using T. halotolerans in sterilized soil was 55 mg kg⁻¹ (82 %) ˃ 155 mg kg⁻¹ (75 %) ˃ 255 mg kg⁻¹ (70 %) after an incubation period of 30 days. Lindane degradation in soil followed the first order reaction kinetics. Phytotoxicity test on seeds of Lactuca sativa showed considerably good vigor index values for the bioremediated sterilized and non-sterilized soil by T. cellulosilytica, T. halotolerans and S. coelicolor in comparison to the contaminated soil without bacteria. This confirms that these actinobacterial species can be implemented in bioaugmentation of contaminated sites to efficiently remediate high lindane concentrations.
... Different techniques, such as electro-kinetic soil flushing [5,6], biodegradation [7][8][9][10], chemical reduction [11][12][13][14], and chemical oxidation [15][16][17], have been studied for remediating HCHscontaminated soils. Persulfate advanced oxidation processes (PS-AOPs) have shown great potential due to their high efficiency and environmental friendliness [18,19]. ...
... where V sample is the volume of the polluted sample and V total the volume sum of the sample, the diluent, and the bacteria. The effective nominal concentration of a compound (EC 50j , g L -1 ) is the concentration value in the aqueous phase that reduces light emission intensity by 50 %, as described in Eq. (8). In the case of reaction supernatants, results have been expressed as EC 50 (mg L -1 ), considering the sum of the COCs concentration. ...
... Thus, from the point of view of acute toxicity, this result points out the need for a more thorough washing of the soils after the PS/NaOH/T on-site treatment. The toxicity results related to the aqueous phases (expressed as 1/ EC 50 , in mL g − 1 , Eqs. (8) and (9)), Microtox® BT), including the reaction supernatant and soils elutriates, are shown in Fig. 4. According to the classification proposed by Libralato, Annamaria and Francesco [79] (EC 50 > 100 g/L = low toxicity, 10 g/L ≤ EC 50 ≤ 100 g/L = moderately toxic, and EC 50 < 10 g/L = very toxic sample), Ref (not detected) and polluted (EC 50 = 307 g/L) soil elutriates presented low toxicity (Fig. 4), indicating that potential landfill surface soil leachates are not an environmental issue in terms of acute toxicity. ...
... However, most technologies are disruptive to the surrounding environment and more expensive, making them impractical (Li et al. 2012;Guo et al. 2021). Because of their autotrophy for removing Cd from the soil, bio-immobilization of Cd by microbes is more cost-effective and environmentally benign than these methods (Govarthanan et al. 2019;Cuaxinque-Flores et al. 2020;Álvarez-Ayuso et al. 2021;Qiao et al. 2021;Usmani et al. 2021). Furthermore, it is viewed as a feasible approach for agricultural soil remediation because it does not necessitate the suspension of agricultural activities during the restoration process . ...
... Soil properties are imperative for evaluating agricultural soil remediation performance. Meanwhile, the bioremediation process is strongly affected by soil properties (Usmani et al. 2021). Thus, soil properties after bioremediation should be understood (Table 3). ...
Microbially induced calcite precipitation (MICP) technique utilizes ureolytic bacteria to decompose urea and generate carbonate ions for metal combination. MICP can remediate heavy metal (e.g., Cd) contaminated soils while maintaining or even improving soil functions, but its efficiency in agricultural soil practical application still needs to be enhanced. Here, we constructed a biochar-bacteria (2B) partnership in which biochar provides high nutrition and diverse sorption sites. Using the 2B system, Cd immobilization effectiveness and the underlying mechanism were examined along with the soil properties and soil functions. Results showed that compared to the single biochar and ureolytic bacteria systems, soil Cd mobility was reduced by 23.6% and 45.8% through co-precipitating with CaCO 3 as otavite (CdCO 3 ) in the 2B system, whereas soil fertility, bacterial diversity, and richness increased by 11.7–90.2%, 5.4–16.1%, and 6.8–54.7%, respectively. Moreover, the abundances of Proteobacteria and Firmicutes were enhanced in the 2B system. Notably, Sporosarcina and Bacillus ( Firmicutes genus) that carry the ure C gene were boosted in the system, further implicating the microbiological mechanism in reducing Cd migration and its bioavailability in soil. Overall, the constructed 2B system was efficient in soil Cd immobilization by strengthening the ureolytic bacteria growth and their nutrient supply in the bacteria-rich soil ecosystem.
... Physico-chemical methods are generally expensive, use large amount of synthetic chemicals, and produce large amount of secondary byproducts of even more toxic nature, whereas bioremediation utilizes biological agents like algae, fungi, bacteria, plants, and derived products for the efficient removal of pesticides. It is eco-friendly, inexpensive, and independent of hazardous chemical application and does not produce harmful secondary by-products (Avila et al. 2021;Bhatt et al. 2021a, b;Loffredo et al. 2021;Usmani et al. 2021;Wongputtisin et al. 2021). Alternatively, the integrated pest management (IPM) strategy can be followed to minimize the introduction of pesticides in agricultural lands. ...
... (Zhang et al., 1998emend. Yang et al., 2008 and Streptomyces coelicolor ((Müller, 1908) Waksman & Henrici, 1948, for the degradation of lindane present in soil as determined by reverse phase high-performance liquid chromatography is demonstrated by Usmani et al. (2021). Thermobifida halotolerans (Yang et al., 2008) was able to degrade maximally 82% of lindane spiked in sterile soil within 30 days of treatment. ...
Continuous rise in application of pesticides in the agro-ecosystems in order to ensure food supply to the ever-growing population is of greater concern to the human health and the environment. Once entered into the agro-ecosystem, the fate and transport of pesticides is determined largely by the nature of pesticides and the soil attributes, in addition to the soil-inhabiting microbes, fauna, and flora. Changes in the soil microbiological actions, soil properties, and enzymatic activities resulting from pesticide applications are the important factors substantially affecting the soil productivity. Disturbances in the microbial community composition may lead to the considerable perturbations in cycling of major nutrients, metals, and subsequent uptake by plants. Indiscriminate applications are linked with the accumulation of pesticides in plant-based foods, feeds, and animal products. Furthermore, rapid increase in the application of pesticides having long half-life has also been reported to contaminate the nearby aquatic environments and accumulation in the plants, animals, and microbes surviving there. To circumvent the negative consequences of pesticide application, multitude of techniques falling in physical, chemical, and biological categories are presented by different investigators. In the present study, important findings pertaining to the pesticide contamination in cultivated agricultural soils; toxicity on soil microbes, plants, invertebrates, and vertebrates; effects on soil characteristics; and alleviation of toxicity by bio-based management approaches have been thoroughly reviewed. With the help of bibliometric analysis, thematic evolution and research trends on the bioremediation of pesticides in the agro-ecosystems have also been highlighted.
Graphical abstract
... La respiración y fermentación bacteriana, que involucran la transformación de compuestos orgánicos, también pueden variar el estado del pH en medios de cultivo contaminados con herbicidas. La inoculación de Thermobifida cellulosilytica TB100 degrada el lindano en condiciones de pH 7 y 8. Sin embargo, el pH ácido y alcalino disminuyó la eficiencia de las especies bacterianas (Usmani et al., 2021). El medio de cultivo envenenado con glifosato influye en una disminución gradual del pH 6,8 a 5,3 para Bacillus tropicus GP1 y de 7,5 a 5,3 para Proteus mirabilis GP2 desde el día 0 al día 30 (Ibrahim et al., 2023). ...
Pendimentalin is anherbicide used in short-cycle crops. Its indiscriminate use reduces the beneficial population of microorganisms in production systems. The objective of this work was to evaluate the effect of pendimentalin on the cell growth of rhizobacteria. The researchwas conducted at the Laboratory of Microbiology and Molecular Biology of the State Technical University of Quevedo, where the following experiments with pendimentalin contamination were carried out: 1) Adaptability of rhizobacteria under in vitro conditions; 2) Tolerance levels of rhizobacteria under different abiotic conditions in vitro; 3) Reduction of stress by rhizobacteria in soils. The rhizobacteria show a higher adaptability at 72 h with absorbance of 2.38 and 2.51 in the strains (CHA0, BA4-19, B03-4, PM3-14 and R4), also during this time they establish a neutral pH, despite the acidic and alkaline conditions. Strain CHA0 presented the highest number of cells under neutral pH (1.09E+09 CFU/mL). Strains BA4-19 and PM3-14 showed a slight improvement in morphological aspects. Rhizobacteria have adaptability at the in vitro level, but their use slightly reduces the toxicity of the herbicide in rice germination and growth processes.
... The total amount of wastewater produced per liter of alcohol is between 40 and 50 liters [8]. Distilleries in India generate 40.72 million/m3 of spent water annually [9,10]. ...
... Of the twelve sampling points at NHC Morogoro, four had detectable amounts of total lindane, compared to only one out of eleven sampling points at PPO Tengeru. Under natural open environmental conditions, lindane has a reported half-life in soil of about 708 days [25,26]. One reason for the purported reduction in dominance on Soil Syst. ...
A study was conducted to test the potential of calabash, sweet potato, pumpkin, simsim and finger millet to phytoaccumulate dichlorodiphenyltrichloroethane (DDT) and its metabolites from NHC Morogoro- and PPO Tengeru-contaminated sites. Parallel field and screenhouse-potted soil experiments were performed to assess the efficacy with which the test plants phytoaccumulate DDT from the soil. In the screenhouse experiment, treatments were laid out following a split-plot arrangement in a completely randomized design (CRD), with the main plots comprising two DDT concentration levels–low (417 mg kg−1) or high (2308 mg kg−1)—and the plant species Cucurbita pepo, Lagenaria siceraria, Ipomoea batatus, Sesamum indicum and Eleusine coracana were considered as subplots. A field experiment with the same crop species as the treatments was laid out in a randomized complete block design, and both experiments were performed in triplicate. In addition to determining the concentration of persistent organic pesticides in the soil profile, parameters such as the total DDT uptake by plants, shoot weight and shoot height were monitored in both potted soil and open field experiments. Overall, calabash and sweet potato exhibited the highest (4.63 mg kg−1) and second highest (3.45 mg kg−1) DDT concentrations from the high residual DDT potted soil experiment. A similar trend was observed when the two plants were grown in low DDT soil. Sweet potato recorded the highest shoot height and weight in the potted soil experiments, indicating that increasing amounts of DDT had a minimal effect on the plant’s growth. Although sweet potato outperformed calabash in the amounts of DDT concentration in the shoots under open field experiments, the uptake of DDT by calabash was the second highest. Calabash—a wild non-edible plant in Tanzania—presents a potential phytoremediation alternative to edible and much studied pumpkin.
... Also, our results matched with El-Sheshtawy et al. [43] who demonstrated that, the biodegradation percentage increased with increasing the incubation time in the degradation of petroleum hydrocarbons using Flavobacterium johnsoniae and Shewanella baltica bacterial strains immobilized on goethite-chitosan nanocomposite. Moreover, Usmani et al. [44] reported that the degradation rate of lindane pesticide was increased with the number of days of incubation in their study of bioremediation of lindane contaminated soil and exploring the potential of actinobacterial strains. ...
Immobilized microorganisms especially bacteria are most used rather than free cells to be protected from the environmental conditions when being used for the bioremediation of environmental pollutants. Herein, two marine’s bacterial isolates were tested for their ability to decompose crude oil. The optimum conditions for effective bacterial degradation e.g., pH, temperature, and inoculum size were investigated. PVA-alginate-clay composite hydrogel beads with different types of incorporated mineral clays were prepared and tested as bacterial carrier for potential bioremediation. Synthesized composite hydrogels were physico-chemically characterized by FTIR, SEM, and thermal analyses. Results showed that, embedded degrading bacteria in PVA-alginate beads recorded degradation rates as 74 and 66.6% for both tested bacterial isolates (S and R) compared to 61.2 and 53% degradation rates by free cells, respectively. Where, attapulgite clay-containing beads recorded maximum degradation% as 78.8 and 75% for both bacterial isolates, when added to immobilization matrices and these percentages could be enhanced under optimal conditions. The 16S rRNA gene of the two marine oils degrading bacterial isolates were amplified and sequenced, where both isolates were identified as Pseudomonas stutzeri and Rhodococcus qingshengii with submitted accession numbers of ON908963 and ON908962, respectively. These results are referring to the ability of using both tested isolates for crude oil bioremediation process and embedded them into PVA-alginate-clay beads as hydrogel carrier under the optimum conditions.
... Available methods for the remediation of lindane-contaminated matrices include chemical oxidation [8], electrooxidation [9], nanoremediation [10], and microbial degradation [11]. The use of nanoparticles for the remediation of organic and inorganic environmental contaminants has been receiving increasing research interest due to the excellent adsorption and catalytic properties of nanoparticles [12]. ...
Zero-valent iron nanoparticles are cost-effective and environmentally benign reducing agents that can be used to degrade several environmental pollutants. Conventional methods of nanoparticle synthesis use toxic chemicals; hence, developing green synthesis approaches is important for safer production and application of nanoparticles. In this study, zero-valent iron nanoparticles (FeNPs) were produced from aqueous extract derived from pomegranate peels, a fruit processing waste product, and the synthesized nanoparticles were coated with 0.4% sodium dodecyl sulfate for better stability. The synthesized nanoparticles were amorphous in nature with an average particle size of 25.1 nm and showed no phytotoxic or antimicrobial effects at concentrations of up to 30% and 100%, respectively. Lastly, the synthesized FeNPs were used to study the degradation of an important persistent organochlorine pesticide, lindane, in liquid medium and it was observed that 0.1 g/L of FeNP degraded ~ 99% of lindane in 24 h. Furthermore, treatment of lindane with the FeNPs synthesized in this study could significantly reduce the cytotoxicity of lindane, implying the degradation of lindane to less toxic and simpler degradation products. Therefore, the FeNPs synthesized in this study using aqueous polyphenol extracts from a food processing waste product are a potential candidate for the remediation of sites contaminated with organochlorine pesticides such as lindane.
... Bacteria are promising microorganisms for bioremediation uses since they can treat several contaminants with efficiency and also include more eco-friendly aspects (Anusha et al., 2021;Talaiekhozani and Rezania, 2017;Viancelli et al., 2020). Actinomycetes are gram-positive bacteria with a great capacity for application in bioremediation processes (Alvarez et al., 2017;Aparicio et al., 2018;Rathore et al., 2021;Usmani et al., 2021). Rhodococcus is a genus of actinomycetes with high potential to be applied in the treatment of organic and inorganic compounds (Rathore et al., 2021), such as PAH's (Subashchandrabose et al., 2019), phenolic compounds (Barik et al., 2021), fungicides (Bai et al., 2017), pharmaceuticals , phthalates (Zhao et al., 2018), steroids (Ye et al., 2019), dyes (Maniyam et al., 2020a), heavy metals (Goswami et al., 2017). ...
Rhodococcus is a genus of actinomycetes that has been explored by the scientific community for different purposes, especially for bioremediation uses. However, the mechanisms governing Rhodococcus-mediated bioremediation processes are far from being fully elucidated. In this sense, this work aimed to compile the recent advances in the use of Rhodococcus for the bioremediation of organic and inorganic contaminants present in different environmental compartments. We reviewed the bioremediation capacity and mechanisms of Rhodococcus spp. in the treatment of polycyclic aromatic hydrocarbons, phenolic substances, emerging contaminants, heavy metals, and dyes given their human health risks and environmental concern. Different bioremediation techniques were discussed, including experimental conditions, treatment efficiencies, mechanisms, and degradation pathways. The use of Rhodococcus strains in the bioremediation of several compounds is a promising approach due to their features, primarily the presence of appropriate enzyme systems, which result in high decontamination efficiencies; but that vary according to experimental conditions. Besides, the genus Rhodococcus contains a small number of opportunistic species and pathogens, representing an advantage from the point of view of safety. Advances in analytical detection techniques and Molecular Biology have been collaborating to improve the understanding of the mechanisms and pathways involved in bioremediation processes. In the context of using Rhodococcus spp. as bioremediation agents, there is a need for more studies that 1) evaluate the role of these actinomycetes on a pilot and field scale; 2) use genetic engineering tools and consortia with other microorganisms to improve the bioremediation efficiency; and 3) isolate new Rhodococcus strains from environments with extreme and/or contaminated conditions aiming to explore their adaptive capabilities for bioremediation purposes.
... 17,18 Considering these problems, extensive research has been carried out in the development of new methodologies that allow their safe disposal, such as: bioremediation or the use of various materials. The most used are zero-valent iron, 19 bioremediation, 20 oxidative dehalogenation 21 and molecular catalysts. 22,23 The main challenge of these technologies is that they present high selectivity and high removal performance. ...
The electrochemical dehalogenation of trans-1,2-dibromocyclohexane will be studied using a family of cobaloximes by the cyclic voltammetry. The cobaloximes used are: Co(dmgH)2Cl(py), Co(mpgH)2Cl(py), Co(dpgH)2Cl(py), Co(chgH)2Cl(py), Co(dmgH)2Cl(PPh3), Co(mpgH)2Cl(PPh3) and Co(dpgH)2Cl(PPh3) (where dmgH is dimethylglyoximato, mpgH is methylphenylglyoximato, dpgH is diphenylglyoximato, chgH is 1,2-cyclohexanedione dioxime, PPh3 is triphenylphosphine and py is pyridine). The dehalogenation kinetics were studied by monitoring the current increases zone near to the Co(II/I) half wave potential as the concentration of the trans-1,2-dibromocyclohexane in the electrochemical cell is increased. The rate constants of the dehalogenation processes were estimated using the foot-of-the-wave analysis (FOWA), finding higher constant values when the potential of the Co(II/I) pair is shifted to more negative values.
Pesticide use in crops is a severe problem in some countries. Each country has its legislation for use, but they differ in the degree of tolerance for these broadly toxic products. Several synthetic pesticides can cause air, soil, and water pollution, contaminating the human food chain and other living beings. In addition, some of them can accumulate in the environment for an indeterminate amount of time. The agriculture sector must guarantee healthy food with sustainable production using environmentally friendly methods. In this context, biological biopesticides from microbes and plants are a growing green solution for this segment. Several pests attack crops worldwide, including weeds, insects, nematodes, and microorganisms such as fungi, bacteria, and viruses, causing diseases and economic losses. The use of bioproducts from microorganisms, such as microbial biopesticides (MBPs) or microorganisms alone, is a practice and is growing due to the intense research in the world. Mainly, bacteria, fungi, and baculoviruses have been used as sources of biomolecules and secondary metabolites for biopesticide use. Different methods, such as direct soil application, spraying techniques with microorganisms, endotherapy, and seed treatment, are used. Adjuvants like surfactants, protective agents, and carriers improve the system in different formulations. In addition, microorganisms are a tool for the bioremediation of pesticides in the environment. This review summarizes these topics, focusing on the biopesticides of microbial origin.
Halogenated persistent organic pollutants (POPs), which are purposefully rendered obsolete, are kept in stockpiles around the world, often in hazardous conditions. They pose a significant risk to both the environment and human health due to their proclivity to migrate and accumulate in the biosphere. Lindane is a dangerous substance that was previously used as a pesticide. Many countries have banned it due to its negative impact on the environment and human health. Lindane is particularly dangerous because it can linger in the environment for extended periods of time and accumulate in the food chain. Lindane contamination can occur from a number of sources, including contaminated soil, water, and air. Lindane can degrade via a variety of mechanisms, including biodegradation, photodegradation, hydrolysis, and chemical oxidation. Mechanochemical treatment has demonstrated the ability to degrade pollutants in both pure pollutants and contaminated soils. Adding co-milling agents to aid in the breakdown of organochlorine chemicals is the most common method of mechanochemically treating contaminated soil. Our research into two types of synthetic soil and genuine soil samples from different locations reveals a compelling relationship between the chemical composition of the soil and the extent of lindane breakdown, especially at low to moderate concentrations. This phenomenon, aptly dubbed "soil's self-healing ability," has far-reaching implications for cost-effective remediation practices. Knowing the magnitude of this impact also encourages economic revitalization, establishing soil remediation efforts as a dynamic engine of positive transformation.
Deteriorated soil pollution has grown into a worldwide environmental concern over the years. Organochlorine pesticide (OCP) residues, featured with ubiquity, persistence and refractoriness, are one of the main pollution sources, causing soil degradation, fertility decline and nutritional imbalance, and severely impacting soil ecology. Furthermore, residual OCPs in soil may enter the human body along with food chain accumulation and pose a serious health threat. To date, many remediation technologies including physicochemical and biological ways for organochlorine pollution have been developed at home and abroad, but none of them is a panacea suitable for all occasions. Rational selection and scientific decision-making are grounded in in-depth knowledge of various restoration techniques. However, soil pollution treatment often encounters the interference of multiple factors (climate, soil properties, cost, restoration efficiency, etc.) in complex environments, and there is still a lack of systematic summary and comparative analysis of different soil OCP removal methods. Thus, to better guide the remediation of contaminated soil, this review summarized the most commonly used strategies for OCP removal, evaluated their merits and limitations and discussed the application scenarios of different methods. It will facilitate the development of efficient, inexpensive and environmentally friendly soil remediation strategies for sustainable agricultural and ecological development.
Soil contamination caused by persistent organic pollutants (POPs) has been a worldwide concern for decades. With lindane-contaminated soil as the target, a mechanochemical method assisted by CaO was comprehensively evaluated in terms of its remediation performance, degradation mechanism and overall assessment. The mechanochemical degradation performance of lindane in cinnamon soil or kaolin was determined under different additives, lindane concentrations and milling conditions. 2,2-Diphenyl-1-(2,4,6-trinitrophenyl) hydrazinyl free radical (DPPH•) and electron spin resonance (ESR) tests evidenced that the degradation of lindane in soil was caused mainly by the mechanical activation of CaO to produce free electrons (e-) and the alkalinity of the generated Ca(OH)2. Dehydrochlorination or dechlorination by elimination, alkaline hydrolysis, hydrogenolysis and the subsequent carbonization were the main degradation pathways of lindane in soil. The main final products included monochlorobenzene, carbon substances and methane. The mechanochemical method with CaO was proved to also efficiently degrade lindane in three other soils and other hexachlorocyclohexane isomers and POPs in soil. The soil properties and soil toxicity after remediation were assessed. This work presents a relatively clear discussion of various aspects of the mechanochemical remediation of lindane-contaminated soil assisted by CaO.
Organochlorine pesticides (OCPs) have been used in agriculture, increasing crop yields and representing a serious and persistent global contaminant that is harmful to the environment and human health. OCPs are typically bioaccumulative and persistent chemicals that can spread over long distances. The challenge is to reduce the impacts caused by OCPs, which can be achieved by treating OCPs in an appropriate soil and water environment. Therefore, this report summarizes the process of bioremediation with commercially available OCPs, considering their types, impacts, and characteristics in soil and water sources. The methods explained in this report were considered to be an effective and environmentally friendly technique because they result in the complete transformation of OCPs into a non-toxic end product. This report suggests that the bioremediation process can overcome the challenges and limitations of physical and chemical treatment for OCP removal. Advanced methods such as biosurfactants and genetically modified strains can be used to promote bioremediation of OCPs.
Contamination of Hexachlorohexane (Lindane) in soil and water has toxic effects due toits persistent nature. In our study, an indigenous HCH (gamma isomer) degrading bacterium viz Bacillus cereus SJPS-2 was isolated from Yamuna river water using enrichment culture method. The growth curve indicated that Bacillus cereus SJPS-2 was able to degrade ϒ-HCH effectively with 80.98% degradation. Further, process was improved by using immobilization using alginate beads which showed enhanced degradation (89.34%). Interestingly, in presence of fructose, the ϒ-HCH degradation was up to 79.24% with exponential growth curve whereas the degradation was only 5.61% in presence of glucose revealing diauxic growth curve. Furthermore, The FTIR results confirmed the potential Lindane degradation capability of Bacillus cereus SJPS-2 and the bonds were recorded at wavelengths viz. 2900-2500 cm-1, 3300-2800 cm-1 and 785-540 cm-1. Similarity, the GC studies also reconfirmed the degradation potential with retention time (RT) of ethyl acetate and lindane was 2.12 and 11.0 respectively. Further, we studied the metabolic pathway involved for lindane utilization in Bacillus cereus using KEGG-KASS and functional gene annotation through Rapid Annotation using Subsystems Technology (RAST) resulted in the annotation of the lin genes (lin A, lin B, lin C, lin X, lin D, lin E) and respective encoding enzymes. The comparative ϒ-HCH degradation potential of B. cereus and P. putida KT2440 was also evaluated. The island viewer showed the different colors on circular genome indicate the coordinates of genomic islands resulted with some common genomic islands (GEIs) between both bacteria indicating the possibility of horizontal gene transfer at contaminated site or natural environment. These genomic islands (GEIs) contribute in the rearrangement genetic material or to evolve bacteria in stress conditions, as a result the metabolic pathways evolve by formation of catabolic genes. This study establishes the potential of Bacillus cereus SJPS-2 for effectual ϒ-HCH degradation.
Aromatic amines (AA) are one of the most commonly used classes of compounds in industry and the most common pollutants found in both soil and water. 3,4-Dichloaniline (3,4-DCA) is a persistent residue of the phenylurea herbicide in the environment. In this study, we used a colorimetric method as a new approach to screen 12 filamentous fungal strains of the genera Aspergillus, Chaetomium, Cladosporium, and Mucor to assess their capacity to perform AA N-acetylation since it is considered a potential tool in environmental bioremediation. Subsequently, the selected strains were biotransformed with different AA substrates to evaluate the product yield. The strains Aspergillus niveus 43, Aspergillus terreus 31, and Cladosporium cladosporioides showed higher efficiencies in the biotransformation of 3,4-DCA at 500 µM into its N-acetylated product. These fungal strains also showed great potential to reduce the phytotoxicity of 3,4-DCA in experiments using Lactuca sativa seeds. Furthermore, N-acetylation was shown to be effective in reducing the cytotoxic and genotoxic effects of 3,4-DCA and other AA in the immortalized human keratinocyte (HaCaT) cell line. The isolated products after biotransformation showed that fungi of the genera Aspergillus and Cladosporium appeared to have N-acetylation as the first and main AA detoxification mechanism. Finally, A. terreus 31 showed the highest 3,4-DCA bioremediation potential, and future research can be carried out on the application of this strain to form microbial consortia with great potential for the elimination of toxic AA from the environment.
Organochlorine pesticides, especially lindane and endosulfan, have been demonstrated to be both biodegradable and frequently coexistent, but their inhibitory effect has never been studied. In this study, we investigated the effect of endosulfan coexistence on lindane degradation to a lindane-degrading isolate, Novosphingobium barchaimii strain LL02, and mixed enrichment cultures from two different inocula. Our results of the lindane degradation batch experiments demonstrated that endosulfan concentration above 20 mg L⁻¹ causes significant inhibition to the lindane degradation efficiency of the strain LL02. Besides, the acidic conditions at pH 5.0 to 6.0 further decreased its lindane degradation rate constants by 57% compared to the neutral and alkaline conditions. For the mixed microbial cultures, the lindane degradation efficiency in the lindane/endosulfan co-contamination conditions decreased by 35.7%–50.7% compared to the lindane alone conditions. From our 16S rRNA amplicon sequencing results through the PacBio platform, most of the predominant bacteria in the lindane-enriched cultures were depressed in the lindane/endosulfan-enriched cultures. Moreover, bacteria of Burkholderia australis, Chujaibacter soli, Flavitalea flava, and one Rhodanobacteraceae bacterium were relatively highly abundant in the co-contamination enrichment cultures, suggesting their potential for lindane degradation under the endosulfan stress. Our results demonstrated that endosulfan coexistence causes inhibitory impacts on lindane biodegradation toward both lindane-degrading bacteria and mixed microbial cultures. The coexistence of multiple organochlorine pesticides on the biodegradation efficiencies should be carefully considered when applying bioremediation to remove organochlorine pesticide contamination.
Lindane (γ-hexachlorocyclohexane) is an organochlorine pesticide that has been widely used in agriculture over the last seven decades. The increasing residues of lindane in soil and water environments are toxic to humans and other organisms. Large-scale applications and residual toxicity in the environment require urgent lindane removal. Microbes, particularly Gram-negative bacteria, can transform lindane into non-toxic and environmentally safe metabolites. Aerobic and anaerobic microorganisms follow different metabolic pathways to degrade lindane. A variety of enzymes participate in lindane degradation pathways, including dehydrochlorinase (LinA), dehalogenase (LinB), dehydrogenase (LinC), and reductive dechlorinase (LinD). However, a limited number of reviews have been published regarding the biodegradation and bioremediation of lindane. This review summarizes the current knowledge regarding lindane-degrading microbes along with biodegradation mechanisms, metabolic pathways, and the microbial remediation of lindane-contaminated environments. The prospects of novel bioremediation technologies to provide insight between laboratory cultures and large-scale applications are also discussed. This review provides a theoretical foundation and practical basis to use lindane-degrading microorganisms for bioremediation.
Lindane is a highly chlorinated and recalcitrant insecticide, capable to accumulate in soil and groundwater. Despite lindane has been banned in many countries, numerous sites still remain contaminated. The present work studies the bioremediation of soils of different textures contaminated with lindane by bioaugmentation with a quadruple Streptomyces consortium. In the three evaluated soils, silty loam soil (SLS), sandy soil (SS), and clayey soil (CS), heterotrophic microbial populations increased during the 14 days of the assay and CFU counts were higher in bioaugmented than in non-bioaugmented soils. Lindane removal was detected in all contaminated treatments, with higher removal percentages in the bioaugmented microcosms (SS 70.3%, SLS 36.3%, and CS 30.7%), than in non-bioaugmented ones (SS 40.4%, SLS 9.3%, and CS 12.2%). The pesticide half-life decreased by 77.3, 50.3, and 10.7 days, in bioaugmented SLS, CS, and SS, respectively. Lindane had an inhibitory effect on soil enzyme activities such as dehydrogenase, fluorescein diacetate hydrolysis, acid and alkaline phosphatases and increased the catalase activity, in non-bioaugmented controls; however, no effect on urease activity was observed. Bioaugmentation of soil microcosms with actinobacteria increased all enzymatic activities. Finally, the survival of the four strains of the consortium was demonstrated at the end of the bioremediation assay. Bioremediation using the Streptomyces sp. A2-A5-A11-M7 consortium represents a promising tool to restore different types of soils contaminated with organochlorine pesticides.
This review describes the biodegradation of Lindane (γ-hexachlorocyclohexane, γ-HCH) from the diverse sources. Environmental degradation of γ-HCH has been described in terms of integrated biological approaches such as metagenomics, cloning, phytoremediation, nanobiodegradation, and biosrfactants, genes and enzymes responsible for γ-HCH degradation and exploration of new strains of γ-HCH-degrading microbes from different environmental sources. Metagenomics-based approaches help in the identification and isolation of new genes from the uncultivable sources and provide insights for future research. There is potential in the elucidation of pathways of degradation of persistent organic pollutants (POPs) from environment by the microorganisms. This is possible by means of new/improved microbial species. The behavior of isolated strains and the microorganisms when present in community is altogether different. Therefore, there is a need to develop new technology which will identify the minor component of the microbial community involved in degradation because the minor part might have profound effect on degradation. This is mediated by the biological activity of the microbial system.
Sixty endosulfan tolerant bacterial strains were
isolated from pesticide stressed agricultural soils. Five
most tolerant strains were tested for plant growth promoting
(PGP) activities and endosulfan degradation under different
optimizing conditions in broth and soil. The strains
PRB101 and PRB77 were the most efficient in terms of
endosulfan degradation and PGP activities and showed
solubilization indexes of 3.3 and 3.1 mm, indole acetic
acid production of 71 and 68 μg mL−1, siderophore zones
of 13 mm each at the recommended dosage, respectively.
Hydrogen cyanide and ammonia production remained unaffected
in the presence of endosulfan. PRB101 and PRB77
strains were able to degrade 74% and 70% of endosulfan in
broth and 67% and 63% in soil, respectively. Based on 16S
rDNA analysis, the strains PRB101 and PRB77 exhibited
99% homology with Bacillus sp. KF984414 and Bacillus
sp. LN849696, respectively.
Background
This study was carried out to isolate and characterize the bacterial strains from lindane-contaminated soil and they were also assessed for their lindane-degrading potential. Methods
In this study the enrichment culture method was used for isolation of lindane degrading bacterial isolates, in which the mineral salt medium (MSM) supplemented with different concentrations of lindane was used. Further, the screening for the potential lindane degrading isolates was done using the spray plate method and colorimetric dechlorinase enzyme assay. The selected isolates were also studied for their growth response under varying range of temperature, pH, and NaCl. The finally selected isolates DAB-1Y and DAB-1W showing best lindane degradation activity was further subjected to biochemical characterization, microscopy, degradation/kinetic study, and 16S rDNA sequencing. The strain identification were performed using the biochemical characterization, microscopy and the species identifies by 16S rDNA sequence of the two isolates using the standard 16S primers, the 16 S rRNA partial sequence was analyzed through BLAST analysis and phylogenetic tree was generated based on UGPMA clustering method using MEGA7 software. This shows the phylogenetic relationship with the related strains. The two isolates of this study were finally characterized as Kocuria sp. DAB-1Y and Staphylococcus sp. DAB-1W, and their 16S rRNA sequence was submitted to GenBank database with accession numbers, KJ811539 and KX986577, respectively. ResultsOut of the 20 isolates, the isolates DAB-1Y and DAB-1W exhibited best lindane-degrading activity of 94 and 98%, respectively, recorded after 8 days of incubation. The optimum growth was observed at temperature 30 °C, pH 7, and 5% NaCl observed for both isolates. Of the four isomers of hexachlorocyclohexane, isomer α and γ were the fastest degrading isomers, which were degraded up to 86 and 94% by isolates DAB-1Y and up to 93 and 98% by DAB-1W, respectively, reported after 8 days incubation. Isomer β was highly recalcitrant in which maximum 35 and 32% lindane degradation was observed even after 28 days incubation by isolates, DAB-1Y and DAB-1W, respectively. At lower lindane concentrations (1–10 mg/L), specific growth rate increased with increase in lindane concentration, maximum being 0.008 and 0.006/day for DAB-1Y and DAB-1W, respectively. The 16 S rRNA partial sequence of isolate DAB-1Y showed similarity with Kocuria sp. by BLAST analysis and was named as Kocuria sp. DAB-1Y and DAB-IW with Staphylococcus sp. DAB-1W. The 16S rDNA sequence of isolate DAB-1Y and DAB-1W was submitted to online at National Centre of Biotechnology Information (NCBI) with GenBank accession numbers, KJ811539 and KX986577, respectively. Conclusions
This study has demonstrated that Kocuria sp. DAB-1Y and Staphylococcus sp. DAB-1W were found efficient in bioremediation of gamma-HCH and can be utilized further for biodegradation of environmental contamination of lindane and can be utilized in bioremediation program.
A high capacity of laccase from Trametes versicolor capable of degrading pesticides has been revealed. The conditions for degrading of five selected pesticides including chlorpyrifos, chlorothalonil, pyrimethanil, atrazine and isoproturon with the purified laccases from Trametes versicolor were optimized. The results showed that the optimum conditions for the highest activity were pH at 5.0 and temperature at 25 °C. The best mediators were violuric acid for pyrimethanil and isoproturon, vanillin for chlorpyrifos, and acetosyringone and HBT for chlorothalonil and atrazine, respectively. The laccase was found to be stable at a pH range from 5.0 to 7.0 and temperature from 25 to 30 °C. It was observed that each pesticide required a different laccase mediator concentration typically between 4.0-6.0 mmol/L. In the experiment, the degradation rates of pyrimethanil and isoproturon were significantly faster than those of chlorpyrifos, chlorothalonil and atrazine. For example, it was observed that pyrimethanil and isoproturon degraded up to nearly 100% after 24 hours while the other three pesticides just reached up 90% of degradation after 8 days of incubation.
Bacterial isolates RP-1, RP-3 and RP-9 were isolated from agricultural soil using enrichment culture technique and screened positive for lindane degradation. RP-1, RP-3 and RP-9 were found to utilize and degrade higher concentrations (100 ppm) of lindane. RP-1 and RP-3 showed 69.5 and 65% lindane degradation after 10 days of inoculation where as RP-9 degraded 62% of lindane after 15 days. The estimated Cl -ion release was 49, 42 and 39 mg/mL, respectively for the three bacterial isolates. Gas chromatography was used for analysis of metabolite formed during lindane degradation and different parameters of degradation kinetics were calculated using first order kinetic equation. A drastic decrease in degradation rate was observed at initial lindane concentrations higher than 200 mg/l in the mineral media. The calculated half-life periods for RP-1, RP-3 and RP-9 were found to be 3.85, 2.77 and 4.00 days, respectively. All three isolates showed maximum degradation activity at: incubation period; 10-15 days, incubation temperatures; 30°C, pH; 7.0, shaking speed 120 rpm, initial substrate concentration; 100 mg/l. Galactose and succinate enhanced the degradation rate up to 10% whereas maltose, lactose and xylose decreased the degradation level up to 40%. Addition of glucose as a co-substrate was found highly favorable for enhancement of lindane degradation.
Rhizoremediation is the use of plant–microbe interaction for the enhanced degradation of contaminants. Rhizosphere bioremediation of pyrethroid pesticides will offer an attractive and potentially inexpensive approach for remediation of contaminated soil. The present study was done with the aim of establishment of highly effective remediation method using plant with degradative rhizosphere and isolation of naturally occurring rhizosphere associated potential degrader providing the possibility of both environmental and insitu detoxification of cypermethrin contamination. The remediation efficacy of Pennisetum pedicellatum was investigated using green house pot culture experiments in cypermethrin amended potting soil mix (10, 25, 50, 75 and 100 mg/kg) for periodic evaluation of changes in concentration. Total proportion of cypermethrin degraders was found to be higher in rhizosphere soil compared to bulk soil. The cypermethrin degrading strain associated with rhizosphere capable of surviving at higher concentrations of cypermethrin was designated as potential degrader. On the basis of morphological characteristics, biochemical tests and 16S rDNA analysis, isolate was identified as Stenotrophomonas maltophilia MHF ENV 22. Bioremediation data of cypermethrin by strain MHF ENV22 examined by HPLC and mass spectroscopy, indicated 100, 50 and 58 % degradation within the time period of 72, 24 and 192 h at concentrations 25, 50 and 100 mg/kg, respectively. This is the first report of effective degradation of cypermethrin by Stenotrophomonas spp. isolated from rhizosphere of Pennisetum pedicellatum. Rhizoremediation strategy will be of immense importance in remediation of cypermethrin residues to a level permissible for technogenic and natural environment.
Endosulfan, a non-systemic organochlorine
pesticide used extensively to control the insect pests of a
wide range of crops is of environmental concern because of
its apparent persistence and toxicity to many non-target
organisms. The present study was aimed to find out the
capability of microorganisms to degrade endosulfan, singly
and/or in consortium and optimization of various growth
parameters to achieve optimal degradation. A total of three
isolates showing significantly higher degradation potential
were selected from eight isolates demonstrating substantial
growth. They were identified as Staphylococcus equorum
CM5, Enterobacter sp. MF1 and Bacillus subtilis MF2.
The effect of various parameters (pH, temperature, inocu-
lum size, endosulfan concentration, incubation conditions
and carbon concentration) were also assessed and opti-
mized for degradation of endosulfan. The consortia of
Staphylococcus and Bacillus strain showed near disap-
pearance of endosulfan from the medium after 21 days of incubation. The maximum degradation percentage of endosulfan was observed at slightly alkaline pH 8.0 under shaking conditions of 150 rpm at 30 �C at a concentration of 1 g l -1 of dextrose and irrespective of the inocula size used in this study. The isolates identified in this study present an efficient, economical and ecological alternative remedy for the removal of endosulfan from contaminated sites
Organochlorine pesticides are notorious, due to their high toxicity, persistence in the environment and their tendency to bioaccumulate. Their extensive use in the northwest of Argentina has left residues in the environment.Microbial degradation is an important process for pesticide bioremediation and actinomycetes have a great potential for that.The current study examined organochlorine pesticides in contaminated soil. Indigenous actinomycetes were isolated from contaminated samples to evaluate bacterial growth as well as pesticide removal and release of chloride ions as a result of degradation.Most of the isolated microorganisms belonged to the Streptomyces genus, except one, which belonged to Micromonospora. Bacterial growth depended on the microorganism and the pesticide present (chlordane, lindane or methoxychlor). Highest growth and pesticide removal were observed with chlordane. Twelve out of 18 studied strains released chloride into culture supernatants, and percentages were higher with chlordane as carbon source than with lindane or methoxychlor. These results are supported by principal component analysis.This is the first report about actinomycetes isolated from an illegal storage of organochlorine pesticide in Argentina with capacity to growth, remove and use different organochlorine pesticide.
gamma-Hexachlorocyclohexane (gamma-HCH) is one of several highly chlorinated insecticides that cause serious environmental problems. The cellular proteins of a gamma-HCH-degrading bacterium, Sphingomonas paucimobilis UT26, were fractionated into periplasmic, cytosolic, and membrane fractions after osmotic shock. Most of two different types of dehalogenase, LinA (gamma-hexachlorocyclohexane dehydrochlorinase) and LinB (1,3,4,6-tetrachloro-1,4-cyclohexadiene halidohydrolase), that are involved in the early steps of gamma-HCH degradation in UT26 was detected in the periplasmic fraction and had not undertaken molecular processing. Furthermore, immunoelectron microscopy clearly showed that LinA and LinB are periplasmic proteins. LinA and LinB both lack a typical signal sequence for export, so they may be secreted into the periplasmic space via a hitherto unknown mechanism.
Ongoing deliberations on the regulation of semivolatile organic chemicals require the assessment of chemical transport in atmospheric and marine systems. The characteristic travel distance was proposed as a measure for the transport potential in air and water. However, the existing definition treats the transport processes separately. It is shown that combined transport in coupled air-ocean systems can accelerate the overall transport into remote regions. Concentration ratios in air and water change with distance from sources depending on the initial concentration ratio and on the difference between the transport velocities. A measure is suggested facilitating the chemical screening with respect to transport potentials in such air-ocean systems. A case study for alpha and gamma-hexachlorocyclohexane shows that the suggested measure qualitatively reveals the transport potentials of these chemicals and exemplifies possible concentration patterns.
We examined the harmful side effects on indigenous soil microorganisms of two organic solvents, acetone and dichloromethane, that are normally used for spiking of soil with polycyclic aromatic hydrocarbons for experimental purposes. The solvents were applied in two contamination protocols to either the whole soil sample or 25% of the soil volume, which was subsequently mixed with 75% untreated soil. For dichloromethane, we included a third protocol, which involved application to 80% of the soil volume with or without phenanthrene and introduction of Pseudomonas fluorescens VKI171 SJ132 genetically tagged with luxAB::Tn5. For both solvents, application to the whole sample resulted in severe side effects on both indigenous protozoa and bacteria. Application of dichloromethane to the whole soil volume immediately reduced the number of protozoa to below the detection limit. In one of the soils, the protozoan population was able to recover to the initial level within 2 weeks, in terms of numbers of protozoa; protozoan diversity, however, remained low. In soil spiked with dichloromethane with or without phenanthrene, the introduced P. fluorescens VKI171 SJ132 was able to grow to a density 1,000-fold higher than in control soil, probably due mainly to release of predation from indigenous protozoa. In order to minimize solvent effects on indigenous soil microorganisms when spiking native soil samples with compounds having a low water solubility, we propose a common protocol in which the contaminant dissolved in acetone is added to 25% of the soil sample, followed by evaporation of the solvent and mixing with the remaining 75% of the soil sample.
Excessive use of pesticides in agricultural fields is a matter of great concern for living beings as well as the environment across the world, in particular, the third world countries. Therefore, there is an urgent need to find out an effective way to degrade these hazardous chemicals from the soil in an environment‐friendly way. In the current project, a bacterial species were isolated through enrichment culture from carbofuran‐supplemented rice‐field soil and identified as a carbofuran degrader. The rate of carbofuran degradation by this bacterial species was evaluated using reverse‐phase high‐performance liquid chromatography (RP‐HPLC), which confirmed the ability to utilize as a carbon source up to 4 µg/ml of 99% technical grade carbofuran. The morphological, physiological, biochemical characteristics and phylogenetic analysis of the 16S rRNA sequence showed that this strain belongs to the genus of Enterobacter sp. (sequence accession number LC368285 in DDBJ), and the optimum growth condition for the isolated strain was 37°C at pH 7.0. Moreover, an antibiotic sensitivity test showed that it was susceptible to azithromycin, penicillin, ceftazidime, ciprofloxacin, and gentamycin, and the minimal inhibitory concentration value of gentamycin was 400 μg/ml against the bacteria. It shows beyond doubt from the RP‐HPLC quantification that the isolated bacterium has the ability to detoxify carbofuran (99% pure). Finally, the obtained results imply that the isolated strain of Enterobacter can be used as a potential and effective carbofuran degrader for bioremediation of contaminated sites through bioaugmentation.
Endosulfan is a broad spectrum insecticide used in agriculture for protection of various food and non-food crops. It is persistent in nature and hence found in soil, air and water. The potential use of plants and microorganisms for the removal of endosulfan from soil was studied. Helianthus annuus plant was grown in soil spiked with 5, 10, 25 and 50 mg kg ⁻¹ concentrations of endosulfan and inoculated with plant growth promoting rhizobacterial strains Paenibacillus sp. IITISM08, Bacillus sp. PRB77 and Bacillus sp. PRB101 for 40, 80 and 120 days. Potential of plant for endosulfan uptake was evaluated by investigating the endosulfan levels in plant tissues (root and shoot). The results indicated that endosulfan accumulation followed the pattern of root > shoot as well as decrease in uptake of endosulfan in root and shoot of a plant grown in bacterial inoculated soil as compared to un-inoculated soil. Bacterial inoculation had a positive effect on endosulfan degradation. Maximum degradation of 92% at 5 mg kg ⁻¹ of endosulfan in soil was observed on inoculation with PRB101 after 120 days of inoculation. The results showed that plant growth promoting bacteria enhances plant biomass production. Lipid peroxidation was also estimated by determining the malondialdehyde (MDA) production, which is a biomarker of oxidative damage. Decrease in MDA formation by root and leaves of plants grown in the bacteria inoculated plant was also observed. The results suggested the effectiveness of plant growth promoting rhizobacteria to boost accumulation potential, biomass production and enhance remediation of endosulfan contaminated soil.
This essential reference provides an introduction to the remarkable soils and landscapes of Australia. It reveals their great diversity and explains why an understanding of soil properties and landscape processes should guide our use of the land. Using striking photographs of characteristic landscapes, it begins by describing the basic properties of soils and how Australia's distinctive soils and landscapes have co-evolved. We gain a greater understanding of why particular soils occur at certain locations and how soil variation can influence landscape processes, agricultural productivity and ecosystem function. The book explains the impact of various forms of land use and the changes they can bring about in soil. This is followed by an invaluable compendium that describes and illustrates over 100 of the more important and widespread soils of Australia, along with their associated landscapes. There is a brief account of each soil's environment, usage and qualities as well as details on chemical and physical properties so we can make more informed decisions about appropriate land-use. Australian Soils and Landscapes will be a valuable resource for farmers, natural resource managers, soil and environmental scientists, students and anyone with an interest in Australia's unique environment.
Exposure to environmental toxicants that target ovarian follicles can have long-lasting effects on women's reproductive health and health of the offspring. Experiments in rodents have contributed knowledge about the effects of individual toxicants on ovarian follicles. However, little is known about the effects of mixtures of toxicants on ovarian follicular health. We studied the combined effects of low, physiologically- and environmentally-relevant concentrations of toxicants on murine secondary ovarian follicles cultured in an encapsulated three-dimensional (3D) system. Exposure to lindane and 7,12-dimenthylbenz(a)anthracene (DMBA) led to decreased follicle survival, impaired development and compromised maturation in a concentration-dependent manner. DMBA showed a greater toxicity to cultured follicles compared to lindane. The mixtures of lindane and DMBA did not produce a synergistic toxic effect on follicles. Rather, ovarian follicles exposed to the mixtures showed survival and growth patterns similar to the follicles exposed to the same concentrations of individual toxicants. Our findings regarding follicle toxicity at such low concentrations help informing what might be overlooked when regulating environmental toxicants. The proposed 3D culture system allowed studying the effects of mixtures of environmental toxicants in a physiological setting, providing much needed information on how simultaneous exposure to multiple toxicants affects complex and sensitive biological structures, such as ovarian follicles.
The biomixture is the major constituent of a biopurification system and one of the most important factors in its efficiency; hence the selection of the components is crucial to ensure the efficient pesticides removal. Besides, bioaugmentation is an interesting approach for the optimization of these systems.
A mixed culture of the fungus Trametes versicolor SGNG1 and the actinobacteria Streptomyces sp. A2, A5, A11, and M7, was designed to inoculate the biomixtures, based on previously demonstrated ligninolytic and pesticide-degrading activities and the absence of antagonism among the strains. The presence of lindane and/or the inoculum in the biomixtures had no significant effect on the development of culturable microorganisms regardless the soil type. The consortium improved lindane dissipation achieving 81–87% of removal at 66 d of incubation in the different biomixtures, decreasing lindane half-life to an average of 24 d, i.e. 6-fold less than t1/2 of lindane in soils. However, after recontamination, only the bioaugmented biomixture of silty loam soil enhanced lindane dissipation and decreased the t1/2 compared to non-bioaugmented. The biomixture formulated with silty loam soil, sugarcane bagasse, and peat, inoculated with a fungal-actinobacterial consortium, could be appropriate for the treatment of agroindustrial effluents contaminated with organochlorine pesticides in biopurification systems.
Microbes are known to be powerful degraders of macromolecules, plant biomass, lignin, cellulose, xylene, pectin, and other complex polysaccharides. Among these microbes, actinomycetes constitute a major part of the microbial population responsible for decomposing various biomolecules by producing extracellular enzymes. Actinobacteria are also known as biofactories of enzymes, with applications in textile, bio-refineries, food, pulp and paper, agriculture, detergent, and pharmaceutical industries. Actinomycetes from extreme environments also produce enzymes with novel properties such as high stability and substrate specificity. These metabolic enzymes of amylase, lipase, and cellulase from these microbes provide the potential for high production, and uphold the industrial requirements for commercialization and societal benefit. A large number of enzymes have been reported from actinobacteria that are being applied in biotechnological industries. This book chapter highlights recent updates on actinobacteria with, particular attention paid to industrially relevant enzymes.
This study focuses on the effect of electrode materials on abatement of lindane (an organochlorine pesticide) by electrooxidation process. Comparative performances of different anodic (platinum (Pt), dimensionally stable anode (DSA) and boron-doped diamond (BDD)) and cathodic (carbon sponge (CS), carbon felt (CF) and stainless steel (SS)) materials on lindane electrooxidation and mineralization were investigated. Special attention was paid to determine the role of chlorine active species during the electrooxidation process. The results showed that better performances were obtained when using a BDD anode and CF cathode cell. The influence of the current density was assessed to optimize the oxidation of lindane and the mineralization of its aqueous solution. A quick (10 min) and complete oxidation of 10 mg L-1lindane solution and relatively high mineralization degree (80% TOC removal) at 4 h electrolysis were achieved at 8.33 mA cm-2current density. Lindane was quickly oxidized by in-situ generated hydroxyl radicals, (M(•OH)), formed from oxidation of water on the anode (M) surface following pseudo first-order reaction kinetics. Formation of chlorinated and hydroxylated intermediates and carboxylic acids during the treatment were identified and a plausible mineralization pathway of lindane by hydroxyl radicals was proposed.
The objective of the present work was to establish optimal biological and physicochemical parameters in order to remove simultaneously lindane and Cr(VI) at high and/or low pollutants concentrations from the soil by an actinobacteria consortium formed by Streptomyces sp. M7, MC1, A5, and Amycolatopsis tucumanensis AB0. Also, the final aim was to treat real soils contaminated with Cr(VI) and/or lindane from the Northwest of Argentina employing the optimal biological and physicochemical conditions. In this sense, after determining the optimal inoculum concentration (2gkg(-1)), an experimental design model with four factors (temperature, moisture, initial concentration of Cr(VI) and lindane) was employed for predicting the system behavior during bioremediation process. According to response optimizer, the optimal moisture level was 30% for all bioremediation processes. However, the optimal temperature was different for each situation: for low initial concentrations of both pollutants, the optimal temperature was 25°C; for low initial concentrations of Cr(VI) and high initial concentrations of lindane, the optimal temperature was 30°C; and for high initial concentrations of Cr(VI), the optimal temperature was 35°C. In order to confirm the model adequacy and the validity of the optimization procedure, experiments were performed in six real contaminated soils samples. The defined actinobacteria consortium reduced the contaminants concentrations in five of the six samples, by working at laboratory scale and employing the optimal conditions obtained through the factorial design.
Large dumps of unused γ-hexachlorocyclohexane (γ-HCH) have become an issue of concern. The overall salinity of soil enhances due to the release of potassium cations by the insecticide in the polluted soil, which may limit microbial degradation. The current work addresses this problem through the isolation of γ-HCH degrading halophilic bacteria from HCH dumpsite using γ-HCH as a sole carbon source by selective enrichment technique. Strain LD2 was found to be the most efficient degrader, degrading 89.6% lindane in 7 days. Low amount of metabolites like 1,2,4-trichlorobenzene (1,2,4-TCB) and 2,5-dichlorophenol (2,5-DCP) were identified during the degradation. The strain was able to utilize lindane at a range of salt concentrations from 10 to 150 g L⁻¹ NaCl where the highest degradation was achieved at 50 g L⁻¹ of NaCl. The bacterial strain LD2 was identified as Chromohalobacter sp. LD2 on the basis of 16S rDNA sequence similarity (KU934224.1). These results revealed that Chromohalobacter sp. LD2 might be a potential candidate for bioremediation in saline environments to decontaminate γ-HCH from polluted sites.
Although the use of organochlorine pesticides (OPs) is restricted or banned in most countries, they continue posing environmental and health concerns, so it is imperative to develop methods for removing them from the environment. This work is aimed to investigate the simultaneous removal of three OPs (lindane, chlordane and methoxychlor) from diverse type of systems by employing a native Streptomyces consortium. In liquid systems, a satisfactory microbial growth was observed accompanied by removal of lindane (40.4%), methoxychlor (99.5%) and chlordane (99.8%). In sterile soil microcosms, the consortium was able to grow without significant differences in the different textured soils (clay silty loam, sandy and loam), both contaminated or not contaminated with the OPs-mixture. The Streptomyces consortium was able to remove all the OPs in sterile soil microcosm (removal order: clay silty loam > loam > sandy). So, clay silty loam soil (CSLS) was selected for next assays. In non-sterile CSLS microcosms, chlordane removal was only about 5%, nonetheless, higher rates was observed for lindane (11%) and methoxychlor (20%). In CSLS slurries, the consortium exhibited similar growth levels, in the presence of or in the absence of the OPs-mixture. Not all pesticides were removed in the same way; the order of pesticide dissipation was: methoxychlor (26%)>lindane (12.5%)>chlordane (10%). The outlines of microbial growth and pesticides removal provide information about using actinobacteria consortium as strategies for bioremediation of OPs-mixture in diverse soil systems. Texture of soils and assay conditions (sterility, slurry formulation) were determining factors influencing the removal of each pesticide of the mixture.
Organochlorine pesticides (OCPs) are toxic and are among the most potent endocrine disrupting chemicals in the environment. Most OCPs are resistant towards oxidation by OH due to presence of electron-withdrawing chlorine group in their molecular structures. Here, we investigated a visible and simulated solar light-assisted sulfur doped TiO2 (S-TiO2)/peroxymonosulfate (HSO5⁻) process to eliminate a selected OCP, lindane. Initially, visible and simulated solar light-assisted S-TiO2 photocatalysis resulted in 31.0 and 63.4% removal of lindane (C0 = 1.0 μM), respectively in 6 h. The photocatalytic activity of S-TiO2 was dramatically increased in the presence of 0.2 mM HSO5⁻, leading to 68.2 and 99.9% lindane removal under visible and simulated solar light illumination, respectively in 6 h. The observed pseudo first-order rate constant for simulated solar light-assisted S-TiO2/HSO5⁻ decreased with increasing initial concentration of lindane, corresponding to 8.98 × 10⁻¹, 6.58 × 10⁻¹ and 3.84 × 10⁻¹ h⁻¹ at [lindane]0 of 0.5, 1.0 and 2.0 μM, respectively. The degradation kinetics were significantly affected by solution pH, leading to 88.2, 99.9 and 71.4% removal of lindane in 6 h at pH 4.0, 5.8 and 8.0, respectively. S-TiO2 film exhibited a high mechanical strength with only 6.4% loss of efficiency after four repeated cycles. Based on the detected reaction intermediates, a possible reaction mechanism was proposed, suggesting dechlorination, dehydrogenation, and hydroxylation via OH, SO4•− and O2•− attack. The results suggest that visible and simulated solar light-assisted S-TiO2/HSO5⁻ is a promising alternative for treatment of water contaminated with most OCPs.
Lindane is a cyclic, saturated and highly chlorinated pesticide with a broad spectrum, which has been used worldwide for many decades to control a variety of pests, and also in human health and veterinary. Afterward, it has been demonstrated that lindane and its isomers may cause serious damage to health in the short and long term. Besides, lindane is known to be persistent in the environment and tends to bioaccumulate along the food chain. Thus, lindane residues remain in the environment for a long time and have been recently found in water, soil, sediments, plants, and animals all over the world, and even in human fluids and tissues. In this context, nowadays, scientists, working all over the world, are involved in developing lindane remediation technologies including physical, chemical, and biological techniques. This article provides updated information on the biologic degradation of lindane using different microorganisms such as bacteria, fungi, and algae, under both aerobic and anaerobic conditions.
Nine endosulfan degrading bacterial strains were isolated by soil enrichment with endosulfan. Bacterial strain M3 was the most efficient degrader. Endosulfan degradation was accompanied by a decrease in pH of the medium and an increase in chloride ion concentration. The bacterium was tested for its ability to degrade endosulfan at different concentrations in broth and soil. Maximum degradation occurred at concentrations of 50 μg/ml of broth and 100 μg/g of soil. Values of Ks and Vmax were different for (α)- and (β)-endosulfan in broth. The kinetic indices (Vmax/Ks) for α-endosulfan and β-endosulfan were 0.051 and 0.048 day(-1) respectively, indicating that (α)-endosulfan was more rapidly degraded. Bacterial strain M3 was identified as Klebsiella sp. M3 on the basis of 16S rDNA sequence similarity (GenBank accession number JX273762).
Methoxychlor is an organochlorine pesticide used worldwide against several insect pests, resulting in human exposure. This pesticide mimics endocrine hormone functions, interfering with normal endocrine activity in humans and wildlife. For this reason, it is imperative to develop methods to remove this pesticide from the environment, and though, bioremediation using microorganisms results as an excellent strategy. Five Streptomyces spp. strains previously isolated from organochlorine-polluted sites and capable to grow and remove methoxychlor were combined as different mixed cultures to increase methoxychlor removal. From the 39 consortia tested, one consortium (Streptomyces spp. A6, A12, A14, M7) was selected because of its high pesticide removal and specific dechlorinase activity to be assayed on slurry and soil systems. This consortium showed higher biomass values (8.3 × 106 ± 5.7 × 105 CFU mL−1) and methoxychlor removal (56.2 ± 2.3 %) on enriched slurry than in non-enriched slurry (7.3 × 105 ± 1.2 × 105 CFU mL−1 and 45.6 ± 7.4 % of pesticide removal). In soil systems, Streptomyces consortium showed higher growth (1.0 × 1011 ± 5.0 × 1010 CFU g−1) than in enriched slurry, although differences in methoxychlor removal between both culture conditions were not statistically significant. Therefore, the selected Streptomyces consortium may be suitable for the development of in situ (soil) and ex situ (slurry bioreactor) bioremediation methods because of their potential to remove methoxychlor from different systems.
The objective of the present study was to study the lindane bioremediation abilities of Streptomyces sp. M7 in soil samples and to know the pesticide effects on maize plants seeded in lindane-contaminated soil previously inoculated with Streptomyces sp. M7.When different initial pesticide concentrations (100, 150, 200, and 300μgkg−1) were added to sterile soil, the microbial growth observed was similar to the control without lindane. A decrease of the residual lindane concentration was detected in soils samples in relation to the abiotic controls (29.1%, 78.03%, 38.81%, and 14.42%, respectively). The optimum Streptomyces sp M7 inoculum was selected in sterile soil spiked with lindane 100μgkg−1soil; it was 2gkg−1 soil for obtaining the most efficient bioremediation process (56% removal).Lindane concentrations of 100, 200, and 400μgkg−1 soil did not affect the germination and vigor index of maize plants seeded in contaminated soils without Streptomyces sp. M7. When this microorganism was inoculated at the same conditions a better vigor index was observed and 68% of lindane removal.These results confirm the lindane-contaminated soil bioremediation potential of Streptomyces sp. M7.
1. The reliability of the Kjeldahl method for the determination of nitrogen in soils has been investigated using a range of soils containing from 0·03 to 2·7% nitrogen.
2. The same result was obtained when soil was analysed by a variety of Kjeldahl procedures which included methods known to recover various forms of nitrogen not determined by Kjeldahl procedures commonly employed for soil analysis. From this and other evidence presented it is concluded that very little, if any, of the nitrogen in the soils examined was in the form of highly refractory nitrogen compounds or of compounds containing N—N or N—O linkages.
3. Results by the method of determining nitrogen in soils recommended by the Association of Official Agricultural Chemists were 10–37% lower than those obtained by other methods tested. Satisfactory results were obtained by this method when the period of digestion recommended was increased.
4. Ammonium-N fixed by clay minerals is determined by the Kjeldahl method.
5. Selenium and mercury are considerably more effective than copper for catalysis of Kjeldahl digestion of soil. Conditions leading to loss of nitrogen using selenium are defined, and difficulties encountered using mercury are discussed.
6. The most important factor in Kjeldahl analysis is the temperature of digestion with sulphuric acid, which is controlled largely by the amount of potassium (or sodium) sulphate used for digestion.
7. The period of digestion required for Kjeldahl analysis of soil depends on the concentration of potassium sulphate in the digest. When the concentration is low (e.g. 0·3 g./ml. sulphuric acid) it is necessary to digest for several hours; when it is high (e.g. 1·0 g./ml. sulphuric acid) short periods of digestion are adequate. Catalysts greatly affect the rate of digestion when the salt concentration is low, but have little effect when the salt concentration is high.
8. Nitrogen is lost during Kjeldahl analysis when the temperature of digestion exceeds about 400° C.
9. Determinations of the amounts of sulphuric acid consumed by various mineral and organic soils during Kjeldahl digestion showed that there is little risk of loss of nitrogen under the conditions usually employed for Kjeldahl digestion of soil. Acid consumption values for various soil constituents are given, from which the amounts of sulphuric acid likely to be consumed during Kjeldahl digestion of different types of soil can be calculated.
10. Semi-micro Kjeldahl methods of determining soil nitrogen gave the same results as macro-Kjeldahl methods.
11. The use of the Hoskins apparatus for the determination of ammonium is described.
12. It is concluded that the Kjeldahl method is satisfactory for the determination of nitrogen in soils provided a few simple precautions are observed. The merits and defects of different Kjeldahl procedures are discussed.
The current study aimed to compare lindane degradation by pure and mixed cultures of Streptomyces sp. Cell-free extracts were assayed for potentiating dechlorinase activity and, based on these results, consortia of two
to six microorganisms were assayed for their growth on and degradation of lindane. Furthermore, the role of bacterial consortia
of lindane-degrading strains was examined in lindane decontamination soil assays. Four actinobacteria, previously isolated
from a pesticide-contaminated area, were selected because of their tolerance to lindane and their ability to use the pesticide
as sole carbon source. These strains as well as Streptomyces sp. M7 and Streptomyces coelicolor A3 were used to study specific dechlorinase activity (SDA) and lindane removal in mixed cultures. Pure cultures presented
SDA in the presence of 1.66mg L-1 lindane as carbon source. SDA was improved by certain mixed cultures until 12 times compared with pure cultures. Mixed cultures
with two, three, and four strains showed maximum lindane removal of 46% to 68%, whereas combinations of five and six strains
did not efficiently remove the pesticide from the culture medium. The Streptomyces sp. A2, A5, M7, and A11 consortium presented the lowest ratio between residual lindane concentration and SDA and could be
a promising tool for lindane biodegradation.
KeywordsLindane–Bioremediation–Actinobacteria–Microbial consortium
The aim of the present study was to select candidate plant species for phytoremediation of soils contaminated with hexachlorocyclohexane (HCH). For this purpose, an experiment was carried out under controlled conditions of germination and growth, with nine plant species of economic and/or agricultural interest, in a soil contaminated with a heterogeneous mixture (at eight different levels of contamination) of the main HCH isomers (alpha-, beta-, gamma- and delta-HCH). The results revealed differences in the plant responses to the control soil and the soils containing HCH. Germination was not as strongly affected as other parameters such as the rate of germination and seedling vigour. In general, all of the species displayed signs of stress in response to the presence of HCH, although to different degrees. Some of the species used in the experiment (Hordeum vulgare L., Brassica sp., Phaseoulus vulgaris L.) were capable of mitigating the negative effects of HCH, and displayed a certain degree of resistance, as their biomass production was not greatly affected by the contaminant. These (tolerant) plants therefore appear to be ideal for phytoremediation purposes.
A mixed bacterial culture consisted of Staphylococcus sp., Bacillus circulans-I and -II has been enriched from contaminated soil collected from the vicinity of an endosulfan processing industry. The degradation of endosulfan by mixed bacterial culture was studied in aerobic and facultative anaerobic conditions via batch experiments with an initial endosulfan concentration of 50mg/L. After 3 weeks of incubation, mixed bacterial culture was able to degrade 71.58+/-0.2% and 75.88+/-0.2% of endosulfan in aerobic and facultative anaerobic conditions, respectively. The addition of external carbon (dextrose) increased the endosulfan degradation in both the conditions. The optimal dextrose concentration and inoculum size was estimated as 1g/L and 75mg/L, respectively. The pH of the system has significant effect on endosulfan degradation. The degradation of alpha endosulfan was more compared to beta endosulfan in all the experiments. Endosulfan biodegradation in soil was evaluated by miniature and bench scale soil reactors. The soils used for the biodegradation experiments were identified as clayey soil (CL, lean clay with sand), red soil (GM, silty gravel with sand), sandy soil (SM, silty sand with gravel) and composted soil (PT, peat) as per ASTM (American society for testing and materials) standards. Endosulfan degradation efficiency in miniature soil reactors were in the order of sandy soil followed by red soil, composted soil and clayey soil in both aerobic and anaerobic conditions. In bench scale soil reactors, endosulfan degradation was observed more in the bottom layers. After 4 weeks, maximum endosulfan degradation efficiency of 95.48+/-0.17% was observed in red soil reactor where as in composted soil-I (moisture 38+/-1%) and composted soil-II (moisture 45+/-1%) it was 96.03+/-0.23% and 94.84+/-0.19%, respectively. The high moisture content in compost soil reactor-II increased the endosulfan concentration in the leachate. Known intermediate metabolites of endosulfan were absent in all the above degradation studies.
gamma-Hexachlorocyclohexane (gamma-HCH, also called gamma-BHC and lindane) is a halogenated organic insecticide that causes serious environmental problems. The aerobic degradation pathway of gamma-HCH was extensively revealed in bacterial strain Sphingobium japonicum (formerly Sphingomonas paucimobilis) UT26. gamma-HCH is transformed to 2,5-dichlorohydroquinone through sequential reactions catalyzed by LinA, LinB, and LinC, and then 2,5-dichlorohydroquinone is further metabolized by LinD, LinE, LinF, LinGH, and LinJ to succinyl-CoA and acetyl-CoA, which are metabolized in the citrate/tricarboxylic acid cycle. In addition to these catalytic enzymes, a putative ABC-type transporter system encoded by linKLMN is also essential for the gamma-HCH utilization in UT26. Preliminary examination of the complete genome sequence of UT26 clearly demonstrated that lin genes for the gamma-HCH utilization are dispersed on three large circular replicons with sizes of 3.5 Mb, 682 kb, and 191 kb. Nearly identical lin genes were also found in other HCH-degrading bacterial strains, and it has been suggested that the distribution of lin genes is mainly mediated by insertion sequence IS6100 and plasmids. Recently, it was revealed that two dehalogenases, LinA and LinB, have variants with small number of amino acid differences, and they showed dramatic functional differences for the degradation of HCH isomers, indicating these enzymes are still evolving at high speed.
Lindane (persistent organic pollutant) in the EU. Directorate General for Internal Policies. Policy Department C: Citizens’ Rights and Constitutional Affairs. Petitions (PETI)
- M Vega
- D Romano
- E Uotila
Lindane (persistent organic pollutant) in the EU. Directorate general for internal policies
- M Vega
- D Romano
- E Uotila
Vega, M., Romano, D., Uotila, E., 2016. Lindane (persistent organic pollutant) in the
EU. Directorate general for internal policies. In: Policy Department C: Citizens'
Rights and Constitutional Affairs. Petitions (PETI). PE, p. 571.