Use In Bioremediation Processes Research Articles

Bioprospecting the potential of the microbial community associated to Antarctic marine sediments for hydrocarbon bioremediation.

Microorganisms that inhabit the cold Antarctic environment can produce ligninolytic enzymes potentially useful in bioremediation. Our study focused on characterizing Antarctic bacteria and fungi from marine sediment samples of King George and Deception Islands, maritime Antarctica, potentially affected by hydrocarbon influence, able to produce enzymes for use in bioremediation processes in environments impacted with petroleum derivatives. A total of 168 microorganism isolates were obtained: 56 from sediments of King George Island and 112 from Deception Island. Among them, five bacterial isolates were tolerant to cell growth in the presence of diesel oil and gasoline and seven fungal were able to discolor RBBR dye. In addition, 16 isolates (15 bacterial and one fungal) displayed enzymatic emulsifying activities. Two isolates were characterized taxonomically by showing better biotechnological results. Psychrobacter sp. BAD17 and Cladosporium sp. FAR18 showed pyrene tolerance (cell growth of 0.03gmL-1 and 0.2gmL-1) and laccase enzymatic activity (0.006 UL-1 and 0.10 UL-1), respectively. Our results indicate that bacteria and fungi living in sediments under potential effect of hydrocarbon pollution may represent a promising alternative to bioremediate cold environments contaminated with polluting compounds derived from petroleum such as polycyclic aromatic hydrocarbons and dyes.

First Isolation and Characterization of Bacteria from the Core's Cooling Pool of an Operating Nuclear Reactor.

Microbial life can thrive in the most inhospitable places, such as nuclear facilities with high levels of ionizing radiation. Using direct meta-analyses, we have previously highlighted the presence of bacteria belonging to twenty-five different genera in the highly radioactive water of the cooling pool of an operating nuclear reactor core. In the present study, we further characterize this specific environment by isolating and identifying some of these microorganisms and assessing their radiotolerance and their ability to decontaminate uranium. This metal is one of the major radioactive contaminants of anthropogenic origin in the environment due to the nuclear and mining industries and agricultural practices. The microorganisms isolated when sampling was performed during the reactor operation consisted mainly of Actinobacteria and Firmicutes, whereas Proteobacteria were dominant when sampling was performed during the reactor shutdown. We investigated their tolerance to gamma radiation under different conditions. Most of the bacterial strains studied were able to survive 200 Gy irradiation. Some were even able to withstand 1 kGy, with four of them showing more than 10% survival at this dose. We also assessed their uranium uptake capacity. Seven strains were able to remove almost all the uranium from a 5 µM solution. Four strains displayed high efficiency in decontaminating a 50 µM uranium solution, demonstrating promising potential for use in bioremediation processes in environments contaminated by radionuclides.

Potential application of fungal biosorption and/or bioaccumulation for the bioremediation of wastewater contamination: A review

The environment pollution or contamination is a serious problem, a great deal of research is being undertaken to combat contaminants such as xenobiotic and recalcitrant compounds, particularly heavy metals, dyes,phenolic compounds and other recalcitrant pollutants produced by a wide range of industrial activities. These compounds have an adverse impact on the environment, particularly when generated by industrial processes and then disposed off without adequate treatment. Mycoremediation is defined as the use of fungi for bioremediation, especially degradation or retention of contaminants. Biosorption and bioaccumulation are two of the mechanisms by which fungi remove contaminants through mycelium. In many cases, these processes involve metabolization and even mineralization of these contaminants, corresponding to a biological contaminant removal system with great potential for use in bioremediation processes. The present review describes the unique characteristics of fungal mycelium that make it a biomaterial with potential applications in various fields of biotechnology, specifically evaluating its biosorption/bioaccumulation properties and potential application for the bioremediation of different water-borne contaminants. This review focus on the researches conducted on the bioremediation of inorganic and organic pollutants, the mechanisms involved in the process, and the main environmental factors affecting it. Moreover, kinetics and equilibrium modeling of the removal efficiency achieved via biosorption/bioaccumulation is analyzed in order to better understand these processes and overcome some of the technical barriers to their large-scale application in the mycoremediation of wastewater. Key words: Bioaccumulation, Biosorption, Fungi, Mycoremediation, Xenobiotics

Comparative Metagenomic Study of Rhizospheric and Bulk Mercury-Contaminated Soils in the Mining District of Almadén.

Soil contamination by heavy metals, particularly mercury (Hg), is a problem that can seriously affect the environment, animals, and human health. Hg has the capacity to biomagnify in the food chain. That fact can lead to pathologies, of those which affect the central nervous system being the most severe. It is convenient to know the biological environmental indicators that alert of the effects of Hg contamination as well as the biological mechanisms that can help in its remediation. To contribute to this knowledge, this study conducted comparative analysis by the use of Shotgun metagenomics of the microbial communities in rhizospheric soils and bulk soil of the mining region of Almadén (Ciudad Real, Spain), one of the most affected areas by Hg in the world The sequences obtained was analyzed with MetaPhlAn2 tool and SUPER-FOCUS. The most abundant taxa in the taxonomic analysis in bulk soil were those of Actinobateria and Alphaproteobacteria. On the contrary, in the rhizospheric soil microorganisms belonging to the phylum Proteobacteria were abundant, evidencing that roots have a selective effect on the rhizospheric communities. In order to analyze possible indicators of biological contamination, a functional potential analysis was performed. The results point to a co-selection of the mechanisms of resistance to Hg and the mechanisms of resistance to antibiotics or other toxic compounds in environments contaminated by Hg. Likewise, the finding of antibiotic resistance mechanisms typical of the human clinic, such as resistance to beta-lactams and glycopeptics (vancomycin), suggests that these environments can behave as reservoirs. The sequences involved in Hg resistance (operon mer and efflux pumps) have a similar abundance in both soil types. However, the response to abiotic stress (salinity, desiccation, and contaminants) is more prevalent in rhizospheric soil. Finally, sequences involved in nitrogen fixation and metabolism and plant growth promotion (PGP genes) were identified, with higher relative abundances in rhizospheric soils. These findings can be the starting point for the targeted search for microorganisms suitable for further use in bioremediation processes in Hg-contaminated environments.

Analysis of the surfactant properties of Eichhornia crassipes for application in the remediation of environments impacted by hydrophobic pollutants

The invasive aquatic plant Eichhornia crassipes may enable the generation of novel compounds with aggregate value for use in bioremediation processes. Thus, the surfactant properties of the plant extract were investigated. The critical micelle concentration (CMC) of the extract was 1.4 ± 0.1 g/L and the surface tension at this point was 25.84 ± 0.7 mN/m. The extract proved to be stable and non-toxic to the bioindicators evaluated. The emulsification index was higher than 65.00 ± 1.8% for motor oil. The chemical characterisation suggested that the structure of the extract was formed by an unsaturated fatty acid. The plant extract was capable of dispersing 100% of oil in seawater. The motor oil removal from sand with the plant extract at twice the CMC reached values around 68.04 ± 0.7% both in the kinetic assay and in the static assay using packed columns. The removal of heavy metals reached rates of around 40.00 ± 2.6%. The plant-derived surfactant clearly demonstrated viability regarding its use as a biotechnological additive for environmental remediation processes. • Surfactant properties of Eichhornia crassipes plant extract were investigated. • The plant biosurfactant proved to be stable and non-toxic to the bioindicators. • The biosurfactant emulsified 65% of motor oil and removed 40% of heavy metals. • The plant biosurfactant was characterized as an unsaturated fatty acid. • The plant biosurfactant dispersed 100% of oil and removed 67% of oil from sand.

Fipronil biodegradation and metabolization by Bacillus megaterium strain E1

AbstractBACKGROUNDFipronil is a broad‐spectrum insecticide that is used extensively due to its effective action in pest control. However, environmental studies have shown it has high toxicity towards non‐target organisms as well. In addition, the degradation of fipronil can generate even more toxic and reactive metabolites in the environment. In the present study, bioprospecting for bacteria with the potential to degrade fipronil was performed using fipronil as the sole source of nitrogen and main source of carbon. From samples of corn culture soil with a history of fipronil application, isolation was performed using the microcosm enrichment method.RESULTSBacteria were isolated using fipronil (0.6 g L−1) as the sole nitrogen source and main carbon source. After preliminary tests, isolate E1 was selected and, following sequencing of 16S rRNA, it was found that the isolate E1 was a bacterium of the Bacillaceae family, Bacillus megaterium species. Growth was evaluated by dry biomass and degradation quantified by gas chromatography–mass spectrometry (GC–MS). Strain E1 presented a 94% degradation of fipronil, as well as 91% and 96% degradation of its metabolites fipronil‐sulfide and fipronil‐sulfone, respectively, in 14 days, reducing its initial concentration from 0.6 g L−1 to 0.036 mg L−1.CONCLUSIONThe results showed that bioprospecting of the E1 strain, isolated from soil, showed efficiency in the biodegradation process of fipronil. This strain is a potential candidate for use in bioremediation processes in areas contaminated with fipronil and for use in further studies on the elucidation of the metabolic pathways of fipronil degradation. © 2021 Society of Chemical Industry (SCI).

Marine associated microbial consortium applied to RBBR textile dye detoxification and decolorization: Combined approach and metatranscriptomic analysis

The combination of different microorganisms and their metabolisms makes the use of microbial consortia in bioremediation processes a useful approach. In this sense, this study aimed at structuring and selecting a marine microbial consortium for Remazol Brilliant Blue R (RBBR) detoxification and decolorization. Experimental design was applied to improve the culture conditions, and metatranscriptomic analysis to understand the enzymatic pathways. A promising consortium composed of Mucor racemosus CBMAI 847, Marasmiellus sp. CBMAI 1062, Bacillus subtilis CBMAI 707, and Dietzia maris CBMAI 705 was selected. This consortium showed 52% of detoxification and 86% of decolorization in the validation assays after seven days of incubation in the presence of 500 ppm of RBBR. Reduction in RBBR color and toxicity were achieved by biosorption and microbial metabolisms. Metatranscriptomic data indicate that the consortium was able to decolorize and breakdown the RBBR molecule using a coordinated action of oxidases, oxygenases, and hydrolases. Epoxide hydrolases and glyoxalases expression could be associated with the decrease in toxicity. The efficiency of this marine microbial consortium suggests their use in bioremediation processes of textile effluents.

Chemotaxis of halophilic bacterium Halomonas anticariensis FP35 towards the environmental pollutants phenol and naphthalene

Chemotaxis can play an important role in bioremediation and substrate bioavailability. The bioremediation of hydrocarbons in saline environments can be carried out by technologies using halophilic bacteria. The aim of this study is to analyse chemotactic responses of the halophilic bacterium Halomonas anticariensis FP35T to environmental pollutants, as well as its catabolic potential for biotechnological use in bioremediation processes under saline conditions. Chemotaxis was detected and quantified using a modified Adler capillary assay. PCR amplification with degenerate primers for genes encoding ring-cleaving enzymes was used to characterize the catabolic versatility of FP35T. The results indicate that phenol (100–1,000 ppm) and naphthalene (100–500 ppm) are chemoattractants for H. anticariensis FP35T in a dose-dependent manner. These hydrocarbons were observed to act as chemoattractants for FP35T grown in a wide range of sea salt solutions (5–12.5% (w/v). However, the 7.5% (w/v) saline concentration was found to have the strongest chemotactic response. We also detected genes encoding ring-cleaving enzymes in the β-ketoadipate pathway for aromatic catabolism. These results suggest that H. anticariensis FP35T has the potential to catabolize aromatic compounds and to be used in bioremediation processes under saline conditions.

Characterization and properties of biosurfactants produced by a newly isolated strain Bacillus methylotrophicus DCS1 and their applications in enhancing solubility of hydrocarbon.

Six biosurfactant-producing bacteria were isolated from hydrocarbon contaminated soils in Sfax, Tunisia. Isolates were screened for biosurfactant production by different conventional methods including hemolytic activity, surface tension reduction, drop-collapsing and oil displacement tests. All these screening tests show that all the isolates behave differently. Among the isolated bacteria, DCS1 strain was selected for further studies based on its highest activities and it was identified as Bacillus methylotrophicus DCS1. This strain was found to be a potent producer of biosurfactant when cultivated in mineral-salts medium supplemented with diesel oil (2%, v/v) as a sole carbon source. Physicochemical properties and stability of biosurfactants synthesized by B. methylotrophicus DCS1 were investigated. The produced biosurfactants DCS1, from Landy medium, possess high surface activity that could lower the surface tension of water to a value of 31 from 72mNm(-1) and have a critical micelle concentration (CMC) of 100mgL(-1). Compared with SDS and Tween 80, biosurfactants showed excellent emulsification activities against different hydrocarbon substrates and high solubilization efficiency towards diesel oil. Biosurfactants DCS1 showed good stability in a wide range of temperature, pH and salinity. These results suggested that biosurfactants produced by B. methylotrophicus DCS1 could be an alternative to chemically synthesized surfactants for use in bioremediation processes to enhance the solubility of hydrophobic compounds.

Characterization and stability of biosurfactant produced byBacillus mojavensisA21 and its application in enhancing solubility of hydrocarbon

BACKGROUND The present work aimed to characterize the physicochemical properties of the biosurfactant produced by Bacillus mojavensis A21 and to evaluate its potential use in diesel recovery. RESULTS The strain B. mojavensis A21 was found to be a potent producer of biosurfactant. Compared with SDS and Tween 80, biosurfactant A21 showed high physicochemical properties in terms of the surface activities and high emulsification index. The biosurfactant A21 reduced surface tension to 30 mN m-1. Biosurfactant A21 was also demonstrated to be stable in a wide range of pH, temperature and salinity. Moreover, it was found that it can solubilize diesel more effectively than SDS and Tween 80. It can be considered as an alternative to chemically synthesized surfactants since it shows high solubilization efficiency towards diesel oil (62% at 0.5 g L-1) in comparison with SDS and Tween 80. CONCLUSION Biosurfactant A21, owing its high emulsification capacity and its high tolerance to acidic and alkaline pH values and salinity, shows great potential for use in bioremediation processes to enhance the solubility of hydrophobic compounds. © 2013 Society of Chemical Industry

Characterization of a phenol-degrading bacterium isolated from an industrial effluent and its potential application for bioremediation

The use of native microorganisms is a useful strategy for phenol bioremediation. In the present work, a bacterial strain, named RTE1.4, was isolated from effluents of a chemical industry. The strain was able to grow at high concentrations of phenol and its derivatives, such as guaiacol, 2,4-dichlorophenol and pentachlorophenol, as well as in a medium containing industrial effluents. This bacterium was identified as Acinetobacter sp. using morphological, physiological, biochemical and 16S rRNA gene analysis. Acinetobacter sp. RTE1.4 degraded phenol (200 to 600 mg/L) at wide pH range and temperature (5–9 and 25–37°C, respectively) demonstrating high adaptation ability to different conditions. The strain would metabolize phenol by the ortho-pathway since catechol 1,2-dioxygenase activity was detected. When bacteria were grown in medium containing phenol, an altered whole-cell protein pattern was observed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), with the lack of some low-molecular mass polypeptides and an increase in the relative abundance of high-molecular mass proteins after treatment. Considering that the use of native strains in bioremediation studies shows several ecological advantages and that the studied bacterium showed high tolerance and biodegradation capabilities, Acinetobacter sp. RTE1.4 could be an appropriate microorganism for improving bioremediation and biotreatment of areas polluted with phenol and/or some of its derivatives. Moreover, the establishment of the optimal growth conditions (pH, temperature, concentration of the pollutant) would provide baseline data for bulk production of the strain and its use in bioremediation processes.

Bacterial strains resistant to inorganic and organic forms of mercury isolated from polluted sediments of the Orbetello Lagoon, Italy, and their possible use in bioremediation processes

Bacteria are able to adapt to heavy metals in contaminated environments, by developing specific mechanisms of resistance. A mercury (Hg)-resistant bacterial community was isolated from polluted sediments of the Orbetello Lagoon, Italy. The members of the Hg-resistant bacterial community showed high levels of resistance both to the inorganic and to the organic forms of Hg. 16S rRNA gene sequencing showed the presence of different genera, and a bacterial strain resistant to Hg belonging to the genus Luteimonas was evidenced for the first time. The merA gene coding for mercury-reductase conferring resistance to inorganic Hg, and the merB gene coding for mercury-lyase enzymes, for resistance to the organic forms of Hg, were detected in the tested bacterial strains. The community showed the presence of bacteria belonging to the genera Pseudomonas and Psychrobacter that highlighted the capability to reduce Hg2+ to the volatile form of Hg0 . Experiments carried out with immobilized cells of the Hg-resistant strains removed 96% of Hg in sediments leachates in a bioremediation laboratory scale pilot plant. A methylating activity of the sulphate-reducing bacteria of the same polluted sediments was moreover evidenced. These results evidenced the presence of microbial communities highly adapted to the presence of Hg into the sediments of the lagoon. The use of the isolated autochthonous bacterial strains for bioremediation of the native sediments contaminated by Hg is suggested.

Characterisation, surface properties and biological activity of a biosurfactant produced from industrial waste by Candida sphaerica UCP0995 for application in the petroleum industry

The development of less toxic, biodegradable, surfactants, such as biosurfactants, is a key strategy for acquiring environmentally friendly compounds. The aim of the present study was to employ an optimised medium containing 9% ground nut oil refinery residue and 9% corn steep liquor for the production of a biosurfactant by Candida sphaerica. Fermentation was carried out at 28°C and 200rpm for 144h. Biosurfactant yield was 9g/l. The biosurfactant reduced the surface tension of the medium to 25mN/m, with a critical micelle concentration of 0.025%. The product demonstrated stability with regard to surface tension reduction and emulsification in a range of temperatures (5–120°C) and pH values (2–12) as well as tolerance to high concentrations of NaCl (2–10%). Hydrophobicity tests indicate two possible insoluble substrate uptake mechanisms: direct interfacial uptake and biosurfactant-mediated transfer (cell contact with emulsified or solubilised hydrocarbons). The biosurfactant was characterised as an anionic glycolipid consisting of 70% lipids and 15% carbohydrates and demonstrated no toxicity to the microcrustacean Artemia salina or the vegetables Brassica oleracea, Solanum gilo, Lactuca sativa L. and Brassica oleracea L. The biosurfactant recovered 95% of motor oil adsorbed to a sand sample, demonstrating considerable potential for use in bioremediation processes, especially in the petroleum industry.

Economic production of Bacillus subtilis SPB1 biosurfactant using local agro‐industrial wastes and its application in enhancing solubility of diesel

AbstractBACKGROUND: The present work aimed to optimize a new economic medium for lipopeptide biosurfactant production by Bacillus subtilis SPB1 for application in the environmental field as an enhancer of diesel solubility. Statistical experimental designs and response surface methodology were employed to optimize the medium components.RESULTS: A central composite design was applied to increase the production yield and predict the optimal values of the selected factors. An optimal medium, for biosurfactant production of about 4.5 g L−1, was found to be composed of sesame peel flour (33 g L−1) and diluted tuna fish cooking residue (40%) with an inoculum size of 0.22. Increased inoculum size (final OD600) significantly improved the production yield. The emulsifier produced was demonstrated to be an alternative to chemically synthesized surfactants since it shows high solubilization efficiency towards diesel oil in comparison with SDS and Tween 80.CONCLUSION: Optimization studies led to a strong improvement in production yield. The emulsifier produced, owing its high solubilization capacity and its large tolerance to acidic and alkaline pH values and salinity, shows great potential for use in bioremediation processes to enhance the solubility of hydrophobic compounds. © 2012 Society of Chemical Industry

Economic Optimized Medium for Tensio-Active Agent Production by Candida sphaerica UCP0995 and Application in the Removal of Hydrophobic Contaminant from Sand

Statistical experimental designs and response surface methodology were employed to optimize the concentrations of agroindustrial residues as soybean oil (SORR) from refinery, and corn steep liquor (CSL) from corn industry, for tensio-active agent produced by Candida sphaerica UCP 0995. Three 22 full factorial design were applied sequentially to investigate the effects of the concentrations and interactions of soybean oil refinery residue and corn steep liquor on the surface tension of free-cell culture broth for 144 h. Two 22 central composite designs and response surface methodology were adopted to derive a statistical model to measure the effect of SORR and CSL on the surface tension of the free-cell culture broth for 144 h. The regression equation obtained from the experimental data using a central composite design was solved, and by analyzing the response surface contour plots, the optimal concentrations of the constituents of the medium were determined: 8.63% v/v (≅9% v/v) of SORR and 8.80% v/v (≅9% v/v) CSL. The minimum surface tension predicted and experimentally confirmed was 25.25 mN/m. The new biosurfactant, denominated Lunasan, recovered 95% of motor oil adsorbed in a sand sample, thus showing great potential for use in bioremediation processes, especially in the petroleum industry.

Cr(VI)-reduction by an halophilic bacterial strain Halomonas sp. VO-04 isolated from contaminated sediments and its use in bioremediation processes

Cr(VI)-reduction by an halophilic bacterial strain Halomonas sp. VO-04 isolated from contaminated sediments and its use in bioremediation processes

Mercury-resistant bacterial strains Pseudomonas and Psychrobacter spp. isolated from sediments of Orbetello Lagoon (Italy) and their possible use in bioremediation processes

This study was aimed to isolate Hg-resistant bacteria from contaminated sediments of the Orbetello Lagoon in Italy and to assess their possible use as biofilms in bioremediation processes. Enrichment cultures prepared from contaminated sediments in the presence of 0.05mM of mercury and under aerobic conditions allowed the isolation of five heterotrophic bacterial strains. 16S rDNA gene sequencing assigned the isolated strains to the genera Pseudomonas and Psychrobacter. For the first time mercury-resistant bacterial strains belonging to the genus Psychrobacter were evidenced. Minimum inhibitory concentrations in the presence of HgCl2 and of CH3HgCl showed high levels of resistance. EC50 values for the isolated bacterial strains in the presence of HgCl2 and of CH3HgCl confirmed the adaptation to the metal. Hg-resistant strains ORHg1, ORHg4 and ORHg5 showed the capacity to volatilize inorganic and organic mercury to elemental mercury, and formed biofilms on pumice particles, and were shown to play a role in the removal of mercury from sediment leachates. This study reports isolation and characterization of new Hg-resistant bacterial strains and provides novel insight into their possible use in bioremediation processes of mercury polluted sediments.

Estudio piloto de aislamiento y fenotipificación de bacterias que participan en los procesos de biolixiviación, en las zonas mineras del Departamento de Boyacá

Una alternativa para disminuir la contaminación ambiental generada por el empleo de sustancias químicas cuando se extraen metales pesados en la industria minera, así como los costos en materiales químicos es utilizar en este proceso microorganismos que han demostrado realizar esta actividad, denominados biolixiviadores. Para ello es necesario identificar y fenotipificar estos microorganismos. El objetivo de este proyecto fue aislar y fenotipificar microorganismos biolixiviadores obtenidos de cuatro minas de esmeraldas del departamento de Boyacá (Muzo, Coscuez, Chivor y Consorcio). El muestreo se realizó en agua y roca, hábitat principal de las bacterias que participan en los procesos de biolixiviación. El aislamiento se realizó previa preparación de cada una de las muestras, las cuales se sembraron en el medio de cultivo 9K, líquido y sólido, e incubaron por siete días a 37°C. Se evidenciaron cambios físicos en la intensidad de color y en el aspecto en los medios de cultivo, lo que permite presumir que ha ocurrido alguna acción de las bacterias lixiviantes sobre los compuestos del medio. La observación microscópica evidenció la presencia de bacilos gram negativos y cristales.Por otra parte, se confirmó la característica de ser bacterias acidófilas ya que su desarrollo se obtuvo a pH entre 1 y 2,5. Los resultados obtenidos en este estudio permitieron concluir que en estas minas hay presencia de organismos bacterianos con morfología y comportamiento bioquímico compatible con bacterias biolixiviantes del género Thiobacillus. El aislamiento y fenotipificación obtenidos in vitro abre la posibilidad de establecer un método óptimo para su conservación y posterior utilización en procesos de bioremediación.

Biodegradation of the herbicide trifluralin by bacteria isolated from soil

Trifluralin (α,α,α-trifluoro-2,6-dinitro- N, N-dipropyl- p-toluidine; TFL) is a pre-emergence, soil-incorporated herbicide that has been in agricultural use since the early 1960s and is moderately persistent in soil. The purpose of this study was to isolate and characterise TFL-resistant bacteria from a soil in which this pesticide has been used for the last four decades and to determine their ability to degrade TFL using HPLC. Eight bacteria were isolated by repeated subculture in liquid medium with TFL as carbon source and a ninth (isolate 9) from growth around TFL crystals on solid medium. The bacteria from enriched liquid culture were identified by biochemical tests and 16S rDNA sequencing. In a mineral salts medium with 0.1% succinate, 0.1% yeast extract and 50 mg l −1 TFL, reductions in the level of pesticide of 24.6% for Klebsiella sp., 16.4% for Herbaspirillum sp., 25.0% and 16.0% for two strains of Bacillus sp. and 21.0% for unidentified isolate number 9 were obtained after 30 days. These were similar to the level obtained using a known TFL-degrading bacterium, Brevundimonas diminuta (NCIMB 10329). Three Pseudomonas sp. and one Bacillus sp. reduced levels by less than 5%. The five positive isolates can be used to study the biochemical and molecular biology of TFL biodegradation with the aim of optimising the degradative ability of one or more of the isolates for future use in bioremediation processes.

Biodegradation of the herbicide trifluralin by bacteria isolated from soil

Trifluralin (alpha,alpha,alpha-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine; TFL) is a pre-emergence, soil-incorporated herbicide that has been in agricultural use since the early 1960s and is moderately persistent in soil. The purpose of this study was to isolate and characterise TFL-resistant bacteria from a soil in which this pesticide has been used for the last four decades and to determine their ability to degrade TFL using HPLC. Eight bacteria were isolated by repeated subculture in liquid medium with TFL as carbon source and a ninth (isolate 9) from growth around TFL crystals on solid medium. The bacteria from enriched liquid culture were identified by biochemical tests and 16S rDNA sequencing. In a mineral salts medium with 0.1% succinate, 0.1% yeast extract and 50 mg l(-1) TFL, reductions in the level of pesticide of 24.6% for Klebsiella sp., 16.4% for Herbaspirillum sp., 25.0% and 16.0% for two strains of Bacillus sp. and 21.0% for unidentified isolate number 9 were obtained after 30 days. These were similar to the level obtained using a known TFL-degrading bacterium, Brevundimonas diminuta (NCIMB 10329). Three Pseudomonas sp. and one Bacillus sp. reduced levels by less than 5%. The five positive isolates can be used to study the biochemical and molecular biology of TFL biodegradation with the aim of optimising the degradative ability of one or more of the isolates for future use in bioremediation processes.