Biotransformation of chlorpyrifos and bioremediation of contaminated soil

Five aerobic consortia capable of degrading chlorpyrifos as a sole carbon source in aqueous medium showed degradation in the range of 46–72% after 20 days. Pseudomonas fluorescence, Brucella melitensis, Bacillus subtilis, Bacillus cereus, Klebsiella species, Serratia marcescens and Pseudomonas aeroginosa, isolated from these consortium, showed 75–87% degradation of chlorpyrifos as compared to 18% in control after 20 days of incubation. Bioremediation of chlorpyrifos-contaminated soil with P. fluorescence, B. melitensis, B. subtilis and P. aeroginosa individually showed 89%, 87%, 85% and 92% degradation, respectively, as compared to 34% in control after 30 days. Population dynamics of the introduced isolates based on antibiotic resistance survival and REP-PCR indicated 60–70% survival based on antibiotic resistance, but only 35–45% of the inoculated population based on REP-PCR. During bioremediation studies, 3,5,6-trichloro-2-pyridinol (TCP) was detected as metabolite of chlorpyrifos degradation by P. aeroginosa after 20 days, which was utilized and disappeared after 30 days. Whole-cell studies also showed that P. aeroginosa gave TCP as the product of chlorpyrifos degradation, which was further metabolized to unknown polar metabolites.

Scientific relevance

Potential application in sites for effective in situ bioremediation of chlorpyrifos, a neurotoxic insecticide widely used in India.     

Biodegradation of chlorpyrifos and its hydrolyzing metabolite 3,5,6-trichloro-2-pyridinol by Sphingobacterium sp. JAS3

Biodegradation of chlorpyrifos and its metabolite 3,5,6-trichloro-2-pyridinol (TCP) were studied in aqueous medium and in soil with a novel bacterial strain JAS3. The molecular characterization based on 16S rRNA sequence analysis revealed the strain JAS3 as Sphingobacterium sp. The strain JAS3 was able to grow in minimal salt medium (MSM) supplemented with 300 mg l^?1 of chlorpyrifos as sole carbon source. The degradation of chlorpyrifos and its primary metabolite TCP were examined by HPLC. After 5 d, Sphingobacterium sp. JAS3 degraded chlorpyrifos and its metabolite TCP to benzene, 1,3-bis(1,1-dimethylethyl) was analyzed by GCMS. Degradation of chlorpyrifos and TCP in soil with and without addition of nutrients was also studied. The ability to degrade chlorpyrifos makes this strain a useful candidate for remediation of pesticide contaminated sites.     

Biodegradation and bioremediation of pesticide in soil: concept,method and recent developments

Biodegradation is a natural process, where the degradation of a xenobiotic chemical or pesticide by an organism is primarily a strategy for their own survival. Most of these microbes work in natural environment but some modifications can be brought about to encourage the organisms to degrade the pesticide at a faster rate in a limited time frame. This capability of microbe is some times utilized as technology for removal of contaminant from actual site. Knowledge of physiology, biochemistry and genetics of the desired microbe may further enhance the microbial process to achieve bioremediation with precision and with limited or no scope for uncertainty and variability in microbe functioning. Gene encoding for enzyme has been identified for several pesticides, which will provide a new inputs in understanding the microbial capability to degrade a pesticide and develop a super strain to achieve the desired result of bioremediation in a short time.     

Microbial community structure changes during bioremediation of PAHs in an aged coal-tar contaminated soil by in-vessel composting

The microbial community structure changes of an aged-coal-tar soil contaminated with polycyclic aromatic hydrocarbons (PAHs) were investigated during simulated bioremediation at the laboratory-scale using an in-vessel composting approach. The composting reactors were operated using a logistic three-factor factorial design with three temperatures (T=38, 55 or 70 °C), four soil to green-waste amendment ratios (S:GW=0.6:1, 0.7:1, 0.8:1 or 0.9:1 on a dry weight basis) and three moisture contents (MC=40%, 60% or 80%). Relative changes in microbial populations were investigated by following the dynamics of phospholipid fatty acid (PLFA) signatures using a ¹³C-labeled palmitic acid internal standard and sensitive GC/MS analysis during in-vessel composting over 98 days. The results of this investigation indicated that fungal to bacterial PLFA ratios were significantly influenced by temperature (p<0.05), and Gram-positive to Gram-negative bacterial ratios were significantly influenced by temperature (p<0.001) and S:GW ratio (p<0.01) during in-vessel composting. Additionally, the Gram-positive to Gram-negative bacterial ratios were correlated to the extent of PAH losses (p<0.005) at 70 °C.     

Biodegradation of cyanide by Trichoderma spp. and Fusarium spp.

The rate of degradation of cyanide by certain strains of the Trichoderma spp. was evaluated. For comparison two Fusarium spp., which had previously been demonstrated to degrade metallocyanides were also studied. Studies were carried out to assess the rate of degradation using cyanide as the sole source of carbon or in the presence of glucose. Biodegradation was observed in flask cultures using cyanide as the sole carbon source. Strong evidence of cyanide biodegradation and co-metabolism emerged from studies with flask cultures where glucose was provided as a co-substrate. The rate of degradation of 2000 ppm CN⁻ was enhanced almost three times in the presence of glucose. A concomitant increase in fungal biomass was also observed in all the strains over the experimental period. Growth yield calculations performed provided values that were comparable to those reported in literature for one-carbon substrates.     

Biodegradation of chlorpyrifos by enterobacter strain B-14 and its use in bioremediation of contaminated soils

Six chlorpyrifos-degrading bacteria were isolated from an Australian soil and compared by biochemical and molecular methods. The isolates were indistinguishable, and one (strain B-14) was selected for further analysis. This strain showed greatest similarity to members of the order Enterobacteriales and was closest to members of the Enterobacter asburiae group. The ability of the strain to mineralize chlorpyrifos was investigated under different culture conditions, and the strain utilized chlorpyrifos as the sole source of carbon and phosphorus. Studies with ring or uniformly labeled [(14)C]chlorpyrifos in liquid culture demonstrated that the isolate hydrolyzed chlorpyrifos to diethylthiophospshate (DETP) and 3, 5, 6-trichloro-2-pyridinol, and utilized DETP for growth and energy. The isolate was found to possess mono- and diphosphatase activities along with a phosphotriesterase activity. Addition of other sources of carbon (glucose and succinate) resulted in slowing down of the initial rate of degradation of chlorpyrifos. The isolate degraded the DETP-containing organophosphates parathion, diazinon, coumaphos, and isazofos when provided as the sole source of carbon and phosphorus, but not fenamiphos, fonofos, ethoprop, and cadusafos, which have different side chains. Studies of the molecular basis of degradation suggested that the degrading ability could be polygenic and chromosome based. Further studies revealed that the strain possessed a novel phosphotriesterase enzyme system, as the gene coding for this enzyme had a different sequence from the widely studied organophosphate-degrading gene (opd). The addition of strain B-14 (10(6) cells g(-1)) to soil with a low indigenous population of chlorpyrifos-degrading bacteria treated with 35 mg of chlorpyrifos kg(-1) resulted in a higher degradation rate than was observed in noninoculated soils. These results highlight the potential of this bacterium to be used in the cleanup of contaminated pesticide waste in the environment.     

Exophiala macquariensis sp. nov., a cold adapted black yeast species recovered from a hydrocarbon contaminated sub-Antarctic soil

A new black yeast species, Exophiala macquariensis is described that is a member of the ascomycete family Herpotrichiellaceae, order Chaetothyriales. The genus Exophiala is comprised of opportunistic pathogens isolated from clinical specimens as well as species recovered from hydrocarbon contaminated environments. Several species have been reported to be able to degrade benzene, toluene, ethylbenzene and xylenes. Here, a novel species of Exophiala (CZ06) previously isolated from a Sub-Antarctic, Macquarie Island soil that was spiked with Special Antarctic Blend diesel fuel (SAB) is described. This isolate has the capacity of toluene biodegradation at cold temperatures. Multilocus sequence typing showed that this fungus was closely related to the pathogenic species Exophiala salmonis and Exophiala equina. With the capacity to utilise hydrocarbons as a sole carbon source at 10 °C, this fungus has great potential for future bioremediation applications.     

Biodegradaon of phenanthrene in soil microcosms stimulated by an introduced Alcaligenes sp.

Abstract A phenanthrene degrading strain of Alcaligenes sp. was isolated from oil polluted soil. Addition of Alcaligenes sp. to soil microcosms supplemented with phenanthrene (1 mg/g dry soil) resulted in degradation of the added phenanthrene within 11 days. The phenanthrene concentration declined only 12% in uninoculated soil during 42 days. The total phenanthrene degradation potential of Alcaligenes sp. was 2.3 mg/g dry soil during a period of 22 days. The amount of CO₂ evolved during 22 days corresponded to the conversion of 91% of the degraded phenanthrene to CO₂. The Alcaligenes sp. were not able to degrade phenanthrene in sterile soil.     

Simultaneous degradation of the pesticides methyl parathion and chlorpyrifos by an isolated bacterial consortium from a contaminated site

The simultaneous degradation of the pesticide methyl parathion and chlorpyrifos was tested using a bacterial consortium obtained by selective enrichment from highly contaminated soils in Moravia (Medellin, Colombia). Microorganisms identified in the consortium were Acinetobacter sp, Pseudomonas putida, Bacillus sp, Pseudomonas aeruginosa, Citrobacter freundii, Stenotrophomonas sp, Flavobacterium sp, Proteus vulgaris, Pseudomonas sp, Acinetobacter sp, Klebsiella sp and Proteus sp. In culture medium enriched with each of the pesticides, the consortium was able to degrade 150 mg l⁻¹ of methyl parathion and chlorpyrifos in 120 h. When a mixture of 150 mg l⁻¹ of both pesticides was used the percentage decreased to 72% for methyl parathion and 39% for chlorpyrifos. With the addition of glucose to the culture medium, the consortium simultaneously degraded 150 mg l⁻¹ of the pesticides in the mixture. 4 treatments were carried out in soil that included the addition of glucose with microorganisms, the addition of sugar cane with microorganisms, microorganisms without nutrient addition and without the addition of any item. In the treatment in which glucose was used, degradation percentages of methyl parathion and chlorpyrifos of 98% and 97% respectively were obtained in 120 h. This treatment also achieved the highest percentage of reduction in toxicity, monitored with Vibrio fischeri.     

Pseudomonas sp. to Sphingobium indicum: a journey of microbial degradation and bioremediation of Hexachlorocyclohexane

The unusual process of production of hexachlorocyclohexane (HCH) and extensive use of technical HCH and lindane has created a very serious problem of HCH contamination. While the use of technical HCH and lindane has been banned all over the world, India still continues producing lindane. Bacteria, especially Sphingomonads have been isolated that can degrade HCH isomers. Among all the bacterial strains isolated so far, Sphingobium indicum B90A that was isolated from HCH treated rhizosphere soil appears to have a better potential for HCH degradation. This conclusion is based on studies on the organization of lin genes and degradation ability of B90A. This strain perhaps can be used for HCH decontamination through bioaugmentation.     

Enantioselective degradation of the herbicide mecoprop [2-(2-methyl-4-chlorophenoxy) propionic acid] by mixed and pure bacterial cultures

Abstract A consortium of three bacteria was isolated from top soil through their capacity to utilise the chlorinated, aromatic herbicide mecoprop as a single growth substrate. The consortium constituted a tight association of Alcaligenes denitrificans, Pseudomonas glycinea and Pseudomonas marginalis . The culture exclusively degraded the ( R )-(+)-isomer of the herbicide while the ( S )-(−)-enantiomer remained unaffected. The mecoprop-degrading community could also degrade 2,4-dichlorophenoxyacetic acid, 2-methyl-4-chlorophenoxyacetic acid and racemic 2-phenoxypropionic acid. Initially, no single member of the consortium was able to degrade mecoprop as a pure culture but after prolonged incubation, A. denitrificans was able to grow on the herbicide as the sole source of carbon and energy.     

Dual augmentation for aerobic bioremediation of MTBE and TCE pollution in heavy metal-contaminated soil

In this work we isolated from soil and characterized several bacterial strains capable of either resisting high concentrations of heavy metals (Cd²⁺ or Hg²⁺ or Pb²⁺) or degrading the common soil and groundwater pollutants MTBE (methyl-tert-butyl ether) or TCE (trichloroethylene). We then used soil microcosms exposed to MTBE (50 mg/l) or TCE (50 mg/l) in the presence of one heavy metal (Cd 10 ppm or Hg 5 ppm or Pb 50 or 100 ppm) and two bacterial isolates at a time, a degrader plus a metal-resistant strain. Some of these two-membered consortia showed degradation efficiencies well higher (49–182% higher) than those expected under the conditions employed, demonstrating the occurrence of a synergetic relationship between the strains used. Our results show the efficacy of the dual augmentation strategy for MTBE and TCE bioremediation in the presence of heavy metals.     

Utilization of monocyclic aromatic hydrocarbons individually and in mixture by bacteria isolated from petroleum-contaminated soil

The fate of benzene, ethylbenzene, toluene, xylenes (BTEX) compounds through biodegradation was investigated using two different bacteria, Ralstonia picketti (BP-20) and Alcaligenes piechaudii (CZOR L-1B). These bacteria were isolated from extremely polluted soils contaminated with petroleum hydrocarbons. PCR and Fatty Acid Methyl Ester (FAME) were used to identify the isolates. In this study, BTEX biodegradation, applied as a mixture or as individual compounds by the bacteria was evaluated. Both bacteria were shown to degrade each of the BTEX compounds individually and in mixture. However, Alcaligenes piechaudii was a better degrader of BTEXs both in the mixture and individually. Differences between BTEX biodegradation in the mixture and individually were observed, especially in the case of benzene. The degradation of all BTEXs in the mixture was lower than the degradation of individual compounds for both bacteria tested. In the all experiments, toluene and m + p- xylenes were better removed than the other BTEXs. No intermediates of biodegradation were detected. Biosurfactant production was observed by culture techniques. In addition, 3-hydroxy fatty acids, important in biosurfactant production, were observed by FAME analysis. The test results indicate that the bacteria could contribute to bioremediation of aromatic hydrocarbon pollution.     

Enhancement of the microbial community biomass and diversity during air sparging bioremediation of a soil highly contaminated with kerosene and BTEX

In order to obtain insights in complexity shifts taking place in natural microbial communities under strong selective pressure, soils from a former air force base in the Czech Republic, highly contaminated with jet fuel and at different stages of a bioremediation air sparging treatment, were analyzed. By tracking phospholipid fatty acids and 16S rRNA genes, a detailed monitoring of the changes in quantities and composition of the microbial communities developed at different stages of the bioventing treatment progress was performed. Depending on the length of the air sparging treatment that led to a significant reduction in the contamination level, we observed a clear shift in the soil microbial community being dominated by Pseudomonads under the harsh conditions of high aromatic contamination to a status of low aromatic concentrations, increased biomass content, and a complex composition with diverse bacterial taxonomical branches. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. The online version of an erratum to this article can be found at http://dx.doi.org/. An erratum to this article can be found at     

Biodegradation potential of oily sludge by pure and mixed bacterial cultures

The biodegradation capacity of aliphatic and aromatic hydrocarbons of petrochemical oily sludge in liquid medium by a bacterial consortium and five pure bacterial cultures was analyzed. Three bacteria isolated from petrochemical oily sludge, identified as Stenotrophomonas acidaminiphila, Bacillus megaterium and Bacillus cibi, and two bacteria isolated from a soil contaminated by petrochemical waste, identified as Pseudomonas aeruginosa and Bacillus cereus demonstrated efficiency in oily sludge degradation when cultivated during 40 days. The bacterial consortium demonstrated an excellent oily sludge degradation capacity, reducing 90.7% of the aliphatic fraction and 51.8% of the aromatic fraction, as well as biosurfactant production capacity, achieving 39.4% reduction of surface tension of the culture medium and an emulsifying activity of 55.1%. The results indicated that the bacterial consortium has potential to be applied in bioremediation of petrochemical oily sludge contaminated environments, favoring the reduction of environmental passives and increasing industrial productivity.     

Biodegradation of diazinon by Serratia marcescens DI101 and its use in bioremediation of contaminated environment

Four diazinon-degrading bacteria were isolated from agricultural soil by using an enrichment technique. The biochemical analysis and molecular method including RFLP indicated that these isolates were identical, and one strain designated DI101 was selected for further study. Phylogenetic analysis based on 16S rDNA sequencing indicated that the strain DI101 clearly belongs to the Serratia marcescens group. The ability of the strain to utilize diazinon as a source of carbon and phosphorus was investigated under different culture conditions. The DI101 strain was able to completely degrade 50 mg/l diazinon in MSM within 11 days with a degradation rate of 0.226 day-1. The inoculation of sterilized soil treated with 100 mg/kg of diazinon with 10(6) CFU/g DI101 resulted in a faster degradation rate than was recorded in non-sterilized soil. The diazinon degradation rate by DI101 was efficient at temperatures from 25 to 30degrees C and at pHs from 7.0 to 8.0. The degradation rate of diazinon was not affected by the absence of a phosphorus supplement, and addition of other carbon sources (glucose or succinate) resulted in the slowing down of the degradation rate. The maximum degradation rate (Vmax) of diazinon was 0.292 day-1 and its saturation constant (Ks) was 11 mg/l, as determined by a Michaelis-Menten curve. The strain was able to degrade diethylthiophosphate-containing organophosphates such as chlorpyrifos, coumaphos, parathion, and isazofos when provided as a source of carbon and phosphorus, but not ethoprophos, cadusafos, and fenamiphos. These results propose useful information for the potential application of the DI101 strain in bioremediation of pesticide-contaminated environments.