• Biotechnology and Bioprocess Engineering:BBE
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• v.11 no.6
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• pp.553-556
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• 2006

A cis-1,2-dichloroethylene (cis-DCE)-degrading anaerobic bacterium, Clostridium sp. strain KYT-1, was isolated from a sediment sample collected from a landfill site in Nanji-do, Seoul, Korea. The KYT-1 strain is a gram-positive, endospore-forming, motile, rod-shaped anaerobic bacterium, of approximately $2.5{\sim}3.0\;{\mu}m$ in length. The degradation of cis-DCE is closely related with the growth of the KYT-1 strain, and it was stopped when the growth of the KYT-1 strain became constant. Although the pathway of cis-DCE degradation by strain KYT-1 remains to be further elucidated, no accumulation of the harmful intermediate, vinyl chloride (VC), was observed during anaerobic cis-DCE degradation. Strain KYT-1 proved able to degrade a variety of volatile organic compounds, including VC, isomers of DCE (1,1-dichloroethylene, trans-1,2-dichloroethylene, and cis-DCE), trichloroethylene, tetrachloroethylene, 1,2-dichloroethane, 1,1,1-trichloroethane, and 1,1,2-trichloroethane. Strain KYT-1 degraded cis-DCE at a range of temperatures from $15\;to\;37^{\circ}C$, with an optimum at $30^{\circ}C$, and at a pH range of 5.5 to 8.5, with an optimum at 7.0.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.04a
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• pp.147-152
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• 2004

Aerobic cometabolism of cis-1,2-dichloroethylene (c-DCE) and c-DCE epoxide by a butane-grown mixed culture was evaluated. Transformation of c-DCE resulted in the concomitant generation of c-DCE epoxide. Chloride release studies showed nearly complete oxidative dechlorination of c-DCE (approximately 75%). Mass spectrometry confirmed tile presence of a compound with mass-to-charge-fragment ratios of 112, 83, 48, and 35. The values are in agreement with the spectra of a chemically synthesized c-DCE epoxide. Some evidences indicating the involvement of the monooxygenase in the transformation of c-DCE epoxide are: 1) $O_2$ requirement for c-DCE transformation and butane degradation; 2) butane inhibition on c-DCE transformation and vice versa; 3) the inactivation of c-DCE and c-DCE epoxide transformations by acetylene (a known monooxygenase inactivator); and 4) tire inhibition of c-DCE epoxide transformation by c-DCE.

• Journal of Microbiology and Biotechnology
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• v.13 no.3
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• pp.366-372
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• 2003

The production of microbiologically enriched cultures that degrade cis- 1,2-dichloroethylene(DCE) under anaerobic conditions was investigated. Among 80 environmental samples, 19 displayed significant degradation of $10{\mu}M$ cis-DCE during 1 month of anaerobic incubation, and one sediment sample collected at a landfill area (Nanji-do, Seoul, Korea) showed the greatest degradation ($94\%$). When this sediment culture was subcultured repeatedly, the ability to degrade cis-DCE gradually decreased. However, under Fe(III)-reducing conditions, cis-DCE degradation by the subculture was found to be maintained effectively. In the Fe(III)-reducing subculture, vinyl chloride (VC) was also degraded at the same extent as cis-DCE No accumulation of VC during the cis-DCE degradation was observed. Thus, Fe(III)-reducing microbes might be involved in the anaerobic degradation of the chlorinated ethenes. However, the subcultures established with Fe(III) could function even in the absence of Fe(III), showing that the degradation of cis-DCE and VC was not directly coupled with the Fe(III) reduction. Consequently, the two series of enrichment cultures could not be obtained that degrade both cis-DCE and VC in the presence or absence of Fe(III). Considering the lack of VC accumulation, both cultures reported herein may involve interesting mechanism(s) for the microbial remediation of environments contaminated with chlorinated ethenes. A number of fermentative reducers (microbes) which are known to reduce Fe(III) during their anaerobic growth are potential candidates involved in cir-DCE degradation in the presence and absence of Fe(III).

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.09a
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• pp.133-137
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• 2004

Tetrachloroethylene(PCE) dechlorination was investigated in an anaerobic enrichment culture from landfill soil. Anaerobic PCE dechlorinating microorganisms could convert 150mg/L of PCE via trichloroethylene(TCE) to cir-1,2-dichloroethylene(CDCE) within 2 days at the optimum temperature of 30 to 35$^{\circ}C$. The enrichment culture could dechlorinate TCE but did not degrade other chlorinated aliphatic compounds, such as cDCE, trans-1,2-dichloroethylene, 1,1-dichloroethylene, 1,1-dichloroethane, 1,2-dichloro- ethane, and 1,1,1-trichloroethane during 5 days incubation. Several isolates from the enrichment culture did not show dechlorinating activity of PCE. Microbial analysis of the dechlorinating enrichment culture by using Polymerase chain reaction-Denaturing gradient gel electrophoresis (PCR-DGGE) method showed that at least three microorganisms were related to the anaerobic PCE dechlorination in the enrichment

• Molecular & Cellular Toxicology
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• v.3 no.2
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• pp.119-126
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• 2007

1, 1-dichloroethylene (DCE) is well known hepatotoxicant as a model acute hepatotoxicity and selectively injure the bile canalicular membrane of centrilobular hepatocytes. In this study, we investigated hepatic gene expression and histopathological changes in response to DCE treatment. DCE was administered once daily at 20 mg/kg up to 14 days via intraperitoneal injection. Five mice were used in each test group and were sacrificed at 1, 7, and 14 days. Serum biochemical and histopathological analysis were performed for evaluation of hepatotoxicity level. Direct bilirubin and total bilirubin activities were slightly elevated in treated group at 7 days. DCE treatment for 7 days resulted in centrilobular hepatocyte hypertrophy and hepatocyte vacuolation, and mild hepatocyte vacuolation and high hepatocyte basophilia were observed in 14 days treated group. One hundred twenty three up-regulated genes and 445 down-regulated genes with over 2-fold changes between treated and control group at each time point were used for pathway analysis. These data may contribute in understanding the molecular mechanism DCE-induced hepatotoxicity.

• Molecular & Cellular Toxicology
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• v.1 no.2
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• pp.99-105
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• 2005

Perchloroethylene (tetrachloroethylene, PCE), a dry cleaning and degreasing solvent, can enter ground-water through accidental leak or spills. PCE can be degraded to trichloroethylene (TCE), 1, 1-dichloroethylene (DCE) and vinyl chloride (VC) as potential bio-product. These compounds have been reported that they can cause clinical diseases and cytotoxicity. However, only a little genotoxic information of these compounds has been known. In this study, we investigated DNA single strand breaks of PCE, TCE, DCE and VC by single cell gel electrophoresis assay, (comet assay) which is a sensitive, reliable and rapid method for DNA single strand breaks with mouse lymphoma L5178Y cells. From these results, $37.5\;{\mu}g/ml$ of PCE, $189\;{\mu}g/ml$ of TCE and $56.4\;{\mu}g/ml$ of DCE were revealed significant DNA damages in the absence of S-9 metabolic activation system meaning direct-acting mutagen. And in the presence of S-9 metabolic activation system, $41.5\;{\mu}g/ml$ of PCE, $328.7\;{\mu}g/ml$ of TCE and $949\;{\mu}g/ml$ of DCE were induced significant DNA damage. In the case of VC, it was revealed a significant DNA damage in the presence of S-9 metabolic activation system. Therefore, we suggest that chloroethylene compounds (PCE, TCE, DCE and VC) may be induced the DNA damage in a mammalian cell.

• Biotechnology and Bioprocess Engineering:BBE
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• v.11 no.3
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• pp.205-210
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• 2006

The widespread use and distribution of chloroethylene organic compounds is of serious concern owing to their carcinogenicity and toxicity to humans and wildlife. In an effort to develop active bacterial consortia that could be useful for bioremediation of chloroethylene-contaminated sites in Africa, 16 combinations of 5 dichloroethylene (DCE)-utilizing bacteria, isolated from South Africa and Nigeria, were assessed for their ability to degrade cis- and trans- DCEs as the sole carbon source. Three combinations of these isolates were able to remove up to 72% of the compounds within 7 days. Specific growth rate constants of the bacterial consortia ranged between 0.465 and $0.716\;d^{-1}$ while the degradation rate constants ranged between 0.184 and $0.205\;d^{-1}$ with $86.36{\sim}93.53\;and\;87.47{\sim}97.12%$ of the stoichiometric-expected chloride released during growth of the bacterial consortia in cis- and trans-DCE, respectively. Succession studies of the individual isolates present in the consortium revealed that the biodegradation process was initially dominated by Achromobacter xylosoxidans and subsequently by Acinetobacter sp. and Bacillus sp., respectively. The results of this study suggest that consortia of bacteria are more efficient than monocultures in the aerobic biodegradation of DCEs, degrading the compounds to levels that are up to 60% below the maximum allowable limits in drinking water.

• Membrane and Water Treatment
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• v.13 no.2
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• pp.85-95
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• 2022

Tetrachloroethylene (PCE) and trichloroethylene (TCE), critical pollutants to human health and groundwater ecosystems, are managed by groundwater quality standards (GQS) in South Korea. However, there are no GQSs for their by-products, such as cis-dichloroethylene (DCE) and vinyl chloride (VC) produced through the dechlorination process of PCE and TCE. Therefore, in this study, we monitored PCE, TCE, cis-DCE, and VC in 111 national groundwater wells for three years (2016 to 2018) to evaluate their distributions, a biological dechlorination possibility, and human risk assessment. The detection frequency of them was 30.2% for PCE, 45.1% for TCE, 43.9% for cis-DCE and 13.4% for VC. The four chlorinated compounds were commonly detected in 21 out of 111 wells. In the results of statistical analysis with 21 wells data, DO and ORP also had a negative correlation with four organic chlorinated compounds, while EC and sulfate has a positive correlation with the compounds. This indicates that the 21 wells were relatively met with suitable environments for a biological dechlorination reaction compared to the other wells. Finally, cis-DCE had a non-carcinogenic risk of 10^-1 and the carcinogenic risk of VC was 10^-6 or higher. Through this study, the distribution status of the four chlorinated compounds in groundwater in South Korea and the necessity of preparing plans to manage cis-DCE and VC were confirmed.

• Journal of Environmental Health Sciences
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• v.36 no.4
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• pp.323-336
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• 2010

We evaluated the properties of a fixed-bed column reactor for high-concentration tetrachloroethylene (PCE) removal. The anaerobic bacterium Clostridium bifermentans DPH-1 was able to dechlorinate PCE to cis-1,2-dichloroethylene (cDCE) via trichloroethylene (TCE) at high rates in the monoculture biofilm of an upflow fixed-bed column reactor. The first-order reaction rate of C. bifermentans DPH-1 was relatively high at $0.006\;mg\;protein^{-1}{\cdot}l{\cdot}h^{-1}$, and comparable to rates obtained by others. When we gradually raised the influent PCE concentration from $30\;{\mu}M$ to $905\;{\mu}M$, the degree of PCE dechlorination rose to over 99% during the operation period of 2,000 h. In order to maintain efficiency of transformation of PCE in this reactor system, more than 6 h hydraulic retention time (HRT) is required. The maximum volumetric dechlorination rate of PCE was determined to be $1,100\;{\mu}mol{\cdot}d^{-1}l$ of reactor $volume^{-1}$, which is relatively high compared to rates reported previously. The results of this study indicate that the PCE removal performance of this fixed-bed reactor immobilized mono-culture is comparable to that of a fixed-bed reactor mixture culture system. Furthermore, our system has the major advantage of a rapid (5 days) start-up time for the reactor. The flow characteristics of this reactor are intermediate between those of the plug-flow and complete-mix systems. Biotransformation of PCE into innocuous compounds is desirable; however, unfortunately cDCE, which is itself toxic, was the main product of PCE dechlorination in this reactor system. In order to establish a system for complete detoxification of PCE, co-immobilization of C. bifermentans DPH-1 with other bacteria that degrade cDCE aerobically or anaerobically to ethene or ethane may be effective.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2000.11a
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• pp.207-208
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• 2000

Since trichloroethylene (TCE), dichloroethylene (DCE), and vinyl chloride (VC) arise from anaerobic degradation of tetrachloroethylene (PCE) and TCE, there is interest in creating aerobic remediation systems that avoid the highly toxic VC and cis-DCE which predonominate in anaerobic degradation. However, it seemed TCE could not be degraded aerobically without an inducing compound (which also competitively inhibits TCE degradation). It has been shown that TCE induces expression of both the toluene dioxygenase of p. putida F1 as well as toluene-p-monooxygenase of P.mendocina KRI. We investigated here the ability of PCE, TCE, and chlorinated phenols to induce toluene-o-xylene monooxygenase (ToMO) from P.stutzeri OX1. ToMO has a relaxed regio-specificity since it hydroxylates toluene in the ortho, meta, and para positions; it also has a broad substrate range as it oxidizes o-xylene, m-xylene, p-xylene, toluene, benzene, ethylbenzene, styrene, and naphthalene; chlorinated compounds including TCE, 1, 1-DCE, cis-DCE, trans-DCE, VC, and chloroform : as well as mixtures of chlorinated aliphatics (Pseudomonas 1999 Maui Meeting). ToMO is a multicomponent enzyme with greatest similarity to the aromatic monooxygenases of Burkholderia pickettii PKO1 and P.mendocina KR1. Using P.sturzeri OX1, it was found that PCE induces P.mendocina KR1 Using P.situtzeri OX1, it was found that PCE induces ToMO activity measured as naphthalene oxygenase activity 2.5-fold, TCE induces 2.3-fold, and toluene induces 3.0 fold. With the mutant P.stutzeri M1 which does not express ToMO, it was also found there was no naphthalene oxygenate activity induced by PCE and TCE; hence, PCE and TCE induce the tow path. Using P.putida PaW340(pPP4062, pFP3028) which has the tow promoter fused to the reporter catechol-2, 3-dioxygenase and the regulator gene touR, it was determined that the tow promoter was induced 5.7-, 7.1-, and 5.2-fold for 2-, 3-, 4-chlorophenol, respectively (cf. 8.9-fold induction with o-cresol) : however, TCE and PCE did not directly induce the tou path. Gas chromatography and chloride ion analysis also showed that TCE induced ToMO expression in P.stutzeri OX1 and was degraded and mineralized. This is the first report of significant PCE induction of any enzyme as well as the first report of chlorinated compound induction of the tou operon. The results indicate TCE and chlorinated phenols can be degraded by P.stutzeri OX1 without a separate inducer of the tou pathway and without competitive inhibition.