• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.04a
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• pp.158-161
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• 2004

Chlorinated aliphatic hydrocarbons (CAHs) especially perchlorethylene (PCE) and trichlooethylene (TCE) are common groundwater contaminants in Korea. PCE and TCE were often reductively dechiorinated in an aquifer. Several isolates dechlorinate PCE to TCE or cis-1,2 dichloroethylene (c-DCE) were obtained from contaminated and pristine sites in USA and Europe. However in Korea, no information on indigenous microorganism being involved in reductive dechlorination of PCE and TCE is available and different dechlorinating microorganisms might be reside in Korea, since geochemical, and hydrogeological conditions are different, compared to those in the other sites. So we evaluate that: 1) if reductive dechlorinating microorganisms are present in PCE-contaminated site in Korea, 2) if so, what kinds of microorganisms are present; 3) to what extent PCE is reductively dechlorinated. As a results in some PCE-contaminated aquifers in Korea other dechlorinating microorganisms but Dehalococcoides ethenogenes may be responsible for PCE dechlorination. More detailed molecular works are required to evaluate that different dechlorinating microorganisms would reside in Korea.

• Journal of Microbiology
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• v.39 no.3
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• pp.195-201
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• 2001

The effect of moisture content an the reductive dechlorination of polychlorinated biphenyls and population dynamics of dechlorinating microorganisms was investigated in sediments spiked with Aroclor 1248. In sediment slurry with an overlying water layer, dechlorination ensued after a 4-week lag period and reduced the average number of chlorines per biphenyl from 3.91 to 3.15 after 48 weeks. In the sediments of reduced moisture content, however, dechlorination occurred after a lag period of 12 weeks and decreased the average number of chlorines per biphenyl to only 3.62, and the dechlorination rate was also slower. When the population size of dechlorinators, methanogens, and sulfate-reducing bacteria was determined by the most probable number techniques, however, no difference was found between the slurry and the low-moisture sediments, except for methanogens. The growth of dechlorinating populations coincided with the end of the lag period and they then increased by 3 orders of magnitude in two conditions. Specific growth rate of dechlorinators showed little difference between the slurry and the low-moisture sediments; however, growth yield was high in the sediments of reduced moisture content. The reduction of sediment moisture decreased the dechlorination rate and extent of PCBs but did not inhibit the growth of PCB dechlorinators.

• 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

• Proceedings of the Microbiological Society of Korea Conference
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• 2004.05a
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• pp.31-34
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• 2004

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.04a
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• pp.332-336
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• 2004

An anaerobic PCE(tetrachloroethylene) dechlorinating bacterial culture from a landfill soil was enriched and characterized. The enrichment culture could dechlorinate 60$\mu$mol/$m\ell$ of PCE during a month of incubation and cis-DCE(cis-dichloroethylene) was observed as a main product of PCE dechlorination. Microbial analysis of the dechlorinating enrichment culture by rising PCR-DGGE (Polymerase chain reaction-Denaturing gradient gel electrophoresis) method showed that at least three microorganisms were related to the anaerobic PCE dechlorination.

• Proceedings of the Microbiological Society of Korea Conference
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• 1998.04a
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• pp.51.2-51.2
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• 1998

• Journal of Microbiology
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• v.44 no.1
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• pp.23-28
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• 2006

We investigated the effects of halogenated aromatic compounds (HACs) including naturally occurring ones (L-thyroxine, 3-chloro-L-tyrosine, 5-chloroindole, 2-chlorophenol, 4-chlorophenol and chlorobenzene) on polychlorinated biphenyl (PCB) dechlorination in sediment cultures. A PCB-dechlorinating enrichment culture of sediment microorganisms from the St. Lawrence River was used as an initial inoculum. When the culture was inoculated into Aroclor 1248 sediments amended with each of the six HACs, the extent of dechlorination was not enhanced by amendment with HACs. The dechlorination patterns in the HAC-amended sediments were nearly identical to that of the HAC-free sediments except the 3-chloro-L-tyrosine-amended ones where no dechlorination activity was observed. When these sediment cultures were transferred into fresh sediments with the same HACs, the dechlorination specificities remained the same as those of the initial inoculations. Thus, in the present study, the substrate range of the highly selected enrichment culture could not be broadened by the HACs. It appears that HACs affect PCB dechlorination mainly through population selection rather than enzyme induction of single population.

• Journal of Microbiology and Biotechnology
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• v.18 no.9
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• pp.1564-1571
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• 2008

We investigated whether the threshold concentration for polychlorinated biphenyl (PCB) dechlorination may be lower in biosurfactant-amended sediments compared with biosurfactant-free samples. At PCB concentrations of 40, 60, and 120 ppm, the surfactant amendment enhanced the PCB dechlorination rate at all concentrations and the rate was also faster at higher concentrations. On a congener group basis, dechlorination proceeded largely with group A (congeners with low threshold) in both surfactant-free and -amended sediments, accumulating mainly group C (residual products of dechlorination) congeners, and surfactant enhanced the dechlorination rate of group A congeners. Since the PCB threshold concentration for the inoculum in the experiment was lower than 40 ppm, we carried out another experiment using sediments with lower PCB concentrations, 10, 20, and 30 ppm. Sediments with 100 ppm were also performed to measure dechlorination at a PCB saturation concentration. Comparison between the plateaus exhibited that the extent of dechlorination below 40 ppm PCBs was much lower than that at a saturation concentration of 100 ppm. There was no significant difference in the extent of dechlorination between surfactant-free and -amended sediments. Moreover, surfactant did not change the congener specificity or broaden the congener spectrum for dechlorination at PCB concentrations below 40 ppm. Taken together, it seems that at a given PCB concentration, dechlorination characteristics of dechlorinating populations may be determined by not only the congener specificity of the microorganisms but also the affinity of dechlorinating enzyme(s) to individual PCB congeners.

• Journal of Microbiology
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• v.43 no.2
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• pp.166-171
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• 2005

In order to determine the effects of sulfate concentration on the anaerobic dechlorination of polychlorinated biphenyls, sediments spiked with Aroclor 1242 were made into slurries using media which had various sulfate concentrations ranging from 3 to 23 mM. The time course of dechlorination clearly demonstrated that dechlorination was inhibited at high concentration of sulfate due to less dechlori-nation of meta-substituted congeners. When the dechlorination patterns were analyzed by the calculation of Euclidean distance, the dechlorination pathway in the 3 mM sulfate samples was found to be different from that observed in the 13 mM samples, although the extent of dechlorination in these two samples was similar. It is possible that the dechlorination in the high sulfate concentration samples is inhibited by the suppression of growth of methanogen, which have been shown to be meta-dechlorinating microorganisms.

• Journal of Wetlands Research
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• v.9 no.1
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• pp.107-114
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• 2007

This study aimed to investigate the hexachlorobenzene (HCB) dechlorinating ability of sediment microbes collected from a natural canal receiving secondary effluents from an industrial estate and nearby factories. Nine sites along the stream and one in the estuary in the Gulf of Thailand into which the canal spills were specified and sampling for sediment and water. Preliminary analysis of the sediments showed that the first four sites nearest to the discharging location were contaminated by HCB within the range of 0.18 to 1.25 ppm. Apart from that, 1,3,5-trichlorobenzene which has never been commercially produced or used in any manufacturing processes except for the transformation from higher chlorinated benzene was also identified in the range of 0.16 to 0.24 ppm. This suggested a possibility of sporadically HCB contamination in this stream. Of more important, people in the community along this canal earn their living by coastal fishery; hence, posing a risk of spreading HCB and its less chlorinated congeners via food chain from caught marine creatures to human. As a result, there is an urgent need to understand the behavior of HCB dechlorination in this stream sediment which can lead to a clean-up action in the future. Serum bottles with sediment slurries (sediment to water ratio of 1:1 (v/v) and filtered to remove particles larger than 0.7 mm) from each site were inoculated with 2 mg/l of HCB, kept anaerobically in the dark at room temperature without any nourishment, and analyzed for HCB and its less-chlorinated congeners every 6 days. Total chemical oxygen demand, suspended solids, and volatile suspended solids were in the range of 21,492-73,584, 158,100-518,100 and 6,000-32,700 mg/l, respectively. It was found that all sediment slurries began to dechlorinate HCB in 12 to 30 days and the HCB was completely removed within 42 to 60 days or so. On the other hand, there was no HCB dechlorination occurred in the controlled set which was sterilized by autoclaving prior to the addition of HCB. This implies that the HCB transformation was solely due to microorganisms' activities. HCB was dechlorinated principally via pentachlolobenzene to 1,2,3,5-tetrachlorobenzene and terminated at 1,3,5-trichlorobenzene which is the major pathway as reported by many researchers. Dichlorobenzene has not been detected in any samples within the dechlorination period of 60 days. The results indicate that the microbial matrix in the sediment of this stream has an outstanding capability to dechlorinate HCB. Existing substrates and nutrients which mainly sorbed onto the solid phase and the typical temperature in Thailand were sufficient and suitable to promote the activities of these HCB-dechlorinating microbes.