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Detoxification of 1,1,2-trichloroethane to ethene by desulfitobacterium and identification of its functional reductase gene.

Zhao S, Ding C, He J - PLoS ONE (2015)

Bottom Line: Later, through transcriptomic and enzymatic analysis, the reductive dehalogenase CtrA, which was previously reported to be responsible for 1,1,1-trichloroethane and chloroform dechlorination, was identified as the 1,1,2-TCA reductive dehalogenase.Interestingly, this co-culture dechlorinated 1,1,2-TCA and TCE to the non-toxic end-product ethene within 48 days without chloroethane production.This novel pathway avoids production of the carcinogenic intermediate dechlorination product vinyl chloride, providing a more environmentally friendly strategy to treat 1,1,2-TCA.

View Article: PubMed Central - PubMed

Affiliation: Department of Civil and Environmental Engineering, National University of Singapore, Singapore, 117576, Singapore.

ABSTRACT
1,1,2-trichloroethane (1,1,2-TCA) has become a common groundwater pollutant due to historically extensive utilization, improper disposal, as well as from incomplete dechlorination of 1,1,2,2-tetrachloroethane. Currently, limited information is available on microbial detoxification of 1,1,2-TCA. Desulfitobacterium sp. strain PR, which was isolated from an anaerobic bioreactor maintained to dechlorinate chloroethenes/ethanes, exhibited the capacity to dechlorinate 1,1,1-trichloroethane and chloroform. In this study, the dechlorinating ability of strain PR was further explored. Strain PR showed the capability to dechlorinate 1,1,2-TCA (~1.12 mM) predominantly to 1,2-dichloroethane (1,2-DCA) and chloroethane, and to trace amounts of vinyl chloride and ethene within 20 days. Strain PR coupled growth with dechlorination of 1,1,2-TCA to 1,2-DCA, while no cell growth was observed with dechlorination of 1,2-DCA to chloroethane. Later, through transcriptomic and enzymatic analysis, the reductive dehalogenase CtrA, which was previously reported to be responsible for 1,1,1-trichloroethane and chloroform dechlorination, was identified as the 1,1,2-TCA reductive dehalogenase. Since trichloroethene (TCE) is usually co-contaminated with 1,1,2-TCA, a co-culture containing Dehalococcoides mccartyi strain 11a capable of detoxifying TCE and 1,2-DCA and strain PR was established. Interestingly, this co-culture dechlorinated 1,1,2-TCA and TCE to the non-toxic end-product ethene within 48 days without chloroethane production. This novel pathway avoids production of the carcinogenic intermediate dechlorination product vinyl chloride, providing a more environmentally friendly strategy to treat 1,1,2-TCA.

No MeSH data available.


Related in: MedlinePlus

Co-culturing strain PR and Dehalococcoides mccartyi strain 11a on 1,1,2-TCA/TCE.(A) Inhibitory effects of 0.05 mM TCE on 1,1,2-TCA dechlorination by strain PR. (B) Dechlorination of 1,1,2-TCA and TCE by a co-culture consisting of strains PR and 11a. Note: CA, chloroethane; VC, vinyl chloride; ETH, ethene.
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pone.0119507.g006: Co-culturing strain PR and Dehalococcoides mccartyi strain 11a on 1,1,2-TCA/TCE.(A) Inhibitory effects of 0.05 mM TCE on 1,1,2-TCA dechlorination by strain PR. (B) Dechlorination of 1,1,2-TCA and TCE by a co-culture consisting of strains PR and 11a. Note: CA, chloroethane; VC, vinyl chloride; ETH, ethene.

Mentions: As a co-contaminant with 1,1,2-TCA, TCE ranging from 0.01 mM to 1.12 mM has no inhibitory effect on dechlorination of 1,1,2-TCA to 1,2-DCA by strain PR and S3 Fig. shows dechlorination profile at a representative low (0.12 mM) and high (0.24 mM) TCE concentration. Moreover, production of chloroethane by strain PR is inhibited by as little as 0.05 mM TCE in the medium, resulting in the production of only 1,2-DCA from the dechlorination of 1,1,2-TCA (Fig. 6A). In order to achieve complete dechlorination of 1,1,2-TCA without accumulation of either 1,2-DCA or chloroethane in the presence of TCE/1,1,2-TCA co-contaminants, another co-culture was established with strain PR and Dehalococcoides mccartyi strain 11a. After spiking TCE (0.29 mM) and 1,1,2-TCA (0.29 mM) to the co-culture, 1,1,2-TCA and TCE were dechlorinated at similar rates to 1,2-DCA (by strain PR) and ethene (by strain 11a), within 24 days (Fig. 6B). The amount of 1,2-DCA peaked (0.28 mM) on day 20, after which it was completely dechlorinated to ethene by strain 11a. Throughout the experiment, the concentration of CA was below detection limit (0.006 mM). A trace amount of VC (0.012 mM) was generated on day 7, but disappeared after 9 days. Overall, the co-culture of strains PR and 11a was able to achieve complete detoxification of 1,1,2-TCA and TCE to ethene.


Detoxification of 1,1,2-trichloroethane to ethene by desulfitobacterium and identification of its functional reductase gene.

Zhao S, Ding C, He J - PLoS ONE (2015)

Co-culturing strain PR and Dehalococcoides mccartyi strain 11a on 1,1,2-TCA/TCE.(A) Inhibitory effects of 0.05 mM TCE on 1,1,2-TCA dechlorination by strain PR. (B) Dechlorination of 1,1,2-TCA and TCE by a co-culture consisting of strains PR and 11a. Note: CA, chloroethane; VC, vinyl chloride; ETH, ethene.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4383557&req=5

pone.0119507.g006: Co-culturing strain PR and Dehalococcoides mccartyi strain 11a on 1,1,2-TCA/TCE.(A) Inhibitory effects of 0.05 mM TCE on 1,1,2-TCA dechlorination by strain PR. (B) Dechlorination of 1,1,2-TCA and TCE by a co-culture consisting of strains PR and 11a. Note: CA, chloroethane; VC, vinyl chloride; ETH, ethene.
Mentions: As a co-contaminant with 1,1,2-TCA, TCE ranging from 0.01 mM to 1.12 mM has no inhibitory effect on dechlorination of 1,1,2-TCA to 1,2-DCA by strain PR and S3 Fig. shows dechlorination profile at a representative low (0.12 mM) and high (0.24 mM) TCE concentration. Moreover, production of chloroethane by strain PR is inhibited by as little as 0.05 mM TCE in the medium, resulting in the production of only 1,2-DCA from the dechlorination of 1,1,2-TCA (Fig. 6A). In order to achieve complete dechlorination of 1,1,2-TCA without accumulation of either 1,2-DCA or chloroethane in the presence of TCE/1,1,2-TCA co-contaminants, another co-culture was established with strain PR and Dehalococcoides mccartyi strain 11a. After spiking TCE (0.29 mM) and 1,1,2-TCA (0.29 mM) to the co-culture, 1,1,2-TCA and TCE were dechlorinated at similar rates to 1,2-DCA (by strain PR) and ethene (by strain 11a), within 24 days (Fig. 6B). The amount of 1,2-DCA peaked (0.28 mM) on day 20, after which it was completely dechlorinated to ethene by strain 11a. Throughout the experiment, the concentration of CA was below detection limit (0.006 mM). A trace amount of VC (0.012 mM) was generated on day 7, but disappeared after 9 days. Overall, the co-culture of strains PR and 11a was able to achieve complete detoxification of 1,1,2-TCA and TCE to ethene.

Bottom Line: Later, through transcriptomic and enzymatic analysis, the reductive dehalogenase CtrA, which was previously reported to be responsible for 1,1,1-trichloroethane and chloroform dechlorination, was identified as the 1,1,2-TCA reductive dehalogenase.Interestingly, this co-culture dechlorinated 1,1,2-TCA and TCE to the non-toxic end-product ethene within 48 days without chloroethane production.This novel pathway avoids production of the carcinogenic intermediate dechlorination product vinyl chloride, providing a more environmentally friendly strategy to treat 1,1,2-TCA.

View Article: PubMed Central - PubMed

Affiliation: Department of Civil and Environmental Engineering, National University of Singapore, Singapore, 117576, Singapore.

ABSTRACT
1,1,2-trichloroethane (1,1,2-TCA) has become a common groundwater pollutant due to historically extensive utilization, improper disposal, as well as from incomplete dechlorination of 1,1,2,2-tetrachloroethane. Currently, limited information is available on microbial detoxification of 1,1,2-TCA. Desulfitobacterium sp. strain PR, which was isolated from an anaerobic bioreactor maintained to dechlorinate chloroethenes/ethanes, exhibited the capacity to dechlorinate 1,1,1-trichloroethane and chloroform. In this study, the dechlorinating ability of strain PR was further explored. Strain PR showed the capability to dechlorinate 1,1,2-TCA (~1.12 mM) predominantly to 1,2-dichloroethane (1,2-DCA) and chloroethane, and to trace amounts of vinyl chloride and ethene within 20 days. Strain PR coupled growth with dechlorination of 1,1,2-TCA to 1,2-DCA, while no cell growth was observed with dechlorination of 1,2-DCA to chloroethane. Later, through transcriptomic and enzymatic analysis, the reductive dehalogenase CtrA, which was previously reported to be responsible for 1,1,1-trichloroethane and chloroform dechlorination, was identified as the 1,1,2-TCA reductive dehalogenase. Since trichloroethene (TCE) is usually co-contaminated with 1,1,2-TCA, a co-culture containing Dehalococcoides mccartyi strain 11a capable of detoxifying TCE and 1,2-DCA and strain PR was established. Interestingly, this co-culture dechlorinated 1,1,2-TCA and TCE to the non-toxic end-product ethene within 48 days without chloroethane production. This novel pathway avoids production of the carcinogenic intermediate dechlorination product vinyl chloride, providing a more environmentally friendly strategy to treat 1,1,2-TCA.

No MeSH data available.


Related in: MedlinePlus