Reductive Dechlorination of High Concentrations of Chloroethenes by a Dehalococcoides mccartyi Strain 11 G

Abstract

Chloroethenes are common groundwater and soil contaminants due to extensive historic utilization and inappropriate discharge. The tendency for chloroethenes to become sequestered as dense nonaqueous phase liquids (DNAPL)—a point source to groundwater contamination and causing high concentrations of chloroethenes in proximal aquifers poses a great challenge for remediation of chloroethenes contamination sites. In this study, we report isolation and characterization of a Dehalococcoides mccartyi strain 11 G which couples growth with reductive dechlorination of trichloroethenes (TCE), dichloroethene (DCE) isomers and vinyl chloride (VC) to ethene at a growth yield ranging from 2.47 ± 0.23 × 10⁸ to 5.64 ± 0.43 × 10⁸ cells/μmoles Cl⁻ released and co-metabolically dechlorinates tetrachloroethene (PCE) in the presence of TCE. Compared with previous D. mccartyi strains showing dechlorination of TCE at up to 2.0 mM, strain 11 G is distinguished by its capacity to dechlorinate chloroethenes at initial concentrations of DCE isomers as high as 4 mM and TCE as high as 3.5 mM to ethene. Bioaugmentation of a contaminated microcosm with strain 11 G resulted in complete detoxification of a mixture of 5 mM chloroethenes (2.5 mM of each TCE and cis-DCE) after 40 days. Strain 11 G is a promising candidate for in situ bioremediation of high-concentration-chloroethene contaminated sites.

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