Comparison Of Anaerobic Dechlorinating
Enrichment Cultures Maintained On Tetrachloroethene, Trichloroethene, cis-Dichloroethene
And Vinyl Chloride.
Water Research. 2002. 36: 4193-4202.
Melanie Duhamela, Stephan D. Wehra,
Lawrence Yua, Homa Rizvi,a
David Seepersada,Sandra Dworatzekb, Evan E. Coxb,
Elizabeth A. Edwardsa
aDepartment Of Chemical Engineering And Applied Chemistry, University
Of Toronto, Toronto, Ont., Canada
bGeosyntec Consultants, Guelph, Ont., Canada
Abstract: An anaerobic mixed microbial culture was enriched from soil and groundwater taken from a site contaminated with trichloroethene (TCE). This enrichment culture was divided into four subcultures amended separately with either perchloroethene (PCE),TCE, cis-dichloroethene (cDCE) or vinyl chloride (VC). In each of the four subcultures,the chlorinated ethenes were rapidly,consistently,and completely converted to ethene at rates of 30–50 mmol/l of culture per day,or an average 160 m-electron equivalents/l of culture per day. These cultures were capable of sustained and rapid dechlorination of VC,and could not dechlorinate 1,2-dichloroethane,differentiating them from Dehalococcoides ethenogenes, the only known isolate capable of complete dechlorination of PCE to ethene. Chloroform (CF) and 1,1,1- trichloroethane,frequent groundwater co-contaminants with TCE and PCE,inhibited chlorinated ethene dechlorination. Most strongly inhibited was the .nal conversion of VC to ethene,with complete inhibition occurring at an aqueous CF concentration of 2.5 mM. Differences in rates and community composition developed between the different subcultures,including the loss of the VC enrichment culture’s ability to dechlorinate PCE. Denaturing gradient gel electrophoresis of ampli.ed bacterial 16S rRNA gene fragments identi.ed three different DNA sequences in the enrichment cultures,all phylogenetically related to D. ethenogenes. Based on the PCR DGGE results and substrate utilization patterns,it is apparent that signi.cant mechanistic differences exist between each step of dechlorination from TCE to ethene,especially for the last important dechlorination step from VC to ethene.