Dechlorination of PCE in the presence of Fe0 enhanced by a mixed culture containing two Dehalococcoides strains

A mixed culture capable of supplying its energy requirements by the oxidation of zero-valent iron (Fe0) and concomitant reduction of chlorinated ethenes was established. The culture contained Dehalococcoides species as determined by polymerase chain reaction (PCR) with genus specific primers. The use of a newly designed ARDRA procedure and subsequent sequencing revealed the presence of two Dehalococcoides strains, one closely related to Dehalococcoides ethenogenes strain 195, a bacterium respiring with chlorinated ethenes, and one closely related to strain CBDB1 a chlorobenzene and dioxin dehalogenating anaerobe. The mixed culture was used to study dechlorination of tetrachloroethene (PCE) to ethene in the presence of Fe0. Whereas abiotic transformation of PCE by Fe0 led to incomplete dechlorination, the mixed culture mediated fast and complete dechlorination of PCE to ethene with Fe0 as electron donor. Compared to cultures with hydrogen added as electron donor, cultures with Fe0 as electron donor showed the same or higher rates of PCE dechlorination. Growth of the Dehalococcoides strains in the mixed culture is linked to the presence of Fe0 as electron donor and PCE as electron acceptor demonstrating that Dehalococcoides spp. play a pivotal role in the dechlorination of chlorinated ethenes in Fe0 systems.