(332e) Rapid Dechlorination of Polychlorinated Biphenyls (PCBs) in an Engineered System

Polychlorinated biphenyls (PCBs) are posing great environmental problems due to their toxicity. Removal of PCB in polluted sites are challenged by the high physical/chemical treatment costs, while microbial dichlorination of PCBs are largely impeded by difficulties in growing PCB dechlorinators to a high cell abundance. In this study, we accelerated the onset of PCB dechlorination by pre-cultivating functional microbes on alternative electron acceptors in an engineered system. Extensive dechlorination of Aroclor 1260 was achieved within 1 week by culture CG4 pre-grown tetrachloroethene (PCE). Compared to control cultures fed solely with Aroclor 1260, the PCB dechlorination rate was up to 30 times greater in cultures pre-cultivated with alternative electron acceptors. However, when culture CG4 was simultaneously exposed to PCE, and PCBs, PCB dechlorination was not observed until complete depletion of PCE. Expression of the bifunctional reductive dehalogenase (RDase) gene pcbA4 was inhibited by the presence of both substrates and continued with only one substrate in the medium. Utilization of chloroethenes and PCBs as substrates by culture CG4 was found to be largely sequential rather than concurrent, suggesting that PCE is a preferred substrate for the RDase responsible for PCE and PCB dechlorination.