Polychlorinated biphenyls (PCBs) are widespread priority toxic pollutants, which are persistent in the environment and tend to bioaccumulate. Phase I of this project will undertake studies to investigate the reductive dechlorination and mineralization of lower chlorinated PCB-defined congeners by anaerobic microbial consortia developed in Grand River Technologies, Inc. laboratory. In the past, reductive dechlorination processes have resulted in the accumulation of ortho-chlorinated congeners. Their current investigations have indicated that the MBI anaerobic granules are capable of dechlorinating all substitutions of chlorines from PCB mixtures and congeners. Higher chlorinated congeners were dechlorinated extensively, but accumulation of corresponding lightly chlorinated products was not seen in these studies. Accumulation of biphenyl as an intermediate or end product was inconsistent and thus, it is difficult to calculate a material balance. These results are intriguing since it is widely accepted that lower chlorinated biphenyls and biphenyl do not undergo further dechlorination and mineralization anaerobically. Since their results strongly indicate that process exists, they intend to obtain evidence to prove it. Further if that is happening then they want to understand the primary mechanism for it. Under Phase I of this proposal, the fate of 2-Chlorobiphenyl, 2,6-Dichloribiphenyl and Biphenyl, and their 14C-labeled isotopes will be examined with their anaerobic microbial consortia under different conditions. Enzymatic evidence will also be sought to determine the mechanism of ring cleavage under anaerobic condition. The ultimate strategy will be to utilize these anaerobic consortia to develop an in situ bioremediation process to treat PCB-contaminated lake or river sediments. This project will be the first demonstration of complete dechlorination and mineralization of PCBs by anaerobic microbial consortia.
