Evidence of Reductive Dechlorination and Mineralization of Lower Chlorinated Biphenyls by Anaerobic Microbial Consortia

多氯联苯（PCBs）是广泛存在的优先毒性污染物，在环境中具有持久性和生物蓄积性。该项目的第一阶段将进行研究，研究由Grand River Technologies， Inc.实验室开发的厌氧微生物联合体对低氯多氯联苯定义的同系物的还原脱氯和矿化。过去，还原性脱氯过程导致了正氯同系物的积累。他们目前的研究表明，MBI厌氧颗粒能够从PCB混合物和同系物中脱氯。高氯同系物被广泛脱氯，但相应的轻氯产物的积累在这些研究中未见。联苯作为中间产品或最终产品的积累是不一致的，因此，很难计算物质平衡。这些结果很有趣，因为人们普遍认为低氯联苯和联苯不进行进一步的脱氯和厌氧矿化。由于他们的结果有力地表明这一过程存在，他们打算获得证据来证明这一点。此外，如果发生了这种情况，他们想要了解其主要机制。在本提案的第一阶段，2-氯联苯、2,6-二氯联苯和联苯以及它们的14c标记同位素将在不同条件下与它们的厌氧微生物群落一起研究。还将寻求酶的证据来确定厌氧条件下环切割的机制。最终的策略将是利用这些厌氧联合体来开发一种原位生物修复工艺来处理多氯联苯污染的湖泊或河流沉积物。该项目将是厌氧微生物联合体对多氯联苯进行完全脱氯和矿化的第一个示范。

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.