| Summary: | 碩士 === 東吳大學 === 微生物學系 === 88 === In this research, we investigated microbial dechlorination of seven kinds of polychlorinated biphenyls (PCBs) by anaerobic microorganisms from sediment. The results showed anaerobic microorganisms from sediment of five rivers in Taiwan all have dechlorination ability, and sediment of Kee-Lung River perform better dechlorination activity than other four rivers. In the five monitoring sites of middle and down Stream of Kee-Lung River, the result showed dechlorination rates of five sampling sites in the order：K6 (0.0230mg l-1day-1) > K8 (0.0211mg l-1day-1) > K11 (0.0193mg l-1day-1) > K12 (0.0107mg l-1day-1) > K10 (0.0092mg l-1day-1). Increasing the amount of sediment in medium, microbial dechlorination rates were delayed. The optimal conditions for 2,4',5-CB、2,2',5,5'-CB and 2,2',4,5,5'-CB were 30 ~ 40℃ and pH 7. Incubation with shaker can increase dechlorination rates of 2,4',5-CB and 2,2',5,5'-CB. Dechlorination rates were also affected by chlorine level of PCBs, when the chlorine level increased the dechlorination rate decreased.
The intermediate products of 2,2',3,4,4',5,5'-CB were 2,2',4,4',5,5'-CB、2,2',4,5,5'-CB、2,2',5,5'-CB、2,2',5-CB and 2-CB, 2,2',3,4,4',5,5'-CB can be transformed to 2,2',4,4',5,5'-CB by meta-dechlorination, 2,2',4,4',5,5'-CB can be transformed to 2,2',4,5,5'-CB、2,2',5,5'-CB by para-dechlorination, and 2,2',5-CB can be transformed to 2-CB by ortho-dechlorination.
Under different anaerobic conditions, we found the dechloronation rate is fastest in methanogenic conditions, but slowest in sulfate reducing conditions. Addition of electro-donor such as acetate、pyruvate and lactate were enhanced dechlorination of PCBs in methanogenic and sulfate reducing conditions, but inhibited in denitrifying conditions. Addition of surfactants such as Brij30、SN70 or Triton N101 were inhibited PCBs dechlorination. By adding microbial inhibitors, we suggest that methanogen, sulfate-reducing bacteria and denitrifying bacteria are all involved in dechlorination. From our result, we can establish the optimal dechlorination conditions which could be used for further application of bioremediation for clean up of PCB-contaminated river sediment.
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