Reductive dechlorination of polychlorinated biphenyls by indigenous anaerobic microorganisms in Taiwan

• Main Authors: Chen, I-Ming, 陳意銘
• Other Authors: Wang Yei-Shung
• Format: Others
• Language: zh-TW
• Published: 1997
• Online Access: http://ndltd.ncl.edu.tw/handle/47420416039588497147

博士 === 國立臺灣大學 === 農業化學系 === 85 === Dechlorination of polychlorinated biphenyl(PCB) congeners and three commercial PCB mixtures Aroclor 1242, Aroclor 1254 and Aroclor 1260 in anaerobic mixed cultures were studied with PCB contaminated sediments from Er-Jen River located in Tainan prefecture. The results showed the microorganisms from sediments of Er-Jen River possessed ability to dechlorinate 234-CB, 345-CB and 2345-CB that containing three chlorine in adjacent position and removed the middle one chlorine to produce 24-CB, 35-CB and 235-CB respectively. Mixed cultures enriching with yeast extract, the lag phase for dechlorination was shortened. The first transferred cultures showed their dechlorination activity after 6 days of incubation, and completely transformed 234-CB to 24-CB for 17 days. Continuously feeding with 345-CB and 2345-CB to the microorganisms precultured in 234-CB, both compounds were immediately dechlorinated without significant lag time. The results suggested that there might be a unique microbial system in charge of the dechlorination of these PCB congeners. In the study on dechlorination of Aroclors, Aroclor 1242, 1254 and 1260 were dechlorinated to the extent of 7.11%, 7.72% and 11.94%, respectively, at m-, p-position by mixed cultures which acclimated with Aroclors for two months. Aroclors showed the same dechlorination pattern in the cultures acclimated by the different PCB congeners , and the 345-CB-acclimated cultures gave the great dechlorination to the extent of 15.23% for m-, p- Cl removal. Addition of surfactants to the culture medium would shortenthe lag phase of Aroclor 1260 dechlorination, but it seemed no influence to Aroclor 1242 dechlorination. The anaerobic mixed cultures also transformed high concentration(50 mg/l and 100 mg/l) of Aroclor 1242 to 10.12% and 11.56% of m-, p-Cl dechlorination in culture medium. Furthermore, microorganisms collected from all sediments and soils showed dechlorination activity to PCBs no matter how contaminated with PCBs they had. It suggestedthat the PCBs dechlorinating bacteria were widespread in Taiwan. Each of PCBs dechlorination reactions with their physical and chemical properties including heat of reaction (△H), related retention time (RRT) and charge distribution were also examined. Selective dechlorination of the indigenous microorganisms in Taiwan was according to the thermodynamic favorable reaction. Actually, reactions with more energy released to proceed dechlorination was selected by microorganisms collected from low-PCB-contaminated sediments. But those bacteria from badly contaminated evironments didn''t follow the same rule, they simply selected the dechlorination reactions which could get rid of the oringinal PCBs toxicity .