Detoxification of Polychlorinated Biphenyls by Microorganisms

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Gouri Mukerjee-Dhar, Ph.D. Chief Researcher, Environmental Biotechnology Laboratory, Fundamental Research Division
Minoru Shimura Researcher, Environmental Biotechnology Laboratory, Fundamental Research Division
Toshio Hayakawa, Ph.D. Researcher, Environmental Biotechnology Laboratory, Fundamental Research Division
Kazuhide Kimbara, Ph.D. Chief Researcher, Environmental Biotechnology Laboratory,Fundamental Research Division

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A Gram-negative biphenyl utilizing bacterium, Burkholderia sp. strain TSN101, which can degrade polychlorinated biphenyls (PCBs) in high concentrations of Kaneclor 300, a complex PCB mixture, was isolated and characterized. At low concentrations of Kaneclor 300, strain TSN101 degraded most of the tri- and tetrachlorobiphenyls while at higher PCB concentrations the congener selectivity pattern was different and the position of chlorine substitution strongly affected degradation of some congeners. At 25 g/ml of Kaneclor 300, strain TSN101 degraded di- and trichlorinated congeners with chlorine substitutions at both ortho- and para- positions. At concentrations of 50 g/ml to 150 g/ml Kaneclor 300, di- and trichlorobiphenyls with ortho- substitutions in both phenyl rings were not well degraded. Trichlorobiphenyls with para- and meta- substitutions were equally well degraded at all concentrations studied. A defined PCB mixture with chlorine substitutions at 2'- and 4'- positions was used to confirm the ability of the strain TSN101 to degrade ortho- and para- substituted congeners. A 5 kb DNA fragment containing the bphBCD genes was cloned. A bphC disrupted mutant of Burkholderia sp. strain TSN101, which was constructed by gene replacement, lost the ability to utilize biphenyl demonstrating that the cloned bph gene was essential for biphenyl metabolism by strain TSN101.
As the degradation potential of the strain TSN101 is retained even in the presence of high concentrations of Kaneclor 300, we believe this strain can be used industrially for the biodegradation of polychlorinated biphenyls.