Enrichment and isolation of anaerobic microorganisms concerned with reductive degradation of hexachlorobenzene from soils

Enrichment culture media, which reduced the recovery ratios of residual hexachlorobenzene (200 ppm) to several % within 2 weeks, were prepared after 4 transfers of paddy field soil and PCB-treated flooded soil. Eleven morphologically identical anaerobic microorganisms, which had a reduced residual HCB recovery ratio, were isolated using aerobic agar plates. The isolated microorganisms remarkably reduced the recovery ratio of residual heptachlor but their reduction of endrin, aldrin, and dieldrin was not so remarkable, and had novel morphological and physiological characters, which clearly distinguished these microorganisms from any of the known microorganisms. (C) Pesticide Science Society of Japan Introduction Because of extremely high resistance to oxidative degradation of aerobic microorganisms, highly-chlorinated chemicals, such as PCBs, dioxins, hexachlorobenzene (HCB), and drins (POPs: Persistent Organic Pollutants), have extremely high environmental persistency. As dechlorinated POPs became less toxic and more easily degradable by aerobic bacteria 1), reductive dechlorination was supposed to be an effective bioremediation method for POPs.