Metabolism of Dibenzo- p -Dioxin and Chlorinated Dibenzo- p - Dioxins by a Beijerinckia Species

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Abstract
Whole cells of the parent strain of Beijerinckia , grown with succinate and biphenyl, oxidized dibenzo- p -dioxin and several chlorinated dioxins. The rate of oxidation of the chlorinated dibenzo- p -dioxins decreased with an increasing degree of chlorine substitution. A mutant strain (B8/36) of Beijerinckia oxidized dibenzo- p -dioxin to cis -1,2-dihydroxy-1,2-dihydrodibenzo- p -dioxin. The mutant organism also oxidized two monochlorinated dibenzo- p -dioxins to cis -dihydrodiols. No metabolites were detected from two dichlorinated dibenzo- p -dioxins. Growth of the parent strain of Beijerinckia on succinate was inhibited after 4 h when 0.05% dibenzo- p -dioxin was present in the culture medium. Resting cell suspensions of the parent organism, previously grown with succinate and biphenyl, oxidized dibenzo- p -dioxin to a compound identified as 1,2-dihydroxydibenzo- p -dioxin. Further degradation of this metabolite was not detected, as the compound was found to be a potent mixed-type inhibitor of two ring-fission oxygenases present in this organism.

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