AEROBIC DEGRADATION OF POLYCHLORINATED-BIPHENYLS BY ALCALIGENES SP JB1 - METABOLITES AND ENZYMES

In contrast to the degradation of penta- and hexachlorobiphenyls in ch emostat cultures, the metabolism of PCBs by Alcaligenes sp. JB1 was sh own to be restricted to PCBs with up to four chlorine substituents in resting-cell assays. Among these, the PCB congeners containing ortho c hlorine substituents on both phenyl rings were found to be least degra ded. Monochloro-benzoates and dichlorobenzoates were detected as metab olites. Resting cell assays with chlorobenzoates showed that JB1 could metabolize all three monochlorobenzoates and dichlorobenzoates contai ning only meta and pam chlorine substituents, but not dichlorobenzoate s possessing an ortho chlorine substituent. In enzyme activity assays, meta cleaving 2,3-dihydroxybiphenyl 1,2-dioxygenase and catechol 2,3- dioxygenase activities were constitutive, whereas benzoate dioxygenase and ortho cleaving catechol 1,2-dioxygenase activities were induced b y their substrates. No activity was found for pyrocatechase II, the en zyme that is specific for chlorocatechols. The data suggest that compl ete mineralization of PCBs with three or more chlorine substituents by Alcaligenes sp. JB1 is unlikely.