DEGRADATION OF 4,4'-DICHLOROBIPHENYL, 3,3',4,4'-TETRACHLOROBIPHENYL, AND 2,2',4,4',5,5'-HEXACHLOROBIPHENYL BY THE WHITE-ROT FUNGUS PHANEROCHAETE-CHRYSOSPORIUM

The white rot fungus Phanerochaete chlysosporium has demonstrated abilities to degrade many xenobiotic chemicals. In this study, the degradation of three model polychlorinated biphenyl (PCB) congeners (4,4'-dichlorobiphenyl [DCB], 3,3',4,4'-tetraehlorobiphenyl, and 2,2',4,4',5,5'-hexachlorobiphenyl) by P. chrysosporium in liquid culture was examined. After 28 days of incubation, C-14 partitioning analysis indicated extensive degradation of DCB, including 11% mineralization. In contrast, there was negligible mineralization of the tetrachloro- or hexachlorobiphenyl and little evidence for any significant metabolism. With all of the model PCBs, a large fraction of the C-14 was determined to be biomass bound. Results from a time course study done with 4,4'-[C-14]DCB to examine C-14 partitioning dynamics indicated that the biomass-bound C-14 was likely attributable to nonspecific adsorption of the PCBs to the fungal hyphae. In a subsequent isotope trapping experiment, 4-chlorobenzoic acid and 4-chlorobenzyl alcohol were identified as metabolites produced from 4,4'-[C-14]DCB. To the best of our knowledge, this the first report describing intermediates formed by P. chrysosporium during PCB degradation. Results from these experiments suggested similarities between P. chrysosporium and bacterial systems in terms of effects of congener chlorination degree and pattern on PCB metabolism and intermediates characteristic of the PCB degradation process.