ENHANCED BIODEGRADATION OF POLYCHLORINATED-BIPHENYLS IN SOIL BY ANALOG ENRICHMENT AND BACTERIAL INOCULATION

14C-polychlorinated biphenyls (PBC) representing the commerical Aroclor 1242 mixture (a mixture of chlorinated biphenyls) were incubated in soil over 210 days to determine if biodegradation could be enhanced by additions of straw and sludge, aerobic and anaerobic incubations or their combination. Although PCB (100 mg/kg) had no effect on microbial respiratory processes in soil, mineralization did not exceed 3% of the total added. 14CO2 or 14CH4 was not produced from anaerobic incubations, although both gases were produced from organic matter additions. Further experimentation was undertaken to investigate the possibility that the soil lacked an indigenous microflora capable of metabolizing PCB or a suitable substrate analog which promoted their activity or growth. Inoculation with Acinetobacter P6 (Furukawa) alone did not enhance mineralization of 14C-PCB. When enriched with substrate analog biphenyl, 20-27% of the label was recovered as 14CO2 over 63 days compared to < 1% 14CO2 for the unenriched controls. Uninoculated and enriched treatments also greatly enhanced mineralization yielding 15-20% as 14CO2, yet the extent of primary degradation of PCB (i.e., disappearance) was greater when Acinetobacter and biphenyl were added. Analog enrichment with biphenyl was the most important factor effecting PCB degradation in soil, but additional enhancement was brought about by inoculation with Acinetobacter, which was superior to the indigenous microflora with respect to diversity towards metabolism of the isomers present in Aroclor 1242.