PCB biodegradation in aged contaminated soil: interactions between exogenous Phanerochaete chrysosporium and indigenous microorganisms

This work investigated whether the interaction between the white-rot fungus Phanerochaete chrysosporium and indigenous microorganisms could enhance polychlorinated biphenyl (PCB) removal from historically contaminated soil in aerobic microcosms. The PCB mixture was composed mainly of 14% tri-, 20% tetra-, 9% penta-, 17% hexa-, 26% hepta-, 11% octa-, and 3% nona-chlorobiphenyl (CB) congeners, determined by GC/MS. The fungus, which was grown on sugarcane bagasse and added via this solid substrate, successfully colonized the contaminated soil. The added fungi and the indigenous soil community biodegraded most PCB congeners, with removing efficiencies ranging from 13% to 100% for the 45-day incubation period. The interaction between the fungus and the microorganisms present in the added bagasse inhibited both heterotrophic activity (measured by CO2 evolution) and PCB degradation, suggesting a possible antagonism. In contrast, analysis of variance (ANOVA) inferred a synergistic effect between fungus and soil microorganisms, which resulted in a heterotrophic activity above 2.5 mg-CO2/g-initial dry matter/day. The statistical analyses also showed that the presence of fungus alone was particularly beneficial for the removal of penta- and hepta-CB.