Degradation of phenanthrene by Phanerochaete chrysosporium occurs under ligninolytic as well as nonligninolytic conditions

In order to delineate the roles of lignin and manganese peroxidases in the degradation of polycyclic aromatic hydrocarbons by Phanerochaete chrysosporium, the biodegradation of phenanthrene (chosen as a model for polycyclic aromatic hydrocarbons) was investigated. The disappearance of phenanthrene from the extracellular medium and mycelia was determined by using gas chromatography. The disappearance of phenanthrene from cultures of wild-type strains BKM-F1767 (ATCC 24725) and ME446 (ATCC 34541) under ligninolytic (low-nitrogen) as well as nonligninolytic (high-nitrogen) conditions was observed. The study was extended to two homokaryotic (basidiospore-derived) isolates of strain ME446. Both homokaryotic isolates, ME446-B19 (which produces lignin and manganese peroxidases only in low-nitrogen medium) and ME446-B5 (which totally lacks lignin and manganese peroxidase activities), caused the disappearance of phenanthrene when grown in low- as well as high-nitrogen media. Moreover, lignin and manganese peroxidase activities were not detected in any of the cultures incubated in the presence of phenanthrene. Additionally, the mineralization of phenanthrene was observed even under nonligninolytic conditions. The results collectively indicate that lignin and manganese peroxidases are not essential for the degradation of phenanthrene by P. chrysosporium. The observation that phenanthrene degradation occurs under nonligninolytic conditions suggests that the potential of P. chrysosporium for degradation of certain environmental pollutants is not limited to nutrient starvation conditions.