Enzyme activities during degradation of polycyclic aromatic hydrocarbons by white rot fungus Phanerochaete chrysosporium in soils

Abstract

The degradation of three polycyclic aromatic hydrocarbons (PAHs), phenanthrene, pyrene and benzo[a]pyrene in soils by Phanerochaete chrysosporium, and the enzyme activities of lignin peroxidase (LiP) and manganese peroxidase (MnP) produced during degradation, were analyzed. The results showed that the 19-d percentage degradation ranged from 72.77+/-1.39% to 25.50+/-3.41% for the three compounds, and the maximum LiP and MnP activities ranged from 0.16+/-0.005 to 0.05+/-0.002 U g(-1) and from 1.92+/-0.03 to 0.54+/-0.03 U g(-1), respectively. Degradation percentage and enzyme activities both exhibited inverse relationships with the octanol/water partition coefficient (K(ow)) of the compounds, indicating that LiP and MnP from P. chrysosporium may be the primary enzymes responsible for PAH degradation in soil. As the soil organic matter (SOM) content increased from 0.3% for Soil 1 to 19% for Soil 4, the 19-d degradation percentage of pyrene decreased from 66.20+/-2.72% to 32.42+/-1.05%, and correspondingly, the maximum of LiP and MnP activities increased from 0.05+/-0.002 to 1.78+/-0.15 U g(-1) and from 0.34+/-0.03 to 1.78+/-0.15 U g(-1), respectively. Hence, it is plausible to conclude that the P. chrysosporium appeared to degrade not only the PAHs with small molecular size but also the macromolecular SOM. When SOM differences are large, as in this study, SOM has greater influence on enzyme activity than low-level exotic pollutants.