Inoculum carrier and contaminant bioavailability affect fungal degradation performances of PAH-contaminated solid matrices from a wood preservation plant

The objective of the study was to investigate the impact of chopped wheat straw (CWS), ground corn cobs (GCC) and commercial pellets (CP), as inoculum carriers, on both growth and polycyclic aromatic hydrocarbons (PAH) degradation performances of Dichomitus squalens, Pleurotus ostreatus and Coprinus comatus. A historically-contaminated soil (HCS) and creosote-treated shavings (CTS) from the Soběslav wood preservation plant, characterized by different relative abundances of the PAH bioavailable fractions, were used to assess the contaminated matrix effect and its interaction with both carrier and fungal strain. In HCS, best results were obtained with CP-immobilized P. ostreatus, which was able to deplete benzo[a]anthracene, chrysene, benzo[b]fluoranthene (BbF), benzo[k]fluoranthene (BkF) and benzo[a]pyrene (BaP) by 69.1%, 29.7%, 39.7%, 32.8% and 85.2%, respectively. Only few high-molecular mass PAHs such as BbF, BkF and BaP were degraded beyond their respective bioavailable fractions and this effect was confined to a limited number of inoculants. In CTS, only phenanthrene degradation exceeded its respective bioavailability from 1.42 to 1.86-fold. Regardless of both inoculum carrier and fungal species, degradation was positively and significantly (P < 0.001) correlated with bioavailability in fungal microcosms on HCS and CTS and such correlation was very similar in the two matrices (Radj2 equal to 0.60 and 0.59, respectively). The ability of white-rot fungi to degrade certain PAHs beyond their bioavailability was experimentally proven by this study. Although CTS and HCS considerably differed in their physico-chemical properties, PAH contents and contaminant aging, the relationship between degradation and bioavailability was not significantly affected by the type of matrix.