Application of a white rot fungus to biodegrade benzo[a]pyrene in soil.

Abstract

The white-rot fungus, Bjerkandera sp. BOS55, recently has been identified as an outstanding degrader of polycyclic aromatic hydrocarbons (PAHs). In this study, the ability of this fungus to degrade a five-ring PAH model compound, benzo(a)pyrene [B(a)P] in soil medium was investigated. An unpolluted sandy loam soil was sterilized and artificially contaminated with 100 mg/kg B(a)P. The B(a)P-laden soil was inoculated with 10-day-old cultures of BOS55 grown on either rice grain or chipped hemp stems. Rapid degradation of B(a)P occurred with up to 80% elimination within 22 days. B(a)P on the other hand was completely recovered from soils inoculated with the dead fungus, indicating that the elimination was biologically mediated. The biodegradation rates achieved in various experiments ranged from 8 to 14 mg B(a)P/kg soil per day. Although, the results are promising, an important drawback is that the last 20% of B(a)P was not bioavailable for further degradation by Bjerkandera sp. BOS55. However, the nonbioavailable fraction of B(a)P could be rendered bioavailable by adding acetone (10% v/v of soil water) to the soil cultures.