Biotransformation of heptachlor and heptachlor epoxide by white-rot fungus Pleurotus ostreatus

The ability of Pleurotus ostreatus to transform heptachlor as well as heptachlor epoxide was investigated. Heptachlor was eliminated completely by this fungus in potato dextrose broth (PDB) and high nitrogen (HN) media during a 14 d incubation period. Heptachlor epoxide was detected as the main metabolite besides chlordene and 1-hydoxychlordene. Based on identification of the metabolites, transformation of heptachlor was proposed which was initially metabolized by epoxidation, dechlorination and hydrolysis. This fungus was also capable of degrading heptachlor epoxide which is a recalcitrant metabolite of heptachlor. Approximately 9%, 8% and 31% of heptachlor epoxide was eliminated by P. ostreatus in low nitrogen (LN), HN, and PDB media during 14 days of incubation, respectively. After acetylation, the metabolite, 2,3-dihydroxyheptachlor (Heptachlor diol), was detected in the PDB medium cultures, suggesting the hydrolysis reaction occurred in the epoxide ring. This indicated that P. ostreatus is a potential source for transformation of heptachlor as well as heptachlor epoxide.