Biotransformation of the organochlorine pesticide trans-chlordane by wood-rot fungi

There is very limited information on the biotransformation of organochlorine pesticide chlordane by microorganisms, and no systematic study on the metabolic products and pathways for chlordane transformation by wood-rot fungi has been conducted. In this study, trans-chlordane was metabolized with the wood-rot fungi species Phlebia lindtneri, Phlebia brevispora and Phlebia aurea, which are capable of degrading polychlorinated dibenzo-p-dioxin and heptachlor epoxide. At the end of 42 days of incubation, over 50% of trans-chlordane was degraded by the fungal treatments in pure cultures. These fungi transformed trans-chlordane to at least eleven metabolites including a large amount of hydroxylated products such as 3-hydroxychlordane, chlordene chlorohydrin, heptachlor diol, monohydroxychlordene and dihydroxychlordene. P. lindtneri particularly can metabolize oxychlordane, a recalcitrant epoxide product of chlordane, into a hydroxylated product through substitution of chlorine atom by hydroxyl group. The present results suggest that hydroxylation reactions play an important role in the metabolism of trans-chlordane by these Phlebia species. Additionally, transformation of trans-chlordane and production of hydroxylated metabolites were efficiently inhibited by the addition of cytochrome P450 inhibitors, piperonyl butoxide and 1-aminobenzotriazole, demonstrating that fungal cytochrome P450 enzymes are involved in some steps of trans-chlordane metabolism, particularly in the hydroxylation process.