Papers by Author: Peng Fei Xiao

Abstract: Although heptachlor epoxide (HE) is the major metabolite of organochlorine pesticide heptachlor in soil, there is very limited information on the biodegradation of HE by microorganisms, and no systematic study on the metabolic products and pathways for HE transformation by fungi has been conducted. In this study, the metabolism of HE was performed with Cordyceps brongniartii ATCC66779, which is capable of degrading polychlorinated dibenzo-p-dioxin. This fungus removed about 27% and 21% of HE in PDB and BSM medium, respectively, after 20 days of incubation. Three hydroxylated products including heptachlor diol, 1,2-dihydroxydihydrochlordene and trihydroxychlordene were detected as metabolites of HE using GC/MS analysis, suggesting that HE was metabolized to hydrophilic products via hydrolysis, dechlorination and hydroxylation.

Abstract: Twelve strains belonging to the genus Cordyceps were investigated for their ability to degrade organochlorine pesticide dieldrin. Based on the screening results, we further investigated Cordyceps militaris KS-92 and Cordyceps brongniartii ATCC66779 to determine their degradation capacity and metabolic products towards dieldrin. C. militaris KS-92 and C. brongniartii ATCC66779 removed about 45% and 36% of dieldrin in PDB medium, respectively, after 28 days of incubation. A hydrolysis product, 6,7-dihydroxydihydroaldrin, was detected as a initial metabolite of dieldrin in both fungal cultures using GC/MS analysis. C. militaris KS-92 particularly can degrade dieldrin to dihydrochlordenedicarboxylic acid through oxidation of 6,7-dihydroxydihydroaldrin or directly oxidation of dieldrin. The results suggested that dieldrin was metabolized to hydrophilic/low-toxicity products by selected fungi.

Abstract: l-Hydroxychlordene is the major metabolite of organochlorine pesticide heptachlor in soil. In this study, the biotransformation of l-hydroxychlordene was performed with the white rot fungus Phlebia acanthocystis TMIC34875, which is capable of degrading heptachlor. As a result, 1-hydroxychlordene was degraded completely by the fungal treatment in pure cultures after 15 days of incubation. A large amount of epoxylation product1-hydroxy-2,3-epoxychlordene was detected as metabolites of 1-hydroxychlordene using GC/MS analysis. This fungus particularly can degrade 1-hydroxy-2,3-epoxychlordene to two trihydroxychlordene isomers through hydrolysis at epoxy ring. The results suggested that 1-hydroxychlordene was metabolized to hydrophilic products via 1-hydroxy-2,3-epoxychlordene by P. acanthocystis TMIC34875.

Abstract: Although heptachlor epoxide is one of the most persistent organic pollutants (POPs) that cause serious environmental problems, there is very limited information of the biodegradation of heptachlor epoxide by microorganisms, and no systematic study on the metabolic products and pathway of endrin by microorganisms has been conducted. Wood-decay fungi can degrade a wide spectrum of recalcitrant organopollutants, including polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated biphenyls (PCBs). In this study, 18 wood-decay fungi strains of genus Phlebia were investigated for their ability to degrade heptachlor epoxide, and Phlebia acanthocystis, Phlebia brevispora, Phlebia lindtneri and Phlebia aurea removed about 16, 16, 22 and 25% of heptachlor epoxide, respectively, after 14 days of incubation. Heptachlor diol and 1-hydroxy-2,3-epoxychlordene were detected in these fungal cultures as metabolites by gas chromatography and mass spectrometry (GC/MS), suggesting that the hydrolysis reaction in the epoxide ring and substitution of chlorine atom with hydroxyl group in C1 position occur in bioconversion of heptachlor epoxide by selected wood-decay fungi, respectively. This is the first report describing the metabolites of heptachlor epoxide by microorganisms.