Transformation of chrysene and other polycyclic aromatic hydrocarbon mixtures by the fungus Cunninghamella elegans
Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous and persistent environmental pollutants; some are mutagenic, toxic, and carcinogenic and remain a public health concern. We investigated the metabolism of mixtures of PAHs and a tetracyclic aromatic hydrocarbon, chrysene, by the filamentous fungus, Cunninghamella elegans ATCC 36112. Cunninghamella elegans metabolized a mixture of PAHs including the carcinogen benzo[a]pyrene, phenanthrene, fluoranthene, pyrene, and acenaphthene completely to hydroxylated intermediates within 24 h. The metabolites from the PAH mixtures were similar to those formed in earlier studies of individual PAH compounds. In separate experiments with chrysene, C. elegans metabolized about 45% of the [5,6,11,12-14C]chrysene added to cultures during 144 h incubation. The two major metabolites of chrysene were separated by reverse-phase high performance liquid chromatography and identified by ultraviolet–visible, mass spectral, and 1H-nuclear magnetic resonance techniques as sulfate conjugates of 2,8-dihydroxychrysene and 2-hydroxychrysene. The two major metabolites accounted for about 33% of the total metabolism. The formation of sulfate conjugates of phenolic chrysene metabolites and glucoside conjugates and hydroxylated products of PAH mixtures by C. elegans may be a detoxification step, because these types of products are generally less toxic than the parent compound. Key words: polycyclic aromatic hydrocarbons, PAH mixtures, chrysene, Cunninghamella elegans, biotransformation, oxidation.