Degradation of a mixture of high‐molecular‐weight polycyclic aromatic hydrocarbons by aMycobacteriumstrain PYR‐1

Abstract

Mycobacterium sp. PYR‐1, which was previously shown to mineralize several individual polycyclic aromatic hydrocarbons (PAHs), simultaneously degraded phenanthrene, anthracene, fluoranthene, pyrene and benzo[a]pyrene in a six‐component synthetic mixture. Chrysene was not degraded significantly. When provided with a complex carbon source, Mycobacterium sp. PYR‐1 degraded greater than 74% of the total PAH mixture during 6 d of incubation. Mycobacterium sp. PYR‐1 appeared to preferentially degrade phenanthrene. No significant difference in degradation rates was observed between fluoranthene and pyrene. Anthracene degradation was slightly delayed but, once initiated, proceeded at a constant rate. Benzo[a]pyrene was degraded slowly. Degradation of a crude mixture of benzene‐soluble PAHs from contaminated sediments resulted in a 47% reduction of the material in 6 d compared with that of autoclaved controls. Experiments using an environmental microcosm test system indicated that mineralization rates of individual ¹⁴C‐labeled compounds were significantly lower in the mixtures than in equivalent doses of these compounds alone. Mineralization of the complete mixture was estimated conservatively to be between 49.7 and 53.6% and was nearly 50% in 30 d of incubation when all compounds were radiolabeled. These results strengthen the argument for the potential application of Mycobacterium sp. PYR‐1 for bioremediation of PAH‐contaminated wastes.