Polycyclic aromatic hydrocarbons biodegradation by fenamiphos degrading Microbacterium esteraromaticum MM1

Abstract

A Gram-positive bacterium, Microbacterium esteraromaticum MM1 able to degrade organophosphorus pesticides such as fenamiphos and malathion, also possessed the ability to degrade high molecular weight polycyclic aromatic hydrocarbon (PAH), pyrene (Pyr) and benzo[a]pyrene (BaP). The strain MM1 degraded 98.7% of initially spiked 100 mg L−1 pyrene within 15 days from the M9 mineral salts medium (pH 7.0) with 0.1% glucose. At optimal pH 7.0, 57.81% of pyrene (100 mg L−1) was degraded as the sole carbon source. In order to determine the influence of carbon sources (glucose, sodium acetate, sodium succinate) and PAHs (Naphthalene (Nap), Phenanthrene (Phe), Benzo[a]pyrene (BaP)) on pyrene degradation, a full factorial design analysis was conducted. Among the carbon sources examined, glucose, sodium acetate, and all the PAHs positively affected pyrene degradation. Interestingly, in the presence of other PAHs, benzo[a]pyrene was degraded by MM1 but not as the sole carbon source. Crude enzyme extracted from MM1 degraded pyrene with the Km and Vmax values of 49.3 μg ml−1 (equivalent to 250 μM) and 9.5 μg ml−1 min−1 mg−1 of crude protein (equivalent to 50 μM), respectively with a specific activity of 0.19 μg ml−1 mg−1 of crude protein. Metabolites such as monohydroxypyrene, 2,6-di-isopropylnaphthalene, and phthalic acid were identified during pyrene degradation by MM1. Differential expression of the protein in the presence of pyrene resulted in the inducement of enolase (phosphopyruvate hydratase) and pyridine nucleotide-disulphide oxidoreductase in MM1. To the best of our knowledge, this is the first report on the degradation of pyrene by M. esteraromaticum MM1.