Successive transformation of benzo[a]pyrene by laccase of Trametes versicolor and pyrene-degrading Mycobacterium strains

We previously hypothesized that polycyclic aromatic hydrocarbon (PAH)-degrading bacteria that produce laccase may enhance the degree of benzoa]pyrene mineralization. However, whether the metabolites of benzoa]pyrene oxidized by laccase can be further transformed by PAH degraders remains unknown. In this study, pyrene-degrading mycobacteria with diverse degradation properties were isolated and employed for investigating the subsequent transformation on the metabolites of benzoa]pyrene oxidized by fungal laccase of Trametes versicolor. The results confirm the successive transformation of benzoa]pyrene metabolites, 6-benzoa]pyrenyl acetate, and quinones by Mycobacterium strains, and report the discovery of the involvement of a O-methylation mediated pathway in the process. In detail, the vast majority of metabolite 6-benzoa]pyrenyl acetate was transformed into benzoa]pyrene quinones or methoxybenzoa]pyrene, via two distinct steps that were controlled by the catechol-O-methyltransferase mediated O-methylation, while quinones were reduced to dihydroxybenzoa]pyrene and further transformed into dimethoxy derivatives.