Natural mediators in the oxidation of polycyclic aromatic hydrocarbons by laccase mediator systems

The oxidation of polycyclic aromatic compounds was studied in systems consi sting of laccase from Trametes versicolor and so-called mediator compounds, The enzymatic oxidation of acenaphthene, acenaphthylene, anthracene, and f luorene was mediated by various laccase substrates (phenols and aromatic am ines) or compounds produced and secreted by white rot fungi. The best natur al mediators, such as phenol, aniline, 4-hydroxybenzoic acid, and 4-hydroxy benzyl alcohol were as efficient as the previously described synthetic comp ounds ABTS [2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid)] and 1- hydroxybenzotriazole. The oxidation efficiency increased proportionally wit h the redox potentials of the phenolic mediators up to a maximum value of 0 .9 V and decreased thereafter,vith redox potentials exceeding this value. N atural compounds such as methionine, cysteine, and reduced glutathione, con taining sulfhydryl groups, were also active as mediator compounds.