DEGRADATION OF ANTHRACENE BY LACCASE OF TRAMETES-VERSICOLOR IN THE PRESENCE OF DIFFERENT MEDIATOR COMPOUNDS

Laccase of Trametes versicolor was generally able to oxidize anthracen e in vitro. After 72 h incubation about 35% of the anthracene was tran sformed stoichiometrically to 9,10-anthraquinone. Transformation of an thracene increased rapidly in the presence of different mediators that readily generate stable radicals: 2,2'-azino-bis-(3-ethylbenzthiazoli ne-6-sulfonic acid) (ABTS) and 1-hydroxybenzotriazole. For the reactio n, the presence of both the laccase and the mediator was necessary. In the presence of 0.005 mM 1-hydroxybenzotriazole this conversion had r emoved 47% of the anthracene after 72 h; 75% of the substrate was oxid ized during this period when ABTS (1 mM) was used as mediator. In cont rast to reactions without or with only low concentrations of a mediato r, there was a discrepancy between the disappearance of anthracene and the formation of 9,10-anthraquinone in mediator-forced reactions. Cou pling-products of mediators with anthracene degradation products were found. Anthracene disappeared nearly completely after incubation for 7 2 h with laccase in a 0.1 mM solution of 1-hydroxybenzotriazole and wa s transformed to 9,10-anthraquinone in about 80% yield; 90% of the sub strate was transformed in the presence of ABTS (2.0 mM) resulting agai n in 80% quinone. Phenothiazine was not effective in this system.