OXIDATION OF POLYCYCLIC AROMATIC-HYDROCARBONS (PAH) BY LACCASE OF TRAMETES-VERSICOLOR

Laccase of Trametes versicolor was able to oxidize in vitro most of th e 14 polycyclic aromatic hydrocarbons (PAH) tested. Acenaphthylene was removed by 37% followed by anthracene and benzo[a]pyrene which were o xidized by 18 and 19%, respectively. Lower but significant oxidation o f about 10% was found for-eight additional PAH: acenaphthene, fluorant hene, pyrene, benzo[a]anthracene, chrysene, benzo[b]fluoranthene, benz o[k]fluoranthene, and perylene. Naphthalene, fluorene, and phenanthren e were recovered unchanged after incubation for 72 h with laccase. Add ition of 1-hydroxybenzotriazole (HBT) to the reaction mixture increase d oxidation of PAH: acenaphthylene, acenaphthene, fluorene, anthracene , benzo[a]pyrene, and perylene were almost completely removed from the reaction mixture. Oxidation of pyrene and benzo[a]anthracene increase d from 8 and 6% without a mediator to 48 and 53% in the presence of HB T. Other PAH were nor significantly influenced by the addition of this mediator. PAH-quinones as oxidation products were formed from all PAH to different extents. A part of PAH was polymerized in the laccase/me diator system to products of weight-average molecular weight (MW) of a pproximately 1,500 Da. The correlation of the ionization potentials of PAH with the oxidation of these compounds is limited to the alternati ng PAH. (C) 1998 Elsevier Science Inc.