Oxidation of polycyclic aromatic hydrocarbons (PAH) by laccase of Trametes versicolor

Laccase of Trametes versicolor was able to oxidize in vitro most of the 14 polycyclic aromatic hydrocarbons (PAH) tested. Acenaphthylene was removed by 37% followed by anthracene and benzo[a]pyrene which were oxidized by 18 and 19%, respectively. Lower but significant oxidation of about 10% was found for-eight additional PAH: acenaphthene, fluoranthene, pyrene, benzo[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, and perylene. Naphthalene, fluorene, and phenanthrene were recovered unchanged after incubation for 72 h with laccase. Addition of 1-hydroxybenzotriazole (HBT) to the reaction mixture increased 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 increased from 8 and 6% without a mediator to 48 and 53% in the presence of HBT. 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/mediator system to products of weight-average molecular weight (MW) of approximately 1,500 Da. The correlation of the ionization potentials of PAH with the oxidation of these compounds is limited to the alternating PAH. (C) 1998 Elsevier Science Inc.