Catalytic properties of yellow laccase from Pleurotus ostreatus D1

The catalytic activity of yellow laccase from Pleurotus ostreatus D1 (YLPO) in the oxidation of 2,6-dimethoxyphenol (DMOP), 2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt (ABTS) and syringaldazine in aqueous buffers of different pH was studied. YLPO showed lower values of Vmax, and higher Km values, in the oxidation of DMOP and syringaldazine than yellow laccase from Panus tigrinus 8/18, and comparable values with blue laccase from other P. ostreatus strain. In order to find the optimum conditions for the oxidation of polyaromatic hydrocarbons (PAHs), the effect of acetonitrile (0–5% (v/v)) on the oxidation of DMOP in acetate buffer, pH 4.0 was investigated. Then, the effect of two surfactants, AOT and Tween 80, on DMOP oxidation in 1% (v/v) acetonitrile solutions was measured. Finally, the oxidation of anthracene and fluoranthene in 2 mM AOT solutions of 1% (v/v) acetonitrile solutions, in the absence of ABTS and presence of ABTS as a mediator of oxidation was examined. YLPO showed a relatively high activity in the degradation of the studied PAHs in the presence of ABTS. For the first time it was shown that the yellow laccase is able to convert PAHs in the absence of exogenous mediators and the observed activity was comparable to that observed in the presence of the mediator (ABTS).