Standard laccase activity was determined by oxidation of ABTS at room temperature [36]. The reaction solution was composed of 1 mM of ABTS in sodium acetate buffer (0.1 M, pH 4.58). Then a suitable amount of soluble enzyme or immobilized preparation (dispersed in acetate buffer) was added and the oxidation of ABTS was followed by measuring the absorbance change at 415 nm [36]. One unit was defined as the amount of the laccase that oxidized 1 μmol of ABTS substrate per min. All experiments were performed in triplicate.