Immobilization of laccase on epoxy-functionalized silica and its application in biodegradation of phenolic compounds

A novel method of laccase immobilization on epoxy-functionalized silica particles was developed. Laccase from Myceliophthora thermophila was covalently immobilized onto epoxy-functionalized matrix by nucleophilic attack of amino groups of laccase to epoxy groups of the support. The enzyme loading on the support was about 30 mg/g under the optimum conditions (pH 4.5, 24 h). The effect of pH, temperature and organic solvent on immobilized enzyme activity was determined and compared with those of free enzyme. In general the immobilized enzyme was found to be stabilized compared to the free enzyme. Lineweaver-Burk plots were used to calculate kinetic parameters for ABTS oxidation. K_M values were 24.0 and 25.3 μM while v_max values were 10.0 and 1.6 μM min^-1 for free and immobilized laccase, respectively. The performance of the biocatalyst was evaluated by the degradation of phenolic compounds including phenol, p-chlorophenol and catechol. The removal efficiency of catechol by immobilized laccase was about 95% after 2 h.