Enzymatic dimerization of phenylacetylene by laccase immobilized on magnetic nanoparticles via click chemistry

Abstract

A heterogeneous biocatalyst composed of laccase immobilized on Fe3O4 magnetic nanoparticles was prepared via a click chemistry reaction for dimerization of phenylacetylene. The physical and chemical characteristics of the catalyst were investigated. Yield and efficiency of immobilization were 68.7% and 76.4%, respectively. The apparent Km value of the immobilized laccase on nanoparticles was 1.5-fold greater than the value of the free enzyme, and the calculated Vmax of free and immobilized laccase was 65 mM min‒1 and 43 mM min‒1, respectively. While the free enzyme completely lost its activity, more than 60% of the initial activity of immobilized laccase was conserved after 30 days. Oxidative dimerization of phenylacetylene was performed using the prepared catalyst and 2,2,6,6-tetramethylpiperidine1-oxyl (TEMPO) as a mediator. The maximum yield was obtained at optimal conditions: immobilized laccase (100 mg, ∼80 U), TEMPO (4 mol%), 40 °C, pH 4.5, and 6 h incubation time. Additional environmental and eco-friendly aspects of this heterogeneous biocatalyst are its potential catalytic activity and ease of separation of the catalyst from the reaction mixture by an external magnetic field.