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

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 K-m value of the immobilized laccase on nanoparticles was 1.5-fold greater than the value of the free enzyme, and the calculated V-max 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 (100mg, similar to 80 U), TEMPO (4 mol%), 40 degrees 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.