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

<p>A heterogeneous biocatalyst composed of laccase immobilized on Fe<sub>3</sub>O<sub>4</sub> 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 <i>K</i><sub>m</sub> value of the immobilized laccase on nanoparticles was 1.5-fold greater than the value of the free enzyme, and the calculated <i>V</i><sub>max</sub> of free and immobilized laccase was 65 mM min<sup>‒1</sup> and 43 mM min<sup>‒1</sup>, 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.</p> <p>Highlights</p><p>A heterogeneous biocatalyst was prepared by immobilization of laccase on Fe<sub>3</sub>O<sub>4</sub> nanoparticles.</p><p>6-Hepynoic acid was used as a linker via a click reaction.</p><p>The heterogeneous biocatalyst was used in dimerization of phenylacetylene.</p><p>A maximal yield was obtained after a 6 h-incubation at 40 °C and a pH of 4.5.</p><p>The catalyst was reused up to 15 runs with more than 80% conversion.</p><p></p> <p>A heterogeneous biocatalyst was prepared by immobilization of laccase on Fe<sub>3</sub>O<sub>4</sub> nanoparticles.</p> <p>6-Hepynoic acid was used as a linker via a click reaction.</p> <p>The heterogeneous biocatalyst was used in dimerization of phenylacetylene.</p> <p>A maximal yield was obtained after a 6 h-incubation at 40 °C and a pH of 4.5.</p> <p>The catalyst was reused up to 15 runs with more than 80% conversion.</p>