BACKGROUNDImmobilization of laccase may cause more or less mass transfer limitation in practical applications. In order to enhance the reaction rate, there is great interest in developing an effective way to increase the rate of diffusion in reactions catalyzed by immobilized laccase. RESULTSThe laccase from Trametes versicolor (p-diphenol: dioxygen oxidoreductases, EC 1.10.3.2) immobilized on different molecular weight polyethylenimine (PEI) modified amine-functionalized Fe3O4 nanoparticles [Fe3O4-NH2-PEI (1200/10 000/60 000)-laccase] was separately fabricated. The oxidation reaction rate of catechol catalyzed by Fe3O4-NH2-PEI (1200)-laccase under an alternating magnetic field (600 Hz, 10 Gs) was separately 2.10 times and 1.16 times higher than the control without any external force and with mechanical stirring at 150 rpm. This was a larger increase than for Fe3O4-NH2-PEI (10 000/60 000)-laccase. In addition, the reaction rate catalyzed by Fe3O4-NH2-PEI (1200)-laccase was enhanced as the magnetic field frequency, strength and Fe3O4-NH2-PEI (1200)-laccase or catechol concentration was increased. The immobilized laccase retained 85% of its initial activity after six consecutive operations. CONCLUSIONUsing an alternating magnetic field was a powerful way to intensify the reaction rate catalyzed by laccase immobilized on branched polymer chains of magnetic nanoparticles and showed potential for large-scale catalytic reaction. (c) 2017 Society of Chemical Industry