Improved performance of immobilized laccase on amine-functioned magnetic Fe3O4 nanoparticles modified with polyethylenimine

Polyethylenimine (PEI) as a spacer-arm polymer was modified on amine-functioned Fe3O4 nanoparticles (Fe3O4-NH2 NPs). PEI modified Fe3O4 nanoparticles (Fe304-NH2-PEI NPs) were chelated with Cu2+ to immobilize laccase through metal affinity adsorption. Meanwhile, PEI un-modified Fe3O4-NH2 NPs acted as a control group. The adsorption capacity of Fe304-NH2-PEI-Cu2+ NPs was larger than Fe3O4-NH2-Cu2+ NPs almost in the whole range of laccase concentration. And the activity recovery of Fe3O4-NH2-PEILaccase was also higher than Fe304-NH2-Laccase when the laccase concentration was lower than 26 pg/mL. The maximum activity recovery of Fe3O4-NH2-PEI-Laccase (107.41%) was much higher than Fe3O4-NH2-Laccase (42.75%). The corresponding specific activity of Fe3O4-NH2-PEI-Laccase and Fe3O4-NH2-Laccase was separately 101.33 and 74.45 times as large as free laccase product. The enzymatic properties of the two immobilized laccases were both improved and the immobilization realized reuse of laccase. The results showed that Fe3O4-NH2-PEI-Cu2+ NPs were more promising than Fe3O4NH2-Cu2+ NPs for purification and immobilization of laccase simultaneously and are potential for large-scale laccase immobilization. (C) 2016 Elsevier B.V. All rights reserved.