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 Fe 3 O 4 nanoparticles (Fe 3 O 4 –NH 2 NPs). PEI modified Fe 3 O 4 nanoparticles (Fe 3 O 4 –NH 2 –PEI NPs) were chelated with Cu 2+ to immobilize laccase through metal affinity adsorption. Meanwhile, PEI un-modified Fe 3 O 4 –NH 2 NPs acted as a control group. The adsorption capacity of Fe 3 O 4 –NH 2 –PEI–Cu 2+ NPs was larger than Fe 3 O 4 –NH 2 –Cu 2+ NPs almost in the whole range of laccase concentration. And the activity recovery of Fe 3 O 4 –NH 2 –PEI–Laccase was also higher than Fe 3 O 4 –NH 2 –Laccase when the laccase concentration was lower than 26   μg/mL. The maximum activity recovery of Fe 3 O 4 –NH 2 –PEI–Laccase (107.41%) was much higher than Fe 3 O 4 –NH 2 –Laccase (42.75%). The corresponding specific activity of Fe 3 O 4 –NH 2 –PEI–Laccase and Fe 3 O 4 –NH 2 –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 Fe 3 O 4 –NH 2 –PEI–Cu 2+ NPs were more promising than Fe 3 O 4 –NH 2 –Cu 2+ NPs for purification and immobilization of laccase simultaneously and are potential for large-scale laccase immobilization.