Enhancement of immobilized lipase activity by design of polymer brushes on a hollow fiber membrane

A polymer brush possessing aminoethanol (AE) functional groups for lipase immobilization was grafted onto a hollow fiber membrane by radiation-induced graft polymerization. Almost the AE groups-grafted polymer brushes unfold through positive charge repulsion between the AE groups, enabling multi-layer immobilization of lipase. The hydroxyl groups in AE can also retain water molecules around hydrophilic part of the lipase. In this study, we controlled the length and density of the polymer brushes consisting of the glycidyl methacrylate (GMA) by changing the concentration of GMA monomer during radiation-induced graft polymerization. Immobilized lipase showed the highest activity on the grafted membrane when 5 wt% of glycidyl methacrylate as monomer for the radiation-induced graft polymerization was used. Consequently high efficiency esterification (approximately 1600 mmol/h/g-membrane) was achieved in five-layer lipase on AE polymer brush than that in monolayer lipase on the polymer brush possessing only hydroxyl groups. Moreover, the polymer brush possessing AE functional groups for lipase immobilization maintained high activity on the reuse for several times. •We grafted a polymer brush possessing aminoethanol onto a hollow fiber membrane to immobilize lipase.•The water molecules which AE retained played an important role for keeping activity of lipase.•We controlled the length and density of the polymer brushes to evaluate the effects to activity of lipase.•The improved polymer brushes achieved nineteen-fold higher esterification than that of before improvement.