Electrospun nanofibrous membranes containing epoxy groups and hydrophilic polyethylene oxide chain for highly active and stable covalent immobilization of lipase

Immobilization of enzymes on nanofibrous membranes could offer easy recycling and feasible continuous operations. In this study, a novel terpolymer poly (glycidyl methacrylate-co-methylacrylate)-g-polyethylene oxide (P(GMA-co-MA)-g-PEO) containing reactive epoxy groups and hydrophilic polyethylene oxide branch chain was synthesized. Electrospun P(GMA-co-MA)-g-PEO nanofibrous membrane was used for the immobilization of lipase molecules by covalent binding with the epoxy groups. The influences of the enzyme loading and activity by nanofibrous membranes with different content of monomers and immobilization temperature were investigated. The immobilized lipase achieved high enzyme loading of 150 mg/g and the maximum activity of 0.673 U/mg under the optimum immobilization conditions. The hydrophilic PEO branch chain was beneficial for the stabilization of the enzyme conformation which would promote the improvement of enzyme activity and stability. The results of FTIR spectra and SEM images of nanofibrous membranes before and after immobilization demonstrated that lipase has been successfully covalently immobilized on the nanofibrous membranes. The optimal pH and temperature were 7.0 and 35 °C for catalysis reaction of the immobilized lipase. The stabilities of the immobilized lipase were also investigated. The results demonstrated that the immobilized lipase has good thermal stability, reusability and organic solvent stability. The good stabilities of immobilized lipase revealed that P(GMA-co-MA)-g-PEO nanofibrous membrane is an excellent carrier for enzyme immobilization.