Preparation and Characterization of Magnetic Microspheres with an Epoxy Group Coating and Their Applications for Lipase Immobilization

Abstract

Magnetic microspheres coated with epoxy groups (Ep) were prepared by suspension polymerization of glycidyl methacrylate (GMA) and styrene (St) in the presence of oleic acid-coated Fe3O4 (OA-Fe3O4) nanoparticles, using ethylene glycol dimethacrylate (EGDMA) as a cross-link reagent. The resulting magnetic microspheres were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometry (VSM). It was verified that the magnetic microspheres had small diameters of 10–30 μm, as well as having super paramagnetism with a saturation magnetization of 10.5 emu/g. Porcine pancreas lipase (PPL) was selected as a model enzyme to be covalently immobilized (IPPL) on the magnetic microspheres via the reactive Ep; they had an activity yield up to 58.6%, when the protein loading reached 55.4 mg/g supports. In addition, the resulting immobilized lipases exhibited a better thermal stability, temperature and pH endurance than that of the free ones. In particular, an excellent reusability of IPPL, which could meet industrial requirements, was achieved.