Immobilization of cellulase on thermo-sensitive magnetic microspheres: improved stability and reproducibility

Magnetic double-shell hybrid microspheres (Fe₃O₄@SiO₂@p(NIPAM-co-GMA)) have been developed as a promising supported substrate for the immobilization of cellulase. Since the surface of the magnetic microspheres not only contains an epoxy group from GMA (glycidyl methacrylate) that can covalently bind to the enzyme, but also has an intelligent temperature response property from NIPAM (N-isopropylacrylamide), the cellulase can be covalently bonded to the magnetic microspheres and have a temperature-sensitive capability. The immobilized cellulase has the recovery ability of cellulase activity after a high-temperature inactivation. The average amount and activity of immobilized enzymes, respectively, was 233 mg g^-1, 57.4 U mg^-1 under the optimized conditions. The experimental results show that the immobilized cellulase has a wider catalytic temperature range, better temperature and storage stability. The residual activity still remained about 65.6% of the initial activity after the sixth catalysis run, which indicated that the immobilized enzyme had high reproducibility.