Preparation and characterization of Fe3O4-NH2@4-arm-PEG-NH2, a novel magnetic four-arm polymer-nanoparticle composite for cellulase immobilization

A geometrically symmetric four – arm dendritic polymer 4-arm-PEG-NH 2 was employed to modify on the surface of Fe 3 O 4 as support for cellulase immobilization. Glutaraldehyde was used as a coupling agent of this magnetic support to covalently immobilize cellulase. The morphology and properties of the synthesized magnetic material were characterized by Fourier transform infrared (FT-IR) spectroscopy, vibrating-sample magnetometer (VSM), thermogravimetric analysis (TGA), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The properties of immobilized enzyme such as the optimum temperature and pH, Michaelis constant, thermal stability, reusability and storage stability were investigated. The loading capacity of cellulase was 132   mg/g. Compared with free cellulase, immobilized cellulase showed wider pH and temperature ranges, higher operational stability and good storage stability. Besides, the results of hydrolysis filter paper and microcrystalline cellulose showed that the catalytic effect of immobilized cellulase on the free cellulase was increased by about 76%.