Immobilization and characterization of cellulase on hydroxy and aldehyde functionalized magnetic Fe2O3/Fe3O4 nanocomposites prepared via a novel rapid combustion process.

In this work, magnetic Fe2O3/Fe3O4 nanocomposites were prepared via a novel rapid combustion process. The silica was precipitated on the surface of Fe2O3/Fe3O4 nanocomposites. The silica-coated magnetic nanocomposites were cross-linked with glutaraldehyde, on which cellulase was covalently immobilized. The morphology, composition, and property of the prepared nanomaterials were characterized by the scanning electron microscopy (SEM), the energy dispersive spectrometry (EDS), the X-ray diffraction (XRD), the vibrating sample magnetometer (VSM), and the Fourier transform infrared (FTIR) spectroscopy. The immobilization conditions were optimized by varying operating parameters and determined to be 0.05 mL of 0.5% cellulase solution for 2 h. The catalytic stabilities of the immobilized cellulase were evaluated. The results showed that the immobilized cellulases performed higher apparent activity at pH 4.5 and exhibited good thermal stability compared with their free counterparts. The Michaelis-Menten equation showed that Km and Vmax of free cellulase were 3.46 mol·L-1 and 0.53 mol·min-1, respectively. The immobilized cellulase had higher Km and Vmax (18.99 mol·L-1 and 0.59 mol·min-1). The retained activity of the immobilized cellulase maintained over 71% of the initial activity after being used for five cycles.