Functionalized magnetic nanoparticles for Cellic Ctec2 cellulase immobilization: Allowing reusability of enzyme in the conversion of cellulosic biomass

Abstract

The method of enzyme immobilization can ameliorate the overall stability and restoration of enzymes, hence facilitating their broader application in several sectors. This investigation utilized cellulase as a hydrolytic enzyme. In order to enhance the stability and performance of the cellulase enzyme, the research employed immobilization technology to secure the Cellic Ctec2 cellulase to the synthesized Cs@Fe3O4 nanocomposites. Fe3O4 nanoparticles (NPs) were coated with chitosan obtained from co-precipitation method that served as enzyme carrier. The NPs (Cs@ Fe3O4) were observed under XRD; VSM (vibrating-sample magnetometer) shows saturation magnetizations (Ms), UV–vis, field emission scanning electron microscopy (FESEM), and Fourier transform infrared spectroscopy (FT-IR). Response surface approach was applied to optimize the conditions for immobilization of cellulase. The optimum immobilization of cellulase reaches to 99.1% of loading efficiency and 69.7% of recovery activity with 2.5% of glutaraldehyde concentration. Furthermore, under ideal circumstances the immobilized enzyme’s thermostability, pH stability, temperature tolerance and reusability, were studied with respect to free cellulase. Higher relative activity of cellulase enzyme was observed at pH 5 with 50 °C temperature than free enzyme. One percent CMC hydrolysis is considered for reusability of free and immobilized enzyme and releases 222 mg glucose/g substrate at 24 h, showing great quiescence in cellulosic biomass conversion. Immobilized cellulase demonstrated high reusability by retaining almost 61.2% up to the 5th cycles and 51.2% of activity-maintained 10th cycle of hydrolysis. Reusability of cellulase enzyme can attain a gradual decrease in relative activity as number of repeats of the cycle increases to 10 during hydrolysis and increases in glucose yield after hydrolysis.