Functionalized iron oxide nanoparticles for covalent immobilization of cellic CTec2 cellulase: enabling enzyme reusability in cellulosic biomass conversion

Abstract

A modified chemical co-precipitation method was employed to synthesize silicacoated-aminefunctionalized iron oxide nanoparticle (IONP@SiO2-NH2) which has been utilized as an anchoring surface for enzyme immobilization. Cellulase Cellic CTec2 cocktail was immobilized covalently onto IONP@SiO2-NH2 using glutaraldehyde as a linker. The morphological, structural, and compositional studies of nanoparticles were characterized by field emission scanning electron microscopy with energy dispersive X-ray (FESEM)-EDX, Fourier transform infrared (FTIR), X-ray diffraction (XRD), zeta potential, and Ultraviolet/visible (UV-Vis) spectroscopy. The FTIR, FESEM, and XRD spectra confirmed the successful immobilization of cellulase onto IONP@SiO2-NH2. The free enzymewith cellulase activity of 127 FPU/mL was optimized for the immobilization process which showed the best binding efficiency at 2% glutaraldehyde, protein loading 100 mg/g with carboxymethyl cellulase activity of 290 IU/g, and total immobilization yield of 70.8%. The immobilized cellulase exhibited enhanced stability for temperature and pH over a broader rangethan the free enzyme. The immobilized enzyme-mediated hydrolysis of 1% carboxymethyl cellulose (CMC) released 0.54 g glucose/g substrate at 24 h, showing potential for cellulosic biomass conversion. The immobilized cellulase which was investigated for reusability assay retained∼80% activity even after repeated 6 cycles of CMC hydrolysis. The results showed good reusability after magnetic separation, which is the main advantage of using this nanobiocatalyst system.