Cellulase immobilized onto amino-functionalized magnetic Fe3O4@SiO2 nanoparticle for poplar deconstruction

A two-step synthesis method was successfully applied to covalently immobilize cellulase Cellic CTec2 onto silicon dioxide-coated functionalized magnetic nano-Fe3O4 particle (Fe3O4@SiO2). The optimized immobilization parameters were as follows: 2% glutaraldehyde, 100 U CMCase activity of Cellic CTec2, pH 4.5, 20 degrees C for 4 h, holding a corresponding CMCase activity of 3341 U/g and protein loading of 50 mg/g, respectively. The morphology and composition of nanoparticles were characterized by transmission electron microscope (TEM), vibrating sample magnetometer (VSM), Fourier transform infrared (FTIR), and X-ray diffraction (XRD). The TEM images showed that Fe3O4 and Fe3O4@SiO2 particles are spherical with non-uniform size (10-20 nm) and typical core-shell shaped (20-40 nm), respectively. The VSM value of Fe3O4, Fe3O4@SiO2, and immobilized cellulase was 91 emu/g, 64 emu/g, and 59 emu/g, respectively, along with notable superparamagnetism. The FTIR and XRD spectra confirmed that cellulase has been successfully immobilized onto the amino-functionalized Fe3O4@SiO2 particles. The polyacrylamide gel electrophoresis analysis showed that there was no significant difference between free and immobilized cellulase. The immobilized cellulase showed good thermal, pH, and storage stability. In addition, the immobilized cellulase was employed for enzymatic saccharification of poplar wood, holding a maximum enzymatic saccharification rate of 38.4% at 72 h, indicating potential for lignocellulosic biomass deconstruction.