Cellulase immobilized on silica coated magnetic nanoparticles for improved stability and reusability

Abstract

The lignocellulosic enzymes have been used in the biomass pretreatment, are getting special attention to produce the sustainable green biofuel. However, free enzymes not only difficult to separate from reaction media but also highly temperature and pH sensitive, so a controlled environment is required to maintain. A proper immobilization supporting material needs to adopt to improve their stability and reusability. In this research, silica coated cellulase immobilized magnetic nanoparticles (MNPs) were prepared to improve temperature and pH stability and reusability of enzyme. The magnetic iron oxide nanoparticles were prepared by the chemical co-precipitation method and tetraethyl orthosilicate (TEOS) used for silica coating. Glutaraldehyde was used as a cross-linker with enzymes and functionalized nanoparticles. The amino groups and aldehyde groups can form stable covalent immobilization that can improve the stability of immobilized magnetic nanoparticles. The field emission scanning electron microscopy (FESEM) demonstrates spare shape monodisperse cellulase immobilized nanoparticles with a size of 40±5 nm. After cellulase immobilization, a vibrating sample magnetometer (VSM) measured strong 62.8 emu/g magnetizations. The prepared nanomaterials demonstrate very high, 97% immobilization efficiency confirmed by the Lowry protein assay. The best activity of immobilized cellulase were achieved at 40C and pH 5. The immobilized nanoparticles exhibit 64% and 47% relative activity at higher pH and temperature, respectively. Immobilized cellulase relative activity was achieved 83% after five cycle of reusability study. Overall, the pH and thermal stability were improved, and a higher reusability of enzyme immobilized nanomaterials was achieved. The immobilized cellulase can be utilized for the biomass hydrolysis to produce biofuels.