Immobilization of β-glucosidase onto a mesoporous silica support: physical adsorption and covalent binding of the enzyme

In this study, the immobilization of beta-glucosidase onto mesoporous silica support by physical adsorption and covalent binding was investigated. The immobilization was performed onto micro-sized silica aggregates with an average pore size of 29 nm. During physical adsorption, the highest yield of immobilized beta-glucosidase was obtained with an initial protein concentration of 0.9 mg mL(-1). The addition of NaCl increased 1.7-fold, while the addition of Triton X-100 decreased 6-fold adsorption yield in comparison to the one obtained without any addition. Covalently bonded beta-glucosidase, via glutaraldehyde previously bonded to silanized silica, had a higher yield of immobilized enzyme as well as higher activity and substrate affinity in comparison to the one physically adsorbed. Covalent binding did not considerably change pH and temperature stability of the obtained biocatalyst in range of values that are commonly used in reactions in comparison to the unbound enzyme. Furthermore, covalent binding provided a biocatalyst that retained over 70 % of its activity after 10 cycles of reuse.