Use of chitosan–clay composite as immobilization support for improved activity and stability of β-glucosidase

Equal weights of cuttlebone chitosan and activated clay were mixed and prepared as the wet (without freeze-drying) and dried (with freeze-drying) beads. The resulting composite beads were then cross-linked with glutaraldehyde as the supports for β-glucosidase immobilization. The immobilization conditions including enzyme loading, immobilization time, cross-linking time, and the amount of glutaraldehye were optimized. The properties of the enzyme immobilized on wet and dried composites were compared. It was shown that the storage stability of immobilized enzyme was higher than that of free enzyme. The activity of immobilized enzyme on dried composite was higher those on wet chitosan beads and wet composite after being repeatedly used for 50 times. The pH and thermal stabilities of free and immobilized enzymes were also investigated.