Thermal inactivation and reactivity of β-glucosidase immobilized on chitosan–clay composite

The dried and wet chitosan–clay composite beads were prepared by mixing equal weights of cuttlebone chitosan and activated clay and then spraying drop-wise through a syringe, with and without freeze-drying, respectively. These beads were then immersed in 5 g/L of glutaraldehyde solution at a dosage of 0.5 g/L and were cross-linked, which were finally used as supports for β-glucosidase immobilization. The properties of the enzyme immobilized on wet- and dried-composite beads were compared. Kinetic modeling of thermal inactivation of free and immobilized enzymes was also investigated. For a given enzymatic reaction, the rate constant related to the decomposition of the enzyme–substrate complex to final product and the uncomplexed enzyme using dried-composite immobilized enzyme was larger than those using both free and wet-composite immobilized enzymes.