Immobilization of α-amylase on chitosan-montmorillonite nanocomposite beads.

Enzyme immobilization is a way to increase efficiency of the enzyme and facilitate its recovery. The aim of this study was to immobilize α-amylase on chitosan-montmorillonite nanocomposite beads. Nanocomposite beads were prepared as the carrier for the enzyme stabilization and their surface was modified by Glutaraldehyde. Alpha-amylase was immobilized on nanocomposite beads by covalent bonding. The results of scanning electron microscopy (SEM) showed that particle size range of montmorillonite was 10-30 nm. This study indicated that the enzyme immobilization efficiency was 87%. The activity of free and immobilized enzyme during 40 days of storage at 4 °C decreased 95% and 36%, respectively. The results showed that the immobilized enzyme activity after reusing five times decreased about 47%. This study indicated that the immobilized enzyme activity was higher than the free enzyme at different temperatures. Also the immobilized enzyme was more stable than the free enzyme at lower pH. The results of kinetic parameters showed that Km values of the immobilized enzyme (9.12 μmol/ml) were higher than free enzyme (6.80 μmol/ml). The Vmax values for the free and immobilized enzyme were 1.30 and 0.629 μmol/mg·min, respectively.