Enzyme immobilization. Part 3: Immobilization of α-amylase on Na-bentonite and modified bentonite

Immobilization of α-amylase on bentonite modified with cetyl trimethylammonium bromide (CTMAB) below and above the critical micelle concentration (CMC) was studied and compared to α-amylase adsorbed on Na-bentonite. The highest enzyme activity for free and immobilized α-amylase was obtained in phosphate buffer 0.1 M at pH 6.2. The kinetic study of starch hydrolysis by the immobilized α-amylase was investigated and compared with the free α-amylase. A 6.2-fold decrease in Vmax and 4-fold increase in Km were observed for the immobilized α-amylase on Na-bentonite. A 7.1-fold decrease in Vmax and 4.2-fold increase in Km were observed for the α-amylase immobilized on modified bentonite with monolayer surfactant (BMS). Approximately no change in Vmax and Km was observed for the enzyme immobilized on bentonite with bilayer surfactant coverage (BBS) in comparison with the free α-amylase.