Efficient hydrolysis of starch by α-amylase immobilized on cloisite 30B and modified forms of cloisite 30B by adsorption and covalent methods

In this paper, alpha-amylase from Bacillus subtilis was successfully immobilized on three supports. First, alpha-amylase was immobilized on cloisite 30B via the adsorption method. Then cloisite 30B was activated with tosyl chloride and epichlorohydrin. These activated supports were used for covalent immobilization of alpha-amylase, and their enzymatic activities were effectively tested in the starch hydrolysis. The results demonstrated that the specific activity of alpha-amylase immobilized on cloisite 30B was 2.39 +/- 0.03, for alpha-amylase immobilized on activated cloisite 30B with epichlorohydrin was 1.96 +/- 0.05 and for alpha-amylase immobilized on activated cloisite 30B with tosyl chloride was 2.17 +/- 0.05 U mg(- 1). The optimum pH for the activity of free alpha-amylase was 7, but for alpha-amylase immobilized on cloisite 30B was 8, and for alpha-amylase immobilized on activated supports was 7.5. The immobilized enzymes had better thermal resistance and storage stability than free alpha-amylase, and they also showed excellent reusability.