Immobilization of Bacillus subtilis alpha-amylase and characterization of its enzymatic properties

Bacillus subtilis 1 alpha-amylase was immobilized on different carriers by different methods of immobilization. The immobilized enzymes were prepared by physical adsorption on aminoalkylsilane-alumina (AS-alumina), ionic bind ing onto DEAE-cellulose, covalent binding on chitin, and entrapment in poly acrylamide had the highest activities. The specific activity of the immobil ized enzymes, calculated on bound protein basis, were 13.5-50% of the origi nal specific activity exhibited by the free enzyme. The optimal pH of the i mmobilized enzymes was shifted to lower values than for the free enzyme. Th e optimum reaction temperature was determined to be 45 degrees C for the fr ee amylase, whereas that for the immobilized enzymes was shifted to 60-65 d egrees C. In all cases, K-m values for the hydrolysis of starch of the immo bilized enzymes were higher than that of the native enzyme. Compared to the free form, the immobilized enzymes exhibited improved thermal stability an d higher Values of activation energy of denaturation.