| Abstract: | Covalent immobilization of thermostable α-amylases from catabolite resistant and sensitive Bacillus licheniformis strains on controlled pore glass (CPG) and porous silica (Spherosil) beads and ionic binding on DEAE-cellulose, Amberlite and Dowex were investigated. Preparations with satisfactory operational stabilities and activities up to 1,600 U/g of support (ionic binding) and 800 U/g carrier (covalent coupling) were obtained. Immobilization led to a narrowing of the pH interval of maximum activity. The fixed amylases were stable in limited pH regions around the optimum pH level. An enhancement of the enzyme thermostability was observed. Apparent shifts of the optimum temperatures were not found. The apparent Vmax decreased up to 80 times. The Km′ remained unchanged (for amylopectin as the substrate) or increased up to 10 times (soluble starch). Maltose, maltotriose and maltopentaose were the main products of the hydrolysis. A significant increase in maltopentaose content was observed. |
