Enzymatic Properties of Mesophilic α-Amylase from Bacillus amyloliquefaciens M23

α-Amylase from B. amyloliquefacens M23 was purified to electrophoretic homogeneity. The molecular weight of the purified α-amylase is 58 kD. Its optimum pH value of is in the range from 5.5 to 6.5,and the optimum temperature is 60 ℃. With in 24 h at room temperature 80% enzyme activity keeps in the pH range from 7.0 to 10.0. The most enzyme activity loses within 15 min at 55 ℃. But, the enzyme would be stable for 1 h with the presence of 10 mmol/L Ca2+. EDTA inhibits the enzyme activity, while, Ca2+, Mn2+ and Co2+ ions are activators. Km and Vmax of α-amylase to soluble starch is 4.33 g/L and 1.19 g/L· min, respectively. The main hydrolysates to soluble starch are oligosaccharides and dextrin.