Abstract
Bacillus subtilis 2633, an extrahyper α-amylase producing strain, was obtained by DNA mediated transformation and mutation of the bacterium. Strain 2633 produced about 40, 000_??_50, 000 u/ml of α-amylase in 72 hr.
The α-amylase was purified from cell-free medium by acetone precipitation, gel filtration on Sephadex G-25 and DEA-Spherosil column chromatography and was crystallized by concentration. The α-amylase was purified into nearly a pure state (99.7%). The optimum pH for the enzyme reaction was 6.0. The α-amylase was stable within the range from pH 5.0 to 7.0 and kept its activity at 40°C but was completely inactivated by heat treatment at 70°C for 10 min.
The molecular weight of the purified α-amylase was 47, 000. With soluble starch as sub-strate, the Km value of the α-amylase was 0.78 mg/ml, and molecular activity was calculated to be about 2.5×104 per minute.
