Isolation and Some Properties of Amylase from Streptomyces hygroscopicus SF‐1084

Abstract

Abstract After screening about three thousands of Streptomyces strains from soils, a strain of Streptomyces hygroscopicus SF‐1084, which gave the highest amylase production was isolated and some properties of the amylase were studied. Amylase production media were examined and a medium which consisted of glucose 2%, corn starch 5.5%, corn meal 1%, wheat germ 0.5%, soy bean meal 1.4%, KH 2 PO 4 0.2% adjusted to pH 7.0 was used to produce the amylase. Amylase production by 30 l jar fermenter was reached at 1500 u/ml in 110 h culture. The amylase was purified from broth filtrate by the method of ammonium sulfate precipitation, DEAE‐sephadex A‐50 column chromatography and Sephadex G‐150 gelfiltration to get single band on a polyacrylamide disc gel electrophoresis. It is shown that the SF‐1084 amylase produced 88% maltose from amylose and 80% maltose from amylopectin in 48 h saccharification. From the pattern of blue value and reducing value, the amylase is supposed to have endogenous action on starch and the activity is not inhibited by PCNB (pentachloronitrobenzene); the SF‐1084 amylase does not belong to β‐amylase. The optimum pH of the amylase was 5 to 6 and the optimum temperature was 50 to 55 °C. The amylase was fairly thermostable and the residual activity after incubation at 90 °C for 15 min and 100 °C for 15 min were revealed more than 50% and 30% respectively.