Isolation and characterization of Schwanniomyces alluvius amylolytic enzymes

Abstract

The extracellular amylolytic enzymes of S. alluvius were studied to determine future optimization of this yeast for the production of industrial ethanol from starch. Both .alpha.-amylase and glucoamylase were isolated and purified. .alpha.-Amylase had an optimum pH of 6.3 and was stable from pH 4.5-7.5. The optimum temperature for the enzyme was 40.degree. C but it was quickly inactivated at temperatures > 40.degree. C. The Km for soluble starch was 0.364 mg/ml. The MW was calculated to be 61,900 .+-. 700. .alpha.-Amylase was capable of releasing glucose from starch but not from pullulan. Glucoamylase had an optimum pH of 5.0 and was stable from pH 4.0- > 8.0. The optimum temperature for the enzyme was 50.degree. C and, although less heat sensitive than .alpha.-amylase, it was quickly inactivated at 60.degree. C. Km values were 12.67 mg/ml for soluble starch and 0.72 mM for maltose. The MW was calculated to be 155,000 .+-. 3000. Glucoamylase released only glucose from both soluble starch and pullulan. S. alluvius is one of the very few yeasts to possess both .alpha.-amylase and glucoamylase as well as some fermentative capacity to produce ethanol.