Isolation and characterization of Schwanniomyces alluvius amylolytic enzymes

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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.