Purification and characterization of the extracellular amylases of the yeast Schwanniomyces alluvius

Abstract

The extracellular amylolytic system of a strain of the yeast Schwanniomyces alluvius consists of an α-amylase, a glucoamylase, and probably a debranching enzyme. Crude enzyme preparations were obtained by fractionation of the culture fluid, at the stationary phase of growth, with isopropanol. Purification was carried out by DEAE-cellulose chromatography. The glucoamylase had the following properties: molecular weight (MW), 117 000 ± 2300; optimum temperature, 50 °C; optimum pH, 4.5; range of pH stability, pH 4–6; final product of starch hydrolysis, glucose; ΔH≠ and ΔS≠ of heat inactivation, 39747 cal∙mol−1 and 274.3 cal∙deg−1∙mo−1; Km(30 °C, pH 4.5) for soluble starch, 22.22 g∙L−1. The α-amylase had the following properties: MW, 62 000 ± 500; optimum temperature, 40 °C; optimum pH, 6.3; range of pH stability, pH 4–7; final product of starch hydrolysis, maltose and glucose; ΔH≠ and ΔS≠ of heat inactivation, 36594 cal∙mol−1 and 256.9 cal∙deg−1 mol−1; Km (40 °C, pH 5.5), 2.7 g∙L−1.