EXTRACELLULAR AMYLOLYTIC SYSTEM OF THE YEAST LIPOMYCES-KONONENKOAE

A strain of the yeast Lipomyces kononenkoae which converted starch into SCP with a high yield, produced three extracellular amylases which were purified from the culture fluid by Ficoll concentration, dialysis, isopropanol precipitation and DE-cellulose chromatography: an α-amylase, a glucoamylase and a debranching transferase. The latter transferred α-1,6-glucosyl units from panose to glucose forming maltose and appeared to have some debranching activity on amylopectin. The α-amylase had the following properties: MW 38000 daltons; no effect of added calcium ions on activity; optimum temperature and pH for activity around 40°C and pH 5.5; ΔH‡ and ΔS‡ of heat inactivation 24360 cal mol-1 and 29.2 cal deg-1 mol-1; range of pH stability pH 4-6.5; pI=7.1; final low molecular weight products of starch hydrolysis, maltose and glucose; Km (40°C, pH 5.5) for starch 2.7 gl-1, for maltotriose 109 gl-1; uncompetitive inhibition by maltose with Ki (40°C, pH 5.5) 29.5 gl-1. The glucoamylase had the following properties: MW 81500 daltons; optimum temperature and pH for activity around 50°C and pH 4.5: ΔH‡ and ΔS‡ of heat inactivation 20400 cal mol-1 and 17.7 cal deg-1 mol-1; range of pH stability pH 4-6.5; pI=6.1; Km (30°C, pH 4.5) for soluble starch 16.2 gl-1, for maltose 0.36 gl-1, for p-nitrophenyl-α-D-glucoside 0.35 gl-1; competitive inhibition by glucose with Ki (30°C, pH 4.5) 4.7 gl-1. © 1979 Springer-Verlag.