Extracellular endodextranase from the yeast Lipomyces starkeyi

Abstract

Strain IGC 4047 of the yeast Lipomyces starkeyi grew well with dextran as sole source of carbon and energy, and was able to hydrolyse blue dextran and Sephadex G-100. The enzyme was partially purified by fractionated isopropanol precipitation from the extracellular fluid of cultures grown in a minimal medium with dextran. The enzyme preparation showed only one band by polyacrylamide gel electrophoresis. The enzyme had the following properties: molecular weight, 23 000; optimum temperature and pH for activity, around 50 °C and pH 5.0, respectively; pH stability, pH 3.5–7.5; after 2 h at 50 °C and pH 5.0, 30% reduction in activity; isoelectric point, pI = 5.4; final products of dextran hydrolysis, isomaltooligosaccharides from glucose up to isomaltohexaose, with high concentrations of isomaltose and isomaltotriose. These results suggest that the enzyme is an endodextranase.