Production and Characterization of β-Galactosidase from Lactose-Fermenting Yeasts

Abstract

Twelve strains of lactose-fermenting yeast isolated from raw milk were evaluated on β-galactosidase producing ability. The enzymes from the four strains (Tolulopsis versatilis M6, Tolulopsis sphaerica J28, Candida pseudotropicalis B57 and A60), selected by high productivity, showed very similar properties and were characterized by a pH optimum of 7.0 or 7.5 and a relatively low optimal temperature of 30°C. The molecular weights were estimated by gel filtration to be 200,000 ~ 233,000. The Km values for o-nitrophenyl-β-D-galactopyranoside were 3.45 mM, 2.09 mM, 3.45 mM and 2.82 mM for enzymes from M6, J28, B57 and A60, respectively. All enzymes were activated by Mn2+ and inhibited by Mg2+, Zn2+ and Ca2+. The enzymes are sulfhydryl dependent and were completely inhibited by Hg2+ and sulfhydryl reagents. The yeasts may be a potential source for the enzyme for industrial use. © 1982, Japan Society for Bioscience, Biotechnology, and Agrochemistry. All rights reserved.