Characterization of the β-galactosidase produced by Streptomyces sp. YB-10 = β-galactosidase를 생산하는 Streptomyces sp. YB-10의 분리 및 효소 특성

Abstract

A strain YB-10 was isolated from soil as a producer of the extracellular β-D-galactosidase, which catalyzes the hydrolysis of lactose. The strain YB-10 was identified as Streptomyces sp. on the basis of its cultural, morphological and physiological properties. After treating culture supernatant of the isolate with ammonium sulfate, the precipitated protein was used as a crude β-galactosidase for analyzing its reaction properties with para-nitrophenyl-β-D-galactoside (pNP-βGal) as a substrate. The β-galactosidase showed its maximal activity at pH 6.0 and 60°C. The enzyme was also active on lactose. The hydrolyzing activity of β-galactosidase for pNP-βGal and lactose was decreased by galactose. Its hydrolyzing activity for lactose was also decreased by glucose, but the activity for pNP-βGal was increased to 1.8-folds by glucose.