Isolation and purification of lactase from lactobacillus acidophilus

Abstract

The enzyme β-galactosidase (β-D-galactoside galactohydrolase, EC 3.2.1.23) commonly known as lactase, has important applications in the dairy industry. From culture of strain Lactobacillus acidophilus having high and stable β-galactosidase activity, the study of crude enzyme isolation were carried out by ultrasonical extraction and precipitation by neutral salts and organic solvents. Best precipitant was isopropanol with enzyme recovery 89,93%, and enzyme purity increased 4,5 folds. Further β-galactosidase purification was carried out using gel permeation chromatography on Ultrahydrogel 250 to increase purity in 14,3 folds. The molecular weight of β-galactosidase was 40 kDa. The purified enzyme had optimum activity at 40oC, pH 7 – 7,5 and kinetic parameters of Vmax and Km were 2,3 μmol/min and 0,73 mM.