Isolation and Identification of ß-Galactosidase Producing Bacterial Strains and Partial Purification of ß-Galactosidase

ß -Galactosidase or Lactase (EC 3.2.1.23) is exoglycosidase which hydrolyzes the ß-glycosidic bond formed between a galactose and its organic moiety, which hydrolyses the ß-1,4-D-galactosidic linkage of lactose, and its related chromogens such as, o-nitro-phenyl-ß-D-galactopyranoside (oNPG), p-nitro-phenyl-ß-D-galactopyranoside (pNPG) and 6-bromo-2-naphthylgalacto-pyranoside (BNG). ß -Galactosidase is an inducible enzyme and is widely distributed in nature, being found in various types of microorganisms, plant and animal tissues. ß -Galactosidase is also used industrially to obtain the hydrolyzates of lactose from milk and milk whey for utilization in bakery products, ice cream, animal feed and as a sugar source for several fermentation products. This enzyme can be produced by large number of bacteria but Streptococcus thermophilus and Bacillus stearothermophilus are considered as potential bacterial sources. In this study, the bacterial strains producing ß-galactosidase enzyme were isolated, indentified on the basis of morphological, cultural and biochemical characteristics. The 16S rRNA gene sequence of the isolates revealed a close relationship to Bacillus cereus. The activity of ß-Galactosidase was measured in crude extract. Ammonium sulphate precipitation, sample dialysis and inhibition studies were carried out for isolated and partially purified ß -Galactosidase.