Author(s): S Princely, N Saleem Basha, J John Kirubakaran, M D Dhanaraju
Beta-galactosidase is one of the important commerci al enzymes having several applications in food and pharmaceutical industry. In dairy industry, β -galactosidase has been used to prevent crystalliza tion of lactose, to improve sweetness, to increase the solubility of th e milk product. Moreover, it has been used to produ ce low lactose containing food products for low lactose tolerance people and for the utilization of whey, which would otherwise be an environmental pollutant. Based on its importance , the present research was aimed to isolate and pur ify β - galactosidase from Streptococcus thermophilus by fe rmentation process. The enzyme was purified by ammo nium sulphate precipitation, dialysis, gel filtration ch romatography using Sephadex G-100, and SDS-PAGE and some properties of the purified enzyme like pH, temperat ure optima and kinetic parameters were determined. Isolate A5 showed highest productivity of 7.76 U/ml with a pro tein content of 67 μg/mL, pH and temperature optima at pH 7.2 and 40 º C. The apparent V max and K m values were found to be 2.8 IU/mL and 3.05 mM, resp ectively. Specific activity and fold purification of beta-galactosidase was fou nd to be 119.38 & 1.13, respectively. These charact eristics of isolated β -galactosidase showed that it could be a promising candidate for various industrial as well as biotechnological applications.