The effect of incubation temperature and pH buffer in β-galactosidase produced by Lactobacillus lactis

β-galactosidase, also known as lactase, is widely applied for industrial uses such as in pharmaceutical and food industry where β-galactosidase is produced as a food supplement for lactose-intolerant people. β-galactosidase is an enzyme that hydrolyzes the complex lactose into simple sugars, glucose, and galactose. Lactobacillus lactis (L. lactis) is one of the lactic acid bacteria which intracellularly produce β-galactosidase. It is better known as a probiotic bacterium which is made in special formula for day-to-day consumption. In this study β-galactosidase was extracted from L. lactis using toluene-acetone with a ratio of 9:1 (v/v). The result of this extraction then has its activity determined at various pH, temperature, and fermentation time of L. lactis. This enzyme's activity was determined by adding oNPG (o-nitrophenol-β-D-galactopyranoside) as a substrate and measuring its absorbance at λmax 420 nm. The result of this study showed that the highest β-galactosidase activity was 13.02 U/mL with the incubation time of β-galactosidase and the fermentation time of L. lactis at 15 minutes and 24 hours, respectively. The optimal pH and temperature for β-galactosidase activity to hydrolize oNPG substrate were pH 7 and 37 °C.