Selecting β-galactosidase producing Bacillus spp. and determining condtions for lactose fermentation

Abstract

The study was conducted to select Bacillus spp. strains capable of producing the enzyme β-galactosidase and determine the suitable temperature and pH for lactose fermentation. Among the 21 Bacillus spp. strains surveyed using the X-gal method, 6 strains (B6, B7, B9, B11, B17, and B18) showed the characteristic blue color of X-gal on agar plates after 72 hours, indicating the presence of β-galactosidase enzyme. Four strains (B6, B9, B17, and B18) displaying the darkest blue color were selected for further enzyme activity determination using ortho-nitrophenyl-β-galactoside (oNPG). The results revealed that strain B18 exhibited the highest enzyme activity and was identified through molecular biological techniques as Bacillus licheniformis. The optimal conditions for lactose fermentation by B. licheniformis B18 were determined to be at 30°C and pH 7.0, with the enzyme activity reaching the highest value of 533.08 U/L. Strain B. licheniformis B18 is recommended for further research to optimize other factors for β-galactosidase production.