Beta galactosidase enzyme activities of Lactobacillus and Bifidobacterium genus

In this study, human-being, nutritional and animal originated 39 Lactobacillus species and 3 Bifidobacterium isolated from new-born faeces were used. Total 42 bacteria were all from the culture collection of Biotechnology Laboratory of Faculty of Science in Gazi University. ß-galactosidase enzyme activities of the cultures were identified by using o-nitrophenyl-b-D-galactopyranoside (o-NPG) as a substrate. L. fermentum ZYN17 (2.468±0.000 U/mg), L. acidophilus BAZ36 (0.947±0.052 U/mg), L. rhamnosus GD11 (1.034±0.027 U/mg) and L. casei LB65 (1.116±0.036 U/mg) strains, from Lactobacillus family and Bifidobacterium breve A26 (0.726±0.032 U/mg) strain from Bifidobacterium family had the highest spesific enzyme activity. Optimization studies were carried out with these cultures with high ß-galactosidase enzyme activity. Different pH, temperature, buffer and nutritional environment conditions had an effect on the enzyme activity. It is observed that, cultures had the highest spesific enzyme activity at pH 6.8, at 37°C and in potassium phosphate buffer. As the strains were grown up in different concentrations of substrate (lactose) containing nutritional environment, 6 % lactose served for the highest enzyme activity. In the artificial gastric juice, at pH 7.0, Lactobacillus fermentum ZYN17 strain (2.262±0.000 U/mg) showed the highest spesific enzyme activity, while in the artificial intestinal fluid, at pH 7.5, L. fermentum ZYN17 strain (1.686±0.000 U/mg) showed the highest spesific ß-galactosidase enzyme activity. Among the chemical extraction methods, Triton X-100 was determined as the most effective ß-galactosidase enzyme extraction method.Key Words : Lactobacillus, Bifidobacterium, ß-galactosidase