Abstract

β-galactosidases enzyme have been used in the dairy industry for the improvement of lactose intolerance. The aim of this study was to detect b-galactosidase enzyme produced by isolated lactobacilli from milk and cheese. Isolated lactobacilli were cultured on MRS agar. Lactobacilli were identified by Gram stain and standard bacteriological and biochemical methods. Their ability to hydrolyze 5-bromo-4-chloro-3-indolyl-β-D-galactopyranoside (X-Gal) and O-nitrophenyl-β-D-galactopyranoside (ONPG) was determined. A protein band of indicated b-galactosidase enzyme was also detected by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) method. The colonies that produced green color on X-Gal plates were lactobacilli with b-galactosidase enzyme which had ONPG positive results. The highest enzymatic value (1,966 U/ml) was observed in one strain of Lactobacillus delbrueckii. A 116 kDa protein band was detected in some strains (37%) with highest enzyme value and in others (63%), protein band was weak by SDS-PAGE method. By adding Lactobacilli producing b-galactosidase enzyme as probiotic to dairy products, could help lactose intolerant people.

Key words: Lactobacillus, β-galactosidase, X-Gal, ONPG, SDS-PAGE.