beta-galactosidase from Lactobacillus delbrueckii and Lactobacillus reuteri: Optimization, characterization and formation of galactooligosaccharides

摘要

Beta-galactosidase (beta-gal) is one of the important commercial enzymes having several applications in food, pharmaceutical industry and in the synthesis of galactooligosaccharides known for their prebiotic properties. The production of beta-gal from Lactobacillus delbrueckii and Lactobacillus reuteri was studied. The highest yield of beta-gal was achieved using wheat flour as carbon source. Beef extract gave the highest value of enzymatic production by L. delbrueckii reached 24.25 U/ml, while L. reuteri produced the highest beta-gal (20.20 U/ml) in the presence of peptone. The optimum beta-gal activity was recorded on 15 mM O-nitrophenyl beta-D-galactopyranoside (ONPG) at 40 degrees C and pH 7. Further enzyme activity was enhanced in the presence of Mg2+, Mn2+ and Fe2+, while it was decreased by Ag+ and Ni+ for both strains. The production of galactooligosaccharides (GalOS) from lactose using the produced beta-gal was investigated. The maximum yield of 40 and 35% (w/w) GalOS could be achieved with beta-gal of L. delbrueckii and L. reuteri, respectively from 40% lactose solution at 40 degrees C and pH 7. These characteristics of produced beta-gal showed that it could be a promising candidate for various industrial as well as biotechnological applications.