Characterization of dairy-related Bifidobacterium spp. based on their beta-galactosidase electrophoretic patterns.

Numerical analysis of phenotypic characteristics based on enzymatic activity and carbohydrate fermentation allowed the discrimination of most strains of bifidobacteria of animal origin from those of human origin. Strains of bifidobacteria studied were separated into nine groups based on numerical analysis. Three groups contained most strains of animal origin, three groups comprised both strains of animal and human origin, and three groups were strictly composed of strains of human origin. The results indicate that one group of animal origin (group II) contained all reference strains of Bifidobacterium animals and 10 strains isolated from fermented milks or commercial preparations. Although numerical analysis of enzymatic activities and carbohydrate fermentation patterns allowed the differentiation of 'wild' strains of B. animalis and B. longum isolated from commercial preparations, this method failed to confirm the species. In the present study, the determination of electrophoretic patterns of beta-galactosidases resulted in the development of a new technique for the differentiation of Bifidobacterium species. Several isoenzymes of beta-galactosidase were detected among strains of bifidobacteria. Each species had a specific electrophoretic pattern. The detection of beta-galactosidase by electrophoresis is a new tool for distinguishing between dairy- and non-dairy-related bifidobacteria. Dairy-related bifidobacteria (B. bifidum, B. breve, B. infantis and B. longum) as well as B. animalis could be better differentiated from other bifidobacteria by comparison of their beta-galactosidase electrophoretic patterns, rather than by numerical analysis of their phenotypic characteristics.