ρ-Nitrophenyl Glycoside-hydrolyzing Activities in Bifidobacteria and Characterization of β-D-Galactosidase of Bifidobacterium longum 401

Bifidobacteria showed higher hydrolyzing activity toward various p-nitrophenyl glycosides (p-NP glycosides) than some other intestinal bacteria. The reactions commonly found in the organisms involved p-NP β-D-galactoside, ρ-NP a-D-glucoside and p-NP β-D-fucoside. Analysis of the enzyme species suggested that the β-D-fucoside-hydrolyzing reaction, which is undetectable in other bacteria, was catalyzed by β-D-galactosidase in many bifidobacteria and by- β-D-glucosidase in some strains. β-D-Galactosidase, which hydrolyzed ρ-NP β-D-fucoside (with 12% of its reactivity to p-NP β-D-galactoside), was purified to homogeneity from Bifidobacterium longum 401. The enzyme was distinct from other bacterial β-D-galactosidases in its higher activity toward lactulose than lactose and the insensitivity of its formation to the carbon source in the culture medium. Some properties of the β-D-galactosidase are described and compared with those of the lactase from the same organism.