P-nitrophenyl glycoside-hydrolyzing activities in bifidobacteria and characterization of β-d-galactosidaseof 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, p-NP α-D-glucoside and p-NP β-D-fucoside. Analysis of the enzymespecies suggested that the β-D-fucoside-hydrolyzing reaction, which is undetectable in otherbacteria, was catalyzed by β-D-galactosidase in many bifidobacteria and by- β-D-glucosidase in somestrains. β-D-Galactosidase, which hydrolyzed p-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 lactoseand the insensitivity of its formation to the carbon source in the culture medium. Some properties ofthe β-D-galactosidase are described and compared with those of the lactase from the sameorganism.