O-β-D-Galactopyranosyl-(1→4)-β-D-glucopyranosyl α-D-glucopyranoside(glucosyl lactoside, GL-95) was hardly hydrolyzed by human saliva, artificial gastric juice and porcine pancreas, but was hydrolyzed about 30% by rat intestinal aceton powder in vitro. GL-95 was selectively utilized by Bifidobacterium, and hardly utilized by Clostridium, Eubacterium and Escherichia.