Hydrolysis and transgalactosylation catalysed by β-galactosidase from brush border membrane vesicles isolated from pig small intestine: A study using lactulose and its mixtures with lactose or galactose as substrates

•Pig small intestinal β-galactosidase synthesizes β-(1 → 3) glycosidic linkages.•Fructose is an acceptor giving rise to the synthesis of β-Gal-(1 → 5)-Fru.•β-(1 → 3) linkages and β-Gal-(1 → 5)-Fru would be hydrolysed by small intestinal lactase.