This beta-galactosidase is also able to catalyze glycosyl transfer to a series of acceptors, including hexose, pentose, beta- or alpha-disaccharides, hexahydroxy alcohol, cyclitol, and aromatic glycosides, resulting in the production of galacto-oligosaccharides (GOS). Hydrolysis of terminal non-reducing beta-D-galactose residues in beta-D-galactosides. Binds 2 magnesium ions per monomer. Can also use manganese and iron. Binds 1 sodium ion per monomer. Can also use potassium. Completely inhibited by Hg(2+), Cu(2+) Ag(2+), and partially inhibited by Zn(2+), imidazole and EDTA. Activated by Ca(2+), Co(2+), Ni(2+). Optimum pH is 7.5-8.0. Stable between 7.5-10.0. Optimum temperature is 37-40 degrees Celsius. Stable below 37 degrees Celsius. Homodimer. Belongs to the glycosyl hydrolase 2 family.