Capable of hydrolyzing the chromogen 5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside (X-Gal) at low temperatures. pNP-beta-galactoside, pNP-beta-fucoside and pNP-beta-galacturonide are also hydrolyzed, but not pNP-beta-galactosidase, pNP-alpha-galactoside, pNP-beta-mannoside, pNP-beta-arabanoside, pNP-beta-xyloside, pNP-beta-glucuronide nor pNP-betacellobioside at 20 degrees Celsius. Hydrolysis of terminal non-reducing beta-D-galactose residues in beta-D-galactosides. Optimum temperature is 30 degrees Celsius for activity with ONPG as substrate. Loses half of its activity at 30 degrees Celsius within 1 hour. Inactivated at 40 degrees Celsius in 10 minutes. In the absence of glycerol, the enzyme is extremely unstable even at low-temperature incubation, with an 85% loss of activity at 20 degrees Celsius after 1 hour. Belongs to the glycosyl hydrolase 42 family.