Hydrolyzes chromogen 5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside (X-Gal) and p-nitrophenyl-beta-D-galactoside (pNPGal). Hydrolysis of terminal non-reducing beta-D-galactose residues in beta-D-galactosides. Optimum pH is around 5.0-6.0. Retains more than 80% of activity at pH range between 4.5 and 6.5. Retains 10% of activity at pH 4.0. Optimum temperature is 90 degrees Celsius. Retains 90% of activity even at 95 degrees Celsius. Retains 80% of activity during a 12-hour period of incubation at 70 degrees Celsius. Half-lives at 80 and 90 degrees Celsius are 23 and 4.7 hours, respectively. Belongs to the glycosyl hydrolase 42 family.