When overexpressed, cleaves several different substrates including o-nitrophenyl-beta-D-galactopyranoside (ONPG), chromogen 5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside (X-Gal) and lactulose, but not lactose. Has also beta-D-fucosidase activity. No beta-L-fucosidase, beta-glucosidase, beta-arabinosidase or beta-xylosidase activity. Hydrolysis of terminal non-reducing beta-D-galactose residues in beta-D-galactosides. Requires 4 M NaCl for maximal activity. Loss of activity if DTT or beta-mercaptoethanol is omitted from buffers. Addition of 5-20 mM EDTA, 1 mM Cu(2+) or 1 mM Zn(2+) results in loss of activity. Stable in 3 M NaCl for several days at room temperature, but approximately 18% and 50% of specific activity is lost when samples are stored overnight at 4 and -20 degrees Celsius, respectively. Activity is irreversibly lost within minutes in low salt buffers. Activity low, but detectable in 30% sorbitol in the complete absence of salt and it is stable in 30% sorbitol for at least four months at -20 degrees Celsius, but at room temperature approximately 20% of specific activity is lost after 48 hours. Homodimer. Highest expression in cells grown on galactose. Glucose or glycerol, alone or in combination with galactose, gives an intermediate level of expression and peptone-containing media gives very low levels of expression. Belongs to the glycosyl hydrolase 42 family.