Identification of the active site residues of Gal308 by alignment of the amino acid residues with other five homologous β-galactosidases from GH family 42. The GenBank accession numbers are as follows: Geobacillus thermocatenulatus, AAW56416; Truepera radiovictrix DSM17093, ADI14846; Thermus thermophilus, ABI35985; Alicyclobacillus acidocaldarius, AAZ81841; Bacillus circulans, AAA22260; This study (Gal308), AFD21844. The alignment was carried out using the Clustal W method. The number flanking the sequences represents amino acid positions of each sequence. Asterisks mean identity. The two putative catalytic residues (E195 and E368) of Gal308 were shown in box.