β-Galactosidases of Lactic Acid Bacteria: Characterization by Oligosaccharides Formed During Hydrolysis of Lactose

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Abstract
Lactic acid bacteria for high .beta.-galactosidase activity were screened by cell-free extracts from 14 strains of 1 Lactobacillus spp. and 4 strains of 4 Streptococcus spp. Cell-free extracts from Lactobacillus spp. exhibited high .beta.-galactosidase activity except for 2 strains of L. casei. In the Streptococcus spp., only S. thermophilus 510 had high .beta.-galactosidase activity. During hydrolysis of 20% lactose solutions, 3-11 types of oligosaccharides were formed in cell-free extracts from 12 strains of Lactobacillus spp. and from S. thermophilus 510. Paper chromatograms of oligosaccharides produced upon lactose hydrolysis showed that the lactic acid bacteria could be classified into 4 groups based upon the chromatographic patterns. .beta.-Galactosidases of group 1 formed 6-O-.beta.-D-galactopyranosyl-D-glucose and a trisaccharide; group 2 formed 6-O-.beta.-D-galactopyranosyl-D-glucose, 6-O-.beta.-D-galactopyranosyl-D-galactose and a trisaccharide; group 3 formed 6-O-.beta.-D-galactopyranosyl-D-glucose, 3-O-.beta.-D-galactopyranosyl-D-glucose and a trisaccharide; and group 4 formed 6-O-.beta.-D-galactopyranosyl-D-glucose, 6-O-.beta.-D-galactopyranosyl-D-galactose, 3-O-.beta.-D-galactopyranosyl-D-glucose, 2-O-.beta.-D-galactoyranosyl-D-glucose and tri- and higher oligosaccharides. Some enzymatic properties were determined on cell-free extracts from L. helveticus B-1, L. plantarum 118, L. lactis L-3 and L. bulgaricus B-6.