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

Abstract

Lactic acid bacteria for high/3-galactosidase activity were screened by cell-free extracts from 14 strains of six Lactobacillus species and 4 strains of four Streptococcus species. Cell-free extracts from Lactobacillus species exhibited high /3-galactosidase activity except for 2 strains of L. casei. In the Streptococcus species, only S. tbermopbilus 510 had high /3-galactosidase activity. During hydrolysis of 20% lactose solutions, 3 to 11 types of oligosaccharides were formed in cell-free extracts from 12 strains of Lactobacillus species and from S. tberrnopbilus 510. Paper chromatograms of oligosaccharides produced upon lactose hydrolysis showed that the lactic acid bacteria could be classified into four groups based upon the chromatographic patterns. /3-Galactosidases of group 1 formed 6-O-~-D-galactopyranosyl-D-glucose and a trisaccharide; group 2 formed 6-O-~3-D-galactopyranosyl-D-glu cose, 6-0-t3-D-galactopyranosyl-D-galactose and a trisaccharide; group 3 formed 6-O-/3-Dgalactopyranosyl-D-glucose, 3-O-/3-D-galactopyranosyl-D-glucose and a trisaccharide; and group 4 formed 6-O-/3-D-galactopyranosyl-D-glucose, 6-O-/3-D-galactopy ranosyl-D-galactose, 3-O-13-D-galacto pyranosyl-D-glucose, 2-O-/3-D-galact opy ranosyl-D-glucose, and tri-