Cell-bound exopolysaccharides of Lactobacillus brevis KB290: protective role and monosaccharide composition

We examined the survivability of Lactobacillus brevis KB290 and derivative strain KB392 in artificial digestive juices and bile salts. The strains have similar membrane fatty acids but different amounts of cell-bound exopolysaccharides (EPS). In artificial digestive juices, KB290 showed significantly higher survivability than KB392, and homogenization, which reduced the amount of EPS in KB290 but not in KB392, reduced the survivability only of KB290. In bile salts, KB290 showed significantly higher survivability than KB392, and cell-bound EPS extraction with EDTA reduced the survivability of only KB290. Transmission electron microscopy showed there to be a greater concentration of cell-bound EPS in KB290 than in either KB392 or EDTA-treated or homogenized KB290. We conclude that KB290's cell-bound EPS (which high performance liquid chromatography showed to be made up of glucose and N-acetylglucosamine) played an important role in bile salt tolerance.