Cellular fatty acid composition and exopolysaccharide contribute to bile tolerance in Lactobacillus brevis strains isolated from fermented Japanese pickles

Abstract

Bile tolerance is a fundamental ability of probiotic bacteria. We examined this property in 56 Lactobacillus brevis strains isolated from Japanese pickles and also evaluated cellular fatty acid composition and cell-bound exopolysaccharide (EPS-b) production. The bile tolerance of these strains was significantly lower in modified de Man – Rogosa – Sharpe (MRS) medium (without Tween 80 or sodium acetate) than in standard MRS medium. Aggregating strains showed significantly higher bile tolerance than nonaggregating strains in MRS medium, but there was no significant difference in the modified MRS media. The relative octadecenoic acid (C18:1) content of the 3 most tolerant aggregating and nonaggregating strains was significantly higher when bile was added to MRS. In MRS without Tween 80, the relative C18:1 content was only marginally affected by addition of bile. In MRS without sodium acetate, only the 3 most tolerant nonaggregating strains increased their relative C18:1 content in the presence of bile. Meanwhile, culture in MRS without sodium acetate reduced EPS-b production in aggregating strains. In conclusion, both EPS-b and cellular fatty acid composition play important roles in bile tolerance of pickle-derived L. brevis.