Structural characterization and in vitro evaluation of the prebiotic potential of an exopolysaccharide produced by Bacillus thuringiensis during fermentation

Abstract

Microbial extracellular polysaccharides possess various beneficial characteristics and are potential prebiotic candidates. The extracellular polysaccharide BPS-1 was isolated from Bacillus thuringiensis (its production being optimized by response surface methodology) and subjected to high-cell-density fermentation. BPS-1 is a heteropolysaccharide (molecular weight 35.6 kDa) composed of rhamnose, arabinose, glucosamine, galactose, glucose, and mannose in respective molar ratios 3.7:1.7:4.5:1:3.1:1.1. Its functional groups and structural features were characterized by FT-IR and NMR. The cytotoxicity of BPS-1 was evaluated against HcoEpiC and LoVo cell lines. BPS-1 was also evaluated for its potential effects on human gut microbiota in an in vitro fermentation model. During 48 h of anaerobic fermentation by healthy human fecal bacteria, BPS-1 significantly enhanced the production of short-chain fatty acids and increased the relative abundance of beneficial bacterial genera. This is the first report of the prebiotic potential of BPS-1 produced by Bacillus thuringiensis and provides a basis for its application in the food industry.