Synbiotics production using Lactobacillus reuteri EC01, a strain that produces alternan-type exopolysaccharide

Abstract

Alternan is an α-glucan polysaccharide with a unique structure that has promise for use as a prebiotic. In this study, we isolated a novel strain of Lactobacillus reuteri BR120 that produces abundant exopolysaccharides (EPSs). Monosaccharide analysis and NMR spectroscopy confirmed the major EPS had an alternan-type structure (α-D-glucan with α-1,6 and α-1,3 linkages), with an average molecular weight of 9.3 × 106 Da. L. reuteri EC01, obtained through gamma-ray mutagenesis of L. reuteri BR120, had a 1.3-fold increased production of alternan-type compound. The prebiotic effect of the alternan-type EPS was similar to that of fructans, metabolized by strains of Bifidobacterium longum and B. breve. Additionally, L. reuteri EC01 had various probiotic activities, with anti-inflammatory, radical scavenging, acid tolerance, bile tolerance, and intestinal adhesion effects. L. reuteri EC01 produced 54.3 g/L of the alternan-type EPS through fed-batch fermentation without aeration at 37 °C, 50 rpm, and pH 5.5. The productivity was 0.91 g/L/h, and the conversion yield was 0.279 g alternan-type EPS/g sucrose. This report describes the highest reported production of an alternan-type EPS from fermentation of Lactobacillus spp. The results suggest the cell biomass and EPS derived from fermentation of L. reuteri EC01 have potential use as synbiotics.