Evaluating the prebiotic potential of a glucan EPS from Enterococcus hirae OL616073: Digestive resistance, probiotic growth stimulation, and gut microbiome modulation

Earlier we have reported extraction, purification and characterization of glucan exopolysaccharide (EPS) from Enterococcus hirae OL616073. In this study, we investigate the potential of glucan EPS as a prebiotic biomolecule through in vitro gastrointestinal (GI) digestion, probiotic growth promotion, and fecal fermentation studies. The glucan EPS showed higher resistance (11.5 % hydrolysis) compared to standard fructooligosaccharide (FOS;18.5 % (p ≤ 0.05)). The impact of various growth media on the viability of Bifidobacterium breve, Lacticaseibacillus rhamnosus, and Escherichia coli was examined. Glucose stimulated the growth of commensal bacteria, such as E. coli (log 8.69 ± 0.06), whereas with glucan EPS and FOS, the growth of E. coli was lower compared to probiotics. The growth viability for E. coli in the presence of EPS and FOS was log 7.97 ± 0.05 and log 7.85 ± 0.02, respectively while the values were log 8.2 ± 0.05 (p ≤ 0.05) for both the probiotics (B. breve and L. rhamnosus). During in vitro fecal fermentation glucan EPS showed a significant drop in pH from 7.56 to 4.60 after 48 h. Further, fermentation of glucan has produced high concentrations of key short chain fatty acids (SCFAs) that have several health benefits. Microbiome analysis after fecal fermentation demonstrated that glucan EPS impacts gut microbiota modification differently than FOS and a non-sugar control. A substantial increase in Bacillota abundance (33.94 to 54.32 % over 24 h) was observed with glucan EPS, indicating improved nutrition utilization and energy metabolism. Together, these findings highlight glucan EPS as a promising prebiotic agent with the potential to modulate gut microbiota and support metabolic health.