Prebiotic Properties of Exopolysaccharides from Lactobacillus helveticus LZ-R-5 and L. pentosus LZ-R-17 Evaluated by In Vitro Simulated Digestion and Fermentation

The in vitro digestion and fermentation behaviors of Lactobacillus helveticus LZ-R-5- and L. pentosus LZ-R-17-sourced exopolysaccharides (LHEPS and LPEPS) were investigated by stimulated batch-culture fermentation system. The results illustrated that LHEPS was resistant to simulated saliva and gastrointestinal (GSI) digestion, whereas LPEPS generated a few monosaccharides after digestion without significant influence on its main structure. Additionally, LHEPS and LPEPS could be consumed by the human gut microbiota and presented stronger bifidogenic effect comparing to α-glucan and β-glucan, as they promote the proliferation of Lactobacillus and Bifidobacterium in cultures and exhibited high values of selectivity index (13.88 and 11.78, respectively). Furthermore, LPEPS achieved higher contents of lactic acid and acetic acid (35.74 mM and 45.91 mM, respectively) than LHEPS (35.20 mM and 44.65 mM, respectively) during fermentation for 48 h, thus also resulting in a larger amount of total SCFAs (110.86 mM). These results have clearly indicated the potential prebiotic property of EPS fractions from L. helveticus LZ-R-5 and L. pentosus LZ-R-17, which could be further developed as new functional food prebiotics to beneficially improve human gut health.