Comparing in vitro digestion-fermentation characteristics and in vivo lipid-lowering effects of hot water and alkali-extracted polysaccharides from Volvariella volvacea

Abstract

In this study, the different characteristics of in vitro digestion and fermentation were investigated and compared with polysaccharides extracted by hot water and alkali in sequence from Volvariella volvacea (VWEP and VAEP, respectively), as well as the in vivo lipid-reducing effects. The results indicated that simulated saliva-gastrointestinal digestion altered the reducing sugar contents, molecular weights (from 7.398 × 10⁴ D to 3.080 × 10³ D, from 4.110 × 10⁴ D to 6.080 × 10³ D), chemical components, and antioxidant activities of VWEP and VAEP, respectively. However, profound distinctions in the preliminary structural characteristics between VWEP and VAEP were hardly observed during in vitro digestion. Furthermore, in vitro fermentation by human gut microbiota elicited greater differences in the short-chain fatty acids (SCFAs)-producing and gut microbiota-regulating properties of VWEP and VAEP (p < 0.05). This was evidenced by VWEP's tendency to enhance acetate and propionate production via facilitating the reproduction of Prevotella and Roseburia genera, while VAEP was more likely to increase valerate level by inhibiting Subdoligranulum, Dialister, and Enterobacter genera. Ultimately, in vivo lipid-lowering effects of VWEP and VAEP were also estimated in Caenorhabditis elegans, where VWEP exerted higher activity in reducing fat accumulation than VAEP (p < 0.05). Overall, these results provide a better understanding of the digestion-fermentation characteristics and saccharide preferences of gut microbes for VWEP and VAEP, which are valuable for functional foods as promising bioactive ingredients.