Gastrointestinal digestion and colonic fermentation of brewer's spent yeast peptides modulate their antioxidant properties and effect on intestinal barrier

The aims of this work were to obtain bioactive peptides from brewer's spent yeast (BSY) and to evaluate the effect of simulated gastrointestinal digestion (SGID) followed by in vitro colonic fermentation (CF) on biopeptide activity. β-Glucuronidase and mucinase inhibitory activities, antioxidant properties, and modulation of intestinal barrier function of BSY bioactive peptides using mouse jejunum organoids were assesed. For this, two BSY hydrolysates were obtained using β-glucanase and alkaline protease. Then, each hydrolyzate was subjected to SGID, generating a dialysate and a digested product. The digested product was subsequently subjected to CF, yielding a colonic dialysate and a fermented product. The SGID produced an effective degradation of proteins and polypeptides from BSY hydrolysates, increasing the proportion of low molecular weight peptides (≈415 Da). Moreover, CF degraded peptides from digested products and released new species with high hydrophilicity and low molecular weight (≈1000 and 550 Da). The dialysates obtained after SGID down-regulated Cxcl1 expression in mouse jejunal organoids, induced antibacterial genes, and had hydrolysate-specific effects on Muc4, antiviral and proliferation associated genes. Moreover, SGID and CF increased electron donor capacity (FRAP assay), β-glucuronidase and mucinase inhibitory activity. For FRAP this effect was due to release of non-glycosylated peptides, while for β-glucuronidase and mucinase enzymes the increase in the inhibitory activity was associated to mannose-linked peptides. Digested products increased the production of acetic and propionic acid during CF, suggesting microbial modulation. Thus, SGID and CF processing of BSY peptides modulates their antioxidant capacity and the regulation of intestinal barrier function in intestinal organoids.