Highland barley polysaccharides promoted lactose intestinal fermentation in vitro: Unveiling the dynamic response of gut microbiota and polysaccharide structure.

Lactose intolerance affects over 70% of the global population due to the untimely metabolism of lactose in the colon. To accelerate lactose metabolism, we innovatively employed highland barley polysaccharides (HBP) to modulate the colonic fermentation efficiency of lactose using an in vitro fermentation model and fecal samples from lactose intolerant patients. With the addition of HBP, the consumption efficiency of lactose began to increase after 6 h of fermentation. At 48 h, lactose consumption increased by 29%, surpassing the effect of commercial prebiotics. Meanwhile, HBP with lower molecular weight (HBP-L, 8.69 × 104 g/Mol) exhibited more effective impacts than HBP with high molecular weight (HBP-H, 1.22 × 105 g/Mol), which was particularly evident during the 12-48 h of fermentation. More importantly, HBP, particularly HBP-L, substantially enriched Segatella, Bifidobacterium, and Ligilactobacillus in a time-dependent manner and was positively correlated with decreased lactose levels and elevated bacterial lactase activity, resulting in significant conversion of lactose to lactic acid and short-chain fatty acids. During the first 12 h of fermentation, HBP-L underwent more significant degradation than HBP-H. Meanwhile, the xylose residues and Glcp glycosidic bonds in HBP-L were preferentially utilized, while it was glucose residue in HBP-H. Thus, it indicated that HBPs were degraded and altered the composition of the gut microbiota, thereby enhancing the fermentation efficiency of lactose. Our findings provide a theoretical basis for developing targeted prebiotic foods to manage lactose intolerance.