龙眼多糖的结构表征及其对肠道菌群和代谢谱的调节

The present work characterized the structure of longan polysaccharide (LP) and investigated its fermentation behavior and modulatory effects on pooled human gut microbiota. LP was composed predominantly of glucose with minor arabinose and galactose in molar ratios of 97.49%: 1.65%: 0.87%, with an average molecular weight of 7.34 × 107 g/mol (PDI 1.09). The LP main chain consists of →6)-α-D-Glcp-(1→ linkages with sparse branches at O-3/O-4 of Glcp and O-2 of Galp. LP selectively enriched saccharolytic species including Bacteroides thetaiotaomicron, B. ovatus, Prevotella copri, and Parabacteroides distasonis that harbor GH97 and other co-enriched CAZyme families. These changes suggest a potential role in LP degradation and potential ABC/PTS-dependent uptake. Functionally, this selective microbiota modulation may drive enhanced short-chain fatty acid production and nitrogen metabolism, generating metabolites including GABA, taurine, and tryptophan/indole derivatives. Collectively, LP functions as a slow-fermentable, microbiota-targeted α-glucan that reshapes gut microbial metabolism toward SCFA and immune-relevant metabolite signature.