多糖是重要的膳食功能因子，对调控肠道稳态具有积极意义。红毛藻是一种具有很强调节血脂和血压功能的特色红藻，多糖是其主要活性成分。在前期研究中，项目组发现红毛藻多糖分子在上消化道（口腔、胃和小肠）中没有被消化酶降解，但能被肠道菌群发酵降解为低聚糖或寡糖。然而，红毛藻多糖在菌群酵解中的动态变化规律及其与肠道菌群互作机制和酵解产生的低聚糖或寡糖对肠道功能调控作用尚不明确。基于此，本项目拟利用人源化肠道菌群体外发酵模型研究红毛藻多糖对菌群结构的影响，测定多糖对菌群中优势菌种胞外分泌蛋白表达的差异，分析多糖在肠道各阶段代谢产物以及酵解产生的低聚糖和寡糖，利用肠道上皮炎症模型评价酵解产物、低聚糖和寡糖对肠道功能的影响。预期阐明红毛藻多糖在菌群酵解过程中的动态变化规律，及其分解产生的低聚糖或寡糖与调控肠道屏障功能之间的构效关系，丰富多糖的食品营养学理论基础，为红毛藻多糖营养食品的开发利用奠定理论基础。

Polysaccharides are important dietary functional factors and possess positive effects on the regulation of gut homeostasis. Bangia fusco-purpurea, belongs to Bangia species, is an important commercial edible red seaweed, abundantly cultivated in Fujian province of China and proposed to be superior to Porphyra sp. in nutritional value and taste. Accordance with some literatures in Chinese, the consumption of B. fusco-purpurea potently reduces the blood lipid levels and lower blood pressure. Polysaccharides are the main active ingredients, which take an important role in these beneficial biological functions of B. fusco-purpurea. In the previous study, we found that the polysaccharides from B. fusco-purpurea were not capable to be digested by enzymes in the upper digestive tract, but could be fermentated by the gut flora and degraded into low molecular weight saccharides or oligosaccharides. However, the fermentation dynamics of B. fusco-purpurea polysaccharides by gut microbiota, the interaction between polysaccharides and the gut microbiota, and the effects of saccharides or oligosaccharides produced by gut microbe fermentation are not clear so far. Based on these, in this project, we aim to study the effects of B. fusco-purpurea polysaccharides on the composition of the gut microbiota with in vitro gut fermentation model and determine the differences in the expression of extracellular secreted proteins by the dominant gut microbe. The characteristics of metabolite composition, saccharides or oligosaccharides produced by gut microbe with different fermentation stages were analyzed and their beneficial effects on gut function with potential mechanisms were evaluated by using in vitro intestinal epithelial inflammation model. Our project expected to clarify the fermentation dynamics of B. fusco-purpurea polysaccharides by gut microbiota and the beneficial effects of saccharides or oligosaccharides on the gut barrier function with the structure-activity relationships. Our expected findings will enrich the theoretical basis of food nutrition for polysaccharides, and further provide theoretical foundation for the development and utilization of B. fusco-purpurea polysaccharides.