Abstract: In order to explore the changes of components and biological activities of polysaccharides from Lachnum during the in vitro simulated digestion (saliva, gastric and intestinal). A novel extracellular polysaccharide (LEP-2a) was isolated and purified from Lachnum YM40. The digestive characteristics of LEP-2a, including the changes of molecular weight (Mw), chemical composition and micromorphology were evaluated by using in vitro simulated digestion model. The antioxidant activities of LEP-2a in different simulated digestive stages and its effect on lipid digestion were also measured. The results showed that LEP-2a was a heteroglycan with the Mw of 50.3 ku, which could not be digested by saliva, but the molecular weight decreased to 47.25 ku and 42.36 ku after in vitro simulated gastric and intestinal digestion, respectively. The reducing sugar content increased significantly and the atomic force microscopy showed that the height and branching degree of LEP-2a decreased significantly after gastrointestinal digestion. The results indicated that LEP-2a was degraded gradually mainly in gastrointestinal digestive stage. Besides, LEP-2a had stronger antioxidant activities after gastrointestinal digestion and could inhibit the decomposition of lipids effectively. These results provided a basis for further investigation of the in vivo activities of Lachnum polysaccharides.

Key words: Lachnum, polysaccharide, in vitro simulated digestion, antioxidant, lipid digestion