Structural characterization and in vitro gastrointestinal digestion and fermentation of litchi polysaccharide.

This study investigated the structural characteristic and in vitro digestion and fermentation behaviours of polysaccharide from litchi pulp (LPII). The results showed that LPII was 161.24kDa, and consisted of arabinose, galactose, rhamnose and glucose. The glycosidic linkages were identified as α-L-Araf-(1→, →5)-α-Araf-(1→ and →3,6)-β-D-Galp-(1→. After 4h gastric digestion, the molecular weight (Mw) of LPII was declined and the reducing sugars content (C) was increased significantly. But, the intestinal digestion had no effect on the structure of LPII. In addition, after 24h gut microbiota fermentation, the neutral sugars content and pH value decreased while total bacteria amount, C, the production of short-chain fatty acids, acetic acid and n-butyric acid increased. These results showed that LPII could be digested in gastric digestion and fermented in large intestine fermentation broth, but not changed in small intestinal fluid. The digestion and fermentation behaviours of LPII may be related with its structural features.