Simulated digestion and fermentation in vitro with human gut microbiota of polysaccharides from Coralline pilulifera

Crude polysaccharides from Coralline pilulifera (CPPS) were purified by DEAE Sepharose Fast Flow to afford four purified fractions of CPPS-1, CPPS-2, CPPS-3 and CPPS-4. The physicochemical property and digestion under simulated saliva, gastric, small intestinal conditions and fermentation of CPPS-3 were investigated in vitro. CPPS-3 was composed of glucose and galactose, its molecular weight was 716 kDa, the contents of carbohydrate, protein, uronic acid and sulfuric radical were 67.84%, 1.00%, 0.38% and 9.07%, respectively. There was no significant difference on the molecular weight and content of reducing sugars, and no monosaccharides were released after saliva, gastric and small intestine digestion, indicating that CPPS-3 could not be digested under the simulated digestion conditions. After fermentation for 24 h in vitro, the carbohydrate content was decreased to 30.76%, suggesting that CPPS-3 could be broken down and utilized by gut microbiota. Some health-promoting gut microbiota such as Bacteroides, Megamonas and Veillonella were significantly enhanced, suggesting that CPPS-3 could regulate the composition of gut microbiota. What's more, CPPS-3 could promote the productions of short-chain fatty acids (22.17 and 16.17 mmol/L at 24 h for CPPS-3 and control, respectively), which could contribute to host health. Therefore, CPPS-3 is expected to be developed as functional foods.