Gut microbiota and metabolic profile affected by pectic domains during in vitro rat fecal fermentation: A comparative study between different glycans rich in pectic monosaccharides

This study aimed to investigate in vitro rat fecal fermentation behavior of pectic polymers and glycans that constitute typical pectic fragments, i.e. homogalacturonan (HG), arabinan (AB), arabinogalactan (AG), rhamnogalacturonan (RG), and xyloglucan (XG). Results showed that galacturonic acid proportion of HG (73.85 mol%) was the highest, followed by pectin (67.99 mol%), whereas arabinose (70.23 mol%) and galactose (86.22 mol%) enriched in AB and AG, respectively. Absolute quantitative microbiome revealed that Bacteroides showed dramatic growth in RG and AG; higher absolute abundances of Bifidobacterium (5.06E+09 and 3.36E+09 copies/g feces, respectively) were found in AB and XG; Escherichia Shigella , Enterococcus , and Klebsiella were inhibited after fermentation with pectin and HG by >95 %. Untargeted metabolomics indicated that the differential metabolite in AG and RG were 7-ketodeoxycholic acid and 9,10-epoxyoctadecanoic acid, respectively, both of which were positively related to arabinose and galactose ( p  < 0.001). Besides, another characteristic monosaccharide, rhamnose was positively correlated with succinic acid ( p  < 0.05), and Parvibacter ( p  < 0.001). Overall, this work help to understand the interactions among pectin structure, gut microbiota and metabolites, thereby guiding the targeted design of the nutrient-directed pectins in future personalized diets.