Microbiota response of pectin determined by its structural characteristics during in vitro fecal fermentation: A comparative study of various pectin sources

To identify the key structural properties of pectic polysaccharides that affect their gut fermentation behavior, structural characteristics and fecal fermentation ability of acid-extractable pectins obtained from 8 kinds of fruit and vegetable were compared. Results showed that the peach pectin presented a single molecular weight (Mw) distribution with large Mw (706.3 kDa), and the broccoli pectin owned high contents of arabinose (99.62 mg/g) and galactose (129.11 mg/g). Fermentation with these two pectins for 24 h improved the relative abundance of Bifidobacterium (13.42 % and 13.04 %, respectively), which had positive relation (p < 0.001) with Mw, arabinose and galactose. Hawthorn pectin was featured with low Mw, which also exhibited high linearity (6.96), supporting the relative abundance of Bacteroides (40.04 %) after fermentation. It had positive relation (p < 0.05) with linearity, acetate and butyrate. Tomato pectin was characterized by tri-Mw distribution with small polydispersity index (1.231, 1.120 and 1.106, respectively). Moreover, it displayed a compact and curved conformation in terms of smaller radius of gyration (Rg, 7.88 nm) and larger cross-sectional radius (Rc, 5.28 nm). Tomato pectin generated the highest content of short-chain fatty acids (61.59 mmol/L) among all the pectins after fermentation. Meanwhile, Ruminococcus was detected as key genera in the tomato pectin substrate, which was positively correlated (p < 0.05) with acetate, propionate, Rg and Rc. The correlation analysis further confirmed that Rg and arabinose content of the pectin have the greatest impact on the microbiota modification, followed by Rc and polydispersity index, promoting a deep understanding of the relationship between pectin structure and gut fermentation.