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.