Modulation of Gut Microbiota by Pectin: The Critical Role of Degree of Esterification and Rhamnogalacturonan-I Ratios

Differences in the prebiotics of pectin cannot be fully explained by the sources and single structure. Microbiota exhibit distinct preferences for different structure of pectin, influencing the microbial composition by lowering pH and producing short-chain fatty acids (SCFAs) in the fermentation. However, the effect on the pectin fine structure on its fermentation properties and microbiota still controversial. Here, three pectin polysaccharides with different degree of esterification (DE) and rhamngalacturonan-I (RGI) ratio while ensuring that either the degree of RGI or the DE remained constant were prepared. By using in vitro fermentation model and microbiomics, the mechanisms by which the pectin fine structure in modulating the composition of gut microbiota and the metabolism of SCFAs were proposed. Pectins enriched with RGI structures promoted the growth of Phascolarctobacterium and Parabacteroides, and increased concentration of the SCFAs (such as acetic acid and propionic acid) associated with fat loss. Bacteria groups such as Tyzzerella , Collinsella , Prevotella-9 , Dialister and Sutterella were sensitive to DE and thereby promote SCFA production (such as hexanoic acid, butyric acid, etc). As pectin promotes the growth of probiotics and an increase in SCFAs, contributing to a decrease in pH, the growth of Lachnospiraceae_UCG-004 , Escherichia-Shigella and Lachnoclostridium is significantly inhibited. We identified thatkey roles of the DE and RGI within pectin in promoting the growth of probiotic microbiota and production of SCFAs. These results provide new a reference for the prediction of the pectin physiological activity and the development of functional pectin polysaccharide prebiotics.