Deciphering the interplay between pectin structural variability, intestinal bioavailability and gut microbiota metabolism: A review

Pectins are parts of fruits, vegetables and other plant-based foods in the human daily diet. They are resilient to gastric digestion but undergo fermentation primarily in the large intestine, peaking in the cecum. The depolymerization of the pectins induced by the gut microbiota generally facilitates the subsequent fermentation of sugar monomers, during which SCFAs are primarily generated to exert multiple beneficial functions. Given structural heterogeneity of pectins and intricate process of microbial metabolism, it is crucial to elucidate how the multi-scale structure of pectins impacts their gut fermentation behavior. This review delves into distinct structural domains and fine structural characteristics of pectins, describes their degradation mechanism and bioavailability in the gastrointestinal tract, and provides an overview of the associated pectinolytic enzymes, gut microbiota community, and microbial metabolites. Moreover, recent advances are summarized in the relationships between gut fermentability and various structural parameters of pectins, including molecular size, esterification degree, monosaccharides composition and molecular conformation. Furthermore, how the structural complexity of pectins influences the interplay between saccharolytic metabolism and proteolytic metabolism during microbial fermentation is proposed. This work would help to unravel the “pectin structure - gut microbiota - host health” interactions, thereby guiding the design of functional foods targeting specific microorganisms in future personalized diets.