Structural characteristics of tobacco leaf pectin and its distinct modulatory effects on gut microbiota during in vitro fecal fermentation

With a global annual production of 6 million tons, tobacco leaves contain pectin as their most abundant polysaccharide. However, the structure and prebiotic-like potential of tobacco leaf pectin remain poorly understood. In this study, crude pectin named TLPA was extracted from tobacco leaves with ammonium oxalate, and further fractionated to obtain the major fraction TLPA-1. Multi-technique structural characterization demonstrated that TLPA-1 is a pectin-rich heteropolysaccharide containing predominant homogalacturonan (HG)-like and rhamnogalacturonan-I (RG-I)-like structural features, together with minor neutral sugar-rich components. The HG region was dominated by 1,4-linked Gal p A residues, whereas the RG-I region additionally contained alternating 1,2-linked and 1,2,4-linked Rha p residues substituted with arabinan-, galactan-, and possibly other structurally diverse side chains. TLPA and TLPA-1 resisted simulated gastrointestinal digestion and were gradually utilized during in vitro fecal fermentation. Both fractions reshaped the gut microbial community, promoted carbohydrate-fermenting bacteria, and enhanced short-chain fatty acid production. These findings provide systematic insight into the structural characteristics, digestive stability, and fermentability of tobacco leaf pectin, suggesting its potential as a microbiota-accessible polysaccharide and provide a structural foundation for the high-value utilization of tobacco leaf biomass.