Black tea polysaccharides: purification, structural characterization, fermentation characteristics, and interaction with gut microbiota.

Although black tea polysaccharides have numerous health benefits, limited studies have investigated the structural and fermentation characteristics. Herein, the structural characteristics and interaction with the gut microbiota of a black tea polysaccharide (BTPS3) fraction were systematically evaluated. Results showed that BTPS3 was an acidic heteropolysaccharide with a molecular weight of 2.10 × 105 Da, primarily composed of arabinose, galactose, and galacturonic acid in a molar ratio of 31.23:24.06:16.69. Methylation and NMR analyses indicated that BTPS3 is a pectic polysaccharide, with glycosidic linkages including →2,5)-α-L-Araf-(1→, →5)-α-L-Araf-(1→, →4)-β-D-Galp-(1→, and →4)-α-D-GalpA-(1→, among others. During in vitro fecal fermentation, BTPS3 promoted the production of short-chain fatty acids, particularly acetic and propionic acids, thereby lowering the pH. This was associated with an increased relative abundance of SCFA-producing bacteria (Bacteroides) and a decreased relative abundance of opportunistic pathogen-associated taxa (Morganella and Bilophila). Thus, BTPS3 shows prebiotic-like potential for gut microbiota modulation under in vitro conditions.