Structural characterization and probiotic activity of Chenpi polysaccharides prepared by fermentation with Bacillus licheniformis

s Chenpi is a traditional medicinal and edible food in China. Chenpi polysaccharide (CP) is one of the main active components of Chenpi. This study established a fermentation process using Bacillus licheniformis to obtain fermented Chenpi polysaccharides (FCP) with a reduced degree of polymerization. FCP is an acidic polysaccharide exhibiting a molecular weight of 3720 Da. The three predominant monosaccharides in FCP were arabinose (31.75%), galactose (24.77%), and galacturonic acid (20.94%). According to comprehensive NMR studies, its main chain primarily comprised two types of residues: →4)-α-GalA p- (1→ and →4)-α-Gal p , while its side chains started with →2)-α-Fuc p- (1→ or →2)-β-Rha p- (1→ residues, which were further linked to extending residues such as →4)-β-Ara p- (1→ or →5)-α-Ara f- (1→, and ultimately terminated with terminal residues T-β-GalA p , T-β-Glc p , or T-α-Ara f . Compared to commercial pectic polysaccharides (PP), FCP exhibited higher solubility, a looser structure, and lower viscosity. In vitro gut microbiota fermentation demonstrated that FCP substantially enhanced the proliferation of beneficial bacteria, including Paraprevotella and Lachnospiraceae , while suppressing pathogenic bacteria like Shigella . Furthermore, FCP enhanced short-chain fatty acids (SCFAs) production by gut microbiota, particularly acetic and propionic acids. In the single-strain fermentation experiment, FCP promoted the growth of Lactococcus lactis , Pediococcus acidilactici , Parabacteroides distasonis , and Bacteroides thetaiotaomicron . Metabolomic analysis of Bacteroides thetaiotaomicron fermentation broth further revealed that FCP altered the composition of bacterial metabolites, enhancing the biosynthesis of beneficial metabolites, including propionate, 4'-O-methylglucoliquiritigenin, and cyclokievitone hydrate. This study indicated that B. licheniformis fermentation improves the physical and prebiotic properties of CP, providing new insights for the bioprocessing of Chenpi.