Structurally Orientated Rheological and Gut Microbiota Fermentation Property of Mannans Polysaccharides and Oligosaccharides

Three mannan polysaccharides and their oligosaccharides were investigated in terms of physicochemical characteristics and effects on gut microbiota. Oligosaccharides from guar gum had the fastest fermentation kinetics for SCFAs generation at the initial stage, while the locust bean of both polymers and oligosaccharides demonstrated the lowest SCFAs through the whole fermentation process. In contrast, konjac gum steadily increased SCFAs and reached its maximum level at 24 h fermentation, indicating its fermentation character may be associated with its rheological properties. Compared to their corresponding polysaccharides, all the oligosaccharides demonstrated a faster fermentation kinetics, followed by an enriched abundance of propionate-producing bacterialPrevotellaand a decreased abundance ofMegamonasandCollinsella. Meanwhile, oligosaccharides reduced theFirmicutes/Bacteroidotaratio as well as the abundance ofBacteroidetesandEscherichia-Shigella. The fermentation of konjac substrate significantly promoted the abundance of butyrate-producing bacterialFaecalibacterium. In contrast, although the fermentation of locust bean and guar gum substrates benefitedBifidobacteriumabundance due to their similar structure and monosaccharides composition, the fermentation of locust bean gum led to greaterBifidobacteriumthan the others, which may be associated with its higher mannose composition in the molecules. Interestingly, the partial hydrolysis of the three polysaccharides slightly reduced their prebiotic function.Keywords:mannan polysaccharides;oligosaccharides;short-chain fatty acids;rheological property;gut microbiota;prebiotic function