Structure and fermentation characteristics of five polysaccharides sequentially extracted from sugar beet pulp by different methods

Pectic polysaccharides can serve as the best alternative for prebiotics, as they can be fermented in the gut by the microbiota. Many reports suggest that pectic polysaccharides' fermentation characteristics are superior to commercially available prebiotics as Inulin. However, these researches have focused on commercial pectin commonly extracted from apples or citrus, while pectins can exhibit complex and diverse structures. In this study, we extracted and characterized five structurally different polysaccharides from sugar beet pulp by water, 1,2-Cyclohexanediaminetetraacetic acid (CDTA), sodium carbonate, and sodium hydroxide, and then assessed their impacts on the human fecal microbiome. CDTA-soluble fraction and sodium carbonate-soluble fraction were identified as pectic polysaccharides, while water-soluble fraction and sodium hydroxide-soluble fractions were rich in the arabinose side chain. All polysaccharides were fermented more easily than inulin. Some neutral sugars were more easily fermented than acid sugar, and arabinose may be the first monosaccharide to be utilized by the microbiota, followed by glucose, fucose and galacturonic acid. After 48h of fermentation, some health-promoting bacteria like Faecalibacterium, Bifidobacterium, Lactobacillus, Blautia, and Prevotella increased, while some pathogenic bacteria like Fusobacterium, Sutterella, and Dorea decreased in all polysaccharides and Inulin. Hereby, through the study of the correlation between monosaccharide composition and microbiota, we showed that monosaccharide composition might be a critical structural feature linked to the polysaccharide-microbiota modulating effect. This could be helpful to have a criterion to choose the polysaccharides to better modulate the microbiota.