Non-digestible galactomannan oligosaccharides from Cassia seed gum modulate microbiota composition and metabolites of human fecal inoculum

[Display omitted] •Cassia seed galactomannan oligosaccharides (CMOS) were stable during gastrointestinal digestion.•CMOS remarkably influenced human colonic microbiota composition.•CMOS fermentation majorly produced acetic acid and propionic acid, thus decreased intestinal pH.•CMOS with DP = 3 and 4 were prior utilized due to the activities of β-mannosidase and α-galactosidase. The digestibility and prebiotic potential of galactomannan oligosaccharides prepared from Cassia seed gum (CMOS) was studied. CMOS were tolerant against simulated gastrointestinal digestion. During in vitro human fecal fermentation with CMOS, the microbiota composition was significantly changed with promoted growth of potential beneficial genera (i.e. Bifidobacterium, Lactobacillus, Bacteroides, Veillonella) while that of potential harmful genera (i.e. Fusobacterium, Lachnospiraceae, and Sutterella) was inhibited. Short chain fatty acids were produced with decreased medium pH, while acetic acid (20.85 mM) and propionic acid (19.77 mM) were the predominant metabolites. For CMOS utilization, α-galactosidase and β-mannosidase were involved with the enzyme activity reached the maximum after 3 h fermentation. The HPAEC chromatograms showed that CMOS with DP = 3 and 4 were prior utilized through enzymatic hydrolysis within 36 h fermentation. Findings gained here will introduce the utilization and targeted production of CMOS (DP = 3 and 4) as prebiotics with defined structural features.