Assessing the in vitro digestion of Sesbania gum, a galactomannan from S. cannabina, and subsequent impact on the fecal microbiota

Abstract

Despite the application as additives to control functional properties of food, little is known about the behavior of Sesbania gum (SG) from Sesbania cannabina seeds, in the gastrointestinal tract. SG is a kind of natural and water-soluble galactomannan consisting of a β-1,4-D-mannan backbone with single α-1,6-galactopyranosyl side branching units every 2.4 residues, mass of which is over 10⁶ Da. Using in vitro human digestion models, we elucidated the molecular weight changes of SG during the digestion and fermentation and the interactions between SG and gut microbiota. The results showed that the molecular weight of SG was not obviously changed during the simulated saliva, gastric and small intestinal digestion, but was rapidly decomposed and consumed by gut microbiota. As revealed by RNA‐seq transcriptome analyses, the CAZyme genes encoded by gut bacteria were significantly up-regulated, especially the families GH5 and 4, which target β-mannopyranoside and α-galactopyranoside, respectively. SG degradation led in turn, to changes in the short-chain fatty acid production and microbiota composition as determined by HPLC and 16S-seq, respectively. Our work is helpful to understand some features of SG subjected to the potential digestion and fermentation, and the results suggest SG has potential to be developed as a functional food ingredient for gut health.