Starch Microspheres Entrapped with Chitosan Delay In Vitro Fecal Fermentation and Regulate Human Gut Microbiota Composition

A slow dietary fiber fermentation rate is desirable to obtain a steady metabolite release and even distribution throughout the entire colon, ensuring to meet the energy needs in the distal colon. In this study, we prepared starch-entrapped microspheres with a variable chitosan-to-starch ratio by means of electrospraying and investigated the fermentability by human fecal microbiota in an in vitro batch system. Starch encapsulation reduced microbial gas production and the concentration of short-chain fatty acids. Butyrate production, in particular, gradually decreased with increasing chitosan proportions. Moreover, the starch and chitosan composites induced a synergistic effect on the gut microbiota composition. Roseburia, Lachnospiraceae, and Clostridiales were promoted by all of the microspheres, and the abundance of the aforementioned health-promoting taxa reached a maximum in chitosan/starch microspheres with a 1:6 (w/w) ratio. Our findings highlight the possible benefits of rationally designing functional foods targeting functional and taxonomic gut microbiota modulation.