Evaluation of fermentation characteristics of different dietary fiber sources using a cecum in vitro fermentation model

Dietary fiber has diverse sources and contains different proportions of soluble dietary fiber and insoluble dietary fiber. In this study, inulin (IN), microcrystalline cellulose (MCC), corn straw soluble dietary fiber (CS) and corn straw insoluble dietary fiber (CI), the mixture of IN and MCC in a 1:2 ratio (IM) and the mixture of CS and CI in a 1:2 ratio (CSI) were used to explore the effect of dietary fiber type and the proportions of soluble dietary fiber and insoluble dietary fiber on gut microbiota and metabolites through in vitro cecum fermentation model. The results showed that MCC and CI reduced gas production, all dietary fibers reduced ammonia nitrogen production, and all dietary fibers except MCC enhanced short-chain fatty acids generation. The lowest production of ammonia nitrogen was IM, followed by CS, IN and CSI. The highest production of short-chain fatty acids and gas was IN, followed by IM, CS and CSI. The Firmicutes / Bacteroidota was decreased by CS and CSI, and increased by IM. IN and CS increased Bacteroides . MCC increased Desulfovibrio . CS, CI and CSI increased unclassified_o_Bacteroidales and Parabacteroides . IM increased Ruminococcus_torques_group , unclassified_f_Lachnospiraceae and Faecalibacterium . It concluded that the source of dietary fiber, and the proportions of soluble dietary fiber and insoluble dietary fiber had impact on microbial composition, which ultimately influenced the production of fermentation metabolites. • The fermentation characteristics of different dietary fiber were evaluated in vitro fermentation. • Microcrystalline cellulose (MCC) and corn straw insoluble dietary fiber (CI) did not produce gas. • Inulin (IN), corn straw soluble dietary fiber (CS), IM (IN:MCC=1:2) and CSI (CS:CI=1:2)reduced ammonia nitrogen. • The highest production of SCFAs and gas was IN, followed by IM, CS and CSI. • The source of dietary fiber and the proportions of SDF and IDF changed microbial composition