Divergent short-chain fatty acid production and succession of colonic microbiota arise in fermentation of variously-sized wheat bran fractions

Abstract

Though the physical structuring of insoluble dietary fiber sources may strongly impact their processing by microbiota in the colon, relatively little mechanistic information exists to explain how these aspects affect microbial fiber fermentation. Here, we hypothesized that wheat bran fractions varying in size would be fermented differently by gut microbiota, which would lead to size-dependent differences in metabolic fate (as short-chain fatty acids; SCFAs) and community structure. To test this hypothesis, we performed an in vitro fermentation assay in which wheat bran particles from a single source were separated by sieving into five size fractions and inoculated with fecal microbiota from three healthy donors. SCFA production, measured by gas chromatography, uncovered size fraction-dependent relationships between total SCFAs produced as well as the molar ratios of acetate, propionate, and butyrate. 16S rRNA sequencing revealed that these size-dependent metabolic outcomes were accompanied by the development of divergent microbial community structures. We further linked these distinct results to subtle, size-dependent differences in chemical composition. These results suggest that physical context can drive differences in microbiota composition and function, that fiber-microbiota interaction studies should consider size as a variable, and that manipulating the size of insoluble fiber-containing particles might be used to control gut microbiome composition and metabolic output.

The Effect of Xylooligosaccharide, Xylan, and Whole Wheat Bran on the Human Gut Bacteria

“…WB stimulated propionate and butyrate production (Duncan et al, 2016;De Paepe et al, 2018;Tuncil et al, 2018). Similarly, we can draw the same conclusion from previous studies that the XO treatment increased the yield of butyric acid and acetic acid (Miguez et al, 2018).…”

New View on Dietary Fiber Selection for Predictable Shifts in Gut Microbiota

“…growth (41). Recently, Tuncil et al showed that in in vitro fecal ferments, larger wheat bran particles selected toward a more butyrogenic microbiota, while smaller particles were associated with a more propiogenic microbiota (42). Examples of how fiber structural complexity is addressed by bacteria are illustrated in Fig.…”

Multi-Omic Analysis of the Microbiome and Metabolome in Healthy Subjects Reveals Microbiome-Dependent Relationships Between Diet and Metabolites

“…Thus, it is not clear whether the effect is specific to fiber, choline, or another phytonutrient common to the same food source. Both fiber and choline can act as substrates or inhibitors of bile acid metabolism (Corbin and Zeisel, 2012; Dziedzic et al, 2015; Wang et al, 2017), and both have been linked to microbial metabolism (LeBlanc et al, 1998; Tang et al, 2013; Mayengbam et al, 2018; Tuncil et al, 2018), suggesting that either or both plausibly lie in a causal pathway linking diet to bile acid metabolism through microbiota.…”