Maize Bran Particle Size Governs the Community Composition and Metabolic Output of Human Gut Microbiota in in vitro Fermentations

Abstract

Differences in the chemical and physical properties of dietary fibers are increasingly known to exert effects on their fermentation by gut microbiota. Here, we demonstrate that maize bran particle size fractions show metabolic output and microbial community differences similar to those we previously observed for wheat brans. As for wheat brans, maize bran particles varied in starch and protein content and in sugar composition with respect to size. We fermented maize bran particles varying in size in vitro with human fecal microbiota as inocula, measuring their metabolic fate [i.e., short-chain fatty acids (SCFAs)] and resulting community structure (via 16S rRNA gene amplicon sequencing). Metabolically, acetate, propionate and butyrate productions were sizedependent. 16S rRNA sequencing revealed that the size-dependent SCFA production was linked to divergent microbial community structures, which exerted effects at fine taxonomic resolution (the genus and species level). These results further suggest that the physical properties of bran particles, such as size, are important variables governing microbial community compositional and metabolic responses.

Dietary Supplementation With Fine-Grinding Wheat Bran Improves Lipid Metabolism and Inflammatory Response via Modulating the Gut Microbiota Structure in Pregnant Sow

“…Microbial community structural and metabolic responses are affected by the DF structure ( Thakkar et al, 2020 ). The study detected fermentability of wheat bran with different particle sizes in vitro .…”

In Vitro Simulation of Human Colonic Fermentation: A Practical Approach towards Models’ Design and Analytical Tools

“…Nevertheless, most of the static colonic fermentation models consist of bottles, vessels, or tubes. They are typically placed in chambers with a gas mixture (H 2 :CO 2 :N 2 ) to maintain the anaerobic conditions, in a shaking incubator, and at corporal temperature (37 • C) [27][28][29].…”

“…-Particle size manipulation: maize bran, cellulose, and whole grain oat flakes. [27,33,[47][48][49][50][51][52][53] To assay the effect of whole foods or additives on gut microbiota and their metabolites.…”

“…Then, the suspension is manually homogenised or is homogenised using a stomacher [31,36,43,56,69]. In addition to the previous homogenisation stage, some protocols include filtering [27,30,54], or centrifugation steps [37,65,80] so that the supernatant is used as faecal inoculum in the fermentation process. In addition, other protocols include the extraction of the bacterial mass from the rest of the components of the faecal sample by means of the use of iohexol (Nycodenz ® ), which is added to the supernatant of a previously homogenised faecal suspension, causing the isolation of viable cells.…”

Microbiota‐directed food formulation

“…One approach is to control food particle size. Modulation of maize bran particle size was shown to exhibit effects both on fermentation by gut microbiota and also short‐chain fatty acid production, with acetate, propionate and butyrate production being particle size dependent 12 . Thermal processing also modifies food composition due to chemical reactions.…”