Effect of Bran Particle Size on Gut Microbiota Community Structure and Function

Riya Thakkar, Purdue University

Abstract

Gut microbiome composition and function are increasingly known to be linked to host health. Many factors control the gut microbiota, including mode of birth, host health status, genetics, and sanitary conditions, but diet has been one of the most-studied factors as a tool to modulate gut microbiota. Dietary fibers that act as prebiotics escape human digestion and reach the colon, where they become available to the microbes as a source of energy. Gut microbes produce various metabolites that are beneficial to the host health. Among those metabolites thought to be most important are the short-chain fatty acids (SCFAs) acetate, propionate, and butyrate. There is high interest in studying prebiotics that increase the production of these SCFAs as they are thought have many health benefits, such as being anti-inflammatory and anti-carcinogenic. Gut commensal preferences for these prebiotics depend on their chemical and physical properties. Other factors like the quantities of prebiotics and in what combinations they are consumed also influence gut microbial populations. There have been many studies conducted to test the effect of chemical differences amongst prebiotics on the gut microbiota, however, research studying the physical properties of dietary fiber and its effect on gut microbes is relatively scarce. To test the hypothesis that physical size of cereal bran particles influences their fermentation by microbiota, we tested different size fractions of wheat and maize bran in in vitro fermentation by fecal microbial communities. Microbes showed size-dependent bran preferences in the case of both wheat and maize bran, both in terms of community structure and metabolites production. For wheat bran, we tested 180-300, 300-500, 500-800, 850-1000 and >1700 m fractions with fecal microbiota from three healthy donors pooled in equal amounts by weight. We saw clear, size-dependent metabolic outcomes (SCFAs production) which were accompanied by divergent microbial community structures as analyzed by 16S rRNA sequencing. We further also linked these responses to size-dependent chemical differences of wheat bran fractions. In the second study with maize bran, we tested 180-250, 250-300, 300-500 and 500-850 m size fractions. Like in the case of wheat bran fractions, maize bran also showed size-dependent microbial community structure and metabolic outputs. Overall, this work demonstrated that bran particle size has potential as a tool for fine-tuning the gut microbiota, which in turn can alter metabolite production and have potential benefits to host health.

Degree

M.Sc.

Advisors

Weaver, Purdue University.

Subject Area

Genetics|Medicine|Nutrition|Systematic biology

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