The human gut microbiota ferments dietary non-digestible carbohydrates into short-chain fatty acids (SCFA). These microbial products are utilized by the host and propionate and butyrate in particular exert a range of health-promoting functions. Here we provide an overview of the metabolic pathways utilized by gut microbes to produce these two SCFA from dietary carbohydrates and from amino acids resulting from protein breakdown. This overview emphasizes the important role played by cross-feeding of intermediary metabolites (in particular lactate, succinate and 1,2-propanediol) between different gut bacteria. The ecophysiology, including growth requirements and responses to environmental factors, of major propionate and butyrate producing bacteria are discussed in relation to dietary modulation of these metabolites. A detailed understanding of SCFA metabolism by the gut microbiota is necessary to underpin effective strategies to optimize SCFA supply to the host. This article is protected by copyright. All rights reserved.
The authors receive financial support from the Scottish Government Rural and Environmental Sciences and Analytical Services (RESAS). We would like to thank Sylvia Duncan for SCFA data of F. prausnitzii grown under different pH regimes and for critically reading the manuscript.
The authors declare that they have no conflicts of interest.