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The Optimization of Butyrate Production by Human Gut Microbiomes in the Presence of Resistant Starches

Author:
Teichmann, June
Published:
[University Park, Pennsylvania] : Pennsylvania State University, 2019.
Physical Description:
1 electronic document
Additional Creators:
Cockburn, Darrell William
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Open Access.
Summary:
A healthy gut microbiome has been linked to prevention of multiple inflammatory related diseases like inflammatory bowel disease, obesity, and colorectal cancer. One of the mechanisms at work is thought to be bacterial production of butyrate, a short chain fatty acid (SCFA) known to provide energy to colon cells and promote apoptosis in cancerous cells in addition to preventing inflammation. Resistant starch (RS) is an emerging fiber that has been shown to modify the SCFA profile in favor of butyrate production in the large intestine. This study uses a human fecal community in a batch fermentation system to determine how different RS and addition of RS degrading organisms (primary degraders, or PD) affect butyrate production. The RSs tested were a type II potato starch, high amylose maize starch, green banana flour, and tiger nut starch; a type IV tapioca starch and high amylose maize starch; and a type III potato starch in a whole food and an extracted form. PD tested were Ruminococcus bromii and Bifidobacterium adolescentis. Briefly, samples containing a fecal inoculum and one of the above RS or PD treatments were incubated at 37C for 24 h in an anaerobic chamber. All RS were predigested with pancreatin and amyloglucosidase and ethanol sterilized before use. Inoculums from ten different people were tested against all treatments in triplicate. Samples were analyzed for organic acid production (butyrate, acetate, propionate, lactate, formate, and succinate) via HPLC and UV-vis and their final community via 16S rRNA sequencing. Results showed that each RS produced a unique fermentation profile from each microbiome. While there was variation among the inoculums, they could be broadly classified as low, medium, or high butyrate producing communities (LBC, MBC, and HBC, respectively). HBC produced the highest levels of butyrate (21.7mM) on average, but values were relatively uniform across treatments. LBC were the opposite, where each community could only use one or two starches to significantly increase their butyrate production, but those that did, produced large increases. Due to this, on average, butyrate production among the LBC was only 7.26mM. MBC were in between and produced 10.67mM butyrate, on average. Addition of primary degraders R. bromii and B. adolescentis did not have consistent significant effects on butyrate production. Results indicate that butyrate production seems to be activated at the expense of lactate production, and vice versa. Linear discriminant analysis effect size (LEfSe) on sequencing data showed that the PD R. bromii was consistently associated with high butyrate production, and that butyrate producers Fecalibacterium prausnitzii and Coprococcus eutactus were enriched in the inoculums and final communities of microbiomes that could produce significant amounts of butyrate from supplementation with type IV high amylose maize starch. These butyrate producers might be especially adept at converting carbohydrates to butyrate, while other butyrate producers, like Intestinimonas butyriciproducens, were often associated with low butyrate production. The PD B. adolescentis was also associated with low butyrate production. Our research on specific RS and their specific effects on bacterial metabolomes brings us one step closer to using personalized approaches to modify the gut microbiome.
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Dissertation Note:
M.S. Pennsylvania State University 2019.
Technical Details:
The full text of the dissertation is available as an Adobe Acrobat .pdf file ; Adobe Acrobat Reader required to view the file.
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