Date of Graduation


Document Type


Degree Name

Master of Science in Food Science (MS)

Degree Level



Food Science


Sun-Ok Lee

Committee Member

Franck Carbonero

Second Committee Member

Brett Savary


Gut, Microbiota, Obesity, Polyphenols, Sorghum


Obesity is an increasing epidemic which during 2015-2016 afflicted 39.8% of adults and 18.5% of youth in the United States. Not only can obesity affect quality of life, but it can lead to life-threatening diseases such as type 2 diabetes, heart disease, stroke, and some cancers. Animal and human research have demonstrated a pattern of gut microbiota perturbation in overweight and obesity, characterized by a reduction of beneficial bacterial species and increase in harmful species. Diet has been established as a contributing factor in gut ecology, and foods including fiber, resistant starch, and polyphenols have been found to both enhance desirable species and inhibit pathogens. Short chain fatty acids (SCFA), the products of microbial fermentation of carbohydrates, have also been implicated in body weight maintenance. Sorghum is the world’s fifth leading crop and highly undervalued in the US as a source of nutrition. The diversity and abundance of polyphenols in sorghum bran has been identified, however limited information is available on the effects of sorghum polyphenols on gut microbiota. We hypothesized that polyphenolic extracts of black and sumac sorghum brans would impact production of SCFA, alter composition of human fecal microbiota in favor of beneficial species, and improve the overall microbiota profile of overweight/obese individuals. The objectives of this study were to determine the contents of polyphenolic compounds in sorghum bran and to evaluate the change of gut microbiota composition and the effect on SCFA production in response to sorghum bran polyphenols in normal weight (NW) and overweight/obese (O/O) subjects. Black and suman sorghum brans displayed individually unique polyphenol profiles. Total SCFA production tended to be higher in the NW group, while butyrate production from FOS tended to be higher in the O/O group. Sorghum bran phenolic extracts modulated the gut microbiota and stimulated Prevotella and the butyrate-producing bacteria Roseburia. They also worked synergistically with FOS to enhance Lactobacillus and Bifidobacterium. Varying responses to sorghum polyphenols were seen between bacteria in NW and O/O. Our results support gut health-enhancing actions of sorghum polyphenols, some of which may depend on body weight status.