EFFECT OF FIBER STRUCTURE ON THE TAXONOMIC COMPOSITION OF THE COLONIC MICROBIOME

The overall objective of this project is to elucidate the impact of dietary fiber physical structure, investigated through cross-linking arabinoxylans with different ferulic acid content and arabinose to xylose ratios(A/X ratio), on taxonomic shifts in the colonic microbiome. The central hypothesis is that arabinoxylans with greater degree of physical matrix structure will increase the relative abundance of butyrogenic bacteria. The central hypothesis of this study will be tested by carrying out two specific goals:1. Determine the change in relative abundance of butyrogenic bacteria during in vitro fecal fermentation in the presence of cross-linked arabinoxylans varying in their degree of structure. For this specific goal, a library of insoluble matrix fibers will be generated that differ in ferulic acid content and A/X ratio. These fibers will be used as substrates for fecal fermentation, and the resulting taxonomic composition and short chain fatty acid output of the colonic microbiome will be assessed. The hypothesis is that the microbial community will shift towards butyrogenic bacteria with fermentation of more highly structured fibers (high ferulic acid content and high A/X ratio).2. Elucidate the biological basis for the relative abundance of butyrogenic bacteria in the fecal fermentation when growing on arabinoxylans differing in their degree of structure. In this specific aim, culture/washing experiments will be used to determine the ability of four different human symbiotic gut bacteria to adhere to each arabinoxylan in the library. The hypothesis is that representative butyrogenic bacteria will more efficiently adhere to the highly structured fibers than non-butyrogenic bacteria. Information from this aim will be used to generate a quantitative and predictive model for shifts in the colonic microbiome as a function of dietary fiber physical structure.Another goal of this project is the development of the project director to serve as an effective future agricultural researcher in the United States.