Our interests center around the processing of dietary fiber by the human gut microbiome. This fiber is composed primarily of the undigested carbohydrates in our diet. Humans can really only directly use the polysaccharide starch (mostly, see below), the disaccharides lactose, sucrose and maltose and their constituent monosaccharides glucose, galactose and fructose. All other carbohydrates are untouched by human digestive enzymes and instead serve as substrates to be fermented by our gut microorganisms.
We are particularly interested in resistant starch, a term for all the various forms of starch that cannot be broken down by human enzymes. Almost all cooked starches are easily digested by humans, but many raw starches such as uncooked potato starch (even uncooked, wheat starch is easily digested) require specialized bacteria for their digestion. Whole grains (the starch is hidden away), retrograded (cooked and cooled starch) and some chemically modified starches are also types of resistant starch. You can see that there are a number of things that can make starch resistant and we study the bacteria and the mechanisms they use to degrade these polysaccharides. But why do we care? Resistant starch has a potent ability to shape the microbiome and has the potential to shift the populations of bacteria so that they produce health boosting compounds like butyrate, regulate the immune system and prevent infection by pathogenic bacteria. However, not everyone's microbiome responds in the same way to each type of resistant starch. This suggests that we need to customize aspects of the diet like fiber and resistant starch to a particular person's microbiome. This development of personalized diets dictated by the microbiome is a major thrust of our lab. Thus using a combination of in vitro assays and feeding trials with humans we are trying to develop the methods of determining how you can get the most health benefits out of your personal microbiome.