Diet is a noninvasive way to change the microbiota towards improved health. Starch, particularly resistant starch (RS), is one prebiotic fiber that seems to consistently enhance beneficial butyrate output. The molecular machinery that gut bacteria use to degrade starch and how these functions may intersect to facilitate complete starch digestion is reviewed in https://www.sciencedirect.com/... 
As part of the next era of microbiome research it will be important to delve further into the molecular details driving these changes in order to prescribe and predict microbiome responses to functional foods.