UC Davis

Carbohydrates are the most abundant biomolecules in nature, and they are involved in many biological functions. These biomolecules play a key role in shaping the human gut microbiome. However, little is known about how the specific structures of food carbohydrates mediate this link between the gut microbiome and health. Characterizing carbohydrate structures remains a significant challenge, and their compositions in food remain unknown. The chapters presented in this dissertation include a series of advance liquid chromatography-mass spectrometry (LC-MS) methods to characterize food carbohydrates. Chapter I includes structures, functions, and biosynthesis of plant carbohydrates. In addition, the chapter describes the functions of dietary carbohydrates serving as prebiotics followed by the modern LC-MS methods to characterize carbohydrates at the monosaccharide, glycosidic linkage, and sequence levels. Chapter II presents a novel high-throughput ultra-high performance liquid chromatography triple quadrupole mass spectrometry (UHPLC-QqQ MS) workflow to determine the absolute quantitation of monosaccharide composition in 850 foods. The resulting monosaccharide compositions were used to generate a glycan encyclopedia (Glycopedia) for feeding studies and personalizing diets. Chapter III presents the development of a de novo multidimensional LC-MS workflow to structurally elucidate oligosaccharides derived from plant polysaccharides at the sequence, monosaccharide, and glycosidic linkage levels. Chapter IV presents a glycosidic linkage method to elucidate linkages in food and feces for monitoring carbohydrate-microbe interactions in clinical feeding studies involving mice and humans.