FIBER CONSUMPTION IS STRONGLY LINKED TO IMPROVEMENTS IN HEALTH OUTCOMES. HOWEVER, CURRENT INTEREST IN PREBIOTIC FIBER SUPPLEMENTS FOCUSES PRIMARILY ON PREBIOTIC FIBERS MADE OFREPEATING UNITS OF VARYING LENGTHS WITH LOW STRUCTURAL DIVERSITY. IN CONTRAST, THEREARE COMPLEX, DIVERSE OLIGOSACCHARIDES COMPOSED OF A WIDER VARIETY OF SUBUNITSAND WITH VARYING DEGREES OF POLYMERIZATION ABUNDANTLY FOUND LINKED TO DIETARY PROTEINS. THE STRUCTURE OF THESE COMPLEX OLIGOSACCHARIDES (I.E. PREBIOTIC FIBERS)RESTRICT ACCESSIBILITY BY MANY GUT BACTERIA AND CAN SELECTIVELY ENRICH BENEFICIAL BACTERIA THAT BENEFIT HUMAN HEALTH. THE RELATIVE STRUCTURAL AND COMPOSITIONAL COMPLEXITY OF THESE COMPLEX OLIGOSACCHARIDES OFFERS AN IMPROVED PALETTE OF SELECTIVE, BIOACTIVE GLYCANS TO QUERY FOR SPECIFICITY IN ENRICHING BENEFICIAL BACTERIA IN THE GUT MICROBIOME.THIS PROJECT SEEKS TO CHARACTERIZE THEUTILIZATION OF THESE DIETARY PROTEIN-LINKED OLIGOSACCHARIDESBY HUMAN GUT MICROBES WITH A FOCUS ON A FAMILY OF ENZYMES KNOWN AS ENGASES, WHICH RELEASE THESE LINKED OLIGOSACCHARIDES FROMDIETARY PROTEINS INTACT. USINGIN VITROHUMAN GUT MICROBIOME MODELS, WE WILL EXAMINE THE DEGRADATION OF THESE OLIGOSACCHARIDES BY THE GUT MICROBIOME. WE WILL ALSO IDENTIFY ENZYMATIC STRATEGIES INVOLVED IN THE CONSUMPTION OF THESE OLIGOSACCHARIDESBY KEY MEMBERS OF THE GUT MICROBIOME TO RECONSTRUCT MICROBIAL TROPHIC NETWORKS. IDENTIFIED ENGASES WILL BE EXAMINED FOR SUITABILITY FOR USE IN FOOD PROCESSING APPLICATIONS TO RELEASE BIOACTIVE GLYCANS. FINALLY, WE WILL COMPARE THE PREBIOTIC ACTIVITY OFOLIGOSACCHARIDES RELEASED BY THESE ENGASES USING HUMAN GUT MICROBIOMES ININ VITRO.THE GOAL OF THIS WORK IS TO DEVELOP FOOD PROCESSING APPROACHES WHICH CAN ENRICH THE 'EFFECTIVE' FIBER CONTENT OF EXISTING FOODS OR FOOD INGREDIENTS (I.E. WHEY, PEA, SOY, EGG WHITE PROTEIN, OR OTHER FOOD PROTEINS) AND ULTIMATELY IMPROVE BOTH HUMAN HEALTH AND THE VALUE OF THESE INGREDIENTS.