(266a) Synthesis of Prebiotic Oligosaccharides from Simple Sugars and Lignocellulosic Biomass

Prebiotics and probiotics have been used to modulate the composition and metabolic function of gut microbiota to improve host health. A prebiotic is a substrate that is selectively utilized by the health-promoting bacteria (probiotics) colonizing the gastrointestinal (GI) tract. The fermentation products (such as short-chain fatty acids) of prebiotics by probiotics confer a health benefit to the host. Most established prebiotics are oligosaccharides, including human milk oligosaccharides (HMOs) and non-digestible oligosaccharides (NDOs) such as fructo-, galacto-, and xylo-oligosaccharides (abbreviated as FOS, GOS, and XOS, respectively). These oligosaccharides are typically composed of 2–10 monosaccharide units linked by glycosidic bonds. Current prebiotic oligosaccharides are synthesized executively via enzymatic processes of controlled enzymatic hydrolysis of polysaccharides or enzyme-catalyzed glycosylation of sugars, which face the challenges of limited feedstock, high cost, and low yield. Recently, we developed facial chemical methods to synthesize oligosaccharides from abundantly available and low-cost feedstock, including the bottom-up approach via the glycosylation of simple sugars and the top-down approach via the simultaneous hydrolysis and glycosylation of polysaccharides in lignocellulosic biomass, using molten salt hydrates (extremely high-concentration salt aqueous solutions) or concentrated inorganic acids (e.g., sulfuric acid and phosphoric acid) as a reaction medium (solvent). Because of their unique properties (e.g., water-deficient nature and super ability to dissolve saccharides and polysaccharides), the solvents allow fast and high-yield synthesis of oligosaccharides from different sources (monosaccharides, disaccharides, and polysaccharides) under moderate conditions. This presentation reports our recent studies on the synthesis, structural characterization, and in-vitro and in-vivo evaluation of the prebiotic activity of the prebiotic oligosaccharides, including glucooligosaccharides, galactooligosaccharides, and glucoxylooligosaccharides. The methods we developed provide alternative approaches to synthesizing prebiotic oligosaccharides at high yield and low cost for potential applications in human foods and animal feeds.