Synthesis of Health-Promoting Carbohydrates

Human milk oligosaccharides (HMOs) are short carbohydrate chains that are found in human milk. HMOs help good bacteria to grow in the gut, and they can protect against infections. This role is especially apparent for fucosylated HMOs. Because it is not always possible to give human milk to infants, other compounds are used in infant formula to mimic the function of HMOs. Those allow good bacteria to grow in the gut but they are not optimized for protecting against infection. Therefore, researchers attempt to find new ways to mimic all functions of HMOs. In this thesis, we synthesized a twice-fucosylated cyclodextrin (FCD) as an HMO-mimic based on β-cyclodextrin,. a compound commonly used in the pharmacy and food sectors. FCD was found to be resistant to digestion, similarly to fucosylated HMOs, meaning it can reach the large intestine intact, and it prevented pathogenic bacteria to adhere to epithelial cells. In addition, exopolysaccharides (EPS), which are found on the outside of beneficial bacteria, are another class of carbohydrates that have healthy effects. To investigate the specific EPS structures that are responsible for certain health effects, polysaccharides and their fragments need to be obtained in high purity. EPS of Bifidobacterium adolescentis has a unique structure, that may be important in communication between cells. Because of its unique structure, synthesis of this molecule is challenging. In this thesis, we developed a method to make the EPS fragment with high precision.