New methods to isolate, characterize and synthesize oligosaccharides used as nutritional ingredients

Galactooligosaccharides (GOS) are used in infant formula to boost the low oligosaccharide content of bovine milk (~0.05g/L) compared to human milk (~20g/L). GOS have been shown to be beneficial to infant health (e.g. improving gut microbiota composition softening stools and modulating immunity and are prepared enzymatically using a selected β-galactosidase, at a high lactose concentration. It is estimated that the GOS mixture produced in this way consists of >75 oligosaccharides at a varying percentage but the exact composition is unknown. Although the health benefits of the overall GOS mixture used as a nutritional ingredient are well established, it is less clear which components are responsible for the effects on infant health. In very rare cases the consumption of GOS is reported to lead to an allergic reaction in older children and adults with pre-existing allergies mainly in the Southeast Asian region. Again, the molecular complexity of GOS complicates the identification of the allergenic GOS components. Recently, primary sensitization against GOS in Singapore has been traced back to an allergic reaction against an unknown glycan found in tropical house dust mite Blomia tropicalis (unpublished results). The aim of this proposal is to develop new methods to isolate and characterize GOS components from a complex GOS mixture. In addition, new methods to prepare well-defined synthetic galactooligosaccharides are proposed. Combined, these methods will lead to the elucidation and preparation of the oligosaccharide structures found in GOS. These compounds will be used to evaluate which oligosaccharides contribute to health and which are allergenic. Finally, new methods are proposed to elucidate the molecular glycan structures in tropical house dust mite Blomia tropicalis responsible for primary sensitization. Overall the proposed work will contribute to the development of next generation GOS mixtures with increased health benefits and reduced allergenicity.