|The project aims to investigate the relationships between the structure of periodic oligosaccharides and their selective fermentation in the human gut. Specifically, the influence of molecular weight, monosaccharidecomposition and linkage type will be evaluated. Fermentation selectivity will be evaluated in faecal batch cultures using fluorescent in site hybridisation to monitor changes in bacterial populations. Data from such studies will bemuse to calculate a periodic index to allow quantitative comparisons of differing carbohydrate structures. Bacterial community profiles will be characterised by denaturing gradient gel electrophoresis. Bacterial metabolic end products such as short chain fatty acids and gas will be measured. To rationalise the metabolism of specificoligosaccharide structures, selected glycosidase enzymes will be isolated from gut bacteria and characterised. In addition, the presence of oligosaccharide transport systems will investigate. Information from the project will underpin functional food development activities around Europe and in several funded projects.