Isolation of Milk Oligosaccharides using Solid-Phase Extraction

A method was developed to isolate mono- and disaccharide-free oligosaccharides from human and bovine milk using a combination of enzymatic digestion of lactose and solid-phase extraction. In the initial trial, 2.5 g of oligosaccha- rides were isolated from one liter of human milk. In subsequent trials this was increased to over 5 g of oligosaccharides per liter. Compared to filtration-based extraction methods, this procedure allows for further isolation of oligosaccharide fractions via modulation of the column rinsing solvent. Neutral monosaccharide composition of the oligosaccharide poly- mers was investigated using gas chromatographic analysis of the monosaccharides as alditol acetate derivatives. Results indicate oligosaccharides are approximately made up of 24% fucose, 41% galactose, 22% glucose and 13% glucosamine. Isolated bovine and human milk oligosaccharides were compared to lactose as fermentation substrates for Bifidobacterium longum biovar infantis. Lactose fermentation yielded the greatest production of biomass followed by bovine and human milk oligosaccharides.