Milk Sialooligosacharides: Biological Implications and Purification Strategies

Free sialooligosaccharides (SOS) are only found in low concentrations in normal tissue. However, an accumulation of these compounds has been described in the case of several lysosomal storage diseases leading to severe pathological changes. In contrast, SOS are found in the blood stream as products of the catabolic pathway of glycoproteins and are excreted in their free form in urine. There are significant changes in composition and level of excreted SOS in the case of lysosomal storage diseases. The analysis of urine from patients with different types of diseases by HPLC has revealed distinct patterns of oligosaccharides depending on the type and stage of disease making it possible to differentiate between these. SOS are also important components of the milk that play an important role in the healthy development of the infant by supporting the brain development, by promoting gut health, by protecting the infant against pathogens and by stimulating the immune system. Since milk and colostrums are complex mixtures, the purification of SOS from these mactrices requires a process comprising several consecutive steps. A simple strategy for the enrichment of SOS includes ‘skimming’and ultrafiltration for the removal of lipids, proteins and larger molecules. Lactose, the major carbohydrate in milk, can then be removed by enzymatic treatment with galactosidase and subsequent chromatography on graphitised carbon. With small modifications this methodology can also be applied to larger scale and can be aligned with the processes in the Dairy industry. The same methodology can also be applied in the purification of synthetic procedures.

Keywords: Sialic acids, Milk sialooligosaccharides, Purification of sialooligosaccharides, Human milk, Bovine milk, Human nutrition, Solid phase extraction, Brain development, Prebiotics.