Supercritical fluid purification of complex carbohydrate mixtures produced by enzimatic transglycosilation and isomerized with complexating reagents

Food-grade complex oligosaccharide mixtures manufactured commercially via transglycosylase reactions using disaccharides, such as sucrose or lactose as the raw material, are, in general, not pure products. Reducing oligosaccharides may be isomerized using borates and aluminates as complexating agents to obtain prebiotic oligosaccharides. Complexating agents are used to avoid side-reactions but are difficult to remove from mixture. In the present work, a new process based on the extraction with supercritical CO2 plus a co-solvent has been developed to purify reaction mixtures leading to pure prebiotic oligosaccharides. A three-step supercritical extraction process has been designed to purify carbohydrates according to its degree of polymerization; the appropriate selection of the co-solvent employed, together with the most suitable extraction conditions allowed the almost complete removal of monosaccharides, and disaccharides from the mixture, leading to pure oligosaccharides as a residue of the extraction process. In this process, not only complete fractionation of mono-, di- and trisaccharides was achieved but also elimination of borates and aluminates from the prebiotic carbohydrates mixture.