Chromatographic separation of prebiotic oligosaccharides. Case study: Separation of galacto-oligosaccharides on a cation exchanger

Abstract

Chromatographic separation of prebiotic oligosaccharides, galacto-oligosaccharides from a typical post-reaction mixture containing unreacted substrate lactose and by-products glucose and galactose was investigated. A commercial cation-exchange resin Dowex 50WX4 was chosen as a prospective preparative-scale adsorbent and separation performance of its four ionic forms, H+, Na+, K+ and Ca2+, was tested. Since adsorption equilibrium isotherms were linear within the entire investigated range of concentrations, they were determined by pulse experiments for all saccharides present in a typical post reaction mixture including tri- and tetragalacto-oligosaccharides. From the four counter ions listed above, hydrogen offered the best selectivity and column performance. The selected H+-form of the cation exchanger was further investigated by means of frontal analysis where high ionic strength and elevated viscosity appear and can play a substantial role. Breakthrough curves were measured for monosaccharides, lactose, glucose-lactose mixture and a multicomponent commercial mixture of galacto-oligosaccharides, Vivinal® GOS. The breakthrough curves were successfully described by the dispersive plug flow model with linear driving force approximation. (c) 2013 Springer Science+Business Media New York.