Galactosyl oligosaccharide purification by ethanol precipitation

Galactosyl oligosaccharides (COS) are prebiotics commonly manufactured by beta-galactosidase conversion of lactose, producing a mixture containing GUS, lactose, glucose and galactose. Enrichment of GUS in this mixture adds value to the product. This study aimed to determine whether the addition of ethanol to aqueous saccharide solutions could be used to selectively precipitate and enrich GUS from a reaction mixture. High concentrations of ethanol (>70% v/v) were required to induce precipitation. The total saccharide concentration was a significant variable, with higher GUS enrichment occurring at lower total saccharide concentrations. Varying the temperature between 10 and 40 degrees C had less impact than had changes in the concentration of saccharide or ethanol. GOS was enriched 2.3 (+/- 0.1) fold in the precipitate formed in a solution of 90% (v/v) ethanol with 28 g/L of total saccharide at 40 degrees C. Performing two such precipitations sequentially reduced the monosaccharides from 48% (w/w) of the total saccharides to 4% (w/w). COS precipitation has potential for industrial application as it is simple in operation and offers levels of purification similar to those by other techniques. (C) 2011 Elsevier Ltd. All rights reserved.