Galacto-oligosaccharides production, properties, applications and significance as prebiotics

Abstract

Abstract: Galacto-oligosaccharides (GOS) have now been definitely established as prebiotic ingredients after in vitro andanimal and human in vivo studies. Currently, GOS are produced by glycoside hydrolases (GH) using lactose as substrate.Converting lactose into GOS by GH results in mixtures containing GOS of different degrees of polymerization (DP),unreacted lactose, and monomeric sugars (glucose and galactose). Recent and future developments in the productionof GOS aim at delivering purer and more efficient mixtures. To produce high-GOS-content mixtures, GH should notonly have good ability to catalyze the transgalactosylation reaction relative to hydrolysis, but also have low affinity forthe GOS formed relative to the affinity for lactose. In this article, several microbial GH, proposed for the synthesis ofGOS, are hierarchized according to the referred performance indicators. In addition, strategies for process improvementare discussed. Besides the differences in purity of GOS mixtures, differences in the position of the glycosidic linkagesoccur, because different enzymes have different regiochemical selectivity. Depending on oligosaccharide composition,GOS products will vary in terms of prebiotic activity, as well as other physiological effects. This review focuses on GOSproduction from synthesis to purification processes. Physicochemical characteristics, physiological effects, and applicationsof these prebiotic ingredients are summarized. Regulatory aspects of GOS-containing food products are also highlightedwith emphasis on the current process of health claims evaluation in Europe.