Optimisation of the synthesis of high galacto-oligosaccharides (GOS) from lactose with β-galactosidase from Kluyveromyces lactis

A rational optimisation for the synthesis of galacto-oligosaccharides (GOS) catalysed by a commercial beta-galactosidase from Kluyveromyces lactis, Lactozym Pure 6500 L, is shown. The study of the main reaction parameters temperature, enzyme concentration, pH, initial lactose concentration and reaction time using surface response methodology, was demonstrated to be an accurate tool to optimise empirical production of the most desired galacto-oligosaccharides (tri-GOS and tetra-GOS) with a higher presumed prebiotic effect. The optimal value for the yield towards these high-GOS predicted by the model was 12.18% at 40 degrees C, 5 U mL(-1) enzyme concentration, pH 7.0, 250 g L-1 initial lactose concentration and 3 h of reaction. The pH was found to be a critical parameter affecting the transgalactosylation/hydrolysis enzyme activity ratio, and was used to tune the relative production of tri- or tetra-GOS. (C) 2016 Elsevier Ltd. All rights reserved.