Enzymatic Synthesis of Prebiotic Carbohydrates From Lactose: Evaluation of Transgalactosylation Activity and Kinetics of Osmotic Membrane Distillation Integrated Reactor

Abstract

This research focused on the augmentation of galactooligosaccharide (GOS) synthesis from lactose through an integrated methodology of osmotic membrane distillation (OMD) and enzymatic synthesis employing β-galactosidase from Aspergillus oryzae. The effect of temperature, initial lactose concentration, and enzyme concentration was explored through a factorial experimental design. Optimal conditions for the OMD integrated reactor (R-Batch+OMD) were established using response surface methodology, yielding a temperature of 36.7°C, an enzyme concentration of 6.0 U g LS⁻¹, and a lactose concentration of 32°Brix (% wt/wt). At these optimal conditions, GOS-4 was predicted at 8.70%, GOS-3 at 19.86%, and the total GOS yield (GY) at 28.57% for lactose conversion of 52.40%. Kinetic analysis revealed that the membrane separation process notably impacts enzymatic reaction parameters. Compared to the non-integrated reactor (R-Batch), a notable result in the R-Batch+OMD was the achievement of higher GY values at the same lactose conversions, which were attributed to the OMD facilitating a shift in enzymatic activity toward transgalactosylation due to water extraction from the reaction medium. An increased ratio of apparent kinetic parameter of GOS formation/decomposition (k₅/k₋₅) in the R-Batch+OMD indicated a more prominent role of transgalactosylation. Also, the R-Batch+OMD highlighted the positive impact of high levels of E:Lac and E:Gal complex formations. This suggests a crucial effect of OMD on GOS synthesis: the maintenance of high E:Gal complex concentrations in the reaction medium, thereby improving enzyme-lactose interactions. Moreover, these outcomes underscore the potential of membrane technology to enhance bioprocess efficiency, leading toward more sustainable and innovative approaches in food engineering.