Biphasic aqueous media containing polyethylene glycol for the enzymatic synthesis of oligosaccharides from lactose

The behavior of aqueous two-phase systems (ATPS) as media for the synthesis of galacto-oligosaccharides (GalOS) from lactose has been studied to determine the effects of changes in the phase compositions on the yield and selectivity of this reaction. Transglycosylation was accomplished using a commercial enzyme preparation (Pectinex Ultra-SP) in biphasic media containing polyethylene glycol (PEG). Factors such as the molecular weight of PEG, the concentration of NaCl, and the pH affected the yield of trisaccharides. The results obtained in the ATPS were better (33% increase in the yield of 6′-galactosyl lactose and 21% higher selectivity to this product) than those obtained in conventional aqueous solutions with the same enzymatic preparation. These results are attributed to the partitioning of the sugars (especially the desired product and inhibitors) and the biocatalyst between the two phases of the system. The ratio of the volumes of the two phases, partition coefficients, and the concentrations of enzyme and lactose in each phase were also determined.