Lactulose production from efficient isomerization of lactose catalyzed by recyclable sodium aluminate

Abstract

An efficient strategy for the synthesis of high-purity lactulose through chemical isomerization of lactose was developed using recyclable catalyst sodium aluminate. Maximum yield of 85.45±1.79% was obtained from 35% (w/v) of lactose using a 1:1M ratio of NaAlO2-lactose after reaction at 60°C and pH 12 for 50min, with a purity ratio (Pu) of approximately 95%. Al(OH)3 precipitation from lactulose syrup through pH adjustment showing a superior decolorizing efficiency was implemented, which simplified the removal of catalyst and provided a convenient approach to achieve catalyst recovery. After dilution by 5 folds, nearly 98.5% of catalyst was removed through centrifugation and 85.50±1.81% of lactulose was recovered. Modified recycle use of catalyst without lactulose loss was carried out, after five consecutive recycles, total yield of lactulose (TYLactulose) and new yield of lactulose (NYLactulose) were of 80.44±1.05% and 73.87±0.50%, respectively, reflecting a high stability by using this recyclable methodology.