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

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 (TY_Lactulose) and new yield of lactulose (NY_Lactulose) were of 80.44±1.05% and 73.87±0.50%, respectively, reflecting a high stability by using this recyclable methodology.