High-yield production of pure tagatose from fructose by a three-step enzymatic cascade reaction.

OBJECTIVE: To produce tagatose from fructose with a high conversion rate and to establish a high-yield purification method of tagatose from the reaction mixture.

RESULTS: Fructose at 1 M (180 g l-1 ) was converted to 0.8 M (144 g l-1 ) tagatose by a three-step enzymatic cascade reaction, involving hexokinase, plus ATP, fructose-1,6-biphosphate aldolase, phytase, over 16 h with a productivity of 9 g l-1 h-1 . No byproducts were detected. Tagatose was recrystallized from ethanol to a purity of 99.9% and a yield of 96.3%. Overall, tagatose at 99.9% purity was obtained from fructose with a yield of 77%.

CONCLUSION: This is the first biotechnological production of tagatose from fructose and the first application of solvent recrystallization for the purification of rare sugars.