Direct production of allitol from D-fructose by a coupling reaction using D-tagatose 3-epimerase, ribitol dehydrogenase and formate dehydrogenase

Allitol was produced from D-fructose via a new NADH-regenerating enzymatic reaction system using D-tagatose 3-epimerase (D-TE), ribitol dehydrogenase (RDH), and formate dehydrogenase (FDH). D-Fructose was epimerized to D-psic ose by the D-TE of Pseudomonas cichorii ST-24 and the D-psicose was subsequ ently reduced to allitol by the RDH of an RDH-constitutive mutant, X-22, de rived from Klebsiella pneumoniae IFO 3321. NADH regeneration for the reduct ion of D-psicose by the RDH was achieved by the irreversible formate dehydr ogenase reaction, which allowed the D-psicose produced from D-fructose to b e successively transformed to allitol with a production yield from D-fructo se of almost 100%, The reactions progressed without any byproduct formation . After separation of the product from the reaction mixture by a simple pro cedure, a crystal of allitol was obtained in a yield exceeding 90%. This cr ystal was characterized and determined to be allitol by HPLC analysis, its IR and NMR spectra, its melting point, and optical rotation measurement.