An improved process for the mass production of D-psicose from D-fructose was developed. A D-fructose solution (60%, pH 7.0) was passed at 45 degreesC through a column filled with immobilized D-tagatose 3-epimerase (D-TE) which was produced using recombinant Escherichia coil, and 25% of the substrate was converted to D-psicose. After epimerization, the substrate, D-fructose, was removed by treatment with baker's yeast. The supernatant was concentrated to a syrup by evaporation under vacuum and D-psicose was crystallized with ethanol. Approximately 20 kg of pure crystal D-psicose was obtained in 60 d.