L-Fructose, which was produced from L-psicose using immobilized D-tagatose 3-epimerase, was utilized as a starting material in the preparation of an uncommon aldose-hexose, L-glucose, by cell reaction. A mutant strain, Klebsiella pneumoniae strain 40bXX, produced D-arabinose isomerase constitutively. Toluene-treated cells of the mutant strain, which were used as the source of crude D-arabinose isomerase, were employed in the conversion of L-fructose to L-glucose. Empirically, 0.35 g of L-glucose was obtained from 1.0 g of L-fructose, viz an overall yield of 35%. The product obtained was purified and identified to be L-glucose by high performance liquid chromatography (HPLC) analysis, and was ultimately confirmed by C-13 nuclear magnetic resonance (C-13 NMR) spectra.