Enterobacter agglomerans strain 221e transformed D-psicose to allitol at a faster rate in the presence of D-glucose in the reaction mixture when the entrance of oxygen was restricted. Cells grown on glycerol were found to be suitable for the transformation reaction. The transformation rates were about 97.0, 95.0 and 62.5%, respectively, when 0.5, 1.0 and 2.0% substrates were used. No consumption of substrate or product was observed in any case. In flask and jar fermenter reactions, the cells of strain 221e showed similar transformation activities. Cells stored at -20 degrees C for 10 d showed almost same transformation activity as intact cells.