Abstract: A complex crystalline sugar comprising D-psicose and D-allose and a method for producing the same are disclosed. The compositional ratio between D-psicose and D-allose in the sugar is about 1:1 to 1:4. A process for producing a complex crystalline sugar comprising D-psicose and D-allose, the process comprising producing a complex crystalline sugar comprising D-psicose and D-allose from a sugar solution containing D-psicose and p-allose and collecting the complex crystalline sugar. The solvent of the sugar solution used in the production of the complex crystalline sugar is water or a mixture of water and ethanol. The sugar solution containing D-psicose and D-allose is produced by a process comprising reacting D-psicose with L-rhamnose isomerase to convert D-psicose into D-allose. The L-rhamnose isomerase is derived from a strain (IPOD FERM BP-08593) belonging to Pseudomonas stutzeri.

Abstract: Problem: To provide a microorganism with an ability to produce deoxy polyol dehydrogenase. Means for Resolution: A microorganism belonging to genus Enterobacter with an ability to produce a dehydrogenase for deoxy polyol of the same structure at the positions C2 and C3 as that of ribitol or L-iditol. The bacterial cell IK7 of the genus Enterobacter (accession No. NITE P-271). A method for producing deoxy ketose comprising allowing a culture containing the deoxy polyol dehydrogenase obtained by the culturing of the microorganism of the invention or allowing the deoxy polyol dehydrogenase to react with a solution containing deoxy polyol of the same structure at the positions C2 and C3 as that of ribitol or L-iditol to oxidize deoxy polyol to produce the corresponding deoxy ketose and then collecting the deoxy ketose. The deoxy polyol is 1-deoxy-D-allitol, while the corresponding deoxy ketose is 1-deoxy-L-psicose.

Abstract: Object: To provide a thermostable L-ribose isomerase. Means for Resolution: The thermostable L-ribose isomerase with MW. 32,000 (by SDS-PAGE), optimal temperature of 45° C., optimal pH of pH 9.0 (glycine-NaOH buffer), and stable physicochemical properties such as temperature stability up to 45° C. during thermal treatment at pH 9.0 for 10 minutes, and with an action to isomerize L-ribose to generate L-ribulose or of inversely to isomerize L-ribulose to generate L-ribose.

Abstract: Problem: To provide a microorganism with an ability to produce deoxy polyol dehydrogenase. Means for Resolution: A microorganism belonging to genus Enterobacter with an ability to produce a dehydrogenase for deoxy polyol of the same structure at the positions C2 and C3 as that of ribitol or L-iditol. The bacterial cell IK7 of the genus Enterobacter (accession No. NITE P-271). A method for producing deoxy ketose comprising allowing a culture containing the deoxy polyol dehydrogenase obtained by the culturing of the microorganism of the invention or allowing the deoxy polyol dehydrogenase to react with a solution containing deoxy polyol of the same structure at the positions C2 and C3 as that of ribitol or L-iditol to oxidize deoxy polyol to produce the corresponding deoxy ketose and then collecting the deoxy ketose. The deoxy polyol is 1-deoxy-D-allitol, while the corresponding deoxy ketose is 1-deoxy-L-psicose.

Abstract: The invention relates to an isolated protein including an amino acid sequence represented by SEQ ID NO:2 and having an L-rhamnose isomerase activity. This novel enzyme has a higher reaction efficiency between D-psicose and D-allose and is excellent in thermal stability.

Abstract: Object: To provide a thermostable L-ribose isomerase. Means for Resolution: The thermostable L-ribose isomerase with MW. 32,000 (by SDS-PAGE), optimal temperature of 45° C., optimal pH of pH 9.0 (glycine-NaOH buffer), and stable physicochemical properties such as temperature stability up to 45° C. during thermal treatment at pH 9.0 for 10 minutes, and with an action to isomerize L-ribose to generate L-ribulose or of inversely to isomerize L-ribulose to generate L-ribose.

Abstract: Disclosed is a process for producing a crystalline sugar comprising D-psicose and D-allose. Also disclosed is a process for producing the sugar. A complex crystalline sugar comprising D-psicose and D-allose. The compositional ratio between D-psicose and D-allose in the sugar is about 1:1 to 1:4. A process for producing a complex crystalline sugar comprising D-psicose and D-allose, the process comprising producing a complex crystalline sugar comprising D-psicose and D-allose from a sugar solution containing D-psicose and p-allose and collecting the complex crystalline sugar. The solvent of the sugar solution used in the production of the complex crystalline sugar is water or a mixture of water and ethanol. The sugar solution containing D-psicose and D-allose is produced by a process comprising reacting D-psicose with L-rhamnose isomerase to convert D-psicose into D-allose. The L-rhamnose isomerase is derived from a strain (IPOD FERM BP-08593) belonging to Pseudomonas stutzeri.

Abstract: [PROBLEMS] To provide the sequence of a thermotolerant L-rhamnose isomerase gene. [MEANS FOR SOLVING PROBLEMS] A DNA comprising the base sequence represented by SEQ ID NO:1. A protein comprising the amino acid sequence represented by SEQ ID NO:2. A protein originating in Bacillus pallidus strain 14a (FERM AP-20172) and having an L-rhamnose isomerase activity. A protein having an L-rhamnose isomerase activity which is specified as having the following characteristics: optimum temperature and working temperature: showing the maximum enzymatic activity at 80° C. (the optimum temperature) and working temperature ranging from 30 to 80° C.; heat stability: concerning the effect of temperature on the enzymatic activity, being stable at up to 50° C. in the case of heating for 1 hour; and catalyzing the isomerization from D-psicose to D-allose.