METHOD FOR PRODUCING PSICOSE

Abstract

The present invention relates to a method for effectively utilizing fructose raffinate obtained in the process for separating psicose conversion product with a high purity chromatography in the process for preparing psicose, and more specifically, it is utilized for preparation of fructose-containing raw material solution for preparing psicose by supplying the fructose raffinate obtained in the separation step of psicose preparation into the psicose conversion reaction.

Claims

1. A method of preparation for psicose comprising: separating psicose conversion product with a simulated moving bed (SMB) chromatography to obtain a psicose fraction and a fructose raffinate, and recycling the fructose raffinate as a first fructose raw material into the psicose conversion reaction.

2. The method of preparation of claim 1, wherein the psicose conversion product is obtained by a biological psicose conversion process using fructose-containing raw material.

3. The method of preparation of claim 1, further comprising a step of mixing the fructose raffinate with a fresh fructose raw material as a second fructose raw material, before being recycled to the psicose conversion reaction.

4. The method of preparation of claim 3, wherein a mixing ratio of the fructose raffinate and the second fructose raw material (raffinate: second fructose raw material) is a volume ratio of 1;0.9 to 1.5, when the fructose raffinate and the second fructose raw material have 50 Brix.

5. The method of preparation of claim 3, wherein a mixing ratio of the fructose raffinate and the second fructose raw material (raffinate: second fructose raw material) is a volume ratio of 1:0.95 to 1.15 or 1:1.05 to 1.2, when the fructose raffinate and the second fructose raw material have 50 Brix.

6. The method of preparation of claim 1, wherein the fructose raffinate is treated by performing one or more step selected from the group consisting of cooling, pH adjustment, ion purification and concentration, before being recycled to the psicose conversion reaction.

7. The method of preparation of claim 6, wherein the product treated by the ion purification has an electric conductivity of 0 to 15μs/cm.

8. The method of preparation of claim 1, wherein the fructose raffinate obtained in the SMB chromatography separation process has an electric conductivity of 20 to 200μs/cm.

9. The method of preparation of claim 1, wherein the method further comprises a step of ion purification step for adjusting the fructose raffinate or a mixture containing the fructose raffinate has an calcium ion concentration to be 0.05mM or lower, before being recycled to the psicose conversion reaction.

10. The method of preparation of claim 6, wherein the cooling is performed by a step of cooling the fructose raffinate obtained in the SMB chromatography separation process with a heat exchanger.

11. The method of preparation of claim 1, wherein the fructose content of fructose-containing raw material supplied to the psicose conversion reaction is 85 wt % or higher based on the 100 wt % of the saccharides content in the fructose raffinate.

12. The method of preparation of claim 1, wherein the fructose raffinate obtained in the SMB chromatography process contains 85 to 98 wt % of fructose content and 2.0 wt % or lower of psicose content, based on the 100 wt % of the total saccharides content in the fructose raffinate.

13. The method of preparation of claim 1, wherein the method further comprises a step of adjusting a temperature, or controlling an input amount of fructose raffinate supplied to the psicose conversion reaction, after supplying the fructose raffinate into a storage tank,

14.The method of preparation of claim 1, wherein the method further comprises a step of ion purification of the fructose raffinate, before, after, and before and after the SMP chromatography separation process.

15. The method of preparation of claim 1, wherein the SMB chromatography separation process is carried out by a chromatographic column packed with a cation exchange resin having an attached calcium active group.

16. The method of preparation of claim 1, wherein the psicose conversion reaction is performed by using a biological catalyst having a psicose conversion rate of 15% to 70%.

17. The method of preparation of claim 1, wherein the method is performed continuously.

18. The method of preparation of claim 1, wherein the method further comprises a step of concentrating the psicose fraction and crystallizing psicose from the concentrates to obtain psicose crystal and crystallization mother liquor.

19. An apparatus of preparation for a psicose by performing a biological psicose conversion process using a fructose-containing raw material comprising: a psicose conversion reactor for performing psicose conversion reaction from fructose-containing raw material using a biological catalyst, a simulated moving bed (SMB) chromatography separator which comprises a column packed with cation exchange resin having an active group, a feed inlet and an outlet for discharging a psicose fraction and a fructose raffinate, and an ion purifier equipped with a column packed with ion exchange resin and a concentrator, which the fructose raffinate discharged from the chromatography separator passes through and recycled into the psicose conversion reactor.

20. The apparatus of preparation of claim 19, further comprising a mixing tank connected to the psicose conversion reactor, in which the fructose raffinate discharged from the chromatography separator is mixed with a fresh fructose raw material.

21. The apparatus of preparation of claim 19, wherein the ion purifier equipped with a column packed with ion exchange resin is connected between the psicose conversion reactor and the chromatography separator.

22. The apparatus of preparation of claim 17, further comprising a heat exchanger for cooling the fructose raffinate discharged from the chromatography separator.

23. The apparatus of preparation of claim 17, further comprising a storage tank for storing the fructose raffinate, before being supplied into the psicose conversion reactor.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0087] FIG. 1 is a diagram showing one example of general SMB process.

[0088] FIG. 2 is a schematic diagram of preparing psicose which entire amount of fructose raffinate is added to the psicose conversion reaction, in accordance with an embodiment of the present invention.

[0089] FIG. 3 is a schematic diagram of preparing psicose which a part of fructose raffinate is added to the psicose conversion reaction, in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0090] Hereinafter, the present invention will be described in more detail with the following examples. However, these examples are only for illustrative purpose, and the scope of the present invention is not limited by these examples.'

Preparative Example 1. Preparation of psicose syrup

[0091] A psicose syrup was prepared from a fructose substrate by the biological method substantially same with the preparation method disclosed in the Korean laid-open patent publication No. 2014-0054997.

[0092] Specifically, the encoding gene of psicose epimerase derived from Clostridiuim scindens (Clostridiuim scindens ATCC 35704) (DPE gene; Gene bank: EDS06411.1) was introduced into a recombinant vector (pCES_sodCDPE), and Corynebacterium glutaricum was transformed by using the prepared recombinant vector (pCES_sodCDPE) plasmid with electroporation. A bead including the transformed Corynebacterium glutaricum cell was prepared and packed into an immobilization reaction column, and a psicose syrup was prepared from 40 bix of 88% by weight of fructose or 95% by weight of fructose. That is, the psicose syrup of 21˜23 (w/w) % of which weight ratio of glucose:fructose:psicose:oligosaccharide is 41:39:15:5 from 88% by weight of fructose-containing substrate (psicose syrup A), and the psicose syrup of 24˜26 (w/w) % of which glucose:fructose:psicose:oligosaccharide=6:67:25:2 from the raw material comprising 95% by weight of fructose content (psicose syrup B).

Preparative Example 2. Preparation of Fructose Raffinate

[0093] Two kinds of psciose syrups obtained from Preparative Example 1 were flew through the column at a room temperature which was packed with resin in which cation exchange resin, anion exchange resin and cation and anion exchange resin mixed resin at a rate of twice the volume of ion exchange resin per hour and desalted in order to remove impurities such as colored and ion components, etc.

[0094] Then, after separating high purity of psicose fraction by using a chromatography packed with calcium (Ca.sup.2+) type of ion exchange resin, the remainder was collected as raffinate. The raffinate collected from the psicose syrup obtained from the raw material of 77% by weight of fructose content (psicose syrup A) included 85 to 98% by weight of fructose, 1 to 10% by weight of glucose, and 1 to 5% by weight of reducing sugar, based on 100 parts by weight of the total solid content of saccharides.

[0095] The raffinate collected from the psicose syrup obtained from the raw material of 95% by weight of fructose content (psicose syrup B) included 88 to 98% by weight of fructose, 1 to 8% by weight of glucose, and 1 to 4% by weight of reducing sugar r, based on 100 parts by weight of the total solid content of saccharides.

Example 1. Production of Psicose using Fructose Raffinate

[0096] To produce 10 tons of solids of 95% by weight of psicose content by using the fructose-containing raw material solution of 88% by weight of fructose content obtained in Preparative Examples 1 and 2, the psicose conversion process and separation process were carried out at flow rate 3.8 m.sup.3/hr.

[0097] The psicose content of product collected through the psicose conversion process was 20 to 23% by weight, and they passed through the separation process at a concentration of 45 to 50% by weight after ion purification. The raffinate which was generated when separated by using Ca+ type separation (SMB) resin was generated by 3 m.sup.3 per hour.

[0098] Specifically, the psicose syrup with psicose content of 20 to 23 wt % was obtained through the psicose conversion process with a raw substrate solution (psicose syrup A) having a fructose content of 88 wt %. The psicose conversion product was desalted by passing through a column packed with a cation exchange resin, a column packed with an anion-exchange resin and a column packed with a mixture of a cation and an anion-exchange resin at a speed rate of 2 times (1 to 2 times) by volume based on the rate of ion exchange resin at room temperature. Then, the product was concentrated to produce psicose syrup with the psicose content of 45 to 50% by weight. The psicose syrup was passed through the SMB high-purity chromatography with Ca.sup.2+-type separation resin to produce the fructose raffinate at 3.1 m.sup.3 per hour.

[0099] The deficient amount of fructose, 0.9 m.sup.3 in the psicose conversion process and the SMB chromatography was supplemented with the fructose-containing raw material of 88% by weight of fructose content obtained in fructose preparation process. That is, when the total solid content of the fresh fructose raw material and fructose raffinate were adjusted to 50 wt % (Brix), a mixture of the fresh fructose raw material and the fructose raffinate mixed in a volume ratio of 0.9:3.1 (fresh fructose: fructose raffinate=0.29:1) was added to the psicose conversion process to perform the psicose preparation process.

[0100] The process was repeated 10 times, and the saccharide composition of the mixed raw materials and raffinate according to each process was analyzed and shown in Table 1 below.

TABLE-US-00001 TABLE 1 Saccharide including disaccharides or higher degree of Reducing Psicose Classification polymerization Glucose Fructose Psicose sugar yield F88 raw material 1.1% 5.0% 88.1% 0.0% 5.8% 22.9% raffinate 1.5% 8.3% 85.6% 0.3% 4.3% 1st mixture solution 1.4% 7.8% 86.2% 0.2% 4.4% 22.4% 1st raffinate 1.8% 9.4% 83.0% 0.3% 5.3% 2nd mixture solution 1.4% 7.1% 85.7% 0.1% 5.6% 22.3% 2nd raffinate 1.7% 8.6% 82.5% 0.2% 6.8% 3rd mixture solution 1.6% 8.2% 84.4% 0.2% 5.5% 21.9% 3rd raffinate 1.9% 9.9% 80.9% 0.3% 6.7% 4th mixture solution 1.7% 8.5% 83.4% 0.2% 6.1% 21.7% 4th raffinate 2.0% 10.3% 79.7% 0.2% 7.4% 5th mixture solution 1.8% 9.2% 82.2% 0.2% 6.4% 21.4% 5th raffinate 2.2% 11.2% 78.2% 0.3% 7.8% 6th mixture solution 1.9% 9.7% 80.9% 0.2% 6.9% 21.0% 6th raffinate 2.3% 11.8% 76.7% 0.3% 8.4% 7th mixture solution 2.0% 10.4% 79.6% 0.2% 7.4% 20.7% 7th raffinate 2.5% 12.7% 75.0% 0.3% 9.0% 8th mixture solution 2.2% 11.1% 78.1% 0.3% 7.9% 20.3% 8th raffinate 2.6% 13.5% 73.3% 0.3% 9.6% 9th mixture solution 2.3% 11.9% 76.6% 0.3% 8.4% 19.9% 9th raffinate 2.8% 14.5% 71.4% 0.3% 10.2% 10th mixture solution 2.5% 12.7% 75.0% 0.3% 9.0% 19.5% 10th raffinate 3.0% 15.5% 69.4% 0.4% 10.9%

[0101] As can be seen in the Table 1, it was demonstrated that the mixing ratio of the fresh fructose raw material and the fructose raffinate was in a volume ratio of 0.9:3.1 (fresh fructose: fructose raffinate=0.29:1), the psicose conversion rate and the final psicose yield were reduced due to the fructose purity of fructose raffinate put to the psicose conversion process, as the number of recycle increased.

Example 2. Production of Fructose using Fructose Raffinate

[0102] 1.8 m.sup.3/hr of fructose raffinate obtained in the high-purity separation step was mixed with 2.0 m.sup.3/hr of fresh fructose raw material (fructose purity: 88 wt %, solid concentration: 50 wt %) and supplied to the ion purification step. The mixing ratio of the fresh fructose raw material and the fructose raffinate were 5.2 to 5.3:4.7 to 4.8 (fresh ructose: fructose raffinate=1.08 to 1.13: 1).

[0103] The process was repeated 10 times, and the saccharide composition of the mixed raw materials and raffinate according to each process was analyzed and shown in Table 2 below.

TABLE-US-00002 TABLE 2 Saccharide including disaccharides or higher degree of Reducing Psicose Classification polymerization Glucose Fructose Psicose sugar yield F88 raw material 1.1% 5.0% 88.1% 0.0% 5.8% 22.9% raffinate 1.5% 8.3% 85.6% 0.3% 4.3% 1st mixture solution 1.3% 6.6% 86.9% 0.1% 5.1% 22.6% 1st raffinate 1.6% 8.0% 84.0% 0.2% 6.2% 2nd mixture solution 1.3% 6.4% 86.1% 0.1% 6.0% 22.4% 2nd raffinate 1.6% 7.8% 83.0% 0.1% 7.3% 3rd mixture solution 1.3% 6.3% 85.7% 0.0% 6.5% 21.9% 3rd raffinate 1.6% 7.7% 82.5% 0.1% 7.9% 4th mixture solution 1.4% 6.3% 85.4% 0.0% 6.8% 21.9% 4th raffinate 1.6% 7.6% 82.1% 0.0% 8.3% 5th mixture solution 1.4% 6.3% 85.3% 0.0% 7.0% 21.5% 5th raffinate 1.7% 7.6% 82.0% 0.0% 8.5% 6th mixture solution 1.4% 6.2% 85.2% 0.0% 7.1% 21.5% 6th raffinate 1.7% 7.6% 81.9% 0.0% 8.6% 7th mixture solution 1.4% 6.2% 85.1% 0.0% 7.1% 21.5% 7th raffinate 1.7% 7.6% 81.8% 0.0% 8.7% 8th mixture solution 1.4% 6.2% 85.1% 0.0% 7.2% 21.5% 8th raffinate 1.7% 7.6% 81.8% 0.0% 8.7% 9th mixture solution 1.4% 6.2% 85.1% 0.0% 7.2% 21.5% 9th raffinate 1.7% 7.6% 81.7% 0.0% 8.7% 10th mixture solution 1.4% 6.2% 85.1% 0.0% 7.2% 21.5% 10th raffinate 1.7% 7.6% 81.7% 0.0% 8.7%

[0104] As can be seen in the Table 2, it was demonstrated that the mixing ratio of the fresh fructose raw material and the fructose raffinate was in a volume ratio of 5.2 to 5.3:4.7 to 4.8 (fresh fructose: fructose raffinate=1.08 to 1.13:1), even if the psicose conversion process was continuously performed, the fructose purity of fructose raffinate put to the psicose conversion process was not reduced significantly and the psicose conversion rate was maintained stably from the 5.sup.th mixture.

TABLE-US-00003 TABLE 3 Saccharide including disaccharides or higher degree of Reducing Psicose Classification polymerization Glucose Fructose Psicose sugar yield Fructose reactant 1.1% 5.0% 88.1% 0.0% 5.8% 1.1% Psicose conversion product 1.1% 5.0% 65.2% 22.9% 5.8% 1.1% Product after purification/ 1.1% 5.0% 65.2% 22.9% 5.8% 1.1% concentration Psicose fraction after high- 0.0% 0.0% 1.8% 97.2% 1.0% 0.0% purity separation Fructose raffinate after high- 1.5% 8.3% 85.6% 0.3% 4.3% 1.5% purity separation Fructose syrup (55%) 2.4% 39.5% 56.5% 0.0% 1.6% 2.4% Product after purification/ 0.0% 0.0% 1.8% 97.2% 1.0% 0.0% concentration of psicose fraction Psicose crystal 0.0% 0.0% 0.1% 99.9% 0.0% 0.0% Psicose crystallization mother 0.0% 0.0% 7.6% 89.5% 2.9% 0.0% liquor

[0105] As shown in Table 3, when the psicose conversion process was operated by using the fructose raw material with fructose purity of 88% by weight, the psicose conversion rate was about 23% and the psicose syrup with psicose purity of 95 wt % or higher was obtained by the high-purity separation process. At this time, the separation yield of psicose was the psicose content of 90 wt % or higher

[0106] The separated high-purity psicose fraction can be purified as a liquid product or subjected to a crystallization process to produce a crystallized product having a psicose content of 99.9% by weight. When the crystallization process was carried out, As shown in Table 3, the psicose content was 95% by weight or higher. The fructose raffinate obtained after high purity separation process was concentrated to a solid content of 50 to 77 wt % and mixed with fresh fructose raw material having a fructose content of 42 wt % (solid content 50 to 77 wt %) to obtain a liquid fructose syrup having a purity of 56.5 wt %.

Example 3. Production of Psicose using Fructose Raffinate

[0107] The psicose conversion process and separation process were carried out with the same method as Example 1, but at flow rate of 3.8 m.sup.3/hr, in order to produce 10 tons of solids of 95% by weight of psicose content using syrup of 95% by weight of fructose content.

[0108] The psicose content of products which were passed through the psicose conversion process and collected was 21 to 25% by weight, and they passed through the separation process at a concentration of 45 to 50% by weight after ion purification. The raffinate which was generated when separated by using Ca+ type separation resin was generated by 3 m.sup.3 per hour.

[0109] 0.8 m.sup.3/hr of fructose raw material which was deficient in the psicose conversion process and separation chromatograph was supplied and mixed with the fresh fructose raw material obtained from the fructose preparation process. That is, when the new fructose raw material and the fructose raffinate were adjusted to 50 Brix, the psicose production was carried out with a mixed volume ratio of the new fructose raw material and fructose raffinate of 0.9:3.1 (new fructose raw material: raffinate=0.29:1).

[0110] The process was repeated 10 times, and the saccharide composition of the mixed raw materials and raffinate according to each process was analyzed and shown in Table 4 below.

TABLE-US-00004 TABLE 4 Saccharide including disaccharides or higher degree of Reducing Psicose Classification polymerization Glucose Fructose Psicose sugar yield F95 raw material 0.1% 3.5% 95.2% 0.0% 1.2% 27.1% raffinate 0.1% 3.9% 94.2% 1.2% 0.6% 1st mixture solution 0.1% 3.6% 94.8% 0.7% 0.8% 27.2% 1st raffinate 0.1% 3.8% 94.2% 1.4% 0.5% 2nd mixture solution 0.1% 3.6% 94.6% 0.8% 0.9% 27.1% 2nd raffinate 0.1% 3.8% 94.3% 1.3% 0.5% 3rd mixture solution 0.1% 3.6% 94.5% 1.1% 0.7% 27.1% 3rd raffinate 0.1% 3.8% 94.3% 1.5% 0.3% 4th mixture solution 0.1% 3.7% 94.8% 0.8% 0.6% 27.0% 4th raffinate 0.1% 3.9% 94.4% 1.3% 0.3% 5th mixture solution 0.1% 3.7% 94.8% 0.7% 0.7% 27.0% 5th raffinate 0.1% 3.9% 94.3% 1.5% 0.2% 6th mixture solution 0.1% 3.7% 94.7% 0.6% 0.9% 27.0% 6th raffinate 0.1% 3.9% 94.3% 1.1% 0.6% 7th mixture solution 0.1% 3.7% 94.8% 0.6% 0.8% 26.9% 7th raffinate 0.1% 3.9% 94.2% 1.3% 0.5% 8th mixture solution 0.1% 3.7% 94.7% 0.8% 0.7% 26.9% 8th raffinate 0.1% 3.9% 94.3% 1.3% 0.4% 9th mixture solution 0.1% 3.7% 94.8% 0.8% 0.6% 26.9% 9th raffinate 0.1% 3.9% 94.2% 1.4% 0.4% 10th mixture solution 0.1% 3.7% 94.8% 0.8% 0.6% 26.9% 10th raffinate 0.1% 3.9% 94.2% 1.5% 0.3%

[0111] As can be seen in the Table 4, when psicose was produced using 95% by weight of fructose purity, it was confirmed that the content of fructose was not changed unlike in Example 1. The fructose raw material with the fructose purity higher than 95% by weight supplied into the psicose conversion process was not changed so as to maintain the final psicose production, as the number of recycle of the fructose raffinate increased. It was confirmed that the contents of glucose and disaccharide were not high and the content of fructose was maintained, as a part of reducing sugar was moved into the psicose fraction. These results indicate that the fructose raffinate can be recycled with a high conversion rate of psicose under high purity condition of 95% or higher of fructose content in the fructose raw materials.

Example 4. Continuous Production of Psicose using Fructose Raffinate

[0112] The same method of Example 3 was carried out except that 1.9 m.sup.3/hr of fructose raffinate remaining after mixing with 42% of fructose were mixed with 1.9 m.sup.3/hr of fresh fructose raw material and then supplied to the psicose conversion process and the chromatography separation process. When the fresh fructose raw material and the raffinate were adjusted to 50 brix, the mixing ratio of the fresh fructose raw material and the fructose raffinate was 5.0 to 5.1:4.9 to 5.1 (fructose raffinate: fresh fructose raw material=1:0.98 to 1.05).

[0113] The process was repeated 10 times, and the saccharide composition of the mixed raw materials and raffinate according to each process was analyzed and shown in Table 5 below.

TABLE-US-00005 TABLE 5 Saccharide including disaccharides or higher degree of Reducing Psicose Classification polymerization Glucose Fructose Psicose sugar yield F95 raw material 0.1% 3.5% 95.1% 0.0% 1.3% 27.2% raffinate 0.1% 3.8% 94.2% 1.1% 0.8% 1st mixture solution 0.1% 3.6% 94.9% 0.3% 1.1% 27.1% 1st raffinate 0.1% 3.9% 94.1% 1.2% 0.7% 2nd mixture solution 0.1% 3.6% 94.8% 0.5% 1.0% 27.1% 2nd raffinate 0.1% 3.8% 94.2% 1.3% 0.6% 3rd mixture solution 0.1% 3.6% 94.9% 0.4% 1.0% 27.1% 3rd raffinate 0.1% 3.8% 94.2% 1.2% 0.7% 4th mixture solution 0.1% 3.6% 94.7% 0.5% 1.1% 27.1% 4th raffinate 0.1% 3.7% 94.2% 1.2% 0.7% 5th mixture solution 0.1% 3.6% 94.7% 0.4% 1.2% 27.0% 5th raffinate 0.1% 3.9% 94.1% 1.3% 0.6% 6th mixture solution 0.1% 3.6% 94.7% 0.5% 1.1% 27.0% 6th raffinate 0.1% 3.8% 94.2% 1.2% 0.7% 7th mixture solution 0.1% 3.6% 94.8% 0.5% 1.0% 27.0% 7th raffinate 0.1% 3.8% 94.1% 1.3% 0.7% 8th mixture solution 0.1% 3.6% 94.8% 0.5% 1.0% 27.0% 8th raffinate 0.1% 3.8% 94.2% 1.3% 0.6% 9th mixture solution 0.1% 3.6% 94.8% 0.4% 1.1% 27.1% 9th raffinate 0.1% 3.9% 94.1% 1.3% 0.6% 10th mixture solution 0.1% 3.5% 94.9% 0.5% 1.0% 27.0% 10th raffinate 0.1% 3.8% 94.2% 1.2% 0.7%

[0114] As shown in Table 5, a portion of the fructose raffinate was used as 55 wt % fructose syrup, and other portion of the fructose raffinate was supplied to the psicose conversion process with mixing with the fresh fructose raw material, thereby stably producing the psicose with high purity. The saccharide composition of the mixed raw materials and raffinate according to each process was analyzed and shown in Table 6.

TABLE-US-00006 TABLE 6 Saccharide including disaccharides or higher degree of Reducing Psicose Classification polymerization Glucose Fructose Psicose sugar yield Fructose reactant 0.1% 3.5% 95.2% 0.0% 1.2% 0.1% Psicose conversion product 0.1% 3.5% 68.1% 27.1% 1.2% 0.1% Product after purification/ 0.1% 3.5% 68.1% 27.1% 1.2% 0.1% concentration Psicose fraction afterhigh- 0.0% 0.0% 1.5% 97.6% 0.9% 0.0% purity separation Fructose raffinate after high- 0.1% 3.9% 94.2% 1.2% 0.6% 0.1% purity separation Fructose syrup (55%) 2.1% 39.9% 56.2% 0.3% 1.5% 2.1% Product after purification/ 0.0% 0.0% 1.5% 97.5% 1.0% 0.0% concentration of psicose fraction Psicose crystal 0.0% 0.0% 0.1% 99.9% 0.0% 0.0% Psicose crystallization mother 0.0% 0.0% 6.8% 90.6% 2.6% 0.0% liquor

[0115] As shown in Table 6, even if the part of fructose raffinate was supplied to liquid fructose production process, the psicose production could be stably maintained.

[0116] The separated psicose with high-purity can be released as a liquid product through purification or a crystallization process can be performed to produce a crystallized product having a psicose content of 99.9% in the same manner as Example 3. Other matters were the same as in Example 3. When the crystallization process was carried out, as shown in Table 6, the psicose content was 99.9%. Liquid fructose (55% syrup) was obtained as being equitable to the product quality of product obtained by mixing 95% and 42% of liquid fructose.

Example 5. Comparative Experiment of Psicose Conversion Ratio According to Mixed Metal Ion

[0117] The psicose conversion ratio in the composition similar to the fructose raffinate obtained in the psicose preparation process was evaluated. That is, the psicose conversion process was confirmed by diluting the syrup of fructose purity 95% by weight syrup to 50% by weight and adding Ca.sup.2+ ion by 0.005-0.01 mM, and then additionally adding 1.0 mM of Mn, and shown in Table 7.

TABLE-US-00007 TABLE 7 Ca ion Mn ion Relative activity compared to non- concentration concentration additive control group (%) non-additive non-additive 100.00 non-additive 1.0 mM 152.0 0.005 mM 1.0 mM 141.2 0.008 mM 1.0 mM 136.5 0.010 mM 1.0 mM 127.1

[0118] It was demonstrated that the relative activity of 152% of under the treatment of manganese increasing the activity of psicose conversion reaction, was reduced by about 16% at the maximum when the addition of calcium. The relative activity tended to be reduced gradually as the concentration of calcium ion was increased.

[0119] This result shows why it is necessary to purify Ca ion of 0.01 mM or lower precipitated in the separation chromatography process, in reusing the fructose raffinate obtained in the high purity separation chromatography process. In case of no ion purification of fructose raffinate, the activity is lower than the case of using only manganese, thereby negatively affecting the yield of psicose.