JPH0678351B2 - Method for desalting solution containing 5'-nucleotide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a method for efficiently removing inorganic salts by concentrating 5'-nucleotides from an aqueous solution containing 5'-nucleosides and inorganic salts using a loose reverse osmosis membrane. Regarding

5'-nucleotide, especially 5'-inosinic acid and 5 '
-Since guanylic acid has an extremely strong taste,
It is a substance known to be useful as a seasoning.

The 5'-nucleotide can be produced by reacting nucleoside with phosphorus oxyhalogenide in a polar organic solvent such as trialkyl phosphate ester, nitrile or organic amine (Japanese Patent Publication No. 36-13579), yeast. Of hydrolyzing nucleic acid contained in (Japanese Patent Publication No. 12672/41) and a method of directly producing by fermentation from sugar as a raw material (Japanese Patent Publication No. 58-4631).
9) etc. Industrially, by these methods, 5'-
When nucleotide is to be produced at a low cost, the concentration of 5'-nucleotide is increased from the mother liquor from which 5'-nucleotide was separated by evaporation or the like, and the 5'-nucleotide remaining in the mother liquor is recovered in the process. Cycle to 5'-
A common method is to repeat the method of improving the yield of nucleotide twice or more in many cases. However, in any of the production methods, in the process of isolating and purifying 5'-nucleotide from the reaction solution, a large amount of an inorganic salt is by-produced in order to consume acid and alkali, and 5'-remains in the mother liquor.
Precipitation of an inorganic salt occurs during recovery of nucleotide, making it difficult to recover 5'-nucleotide in high yield. Therefore, in order to obtain 5'-nucleotide from the reaction solution in high yield, it is necessary to efficiently remove the inorganic salt by-produced by some method.

Conventionally, as a desalting method, (1) a method using an ion exchange resin, (2) 5'-
Known is a method of adsorbing nucleotide and allowing coexisting salt to flow through as a non-adsorbate, and then eluting the adsorbed 5'-nucleotide with a polar solvent such as alkali or methanol. (3) A method by electrodialysis .

These methods consume a large amount of auxiliary raw materials during elution and regeneration, and require more complicated operations, resulting in higher equipment costs (methods (1) and (2)), or 5'-nucleotide. As described above, when the valuable material is an electrolyte, the valuable material is dialyzed at the same time as desalting, and the recovery rate of the valuable material is significantly reduced (method (3)). Further, since the desalination solution obtained by any of the methods becomes diluted, it is necessary to consume a large amount of energy for the recovery of the desalting valuable material, and the concentration is required, which causes a drawback that the recovery cost increases. It was

The present inventors have conducted various studies on methods for efficiently removing coexisting inorganic salts and simultaneously concentrating 5'-nucleotide in order to overcome the above-mentioned drawbacks. It has been found that the drawbacks of can be overcome. That is, it is known that a low molecular weight substance and a high molecular weight substance can be separated using a loose reverse osmosis membrane (JP-A-58).
-175438, JP-A-59-156402, etc.), the inventors of the present invention have found that a loose reverse osmosis membrane having characteristics that the rejection of NaCl is 20 to 80% and that of 5'-disodium inosinate is 95% or more. The solution having a salt concentration and a concentration of 5'-nucleotide of not less than a certain concentration is subjected to reverse osmosis treatment using the above-mentioned reverse osmosis membrane to efficiently remove coexisting inorganic salts and simultaneously to obtain 5 '
-Finding that nucleotide can be concentrated efficiently,
The present invention has been completed.

According to the present invention, at a high rate, a separation mother liquor of 5'-nucleotide containing a large amount of an inorganic salt discharged during the isolation and purification of 5'-nucleotide from a reaction solution for producing 5'-nucleotide is used. Moreover, a method for obtaining a high-concentration desalted solution of 5'-nucleotide is provided, and in the production of 5'-nucleotide on an industrial scale, consumption of auxiliary raw materials and energy consumption such as steam, which are disadvantages of the conventional methods, are consumed. Can be greatly reduced, and 5'-nucleotide can be easily recovered with high yield, which can contribute to a large reduction in manufacturing cost. Further, since the operating temperature is low, the decomposition of 5'-nucleotide can be suppressed, and it can contribute to the prevention of the deterioration of the quality of 5'-nucleotide due to the decomposition products.

The 5'-nucleotide solution containing an inorganic salt which is the subject of the method of the present invention is a solution which is produced during industrial production of 5'-nucleotide such as 5'-inosinic acid and 5'-guanylic acid. In addition, the inorganic salt is mainly NaCl, and 5'-nucleotide includes 5'-inosinic acid, 5'-guanylic acid, and / or 5'-adenylic acid, or nucleoside diphosphoric acid, triphosphoric acid, etc. The thing
A solution having a NaCl concentration of 1% to a saturated concentration, preferably 5 g / dl to a saturated concentration, and a 5'-nucleotide of 0.01 to 40 g / dl, preferably 2-35 g / dl.

Further, as will be described later, it was found that the higher the concentration of the salt or nucleotides, the more efficiently the nucleotide is concentrated and the salt is separated, and the present invention was completed. In the case of 1, the separation efficiency of both is lowered, so that efficient concentration and desalting cannot be achieved. If only for the purpose of concentration, even in a low concentration range, it can be an industrially advantageous concentration method as an energy-saving concentration method. Also, in the case of such a low concentration target liquid, a commonly known reverse osmosis membrane is used to concentrate both the salt and nucleotide to the appropriate concentration range described above, and then the loose reverse osmosis described later. Desalting / concentration with a membrane is preferable.

Loose reverse osmosis membrane used in the present invention, such as cellulose acetate type, polyamide type, polybenzimidazole type, polysulfone type at a pressure of 56 atm and a temperature of 25 ° C.
Membrane rejection of NaCl was 20-80% when reverse osmosis treatment was performed on a mixed solution of NaCl and disodium 5'-inosinate 7.5 hydrate with both solute concentrations of 3.5 g / dl. And inhibition rate of disodium 5'-inosinate 7.5 hydrate 9
It is adjusted to 5% or more, preferably 98% or more, regardless of the material of the film. Here, the blocking rate (%) is defined as follows.

It is known that low molecular weight substances and high molecular weight substances can be separated when a loose reverse osmosis membrane is used as described above.
As a result of diligent study on the inhibition rate of the salt, it was found that the inhibition rate greatly changes depending on the salt concentration even in the same film, and a method for efficiently desalting from a solution containing a high concentration of inorganic salt was found using this. It was Salt has an N of about 100 or less
aCl, KCl, NH ₄ Cl, etc. are easily desalted, but the molecular weight is 100
The above CaCl ₂ , ZnCl ₂ , FeCl ₃ , phosphate, sulfate and other salts have poor permeability and are difficult to be efficiently desalted.
It is not preferable to employ a process in which such a salt is mixed in the liquid to be treated of the present invention.

By increasing the concentration of 5'-nucleotide, Na
It was discovered that Cl has the effect of increasing the desalination rate. This can be further followed by efficient recovery of disodium 5'-inosinate from the concentrated liquid.

Even more surprisingly, it has been conventionally known that the permeation rate increases and the rejection rate decreases when the pH is raised (Chemical Technology Journal MOL, December 60 issue, “Causes of changes in polymer separation membrane module performance”). And its prevention method "), in the case of the target liquid of the present invention, the permeation rate decreases with an increase in pH, and the inhibition rate of 5'-nucleotide is improved. I was found not to receive it. Using this finding, it was revealed that 5'-nucleotide and low-molecular salt can be efficiently separated by appropriately selecting pH. That is, the pH is 3-12, preferably 5-11.

It was also discovered that the behavior behaves uniquely depending on the pressure. That is, in the case of loose reverse osmosis membranes, small molecules such as NaCl show a small change in the blocking rate with increasing pressure, but nucleotide was found to improve the blocking rate with increasing pressure, and operated at higher pressure. It became clear that the low-molecular salt and the nucleic acid can be separated more efficiently together with the improvement of the permeation rate. That is, the pressure is 10 to 70 atm, and if the pressure is lower than this, there are disadvantages such as a reduction in the blocking rate of 5'-nucleotide and a reduction in the processing capacity.

The temperature is 5 to 60 ° C., preferably 20 to 40 ° C. Outside this range, reduction of the inhibition rate of 5′-nucleotide and decomposition of the substrate are likely to occur, and at low temperature, disadvantages such as crystal precipitation occur. Needless to say, the pH, pressure, and temperature must be within the range that the material of the membrane can withstand them. Further, an organic solvent such as methanol, ethanol, or a trialkyl phosphate ester may be mixed within the durability of the membrane.

In addition, a usual method may be used to recover the target 5'-nucleotide from the 5'-nucleotide solution from which the inorganic salt is removed according to the present invention.

Hereinafter, the present invention will be described in detail with reference to Examples. The rejections of NaCl and 5'-disodium inosinate as performance definitions of the membranes used in Examples are the same as above, at a pressure of 56 atm and a temperature of 25 ° C. When a mixed solution of NaCl and disodium 5'-inosinate 7.5 hydrate with both solute concentrations of 3.5 g / dl was subjected to reverse osmosis treatment Is.

Also Is.

Example 1 Nucleotide 5 g / dl, Nucleoside 0.1 g / dl, NaCl17
The pH of an aqueous solution containing g / dl and sodium phosphate (as P) of 0.6 g / dl was adjusted using a loose reverse osmosis membrane with a NaCl inhibition rate of 30% and a disodium 5'-inosinate inhibition rate of 99%. = 7,
Desalination and concentration were performed by reverse osmosis treatment in which the non-permeate was circulated and mixed with the original raw material liquid at a pressure of 60 atm and a temperature of 30 ° C. As the concentration of nucleotide in the non-permeate was increased, the inhibition rate of nucleotide was improved and the inhibition rate of NaCl was decreased from 30% to 0%, whereby desalting and concentration could be efficiently performed. The results are shown in Table 1.

Reference Example 1 (Influence of pH) Nucleotide 6.5g / dl, Nucleoside 0.2g / dl, NaCl
A raw material solution containing 17 g / dl, sodium phosphate (as P) 0.6 g / dl, etc., at a temperature of 30 ° C. and a pressure of 40 atm, NaCl rejection rate of 35
%, 5′-disodium inosinate 97% rejection rate was used for reverse osmosis membrane treatment. The permeated liquid and the non-permeated liquid were subjected to desalting and concentration by changing the pH while circulatingly mixed with the raw material liquid. The results are shown in Table 2.

It will be understood from Table 2 that the desalting concentration of the nucleotide solution containing the inorganic salt by the reverse osmosis treatment is influenced by the pH of the reverse osmosis treatment.

Reference Example 2 (Influence of pressure) Nucleotide 4.5g / dl, Nucleoside 0.3g / dl, NaCl
A raw material solution containing 16.4 g / dl, 0.6 g / dl of sodium phosphate (as P), etc. was adjusted to a temperature of 30 ° C. and pH = 6, and Example 1 was used.
It was subjected to reverse osmosis treatment using the same membrane used in.
Both the permeated liquid and the non-permeated liquid were circulatively mixed with the original raw material liquid, and the pressure was changed to perform desalting and concentration.

The results are shown in Table 3.

From Table 3, desalination concentration of nucleotide solution containing inorganic salt by reverse osmosis treatment was affected by the pressure of the reverse osmosis treatment, and especially at high pressure, the permeation rate and the nucleotide rejection rate were improved, and NaCl was efficiently removed. It will be appreciated that salt is possible.

Example 2 Nucleotide 8 g / dl, Nucleoside 1 g / dl, NaCl 25 g /
An aqueous solution containing dl, sodium phosphate (as P) 0.5 g / dl, etc. was subjected to reverse osmosis treatment using the same membrane used in Example 1. The treatment conditions were pH = 10, pressure of 40 atm, and temperature of 35 ° C., while performing desalting and concentration while circulatingly mixing the non-permeate with the original raw material liquid. When the concentration of NaCl was 3.5 g / dl, the inhibition rate was 3 by increasing the concentration of nucleotide in the impermeable liquid.
0% is NaC when NaCl is as high as 25 g / dl as in this embodiment.
The concentration of l was higher in the permeate than in the non-permeate, and
The rejection rate of l decreased to -43%, and desalting and concentration could be efficiently performed.

The results are shown in Table 4.

Example 3 Nucleotide 20 g / dl, Nucleoside 0.2 g / dl, NaCl1
A solution containing 5 g / dl, sodium phosphate (as P) 0.7 g / dl, and a trialkyl phosphate ester 1.5 g / dl was used for NaCl inhibition 2
It was subjected to reverse osmosis membrane treatment using a loose reverse osmosis membrane with 5% disodium 5'-inosinate inhibition of 99.5% at 0%. The treatment conditions were pH = 10, a pressure of 40 atm, and a temperature of 40 ° C., and the non-permeated liquid was circulated and mixed with the original raw material liquid for concentration.

The results are shown in Table 5.

Claims (3)

[Claims] 1. A NaCl concentration of 5 g / dl to a saturated concentration of 5 '.
A 5'-nucleotide solution having an pH of 3 to 12 and containing an inorganic salt having a nucleotide concentration of 2 g / dl to 35 g / dl and having a NaCl rejection of 20 to 80% and 5'-disodium inosinate. A method for removing inorganic salts from a solution, which comprises subjecting to reverse osmosis treatment using a loose reverse osmosis membrane having a rejection rate of 95% or more. 2. The method according to claim 1, wherein reverse osmosis treatment is carried out at pH 5-11. 3. The method according to claim 1 or ^2, wherein the reverse osmosis treatment is performed at a pressure of 10 to 70 kg / cm ² .