JP6492716B2 - Amino acid aqueous solution concentration method and amino acid separation method - Google Patents

Description

  The present invention relates to a method of using dimethyl ether (DME) to concentrate an aqueous solution of various amino acids produced by a fermentation method, a synthesis method or the like, or to precipitate and separate an amino acid therefrom.

  Amino acids are important as biological components, and now a wide variety of amino acids are produced by fermentation and synthesis methods. Amino acids are generally produced in the form of an aqueous solution, which is produced by concentrating the aqueous solution to precipitate amino acid crystals and separating them. This concentration is generally performed by heating with steam.

  The proportion of energy in the production cost of amino acids is quite high, and there is a demand for reduction thereof.

  An object of the present invention is to reduce the concentration cost of an aqueous amino acid solution.

  By the way, a method of dehydrating a liquid by evaporating and removing moisture in the liquid by blowing dry inert gas into the liquid which is a water-containing solvent or a water-containing solution and bringing them into contact with each other is known (Japanese Patent Laid-Open No. Hei 10-2010). 338653), and this dry inert gas includes nitrogen, air, hydrogen, carbon dioxide, helium, neon, argon, krypton, methane, ethane, propane, butane, freon, dimethyl ether, diethyl ether, monochloromethane, and dichloromethane. This is exemplified (claim 13).

  As a method for concentrating an amino acid aqueous solution, the present inventor has studied that a part of water in the amino acid aqueous solution is transferred to the dimethyl ether phase by bringing dimethyl ether into contact with the liquid. As a result, it was found that the water in the amino acid aqueous solution can be transferred to the dimethyl ether phase, and the transfer amount has a high amino acid concentration. Surprisingly, it has also been found that the solubility of amino acids is lowered and the amino acids are precipitated in a high yield. This is considered to be a poor solvent effect due to the transfer of a part of dimethyl ether to the amino acid aqueous solution phase.

  There is no example of dimethyl ether having a boiling point of −25 ° C. that has been liquefied at high pressure and brought into contact with the target substance. There are other crystallization systems that promote the poor solvent effect by forcibly transferring the solvent to the aqueous phase and increasing the pressure. Not. There is no example of using an organic substance having a lower boiling point than diethyl ether for the poor solvent effect of crystallization.

  In the present invention, the dimethyl ether having a low boiling point temperature is liquefied and used at a high pressure, thereby reducing the concentration cost of the amino acid aqueous solution and efficiently depositing the amino acid to successfully reduce the production cost of the amino acid. It is.

  That is, the present invention is a method of concentrating an aqueous amino acid solution characterized by bringing liquid dimethyl ether into contact with an aqueous amino acid solution to transfer a part of water in the aqueous amino acid solution to the dimethyl ether phase, and then separating the aqueous amino acid phase and the dimethyl ether phase And a method in which liquid dimethyl ether is brought into contact with an aqueous amino acid solution to transfer a part of water in the aqueous amino acid solution to the dimethyl ether phase, and a part of the dimethyl ether is transferred to the amino acid aqueous solution phase to precipitate amino acid crystals from the aqueous amino acid solution. The present invention provides a method for separating an amino acid from an aqueous amino acid solution, characterized in that

  In the present invention, when dimethyl ether having a boiling point significantly lower than the boiling point of water is brought into a liquefied state at high pressure and brought into contact with an amino acid aqueous solution, it is separated into a dimethyl ether phase and an aqueous phase, and part of the dimethyl ether is transferred to the aqueous phase. . At this time, dimethyl ether is actively transferred to the aqueous phase by increasing the pressure. As a result, amino acid crystals are precipitated and recovered due to the poor solvent effect.

  According to the present invention, the aqueous amino acid solution can be efficiently concentrated by transferring a part of the water in the aqueous amino acid solution to the dimethyl ether phase and separating it. Moreover, since a part of dimethyl ether moves into the amino acid aqueous solution thereby lowering the solubility of amino acids, the precipitation rate of amino acids can be increased and separation can be performed efficiently. In the present invention, by using dimethyl ether having a low boiling point temperature at a high pressure, it becomes possible to use a low-temperature heat source that has been conventionally discarded for evaporation and recovery, thereby reducing the cost.

It is process drawing which shows the one aspect | mode of the method of this invention. It is a graph which shows the result of having measured the relationship between the ratio of initial stage amino acid aqueous solution / DME, and a water dehydration rate. It is the process figure which applied the method of this invention to the valine fermentation liquid, and calculated | required the material balance. It is a graph which shows the relationship between each pressure and boiling point of DME and water.

  The amino acid of the amino acid aqueous solution to which the present invention is applied is glycine, alanine, valine, leucine, isoleucine, phenylalanine, tyrosine, proline, serine, threonine, tryptophan, cystine, cysteine, methionine, asparagine, glutamine and other neutral amino acids, asparagine Acidic amino acids such as acid and glutamic acid, and basic amino acids such as lysine, histidine, arginine and ornithine. These can be obtained by fermentation, synthesis, protein hydrolysis, etc., and there are L-form, D-form, racemic form, etc., any of which may be used.

  In the case of a fermentation broth, there are a fermentation broth, a sterilized fermentation broth from which bacterial cells have been removed, and various intermediate process liquids from which the amino acid crystals are separated, but the present invention is applicable to any process of concentrating them. it can. In particular, recent amino acid fermentation broths are particularly preferred because amino acids are accumulated up to near saturation solubility, so that a large amount of amino acid crystals can be precipitated by the method of the present invention. In the case of the synthesis method, the present invention can be applied to any process liquid that leads to separation of amino acid crystals from the synthesized liquid.

  The concentration of the amino acid in the aqueous solution is not limited, but a higher concentration is preferable because the water removal rate becomes higher. The preferred concentration is about 30 to 60% by mass, more preferably 50 to 60% by mass, and the degree of saturation is about 0 to 110%, more preferably about 70 to 100%. The aqueous amino acid solution may be one in which amino acid crystals are already precipitated, and in that case, the amino acid crystals are not counted in the above concentration.

  The addition amount of dimethyl ether is about 1: 1 to 1: 5, preferably about 1: 3 to 1: 5 in terms of mass ratio to the water content in the aqueous amino acid solution. In the liquid volume ratio with the amino acid aqueous solution, about 1: 1 to 1: 5 is obtained, preferably about 1: 3 to 1: 5.

Since dimethyl ether has a boiling point of −25 ° C., it needs to be added at a high pressure. The pressure only needs to be equal to or higher than the pressure at which diethyl ether liquefies, and this varies depending on the temperature, but is, for example, 0.5 MPa or higher at 20 ° C. This liquefaction pressure is documented (Nobuyuki Kamiya “Environmentally Friendly New Energy in the 21st Century: Dimethyl Ether” Hydrogen Energy System Vol.30,
No. 2 (2005) p. 103) Practically, the pressure may be set to 0.4 MPa to 0.9 MPa at 10 to 40 ° C. FIG. 4 shows the relationship between pressure and boiling point for dimethyl ether and water. The frame in the figure shows an example of a range in which dehydration / condensation swings. The upper limit of the pressure is not particularly limited, but is about 1.0 MPa, preferably about 0.7 MPa from a practical viewpoint. Accordingly, a pressure vessel that can withstand this pressure in a sealed form is used as the container in which the aqueous amino acid solution and dimethyl ether are brought into contact. The vessel should be replaced with DME vapor prior to processing.

  In order to efficiently contact the amino acid aqueous solution and dimethyl ether, it is preferable to provide a stirrer in the container, or to blow dimethyl ether into the amino acid aqueous solution, or to blow the amino acid aqueous solution into the dimethyl ether solution. The contact time is preferably until the movement of water and dimethyl ether between the aqueous amino acid phase and the dimethyl ether phase almost reaches equilibrium, but may be about 1 to 5 minutes in practice.

  When the contact between the aqueous amino acid solution and dimethyl ether is completed, the two phases are separated. Since the specific gravity of the dimethyl ether phase is considerably lighter than that of the amino acid aqueous solution phase, the separation can be performed by standing. In addition, filter separation is also possible. In the case where amino acid crystals are present in the aqueous amino acid solution, the amino acid crystals may be separated first, or the dimethyl ether may be separated and then the amino acid crystals may be separated from the aqueous amino acid solution.

  The separated amino acid crystals may be sent to the purification step as they are or after removing the remaining dimethyl ether by vaporization or the like.

  Since the separated amino acid aqueous solution contains a considerable amount of dimethyl ether, the diethyl ether is first separated. This separation can be carried out by distilling dimethyl ether under reduced pressure. The distillation temperature is preferably about 40 to 50 ° C. from the viewpoint that low-temperature exhaust heat discharged from the factory or groundwater can be used. For example, if the system pressure is set to 5 atm, dimethyl ether can be separated by evaporation and condensation at a boiling point of 20 ° C.

  The separated dimethyl ether can be reused for concentration of the aqueous amino acid solution. On the other hand, amino acids are separated from the aqueous amino acid solution from which dimethyl ether has been removed by a conventional method.

  On the other hand, since the dimethyl ether phase from which the amino acid aqueous phase has been separated contains water, it is separated by a distillation method or the like. The distillation conditions may be the same as those for the separated aqueous amino acid solution, and the distillation temperature is preferably about 40 to 50 ° C. The separated dimethyl ether can be reused for concentration of the aqueous amino acid solution. On the other hand, the moisture can be discharged as it is or further processed or reused in the factory.

  One embodiment of the present invention is shown in FIG. As shown in the figure, liquefied dimethyl ether is added to an amino acid aqueous solution at 20 ° C. and 5 atm, and the mixture is allowed to stand to separate the layers. The aqueous phase, which is an amino acid phase, and the dimethyl ether phase are separated, and the aqueous phase is heated to 40 ° C. to evaporate dimethyl ether to obtain an amino acid concentrate. The amino acid concentrate is further concentrated as necessary to separate the precipitated amino acid crystals. The dimethyl ether phase is also heated to 40 ° C. to evaporate dimethyl ether, which is cooled to 10 ° C. and condensed. Dimethyl ether evaporated from the aqueous phase can also be cooled and condensed here. The obtained liquefied dimethyl ether is recycled to the aqueous amino acid solution to be concentrated.

  A pure aqueous solution of L-leucine, L-phenylalanine and L-lysine (free form) and a sterilized fermentation liquid of L-valine were prepared at the concentrations shown in Table 1.

上記の各アミノ酸水溶液の表１に示す液量をそれぞれ圧力容器に入れて、これに表１に示す液量のジメチルエーテルを加えて２０℃５気圧で1分間混合後、3分間静置して分層させた。純系アミノ酸水溶液（Ｅｘｐ．１〜５）について、分層した水相のアミノ酸濃度を測定した結果を表２に示す。

Put each of the above-mentioned aqueous solutions of amino acids shown in Table 1 into a pressure vessel, add the dimethyl ether of the amount shown in Table 1 to this, mix at 20 ° C. and 5 atm for 1 minute, and then let stand for 3 minutes to separate. Layered. Table 2 shows the results of measuring the amino acid concentration of the separated aqueous phase for pure amino acid aqueous solutions (Exp. 1 to 5).

上記の水分除去率は、除去水分量／初期アミノ酸水溶液中水分量ｗ／ｗ％である。

The water removal rate is the amount of water removed / the amount of water in the initial amino acid aqueous solution w / w%.

  Table 3 shows the results of measuring the amounts of water, dimethyl ether and amino acids in the aqueous phase and the dimethyl ether phase.

得られた、初期アミノ酸水溶液中の水分とジメチルエーテルの比率と水分の脱水率の関係を図２に示す。同図に示すようにアミノ酸の濃度が高い程高い脱水率になる。また、アミノ酸がジメチルエーテル相に移行しないことも明らかになり、ジメチルエーテルによってアミノ酸水溶液を脱水濃縮できることを確認した。

FIG. 2 shows the relationship between the ratio of water and dimethyl ether in the initial aqueous amino acid solution and the water dehydration rate. As shown in the figure, the higher the amino acid concentration, the higher the dehydration rate. Moreover, it became clear that an amino acid did not transfer to a dimethyl ether phase, and it was confirmed that an aqueous amino acid solution could be dehydrated and concentrated with dimethyl ether.

  Table 4 shows the measurement results of the sterilized fermented liquid of valine.

この結果をバリン発酵液の処理に適用すると、例えば、図３に示す物質収支が得られる。

When this result is applied to the treatment of valine fermentation broth, for example, the mass balance shown in FIG. 3 is obtained.

  That is, 65.0 ml (46 g) of liquid dimethyl ether is added to and mixed with 15 ml of valine sterilized fermentation liquid (valine concentration 5.7 w / w%) containing 0.86 g of valine and 14 g of water, and the mixture is allowed to stand to separate the layers. Then, valine crystals, an aqueous phase of 15 ml, and a dimethyl ether phase of 65 ml (45.5 g) are separated therefrom. Valine crystals are separated by filtration. The valine crystals contain 0.51 g valine, the aqueous phase contains 0.35 g valine, 11 g water, 3 g dimethyl ether, and the dimethyl ether phase contains 43 g dimethyl ether, 3.0 g water, and 0.000 g valine. It is. Dimethyl ether is removed from the aqueous phase to obtain 12 g of a valine concentration solution (valine concentration: 3.1 w / w%) containing 11 g of water and 0.35 g of valine. Separation of dimethyl ether from a 12 g sample (water content 0.8 g, 6.5 w / w%) taken from the dimethyl ether phase gives 0.78 g of water.

  INDUSTRIAL APPLICABILITY The present invention can be applied to the production process of various amino acids because an aqueous amino acid solution can be efficiently concentrated, from which amino acid crystals can be crystallized at a high crystallization rate and separated.

Claims (2)

  A method for concentrating an amino acid aqueous solution, comprising bringing a liquid dimethyl ether into contact with an amino acid aqueous solution to transfer a part of water in the amino acid aqueous solution to the dimethyl ether phase, and then separating the amino acid aqueous phase and the dimethyl ether phase.   Liquid dimethyl ether is brought into contact with the amino acid aqueous solution to transfer a part of the water in the amino acid aqueous solution to the dimethyl ether phase, and a part of the dimethyl ether is transferred to the amino acid aqueous solution phase to precipitate amino acid crystals from the amino acid aqueous solution to separate them. For separating amino acids from aqueous amino acid solutions

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