JPH09202754A - Production of l-aspartic acid metal salt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently obtain a highly transparent L-aspartic acid metal salt useful as e.g. an intermediate for medicines in high yield without deposit contamination and discoloration by reaction of ammonium L-aspartate with a metal hydroxide in an aqueous medium. SOLUTION: This L-aspartic acid metal salt is obtained by reaction of pref. 1mol of ammonium L-aspartate with pref. 0.8-3.5mol of a metal hydroxide such as sodium hydroxide in an aqueous medium in the presence of a chelating agent such as ethylenediaminetetraacetic acid. In preparing the ammonium L-aspartate by reaction between maleic acid or fumaric acid and ammonia, it is preferable that the ammonia is recovered and reused.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a metal salt of L-aspartic acid, and more specifically, to produce a high quality metal salt of L-aspartic acid by reacting an ammonium salt of L-aspartic acid with a metal hydroxide. On how to do. L
-A metal salt of aspartic acid is useful as a raw material for pharmaceutical intermediates, surfactants, chelating agents and the like.

[0002]

2. Description of the Related Art L-aspartic acid is prepared by first using fumaric acid and ammonia in the presence of an enzyme-containing substance having aspartase activity, magnesium chloride as an enzyme activity promoter,
Compounds of divalent metals such as magnesium sulfate and manganese chloride (hereinafter, these compounds are collectively referred to as "divalent metal compounds") are added and reacted to obtain ammonium L-aspartate, and then L-aspartic acid It is synthesized by adding an acid such as sulfuric acid to ammonium to crystallize and separate L-aspartic acid, and there are many documents regarding this synthesis reaction.

Further, maleic acid and ammonia are used as an enzyme activity promoter in the presence of an enzyme-containing substance having maleate isomerase activity and an enzyme-containing substance having aspartase activity as described above and mercapto. It is also known to add a compound having a -SH group such as ethanol, glutathione, cystine, and dithiothreitol, and to react them to give an L-aspartic acid ammonium salt. However, in these documents, there is no description concerning the production of L-aspartic acid metal salt,
At present, L-aspartic acid metal salts are usually produced via the aspartic acid obtained as described above. That is, according to the conventionally known method, L-aspartic acid is once precipitated as crystals from ammonium L-aspartate as described above, and this L-aspartic acid and metal hydroxide are reacted (neutralized) to form L-aspartic acid. -Aspartic acid metal salt. However, this method requires the steps of precipitation, filtration and neutralization of L-aspartic acid, and cannot be considered advantageous in terms of process and economy in industrial practice.

[0004]

In view of the above-mentioned conventional techniques, the present inventors intend to provide a novel method for directly producing a metal salt of L-aspartic acid directly from ammonium L-aspartate. is there. Then, the present inventors have investigated a method for directly producing a metal salt of L-aspartate from ammonium L-aspartate, and as a result of simply reacting ammonium L-aspartate with a metal hydroxide, L -While a metal salt of aspartic acid can be obtained, a precipitate such as a hydroxide of a divalent metal is formed during the reaction and mixed into the metal salt of L-aspartic acid, or a metal salt of L-aspartic acid is generated. It turned out to be a coloring problem.

Occurrence of such a precipitate and its incorporation into L-aspartic acid metal salt (thus decreasing purity),
Also, coloring of the metal salt of L-aspartic acid significantly impairs product value and is not desirable. Also,
When the generation of deposits becomes remarkable, the reaction tube may be clogged and the reaction may have to be stopped. Thus, one of the objects of the present invention is to provide a novel method for producing L-aspartic acid metal salt directly from ammonium L-aspartate without passing through L-aspartic acid.

Another object of the present invention is to solve the problem of the formation and coloring of precipitates which occur during the production of L-aspartic acid metal salt directly from ammonium L-aspartate and metal hydroxide, It is an object of the present invention to provide a method for producing a high quality metal salt of L-aspartate from ammonium L-aspartate and a metal hydroxide.

[0007]

Means for Solving the Problems The inventors of the present invention have studied the above-mentioned problems. As a result, when the L-ammonium aspartate was added as an activity promoter when it was produced in the presence of an enzyme-containing product, It was clarified that the divalent metal of the valent metal compound is precipitated as a hydroxide during the reaction, which causes coloring. In addition, we
-The above problems can be solved by reacting ammonium aspartate with a metal hydroxide in the presence of a chelating agent, or by adjusting the molar ratio of ammonium L-aspartate and the metal hydroxide within a specific range. Know
Based on this finding, the present invention has been completed.

That is, the present invention is a method for producing an L-aspartic acid metal salt, which comprises reacting ammonium L-aspartate with a metal hydroxide in an aqueous medium.

The present invention is also a method for producing a metal salt of L-aspartic acid, characterized in that a chelating agent is allowed to coexist in the above method.

The present invention also provides the method described above, wherein L-
0.8-2. To 1 mol of ammonium aspartate.
A method for producing a metal salt of L-aspartic acid, which comprises using a metal hydroxide in a range of 2 mol.

Further, the present invention is characterized in that, in the above method, a chelating agent is allowed to coexist and a metal hydroxide in the range of 0.8 to 3.5 mol is used with respect to 1 mol of ammonium L-aspartate. Is a method for producing a metal salt of L-aspartic acid.

Further, according to the present invention, (1) L-aspartic acid ammonium salt is produced by reacting maleic acid or fumaric acid with ammonia, and then (2) L-aspartic acid obtained in step (1). In producing an L-aspartic acid metal salt by reacting an ammonium salt with a metal hydroxide in an aqueous medium, the ammonia recovered in the step (2) is recycled to the step (1) for reuse. Let L
-A method for producing a metal salt of aspartic acid.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The L-aspartic acid ammonium salt used in the present invention can be easily prepared by a conventionally known method. For example, fumaric acid and ammonia are reacted in the presence of an enzyme-containing substance having aspartase activity, or maleic acid and ammonia are reacted with an enzyme-containing substance having maleate isomerase activity and an enzyme-containing substance having aspartase activity. The reaction may be performed in the presence. Ammonia is usually used in a molar ratio of 1 to 3 times with respect to fumaric acid or maleic acid. At the time of the above reaction, at least one divalent metal compound such as magnesium chloride, magnesium sulfate and manganese chloride is added as an activity promoter of the enzyme-containing substance. In the case of the reaction between fumaric acid and ammonia, ammonia may be supplied as ammonium fumarate. Since the above-mentioned activity promoter remains as it is in the ammonium salt of L-aspartate thus obtained, the amount of the divalent metal compound in ammonium L-aspartate is used as the activity promoter during the reaction. It is the same as the amount. Usually, about 0.05 to 1 mol% (to L-aspartate ammonium) of the above divalent metal compound is contained as an impurity.

According to the method of the present invention, L-
Ammonium aspartate is reacted with a metal hydroxide to produce L-aspartic acid metal salt.

As the metal hydroxide, an alkali metal hydroxide, such as sodium hydroxide or potassium hydroxide, is usually selected appropriately according to the intended use (that is, the intended product). Of these, sodium hydroxide is particularly preferably used. Water is usually used as the aqueous medium.

The reaction conditions for carrying out the method of the present invention are not particularly limited and can be appropriately determined. Regarding the reaction temperature, the reaction is usually carried out at a temperature in the range of 70 to 130 ° C, but it is particularly preferable to carry out the reaction in the temperature range of 90 to 110 ° C. If the reaction temperature is too low, the produced ammonia cannot be efficiently removed or recovered, and the reaction rate will also decrease. On the other hand, if the reaction temperature is too high, the aspartic acid may deteriorate, which is not preferable. The reaction pressure may be reduced pressure, increased pressure or normal pressure, but the reaction is usually performed at normal pressure. The concentration of ammonium L-aspartate in the aqueous medium is also not particularly limited, and it does not cause precipitation of the raw material ammonium L-aspartate or the produced metal salt of L-aspartate and does not significantly reduce the productivity. All you have to do is react. Usually, the reaction is carried out at a concentration in the range of 5 to 50% by weight, but it is particularly preferable to carry out the reaction at a concentration in the range of 15 to 35% by weight.

According to one method of the present invention, the above L-
The reaction between ammonium aspartate and metal hydroxide is carried out in the presence of a chelating agent. This can effectively prevent the precipitation or coloring of the divalent metal hydroxide.

As the above chelating agent, any chelating agent can be used as long as it is water-soluble and can form a chelate bond with the divalent metal. A typical example is E
DTA (ethylenediaminetetraacetic acid), NTA (nitrilotriacetic acid), iminodiacetic acid, hydroxyethylenediamineacetic acid, hydroxyethyliminodiacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraminehexaacetic acid, diglycolic acid, hydroxyiminodisuccinic acid, carboxymethylimino Examples thereof include succinic acid, oxydisuccinic acid, citric acid, iminodisuccinic acid, acrylic acid polymers, acrylic acid-maleic acid copolymers and the like. The amount of the chelating agent used is 0.5 to 20 times mol, preferably 1 to 20 times mol of the divalent metal compound contained in ammonium L-aspartate. If the amount of the chelating agent used is too small, the effect of preventing the precipitation of the hydroxide of the divalent metal is insufficient. On the other hand, if the amount is too large, the purity of the product deteriorates and quality problems occur, which is also economically disadvantageous. .

When the above chelating agent is used, a metal salt of L-aspartic acid containing the chelating agent can be obtained.
It can be used as it is depending on the application. For example, one of the uses of the L-aspartic acid metal salt is the production of a builder for detergents. The chelating agent described above can also be generally used as a builder for detergents, and thus the chelating agent obtained by the method of the present invention. Containing L-
The metal salt of aspartic acid can be used as it is as a raw material for manufacturing a builder for a detergent. For example, (hydroxy) iminodisuccinic acid (a metal salt) is currently considered to be a promising builder for detergents, and can be easily obtained by reacting a metal salt of aspartic acid with a metal salt of epoxysuccinic acid or maleic acid. Therefore, it can be mentioned as one of the compounds which is conveniently used as the above chelating agent. The chelating agent used can be appropriately selected depending on the use of the metal salt of aspartic acid.

In this method, the amount of the metal hydroxide used is not particularly limited, but it is usually used in the range of 0.8 to 2.2 mol per mol of L-aspartate ammonium.

According to another method of the present invention, the reaction of the above-mentioned ammonium L-aspartate with a metal hydroxide is carried out by L
-0.8 to 1 mol of ammonium aspartate
It is carried out using 2.2 mol, preferably 1 to 2 mol of metal hydroxide. This can effectively prevent the precipitation or coloring of the divalent metal hydroxide. When the amount of the metal hydroxide used is less than 0.8 mol or more than 2.2 mol per mol of L-aspartic acid ammonium salt, the precipitation or coloring of the divalent metal hydroxide is effectively prevented. become unable.

According to another method of the present invention, the reaction between the above-mentioned ammonium L-aspartate and metal hydroxide is carried out in the presence of a chelating agent at 0.8 mol / mol ammonium L-aspartate. ~ 3.5 mol, preferably 1-3.2 mol of metal hydroxide. This makes it possible to more effectively prevent the precipitation and coloration of the divalent metal hydroxide, and to produce a high-quality metal salt of L-aspartic acid. L-ammonium aspartate 1
If the amount of the metal hydroxide used is less than 0.8 mol or more than 3.5 mol per mol, precipitation or coloring of the divalent metal hydroxide cannot be effectively prevented.

According to the above method of the present invention, ammonia is produced in addition to the desired metal salt of L-aspartic acid as a result of the reaction between ammonium L-aspartate and the metal hydroxide. Therefore, this ammonia is recovered and L-
By reusing as a raw material for the production of ammonium aspartate, the production cost of the L-aspartic acid metal salt can be reduced.

Thus, according to another method of the present invention, maleic acid or fumaric acid is reacted with ammonia to obtain L.
-Manufacturing an ammonium salt of aspartic acid (step (1)), and then reacting the obtained ammonium salt of L-aspartic acid with a metal hydroxide in an aqueous medium to manufacture a metal salt of L-aspartic acid (step (2) ))
The ammonia recovered in step (2) is recycled to step (1) for reuse.

Step (1) can be carried out according to a conventionally known method as described above. In step (2),
Ammonia is usually recovered as ammonia water, but this ammonia water may be recycled to the step (1) as it is, or if necessary, separated and recycled to the step (1) for reuse. Good.

The method of the present invention may be carried out by either a batch system or a continuous system.

The aqueous solution of L-aspartic acid metal salt obtained by the method of the present invention may be used as it is for desired applications, for example, reaction with other compounds, or L-aspartic acid may be precipitated from this aqueous solution. You may use it as a crystal of a metal salt.

[0028]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. The outline of the apparatus used and the method of analyzing products and the like are as follows.

The apparatus heating mantle was equipped with a reaction vessel having an inner volume of 1 liter equipped Oldershaw (Older-Show) distillation column (10 plates) top from L- aspartate ammonium aqueous sodium solution and a respective predetermined hydroxide Mixing and mixing were carried out at a concentration and a ratio, and the produced aqueous ammonia was taken out from the upper part of the distillation column, while the aqueous solution of L-aspartic acid alkali metal salt was taken out from the lower part of the reaction vessel. A liquid level gauge is attached to the reaction kettle so that the L-aspartic acid alkali metal salt aqueous solution can be continuously collected while keeping the liquid quantity in the reaction kettle constant.

Analysis The concentration of the alkali metal aspartic acid salt was measured by high performance liquid chromatography, and the concentration of the recovered ammonia was measured by titration with sulfuric acid or the ion electrode method.

Synthesis Example 1 Fumaric acid (20 g), potassium phosphate (1 g), magnesium sulfate heptahydrate (0.5 g), yeast extract (20 g) and corn steep liquor (20 g) were dissolved in 5 liter jar fermenter, and the pH was dissolved. After sterilizing by adding 3 liters of medium adjusted to 6.8 with ammonia,
Separately, 50 ml of the above medium was placed in a 500 ml shake flask and cultured, and Escherichia coli (ATCC) was cultured.
11303) was inoculated and cultured with aeration and stirring at 37 ° C. When the fumaric acid in the medium disappeared, acetic acid was added to the cell culture solution to adjust the pH to about 5 and left at 45 ° C. for 1 hour, and then the culture solution was centrifuged to separate the cells.

The separated cells were treated with 50 mM phosphate buffer solution 5
Ion exchange resin Duolite A-7 (US Diamond Shamrock Chemical) suspended in 1 liter
1.5 L was added, and the mixture was stirred at 4 ° C. for 24 hours to adsorb the enzyme in the bacterial cells on the ion exchange resin. An enzyme protein containing 14.5 g of aspartase was adsorbed per liter of the ion exchange resin. 1.5 liters of the ion-exchange resin having the enzyme adsorbed therein was packed in a cylindrical column having a total volume of 2 liters, and the whole column was covered with a heat-retaining agent of expanded polystyrene to keep it warm.

This column was charged with 20 fumaric acid in 1 liter.
An ammonium fumarate aqueous solution (pH 8.3) containing 0 g and 0.2 g of magnesium sulfate heptahydrate was passed as a substrate medium at a rate of 1.5 l / Hr. The reaction temperature was set to a constant temperature bath of 30 ° C. immediately before the column so that the temperature of the substrate medium flowing into the column was 30 ° C. The reaction was carried out under these conditions, and ammonium L-aspartate was stably obtained at a conversion rate of almost 100%. The amount of magnesium sulfate in 1 liter of this aqueous solution of ammonium L-aspartate was 0.2 g.

Example 1 1.5 times mol of hydroxyiminodisuccinic acid (HIDS) was used as a chelating agent for magnesium sulfate in the ammonium L-aspartate aqueous solution (23.8% by weight) obtained in Synthesis Example 1. The added L-ammonium aspartate aqueous solution (23.8% by weight) and the sodium hydroxide aqueous solution (48% by weight) at a rate of 500 g / hr and 121 g / hr (sodium hydroxide / L-ammonium aspartate (molar ratio), respectively. = 1.83 / 1) from the upper part of the distillation column, the reaction vessel internal temperature is 100 to 103 ° C.,
When continuously operated at a vapor temperature of the distillation column upper part of 94 to 97 ° C., 98 g / hr of ammonia water having an ammonia concentration of about 15% by weight was obtained from the upper part of the distillation column, and an aqueous solution of sodium L-aspartate (concentration: L-aspartic acid was obtained from the lower part of the reaction vessel). 26.4% by weight in terms of disodium) was obtained at a rate of 540 g / hr. The obtained aqueous solution of sodium L-aspartate had no precipitate and was colorless and transparent. Further, the residual ammonia was less than 20 ppm and was not odorous.

Example 2 In Example 1, the amount of HIDS added was tripled and the supply rate of the aqueous sodium hydroxide solution was 127 g / hr.
Example 1 with the exception of changing to (sodium hydroxide / L-ammonium aspartate (molar ratio) = 1.92 / 1)
Ammonia concentration of about 15% by weight
99 g / hr of aqueous ammonia, and L-sodium aspartate aqueous solution (concentration: 26.2 wt% in terms of disodium L-aspartate) was obtained at a rate of 522 g / hr. The obtained aqueous solution of sodium L-aspartate had no precipitate and was colorless and transparent. Further, the residual ammonia was 20 ppm or less and was not odorous.

Example 3 In Example 1, iminodisuccinic acid as a chelating agent was added in a 6-fold molar amount with respect to the divalent metal compound, and the supply rates of the ammonium L-aspartate aqueous solution and the sodium hydroxide aqueous solution were each 450 g / hr. And 1
A continuous reaction was performed in the same manner as in Example 1 except that the amount was changed to 39 g / hr (sodium hydroxide / L-ammonium aspartate (molar ratio) = 2.34 / 1), and ammonia water having an ammonia concentration of about 15% by weight was added. A 85 g / hr aqueous solution of sodium L-aspartate (concentration: 25% by weight in terms of disodium L-aspartate) was obtained at a rate of 506 g / hr. The obtained aqueous solution of sodium L-aspartate had no precipitate and was colorless and transparent. Further, the residual ammonia was 20 ppm or less and was not odorous.

Example 4 In Example 1, the addition amount of HIDS was increased to 12 times mol.
Further, the supply rates of the L-ammonium aspartate aqueous solution and the sodium hydroxide aqueous solution were each 400 g / h.
r and 169 g / hr (sodium hydroxide / L-ammonium aspartate (molar ratio) = 3.2
/ 1) except that the continuous reaction was carried out in the same manner as in Example 1 to obtain ammonia water having an ammonia concentration of about 15% by weight at 76 g / hr.
511 an aqueous solution of sodium L-aspartate (concentration: 22% by weight in terms of disodium salt of L-aspartic acid)
g / hr. The obtained aqueous solution of sodium L-aspartate had no precipitate and was colorless and transparent. Further, the residual ammonia was 20 ppm or less and was not odorous.

Example 5 The ammonium L-aspartate aqueous solution (23.8% by weight) and the sodium hydroxide aqueous solution (48% by weight) obtained in Synthesis Example 1 were mixed with 473 g / hr and 115, respectively.
It was supplied from the upper part of the distillation column at a rate of g / hr (sodium hydroxide / L-aspartic acid ammonium salt (molar ratio) = 1.84 / 1), the reactor inner temperature was 100 to 103 ° C., the distillation column upper part steam temperature was 94. When continuously operated at ˜97 ° C., 81 g / hr of ammonia water having an ammonia concentration of about 15% by weight was supplied from the upper part of the distillation column, and an aqueous solution of sodium L-aspartate (concentration: 25% in terms of L-aspartic acid disodium salt was converted from the lower part of the reaction vessel. 0.4 wt%) was obtained at a rate of 524 g / hr. The obtained aqueous solution of sodium L-aspartate had no precipitate and was colorless and transparent. Further, the residual ammonia was less than 20 ppm and was not odorous.

Example 6 In Example 5, 473 g each of an aqueous solution of ammonium L-aspartate and an aqueous solution of sodium hydroxide were prepared.
/ Hr and 68 g / hr rates (sodium hydroxide /
L-ammonium aspartate (molar ratio) = 1.1 /
A continuous operation was performed in the same manner as in Example 5 except that the ammonia water was supplied in 1), and ammonia water having an ammonia concentration of about 15 wt% was added to
g / hr, L-sodium aspartate aqueous solution (concentration: 27.5% by weight aspartic acid disodium salt) was obtained at a rate of 475 g / hr. The obtained aqueous solution of sodium L-aspartate had no precipitate and was colorless and transparent. Further, the residual ammonia was less than 20 ppm and was not odorous. Example 7 The reaction was performed in the same manner as in Example 1 except that 2 mol of EDTA was used instead of HIDS as the chelating agent. 97 g / hr of ammonia water having an ammonia concentration of about 15% by weight from the top of the distillation column, and L from the bottom of the reaction vessel
540 an aqueous solution of sodium aspartate (concentration: 26.4% by weight in terms of disodium L-aspartate)
g / hr. The obtained aqueous solution of sodium L-aspartate had no precipitate and was colorless and transparent. Further, the residual ammonia was less than 20 ppm and was not odorous.

Example 8 Ammonia concentration 15 recovered from the upper part of the distillation column in Example 5
660 g of wt% ammonia water, 400 g of fumaric acid, 0.5 g of magnesium sulfate heptahydrate and 800 ml of distilled water
After adjusting the pH of the liquid containing the above to 8.5 with the above ammonia water, distilled water was added to obtain a 2 liter aqueous solution. A cylindrical column filled with 1.5 liters of the ion-exchange resin having the enzyme described in Synthesis Example 1 was used as a substrate medium with the aqueous solution as a substrate medium at a rate of 1.5 liters / hr so that the temperature at the column inlet was 30 ° C. It was distributed to. Ammonium L-aspartate was obtained with a conversion rate of almost 100%, and the same results as in Synthesis Example 1 were obtained.

Comparative Example 1 In Example 5, 473 g each of the L-ammonium aspartate aqueous solution and the sodium hydroxide aqueous solution were prepared.
/ Hr and 35 g / hr rates (sodium hydroxide /
L-ammonium aspartate (molar ratio) = 0.56
Continuous operation was performed in the same manner as in Example 5 except that the supply was performed in / 1). Ammonia water with an ammonia concentration of about 15% by weight is 6
Only 0 g / hr was obtained, and the ammonia recovery rate was about 70%. In addition, residual ammonia is 200 ppm
There was also a problem in terms of odor.

Comparative Example 2 In Example 5, 400 g of each of the ammonium L-aspartate aqueous solution and the sodium hydroxide aqueous solution was added.
/ Hr and 169 g / hr (sodium hydroxide / L-aspartic acid ammonium salt (molar ratio) = 3.
The continuous operation was performed in the same manner as in Example 5 except that the water was supplied in 2/1), and the ammonia water having an ammonia concentration of about 15% by weight was used for 9 times.
0 g / hr, L-sodium aspartate aqueous solution (concentration: 22.5 wt% in terms of disodium L-aspartate) were obtained at a rate of 497 g / hr. However, the recovered liquid was initially colorless and transparent, but became cloudy after 30 minutes. When the experiment was continued, the lower part of the distillation column was clogged and the experiment was stopped.

[0043]

According to the method of the present invention, there is no precipitate,
A clear aqueous solution of metal L-aspartate can be prepared directly from ammonium L-aspartate.

The L-aspartic acid metal salt obtained by the method of the present invention is of high quality without inclusion of precipitates or coloring, and can be suitably used for various purposes.

According to the method of the present invention, ammonia produced by the reaction can be recovered, circulated and reused, so that the metal salt of L-aspartic acid can be produced economically.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koichi Sakano 12-25 Kannondai, Tsukuba-shi, Ibaraki 12 12

Claims (5)

[Claims] 1. A method for producing a metal salt of L-aspartic acid, which comprises reacting ammonium L-aspartate with a metal hydroxide in an aqueous medium. 2. A L-aspartic acid, characterized in that a chelating agent coexists when the L-aspartic acid metal salt is produced by reacting ammonium L-aspartate with a metal hydroxide in an aqueous medium. Method for producing metal salt. 3. In producing an L-aspartic acid metal salt by reacting ammonium L-aspartate with a metal hydroxide in an aqueous medium, 0.8 to 2 per mol of L-aspartic acid ammonium is produced. A method for producing a metal salt of L-aspartic acid, which comprises using a metal hydroxide in a range of 2 mol. 4. A chelating agent is allowed to coexist and 1 mol of ammonium L-aspartate is used in the production of L-aspartic acid metal salt by reacting ammonium L-aspartate with a metal hydroxide in an aqueous medium. Against 0.8
A method for producing a metal salt of L-aspartic acid, which comprises using a metal hydroxide in an amount of ˜3.5 mol. 5. (1) L-aspartic acid ammonium salt is produced by reacting maleic acid or fumaric acid with ammonia, and then (2) the L-aspartic acid ammonium salt obtained in step (1) is used as a metal. In producing L-aspartic acid metal salt by reacting with hydroxide in an aqueous medium, ammonia recovered in step (2) is recycled to step (1) for reuse. Method for producing metal salt of aspartic acid.