JP2006083118A - Method for purifying methionine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for purifying methionine by which the methionine having a crystal form enabling solid-liquid separation to be carried out well is obtained in good efficiency even if a methionine solution containing high-concentration methionine is used. <P>SOLUTION: The method for purifying the methionine involves gradually adding the solution of the methionine and a solution containing polyvinyl alcohol or gluten dissolved in water to the water or an aqueous solution containing at least one kind of compounds selected from the group consisting of polyvinyl alcohol, gluten and methionine. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for purifying methionine, which can obtain methionine crystals having a low water content and a small specific volume.

  In the methionine production process, after obtaining a methionine solution, purified methionine is obtained by performing a crystallization operation. In addition, when the product specifications of the obtained purified methionine are less than the standard, repurification such as recrystallization may be required. In any case, as a method for purifying methionine, a method of crystallizing methionine from water is generally employed. However, the methionine crystal obtained by the method of crystallizing methionine from water is a scaly or plate-like crystal, and has a high water content and a large specific volume. there were.

  In order to solve this problem, several methods have been proposed for obtaining methionine crystals having a low water content, a small specific volume, and easy handling. For example, a method of crystallizing methionine in the presence of a soluble fiber derivative (see Patent Document 1), a method of crystallizing methionine in the presence of alcohols, phenols and ketones (see Patent Document 2), anion Of crystallizing methionine in the presence of a neutral or nonionic surfactant (see Patent Document 3), a water-soluble cellulose derivative, a water-soluble or polar organic solvent-soluble polyvinyl compound, a water-soluble starch derivative, gelatin or its partial hydrolysis Examples thereof include a method of crystallizing an amino acid (see Patent Document 4) in the presence of one or more of a decomposed polypeptide, alginate or polyacrylate.

Japanese Patent Publication No.43-22285 Japanese Patent Publication No.43-24890 Japanese Patent Publication No.46-19610 Japanese Patent Laid-Open No. 60-237054

  The inventors of the present invention attempted to produce methionine having a crystal form with a low water content, a small specific volume, and easy handling by the method described in the above literature, and the effect of improving the crystal habit of methionine crystals was stable. It is only possible to crystallize methionine from a methionine solution having a low methionine concentration. In general, the additive effect decreases as the methionine concentration in the methionine solution used for crystallization increases. It was the target. Lowering the methionine concentration of the methionine solution used for crystallization is not preferable as an industrial purification method because the reaction vessel becomes larger and the dissolution loss in the solvent increases.

  Therefore, the present invention provides a method for purifying methionine that can efficiently obtain methionine having a crystal form with good solid-liquid separation even when a methionine solution containing a high concentration of methionine is used. This is the issue.

  As a result of diligent research to solve the above problems, the present inventors gradually put water or an aqueous solution containing polyvinyl alcohol and methionine into a solution obtained by dissolving a solution of methionine and polyvinyl alcohol in water. The inventors have found that purified methionine having a crystal form with a low water content, a small specific volume and a good solid-liquid separation property can be efficiently obtained, and the present invention has been completed.

Thus, according to the present invention, there is provided a method for purifying methionine according to any one of (1) to (5) below.
(1) Gradually adding a methionine solution and a solution in which polyvinyl alcohol or gluten is dissolved in water into water or an aqueous solution containing at least one compound selected from the group consisting of polyvinyl alcohol, gluten and methionine. A method for purifying methionine characterized by the above.
(2) The methionine solution is (i) a liquid obtained by heat-treating a methionine reaction solution produced by a microbial cell having nitrilase or amidase enzyme or a processed product thereof, and (ii) water or an aqueous solution containing methionine. The method for purifying methionine according to (1), wherein the methionine crystal is added and heated and dissolved.
(3) The methionine according to (1) or (2), wherein the temperature of the aqueous solution containing water or at least one compound selected from the group consisting of polyvinyl alcohol, gluten and methionine is kept at 40 ° C. or lower. Purification method.
(4) The method for purifying methionine according to any one of (1) to (3), wherein the methionine solution is added dropwise or dividedly.
(5) The method for purifying methionine according to any one of (1) to (4), wherein the methionine solution is an aqueous solution containing 8 to 10% by weight of methionine with respect to the whole solution.

  According to the purification method of the present invention, even when a high-concentration methionine solution (solution having a methionine concentration of 8 to 10% by weight) is used, the water content is low, the specific volume is small, and the solid-liquid separation property is low. Purified methionine having a good crystal form can be obtained efficiently.

Hereinafter, the method for purifying methionine of the present invention will be described in detail.
The method for purifying methionine according to the present invention is water or an aqueous solution containing at least one compound selected from the group consisting of polyvinyl alcohol (hereinafter abbreviated as “PVA”), gluten and methionine (hereinafter collectively referred to as these). Methionine solution and a solution obtained by dissolving polyvinyl alcohol or gluten in water are gradually added into the base solution.

(1) Base solution The method for crystallizing methionine of the present invention crystallizes methionine in the methionine solution in the base solution.
The base solution used is (a) water, preferably cooled water, or (b) an aqueous solution in which PVA or gluten is dissolved in water. In the present invention, the base liquid preferably further contains methionine because methionine crystals can be precipitated more rapidly.

As a base solution containing methionine, a solution in which methionine is dissolved in cooled water or an aqueous solution in which PVA or gluten is dissolved in water, a mother solution obtained by filtering a solution in which methionine crystallizes, or a solution in which methionine crystallizes is used as a slurry solution. Things can be used.
In this case, the concentration of methionine in the base solution is not particularly limited, but it is preferably about the solubility of methionine at the temperature at which the methionine is precipitated in consideration of improvement in the methionine recovery rate.

(2) Methionine Dissolving Solution The methionine dissolving solution used in the present invention is not particularly limited as long as it is a solution in which methionine is dissolved in water. Among them, (i) a microbial cell having a nitrilase or amidase enzyme, or a solution obtained by heat-treating a methionine reaction solution produced by a processed product thereof, or (ii) a methionine crystal that is solid-liquid separated into an aqueous solution containing water or methionine. It is preferable that the liquid is added and dissolved by heating.

  The microbial cells having the nitrilase or amidase enzyme are not particularly limited. For example, JP-A-9-510623, JP-A-2000-253256, JP-A-2002-532096, JP-A-2003-524608 are disclosed. The thing described in the gazette etc. is mentioned. Examples of the treated product include a microbial cell disruption product, an enzyme, an immobilized microbial cell, and an immobilized enzyme of a microbial cell having a nitrilase or amidase enzyme.

  The methionine concentration in the methionine solution is not particularly limited, but is usually 6 to 15% by weight, preferably 7 to 12% by weight, and more preferably 8 to 10% by weight. According to the present invention, purified methionine having a crystal form with good solid-liquid separation can be efficiently obtained even when a high-concentration methionine solution having a methionine concentration of 6 to 15% by weight is used. Of course, the present invention can be carried out even when the methionine concentration is 6% by weight or less, but problems such as an increase in the container for purification and an increase in dissolution loss in the solvent arise.

(3) Liquid in which PVA or gluten is dissolved in water The amount of PVA or gluten used in the liquid in which PVA or gluten is dissolved in water is not particularly limited, but is preferably 0.1 with respect to methionine in the methionine solution. -1.0 wt%, more preferably 0.2-0.5 wt%. If the amount is less than 0.1% by weight, the crystal form of methionine is deteriorated. If the amount is 1.0% by weight or more, an effect corresponding to the amount added cannot be obtained, and the product cost increases.

  The PVA used is generally a polymer produced by hydrolyzing polyvinyl acetate with acid or alkali. Various types of PVA having different densities and secondary transfer points are known, but are not particularly limited thereto.

  The gluten to be used may be a mixture of prolamin and glutelin, which are proteins constituting the plant, and there are no particular restrictions on the kind of plant, the mixing ratio of prolamin and glutelin, and the like.

(4) Purification method Purification of methionine can be performed as follows. First, a predetermined amount of base liquid is put into a stirring tank for crystallization of methionine, and the temperature of the base liquid is set to a predetermined value. Next, a methionine solution and a solution in which PVA or gluten is dissolved are gradually added to this solution with stirring to crystallize methionine.

  The temperature of the base solution is not particularly limited as long as it is a temperature at which methionine crystals precipitate when the methionine solution is added, but the lower the better, the better the crystals are precipitated. However, since water is used for the base solution, if it is too low, the base solution may freeze. Therefore, the temperature of the base solution is usually 5 to 40 ° C., preferably 5 to 30 ° C.

  The temperature of the methionine solution to be added is not particularly limited as long as methionine is completely dissolved, but is usually 50 to 100 ° C., preferably 80 in order to suppress precipitation of methionine in the pipe during supply. ~ 95 ° C.

  The method for adding a methionine solution and a solution in which PVA or gluten is dissolved to the base solution is not particularly limited, and both solutions may be added simultaneously or alternately. However, it is not preferable to add only the methionine solution first, because it may be difficult to obtain a methionine crystal having a low water content and a low specific dissolution product that is easy to handle.

  The methionine solution and the solution in which PVA or gluten is dissolved do not need to be added separately, and a mixed solution in which both solutions are mixed may be added, or prepared by adding PVA or gluten to the methionine solution. The solution may be added.

  The methionine solution and the solution in which PVA or gluten is dissolved are preferably added to the base solution little by little. This is because, if added all at once, the temperature of the base solution rises locally, and crystals may not be deposited smoothly.

  The rate at which the methionine solution and the solution in which PVA or gluten is dissolved is added to the base solution varies depending on the scale of the crystallization operation, the methionine concentration, the PVA or gluten concentration, and the like. In the present invention, the rate at which a methionine solution and a solution in which PVA or gluten is dissolved is added to the base solution as appropriate so that a methionine crystal having the desired water content and specific volume can be obtained. be able to.

  Examples of a method for adding a methionine solution and a solution in which PVA or gluten is dissolved in small amounts include a method in which a methionine solution is added in small portions or a method in which a solution is added dropwise in small portions.

  In any case, the base liquid is preferably added so that the temperature of the base liquid is kept at 40 ° C. or lower so that the temperature of the base liquid does not change abruptly. The optimum holding temperature of the base solution is also related to the addition rate of the methionine solution, and the optimum holding temperature tends to increase as the addition rate increases.

  After adding all of the methionine solution and the solution in which PVA or gluten is dissolved, the mixture is allowed to stand at a predetermined temperature, preferably 20 ° C. or lower for a predetermined time, and then ripened, and then purified using a known solid-liquid separator. Methionine crystals can be isolated.

  Although the solid-liquid separation apparatus to be used is not specifically limited, For example, general filtration apparatuses, such as a centrifuge, a Nutsche type filter, a rotary drum type continuous filter, can be used. The obtained crystal has good filterability in solid-liquid separation.

  As described above, a granular methionine crystal can be obtained. The volume average particle size is 100 to 700 μm, preferably 300 to 600 μm, the moisture content on a wet basis is 5 to 20% by weight, preferably 5 to 18% by weight, and the specific volume is 1.4 to 1.9 ml / g, Preferably it is 1.5-1.8 ml / g. Crystals of methionine having a water content and specific volume in such a range have a high bulk density, high purity, and easy handling.

The obtained methionine crystal may be a crystal of an optically active form of D-methionine or L-methionine, or a racemic compound composed of D-methionine and L-methionine.
The resulting methionine is useful as a feed additive for ruminants.

Next, the present invention will be described in more detail with reference to examples. In addition, this invention is not limited at all by the Example.
(1) Moisture content of methionine crystals (% by weight)
The water content of methionine crystals was measured with an infrared moisture meter.
(2) Specific volume of methionine crystals (ml / g)
The specific volume of methionine crystals was determined by weighing in a constant volume cylinder after dapping.

Example 1
A 1000 ml four-necked flask (dissolution tank) equipped with a reflux condenser and a thermometer was charged with 60 g of methionine and 690 g of water (methionine concentration: 8% by weight), and the whole volume was heated and dissolved at 90 ° C. 6 ml of a 5% aqueous solution was added (0.5 wt% vs. methionine) and stirred until uniform to obtain a methionine solution (1).
Next, 50 ml of a 3% by weight aqueous solution of methionine was added in advance, and the methionine solution (1) was added dropwise at a rate of 10 ml / min to the other 1000 ml four-necked flask (precipitation tank) cooled to 10 ° C. with a quantitative feed pump. . After completion of dropping, the mixture was allowed to stand for 2 hours, and then the crystals were filtered and dried at 10 ° C. to obtain methionine crystals.
The water content (% by weight) and specific volume (ml / g) of the obtained methionine crystals were measured. The results are shown in Table 1 below together with the crystal shape.

(Example 2)
A methionine crystal was obtained in the same manner as in Example 1 except that the methionine solution (2) in which the methionine concentration in the dissolution tank was 10% by weight was used. The water content (% by weight) and specific volume (ml / g) of the obtained methionine crystals were measured. The results are shown in Table 1 below together with the crystal shape.

(Example 3)
In Example 1, an aqueous solution of gluten (0.5 wt% vs. methionine) was used instead of the aqueous solution of PVA, and methionine crystals were obtained by performing the same operation as in Example 1 except that 50 ml of water was added to the precipitation tank. It was. The water content (% by weight) and specific volume (ml / g) of the obtained methionine crystals were measured. The results are shown in Table 1 below together with the crystal shape.

Example 4
In Example 1, as the methionine used in the dissolution tank, the methionine reaction solution produced by the microbial cells having the amidase enzyme was reduced in pressure to remove ammonia contained in the reaction solution, so that the methionine concentration became 10% by weight. A methionine crystal was obtained in the same manner as in Example 1 except that a liquid (methionine solution (3)) concentrated by heating was used. The water content (% by weight) and specific volume (ml / g) of the obtained methionine crystals were measured. The results are shown in Table 1 below together with the crystal shape.

(Example 5)
A 1000 ml four-necked flask (dissolution tank) equipped with a reflux condenser and a thermometer was charged with 75 g of methionine and 675 g of water (methionine concentration: 10% by weight) and dissolved by heating at 90 ° C., and 5% aqueous solution of PVA was added thereto. 4.5 ml is added (0.3 wt% vs. methionine). The mixture was stirred until uniform to obtain a methionine solution (4).
Next, 300 ml of a 3% by weight aqueous solution of methionine was added in advance, and 20 ml of the methionine solution (4) was added to a separate 1000 ml four-necked flask (precipitation tank) that had been stirred at a solution temperature of 30 ° C. using a quantitative feed pump. The solution was dropped at a rate of / min. After completion of the dropwise addition, the solution was cooled to 5 ° C. and aged for 1 hour, and then the crystals were filtered and dried to obtain methionine crystals.
The water content (% by weight) and specific volume (ml / g) of the obtained methionine crystals were measured. The results are shown in Table 1 below together with the crystal shape.

(Example 6)
A methionine crystal was obtained in the same manner as in Example 5 except that the dropping rate of the methionine solution (4) was 30 ml / min.
The water content (% by weight) and specific volume (ml / g) of the obtained methionine crystals were measured. The results are shown in Table 1 below together with the crystal shape.

(Comparative Example 1)
In Example 1, except that polyvinyl alcohol was not added, the same treatment as in Example 1 was performed to obtain a methionine crystal. The water content (% by weight) and specific volume (ml / g) of the obtained methionine crystals were measured. The results are shown in Table 1 below together with the crystal shape.

(Comparative Example 2)
A 1000 ml four-necked flask equipped with a reflux condenser and a thermometer was charged with 60 g of methionine and 690 g of water (methionine concentration: 8% by weight) and dissolved by heating. Here, 6 ml (0.5% by weight) of a 5% by weight aqueous solution of PVA was dissolved. % Vs. methionine) was added and stirred. This solution was cooled at a rate of 30 ° C./hour to precipitate methionine crystals. After finally cooling the temperature to 10 ° C., the methionine crystals were filtered and dried. The water content (% by weight) and specific volume (ml / g) of the obtained methionine crystals were measured. The results are shown in Table 1 below together with the crystal shape.

(Comparative Example 3)
In Comparative Example 2, a methionine crystal was obtained in the same manner as in Comparative Example 2 except that the methionine concentration was 10% by weight. The water content (% by weight) and specific volume (ml / g) of the obtained methionine crystals were measured. The results are shown in Table 1 below together with the crystal shape.

(Comparative Example 4)
In Comparative Example 2, a methionine crystal was obtained in the same manner as in Comparative Example 2 except that the methionine concentration was 6% by weight. The water content (% by weight) and specific volume (ml / g) of the obtained methionine crystals were measured. The results are shown in Table 1 below together with the crystal shape.

From Table 1, from Examples 1 to 6 in which the methionine purification method of the present invention was carried out, the water content was as low as 6 to 18% by weight and the specific volume was as small as 1.5 to 1.8 ml / g. Methionine crystals were obtained.
On the other hand, when PVA was not added (Comparative Example 1), scaly methionine crystals having a high water content, a large specific volume, a high bulk, and poor handleability were obtained.
When crystallization was performed without using a base solution, in Comparative Example 4 using a methionine aqueous solution (6 wt% aqueous solution) having a low methionine concentration, granular methionine crystals having a low water content and a relatively small specific volume were obtained. However, in Comparative Examples 2 and 3 using a methionine aqueous solution having the same methionine concentration as in the Examples, scaly methionine crystals having a high water content, a large specific volume, a bulky shape and poor handleability were obtained. .

Claims (5)

  A methionine-dissolved solution and a solution obtained by dissolving polyvinyl alcohol or gluten in water are gradually added into water or an aqueous solution containing at least one compound selected from the group consisting of polyvinyl alcohol, gluten and methionine. To purify methionine.   The methionine solution is (i) a solution obtained by heating a methionine reaction solution produced by a microbial cell having a nitrilase or amidase enzyme or a processed product thereof, and (ii) a methionine crystal separated into a liquid or an aqueous solution containing methionine. The method for purifying methionine according to claim 1, wherein the methionine is any one of a solution obtained by adding and dissolving under heating.   The method for purifying methionine according to claim 1 or 2, wherein the temperature of the aqueous solution containing water or at least one compound selected from the group consisting of polyvinyl alcohol, gluten and methionine is maintained at 40 ° C or lower. .   The method for purifying methionine according to any one of claims 1 to 3, wherein the methionine solution is dropped or dividedly added. The method for purifying methionine according to any one of claims 1 to 4, wherein the methionine solution is an aqueous solution containing 8 to 10% by weight of methionine with respect to the whole solution.