JPS60217897A - Method for separating and purifying lactic acid - Google Patents

Abstract

PURPOSE:To separate lactic acid economically and efficiently from a fermentation liquor, by concentrating a magnesium lactate solution obtained by the fermentation method to deposit magnesium lactate crystals, separating the crystals, dissolving the separated crystals in water, and bringing the resultant solution into contact with an H-type ion exchange resin. CONSTITUTION:Lactic acid is formed by the fermentation method. After completing the fermentation, the lactic acid is neutralized with a magnesium compound to give a magnesium lactate solution, which is then fittered to afford a magnesium lactate solution. The resultant filtered solution is concentrated under heating at >=50 deg.C to deposit magnesium lactate crystals, which are then separated by a separation means, e.g. a centrifuge, filter press, etc. The separated crystals are dissolved in water to give a 5-20% aqueous solution is then passed through an H-type ion exchange resin to afford the aimed purified lactic acid.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for separating and purifying lactic acid from a fermentation-finished liquid containing lactate obtained by a fermentation method, and in particular, by precipitating and separating magnesium lactate crystals, H- The present invention relates to a method for separating and purifying lactic acid using a type ion exchange resin.

Chemical synthesis methods and fermentation methods have been industrially established as methods for producing lactic acid.

Lactic acid obtained by chemical synthesis is an optically inactive racemic form, so it can be converted into an optically active form or L.
Fractionation into types is technically and economically extremely difficult. On the other hand, when using the fermentation method, L-type or L-type lactic acid can be obtained by selecting the bacterial species used and culture conditions, and the yield based on sugar is, for example, 90% for homozygous lactic acid bacteria. Above, Rhizops, Orise
US oryzae) has the advantage of having a high rate of about 70%.

However, in the fermentation method, the fermented liquid contains a lot of impurities such as residual sugar and various inorganic salts, as well as amino acids, proteins, pigments, and other organic acids, so pure lactic acid must be separated and purified from the liquid. It requires many steps and is economical.

So far known lactic acid purification methods include the ether/I/bucc extraction purification method, the method of extracting and purifying the lactate of a 6th class amine with an organic solvent, the method of esterification and distillation purification, and the method of purifying by distillation under reduced pressure. There are distillation methods, separation and purification methods as calcium lactate crystals, etc. Although these methods each have their own advantages, they also suffer from incomplete removal of impurities, low product yields, or operational problems.
However, it is not necessarily satisfactory as it can avoid disadvantages such as economic disadvantage.

The following is an explanation of the purification method using calcium lactate precipitation, which is currently the most widely used industrially. That is, in this method, calcium carbonate is continuously or semi-continuously added during lactic acid fermentation to neutralize the produced lactic acid to obtain a calcium lactate-containing liquid, and the liquid is subjected to bacterial cell isolation, deproteinization, decolorization, etc. After that, this is concentrated and cooled to precipitate and separate calcium lactate, and the separated calcium lactate is redissolved and precipitated repeatedly to obtain pure calcium lactate crystals, which are then diluted with sulfuric acid. A lactic acid solution is obtained.

This method has poor precipitation efficiency, and if the degree of concentration is increased in order to increase the precipitation efficiency, the entire liquid during cooling will solidify, and the ratio of liquid to the amount of precipitated crystals is small (crystals are also small). Becomes needle-like.

As a result, the amount of impurities in the calcium lactate crystals increases, and the purification efficiency does not improve. Therefore, it is necessary to carry out recrystallization at least several times.

Furthermore, various ion exchange resin methods have recently been proposed. For example, a calcium lactate-containing solution or a sodium lactate-containing solution is mixed with an H-type strongly acidic cation exchange resin and an OH
A method of treatment with a type or lactic acid type strongly basic anion exchange resin (Japanese Patent Publication No. 5+12990) and a method of treatment with an amphoteric ion exchange resin (Japanese Patent Publication No. 57-53078)
) etc. All of these methods have problems such as incomplete separation of nonionic impurities such as residual sugar, or deterioration of the ion exchange resin due to impurities.

In view of the current situation, the inventors of the present invention have conducted extensive research into an economical and efficient method for separating and purifying lactic acid from fermented lactate-containing solutions, and have established the method for separating and purifying lactic acid as detailed below. This is what I came to do.

That is, the present invention produces a magnesium lactate salt solution in the production of lactic acid by a fermentation method, heats and concentrates the solution to 50°C or higher to precipitate magnesium lactate crystals, separates the magnesium lactate, and then dissolves it in water. The present invention relates to a method for separating and purifying lactic acid, which comprises contacting with an H-type cation exchange resin to obtain an aqueous lactic acid solution.

The production of lactic acid by the fermentation method uses lactic acid bacteria, bacteria, thermophilic spore-forming bacteria, etc., and uses a culture medium containing glucose, sugar, starch, etc. as a carbon source, and urea, ammonium sulfate, etc. as a nitrogen source. , yeast extract, peptone, etc., and other inorganic nutritional sources as necessary, K , MjF s Zn, .
It is carried out by culturing in a culture medium containing various salts such as So, PO, etc., and fermenting lactic acid.

When a magnesium compound is used as a neutralizing substance in the fermentation-finished liquid thus obtained, the solution after completion of fermentation becomes a magnesium lactate salt solution, and can be left as is to the next step. On the other hand, when using a neutralizing substance other than a magnesium compound, the magnesium compound is added to the lactate solution after fermentation to obtain a magnesium lactate solution. As the magnesium compound in such a case, in addition to the above-mentioned magnesium compounds, water-soluble magnesium salts such as magnesium chloride and magnesium sulfate can be used. The amount of magnesium compound added is
It is approximately equivalent to lactic acid in terms of wO.

Now, the magnesium lactate salt solution obtained as described above is then heated and concentrated. The heating temperature is 50℃ or higher,
Preferably the temperature is 70°C or higher. When the temperature is lower than 50°C, the magnesium lactate crystals become needle-shaped, and the ability to remove impurities becomes poor. The pH of the concentrate is preferably 4 to 9, preferably 5 to 6.

The crystals obtained by heating and concentrating under these conditions are separated from the liquid by any separation means such as centrifugation or filter press to obtain magnesium lactate crystals. The crystals are dissolved as necessary and heated and concentrated again, that is, by repeating the usual recrystallization method.
Furthermore, the purity of the crystal can be increased. Furthermore, it is a matter of course that the fermentation-finished liquid can be subjected to bacterial cell isolation and protein removal steps prior to crystallization as in conventional methods, and that a decolorization step using activated carbon can be incorporated into an appropriate step.

After being redissolved, the magnesium lactate crystals made highly pure by straining and straining are brought into contact with an H-type cation exchange resin and recovered as a high purity lactic acid solution. That is, according to the present invention, highly purified lactic acid can be obtained extremely economically and efficiently.

Now, in order to facilitate understanding of the present invention, the present invention will be specifically compared with a conventional calcium lactate purification method as follows.

The fermented liquid obtained by lactic acid fermentation usually contains 10-12% of lactic acid when using lactic acid bacteria, and Rhizopus.
RhizOpus oryzae 6-1
If it is based on 0, it also includes a Japanese koan %. The liquid is then subjected to deproteinization and decolorization steps, and then transferred to a crystallization step. That is, the ## completed liquid is cooled to the above concentration to precipitate crystals, and the remaining liquid is concentrated and further cooled to crystallize. If the fermented liquid is heated and concentrated to increase the degree of crystallization, since the solubility of calcium lactate is extremely high at high temperatures, no crystals will precipitate during concentration, and the entire liquid will solidify after cooling.

Therefore, in crystallizing calcium lactate, it is difficult to separate it from the liquid unless the crystallization is performed at normal room temperature or at a temperature slightly lower than normal room temperature, and at a not very high concentration.

The crystals thus obtained are aggregates of needle-like crystals and contain many impurities.

Furthermore, even when cooling from a high temperature results in no crystallization, the crystallinity can hardly be improved.

For this reason, the crystals that have been allowed to separate have a high water content and
The content of impurities is high, for example, the water content of crystals allowed to be reduced under reduced pressure by Nutsche ranges from 50 to 90%.

On the other hand, magnesium lactate has a solubility of about 30% at high temperatures, and even if it is heated and concentrated without cooling, high-quality coarse crystals with a diameter of 51 to sonμ begin to precipitate during the heating and concentration step. Therefore, in the case of a magnesium lactate solution, it is also possible to separate the precipitated crystals directly after concentration. Furthermore, even when the solution is cooled after being heated and concentrated, the entire solution does not solidify unlike calcium lactate, even though it is in a supersaturated state. Therefore, crystal precipitation and impurity removal can be carried out extremely efficiently, and since the crystals are of good quality and coarse, even by vacuum filtration, 5 to 15
% moisture content.

As described above, in the method of the present invention, p-separation is extremely easy, and therefore, the impurity content is also extremely small.

Now, the F solution and washing solution after magnesium lactate crystal separation are as follows:
Further heating and concentration are performed to precipitate crystals, and the p-liquid produced after recrystallization is disposed of as desired, such as by disposal. On the other hand, the separated magnesium lactate crystals may be combined with the first precipitated crystals, or may be dissolved in the first concentrated solution. The initial concentration ratio of the magnesium lactate solution and the subsequent concentration ratio of the magnesium lactate solution vary depending on the type of salt coexisting in the magnesium lactate solution, the type of lactic acid, etc., but the most preferable concentration ratio is that crystals to liquid are 1 = 2. ~2:1 (weight ratio), and within this range, crystallinity and p-overoperation are best. still,
When by-product salts coexist in the magnesium lactate solution, that is, when Na0J, NH, and Ct1caam coexist, even if the solution is concentrated until the crystals of these salts begin to precipitate, no p overseparability is recorded.

The crystallized magnesium lactate is about 5-20%
The solution is made into an aqueous solution and passed through an H-type ion exchange resin to obtain purified lactic acid. On the other hand, magnesium ions adsorbed on the resin are recovered by regenerating the resin with hydrochloric acid, sulfuric acid, etc., and reused as a magnesium compound.

As described in detail above, according to the method of the present invention, 70 to 90% of lactic acid can be recovered by the initial heating concentration operation.

The present invention will be further explained below with reference to Examples.

Example 1゜Rhizopus oryzae (Rhizopus) according to conventional methods
During the fermentation with Oryzae), magnesium oxide was continuously added, and the resulting fermentation-finished liquid after bacterial cell isolation (
83 l/d) 5 J as lactic acid was transferred to a +02 container and heated and concentrated at 80 to 90°C while stirring in a water bath. When crystals precipitated and the total volume became about 11, heating was stopped, and after cooling, the nullary was filtered through Nunoche. The crystals were washed with 100% distilled water.

Crystal yield: 554 f, moisture: 72%, average crystal grain size: 6
0 to 200μ, yield 87%, crystal analysis results after drying at 105°C for 2 hours: My+0.2%, lactic acid 725%
Met. This crystal 200y was heated and dissolved in distilled water 11, and the H-type ion exchange resin column (amparite + RI
20B +000d) and extracted with 500-distilled water. Heat and concentrate the passed liquid 151 to a lactic acid concentration of 503
% L-lactic acid aqueous solution 285y was obtained.

Example 2 lactic acid bacteria (Lact-DeJbruckii)
), a hydroxylated 1-U rum aqueous solution was automatically added so that the pH of the culture solution was 55 to 60, and the resulting fermentation-finished liquid after bacterial cell separation (108 to 60% as lactic acid)
Add magnesium hydroxide to 1) to make it 7 alkaline, and make 5
After boiling for 0 minutes, the lactic acid obtained was treated with activated carbon and filtered.
IJum solution (++2 q/l as lactic acid) 5 l
Dissolve M5'Q4 ・6 Hz 0665y in 90
After heating and concentrating at ~95°C to precipitate crystals, the crystals were allowed to cool, filtered through a Nutsche filter, and washed with +00 me distilled water. The obtained crystals were 860y, water content 125%, and particle size 2.
It was a rod-shaped crystal with a diameter of 0 to 120 μm, and the crystal analysis results after drying at 105° C. for 2 hours were 8.9% My and 64.4% lactic acid.

Example 6゜According to a conventional method, Siges oryzae (Rhizopu)
In the fermentation with sOryzae), calcium carbonate was added to remove the protein (containing 92~/d) without decolorizing the solution 5/! Dissolve Myal+・6HzO535f in 9
After crystals were precipitated at 2 to 95°C in the same manner as in Example 2, they were immediately filtered through p filter and washed with water to obtain rod-shaped crystals 545y with a particle size of 100 to SOOμ.

Crystal analysis result after drying at 105℃ for 2 hours is My9.72
%, lactic acid 657%. After heating and dissolving 500 y of this dry crystal in distilled water 21, activated carbon o and sy were added, stirring and extrusion filtration were carried out for 60 minutes, and the mixture was heated and concentrated to 90° C. or higher for recrystallization. After cooling, the magnesium lactate crystals were washed with 11 ffiL of water using a Nusoche to obtain rod-shaped crystals with a particle size of 5o to 200μ.

The obtained crystal was 420p, and the analysis result after drying was My+o.
, s%, milk e y 25%. The first crystal and this crystal were completely identical in terms of X-rays. This crystal 2001 was heated and dissolved in distilled water 11, passed through the resin column used in Example 1, and extracted with 500-g distilled water. The extract was concentrated under reduced pressure to obtain an aqueous L-lactic acid solution with a lactic acid concentration of 87% + so p
I got it.

This lactic acid aqueous solution passed the pharmacopeia standards.

[Brief explanation of drawings]

FIG. 1 shows a microscopic photograph of magnesium lactate crystals. FIG. 2 shows a microscopic photograph of calcium lactate crystals. Applicant: Taki Chemical Co., Ltd.

Claims (1)

[Claims] In the production of lactic acid by the fermentation method, a magnesium lactate salt solution is generated, and this is heated and concentrated at 50°C or higher to precipitate magnesium lactate crystals. After separation, this is dissolved in water to form an H-type ion exchange resin. A method for separating and purifying lactic acid, which comprises contacting and obtaining an aqueous lactic acid solution.