SK50392A3 - Method of isolation of l-threonine - Google Patents

Abstract

L-threonine is isolated from fermentation substrate in such a manner that fermented substrate is filtered through membranes with maximum pore size of 0.3 microns and from a filtrate a first product part is prepared by evaporation and crystallization. Mixture of the first mother liquor and wash water after first crystallization is then purified by ultrafiltration on membranes with permeability of substances with molecular weight at the most 50 000. Subsequently concentration thereof is carried out by making use of evaporator and a second part of the product is prepared by another crystallization. The second mother liquor is then returned back to technological process, i.e. either in the fermentation substrate or into the micro-filtrate. In such a manner a high yield and quality of both the first and second parts of the product exceeding 98 percent of L-threonine is achieved, whereby the latter is used predominantly for feeding domestic animals.

Description

Technical field

The invention relates to a process for the isolation of L-threonine from a fermentation broth.

BACKGROUND OF THE INVENTION

The isolation of L-threonine, but also of other amino acids from a hydrolyzate of various protein sources, especially after acid hydrolysis, is described in several patents (German Pat. No. 3,366,663, Japanese Pat. No. 8173051). The principle is acidic or enzymatic hydrolysis of a protein source, e.g. soya flour, subsequent fractionation on ion exchangers and further treatment through concentration by evaporation and crystallization. A disadvantage of this method of isolation is the low content of L-threonine in the starting material. Methods for isolating L-threonine prepared by a fermentation process wherein its content in the starting material is substantially higher than in the previous process are based on different principles. The principle of isolating L-threonine from the fermentation liquid according to Japanese Pat. file no. 78140290 and 8800294 are the use of various ion exchangers to which L-threonine is captured either directly from the fermentation liquid or from the supernatant or filtrate after prior separation of the solid particles, e.g. filtration, or centrifugation. After elution from the columns, the L-threonine solution was concentrated by evaporation, crystallized, washed and dried. The disadvantage of these methods is high labor costs and high investment costs, i

but the product quality is achieved at about 95% of the L-threonine content of the finished product. Reducing labor and investment costs, but also increasing the content of L-threonine in the finished product is addressed by europ. pat. No. 24,436, French Pat. No. 2,619,380, Japanese Pat. No. 7,799,996, which discloses a process for isolating L-threonine by subjecting a fermentation liquid supernatant obtained, e.g., by centrifugation, to ultrafiltration with membranes having a permeability of from 6,000 to 50,000 daltons. In subsequent steps, it is either purified by ion exchange or directly concentrated by evaporation and L-threonine is obtained by crystallization and drying. In the first case, a purer product is obtained, but at the cost of increased laboriousness and reduction; yield. It can decisively influence the efficiency of the whole process of isolation of the first and third mother liquors. In most cases, it is preferred to prepare L-threonine by a second crystallization without first treating the first mother liquors, resulting in a reduced quality of L-threonine after the second crystallization.

SUMMARY OF THE INVENTION

The above-mentioned drawbacks are eliminated by the process of isolating L-threonine from fermented soil according to the invention, which consists in that the fermented soil is microfiltered, and L-threonine is isolated from the filtrate obtained by crystallization. The mixtures of the first mother liquors and the wash solution after the first and second crystallizations are ultrafiltered and further L-threonine is isolated from the filtrate by crystallization. The second mother liquors are added to the fermentation broth or filtrate after microfiltration of the next batch. The second mother liquor returns to the technological process at most 10x.

According to the method of the invention, microfiltration takes place through membranes with a pore size of up to 0.3 microns at maximum and ultrafiltration takes place through membranes with a permeability of substances having a molecular weight of at most 50,000 daltons.

The process according to the invention is carried out by microfiltration of the fermented soil, the filtrate is concentrated by evaporation, and crystallization is carried out to prepare 1 part of L-threonine. The first mother liquors are ultrafiltered from The filtrate obtained after evaporation and crystallization is prepared to prepare a second part of L-threonine from the mother liquor after this second crystallization is added to the next batch of fermentation broth. This second mother liquor process can be repeated up to a maximum of 10x, then the second mother liquor is discarded and the process repeated.

The main advantage of the proposed process lies in the combination of microfiltration of fermentation broth with ultrafiltration of mother liquors and washing waters of the 1st and 2nd crystal, which results in high product quality and high yield in a simple procedure of the given amino acid L-threonine.

Examples x

Example 1

1 of fermented broth, adjusted to pH 6.2 with concentrated sulfuric acid, containing 75 g of L-threonine, was filtered on a filter device with a maximum pore size of 0.3 microns. After subsequent washing of the biomass, 36 L of microfiltrate was obtained. The micro-filter shall be concentrated on the evaporator to a concentration of 180 gl ^1, and crystallized at 5 ° C. The product after filtration and washing with cold water at a maximum temperature of 5 ° C was dried at 70 ° C to a residual moisture of 1.5%. 13.6 kg of product were obtained, containing 99.5% of L-threonine, which is 50.5% yield.

Example 2

A mixture of mother liquors and wash water after the first crystal of Example 1 in an amount of 15.2 L is ultrafiltered on an ultrafiltration device having a maximum molecular weight permeability. 50,000 Daltons. After ultrafiltration, 14 L of filtrate was obtained, which was further processed as in Example 1 by evaporation, crystallization, separation, washing and drying.

5.2 kg of product were obtained after a second crystallization containing 99.1% L-threonine. The total amount obtained from the first and second crystallizations was 18.8 kg of L-threonine, i. 69.9% recovery calculated on threonine content in fermented soil.

Example 3

To 36 L of microfiltrate obtained by filtration of 36 L of fermented soil according to Example 1 was added 6.5 L of second mother liquor from the previous batch obtained according to Example 2. The mixture of microfiltrate and second mother liquor 42.5 L was treated according to the procedure of of Examples 1 and 2, except that the wash water after the second crystallization was added to the mixture of the first mother liquors and the wash water after the first crystallization.

23.0 kg of a product containing 99.0% of L-threonine, ie.

85.4% yield) calculated on the L-threonine content of the fermented soil.

Example 4

B

The procedure is the same as in Example 3, except that the addition of the second mother liquor is repeated up to the 10th batch. After working up the product after the second crystallization of the 10th batch, the mother liquors are discarded. The whole procedure is repeated. By this procedure, an average of 23.57 kg of the product from a batch with a content of 8.7% of L-threonine, i.e. L-threonine, was obtained from 10 batches. 87.3% recovery calculated on L-threonine content in fermented soil.

Industrial usability

The L-threonine isolated by the process of the invention can be used to make livestock fattening in admixture with other substances more efficient. It can also be used to prepare pure L-threonine for human medicine and nutrition.

Claims (3)

Method for isolating L-threonine from fermented soil, characterized in that the fermented soil is microfiltered, L-threonine is isolated from the filtrate obtained by concentration and crystallization, the mixture of the first mother liquors and the washing solution after the first and second crystallization is ultrafiltered, After concentrating and crystallizing further L-threonine is isolated and the second mother liquors are added to the fermentation broth or filtrate from the fermented broth of the subsequent fermentation, the second mother liquors returning to the process at a maximum of 10x. 2. Method according to claim 1, characterized in that the microfiltration is carried out through membranes with a pore size of at most 0.3 microns. 3. The process of claim 1, wherein the ultrafiltration is carried out through membranes having a permeability of substances having a molecular weight of at most 50,000 daltons.