CN116283711A - Preparation method of high-purity cake-shaped L-tryptophan crystal and product thereof - Google Patents
Preparation method of high-purity cake-shaped L-tryptophan crystal and product thereof Download PDFInfo
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- QIVBCDIJIAJPQS-VIFPVBQESA-N L-tryptophane Chemical compound C1=CC=C2C(C[C@H](N)C(O)=O)=CNC2=C1 QIVBCDIJIAJPQS-VIFPVBQESA-N 0.000 title claims abstract description 197
- 239000013078 crystal Substances 0.000 title claims abstract description 162
- 229960004799 tryptophan Drugs 0.000 title claims abstract description 104
- 238000002360 preparation method Methods 0.000 title claims abstract description 19
- 239000002245 particle Substances 0.000 claims abstract description 29
- 238000000034 method Methods 0.000 claims abstract description 28
- 238000002425 crystallisation Methods 0.000 claims abstract description 24
- 230000008025 crystallization Effects 0.000 claims abstract description 23
- 238000001816 cooling Methods 0.000 claims abstract description 19
- 238000009826 distribution Methods 0.000 claims abstract description 18
- 230000001276 controlling effect Effects 0.000 claims abstract description 15
- 230000001105 regulatory effect Effects 0.000 claims abstract description 11
- 238000003756 stirring Methods 0.000 claims description 43
- 239000002002 slurry Substances 0.000 claims description 30
- 238000004042 decolorization Methods 0.000 claims description 24
- 238000001914 filtration Methods 0.000 claims description 13
- 239000007788 liquid Substances 0.000 claims description 11
- 238000004519 manufacturing process Methods 0.000 claims description 11
- 238000010438 heat treatment Methods 0.000 claims description 5
- 238000005406 washing Methods 0.000 claims description 2
- 239000003960 organic solvent Substances 0.000 abstract description 4
- 238000009776 industrial production Methods 0.000 abstract description 3
- 239000000243 solution Substances 0.000 description 34
- 230000000052 comparative effect Effects 0.000 description 15
- 238000012360 testing method Methods 0.000 description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 9
- 238000001704 evaporation Methods 0.000 description 8
- 230000008020 evaporation Effects 0.000 description 8
- 238000004128 high performance liquid chromatography Methods 0.000 description 8
- XEKOWRVHYACXOJ-UHFFFAOYSA-N Ethyl acetate Chemical compound CCOC(C)=O XEKOWRVHYACXOJ-UHFFFAOYSA-N 0.000 description 6
- 238000002474 experimental method Methods 0.000 description 6
- 238000000855 fermentation Methods 0.000 description 6
- 230000004151 fermentation Effects 0.000 description 6
- 238000001878 scanning electron micrograph Methods 0.000 description 6
- 230000001788 irregular Effects 0.000 description 5
- 238000012512 characterization method Methods 0.000 description 4
- 238000001035 drying Methods 0.000 description 4
- 239000011259 mixed solution Substances 0.000 description 4
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 3
- 238000007605 air drying Methods 0.000 description 3
- 239000003513 alkali Substances 0.000 description 3
- 150000001413 amino acids Chemical class 0.000 description 3
- 230000015556 catabolic process Effects 0.000 description 3
- 238000006731 degradation reaction Methods 0.000 description 3
- 239000012153 distilled water Substances 0.000 description 3
- 244000005700 microbiome Species 0.000 description 3
- 239000000843 powder Substances 0.000 description 3
- 238000010025 steaming Methods 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- HEDRZPFGACZZDS-UHFFFAOYSA-N Chloroform Chemical compound ClC(Cl)Cl HEDRZPFGACZZDS-UHFFFAOYSA-N 0.000 description 2
- 241000588724 Escherichia coli Species 0.000 description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 230000003321 amplification Effects 0.000 description 2
- XBDQKXXYIPTUBI-UHFFFAOYSA-N dimethylselenoniopropionate Natural products CCC(O)=O XBDQKXXYIPTUBI-UHFFFAOYSA-N 0.000 description 2
- 239000004744 fabric Substances 0.000 description 2
- 239000010419 fine particle Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000001000 micrograph Methods 0.000 description 2
- 238000003199 nucleic acid amplification method Methods 0.000 description 2
- IFGCUJZIWBUILZ-UHFFFAOYSA-N sodium 2-[[2-[[hydroxy-(3,4,5-trihydroxy-6-methyloxan-2-yl)oxyphosphoryl]amino]-4-methylpentanoyl]amino]-3-(1H-indol-3-yl)propanoic acid Chemical compound [Na+].C=1NC2=CC=CC=C2C=1CC(C(O)=O)NC(=O)C(CC(C)C)NP(O)(=O)OC1OC(C)C(O)C(O)C1O IFGCUJZIWBUILZ-UHFFFAOYSA-N 0.000 description 2
- 238000005303 weighing Methods 0.000 description 2
- 102000004190 Enzymes Human genes 0.000 description 1
- 108090000790 Enzymes Proteins 0.000 description 1
- 241001465754 Metazoa Species 0.000 description 1
- QIVBCDIJIAJPQS-UHFFFAOYSA-N Tryptophan Natural products C1=CC=C2C(CC(N)C(O)=O)=CNC2=C1 QIVBCDIJIAJPQS-UHFFFAOYSA-N 0.000 description 1
- 239000003929 acidic solution Substances 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 239000003674 animal food additive Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 150000001720 carbohydrates Chemical class 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 238000011010 flushing procedure Methods 0.000 description 1
- 238000005187 foaming Methods 0.000 description 1
- 239000002778 food additive Substances 0.000 description 1
- 235000013373 food additive Nutrition 0.000 description 1
- 238000009775 high-speed stirring Methods 0.000 description 1
- 230000002779 inactivation Effects 0.000 description 1
- 238000005374 membrane filtration Methods 0.000 description 1
- 238000001471 micro-filtration Methods 0.000 description 1
- 230000000877 morphologic effect Effects 0.000 description 1
- 239000012452 mother liquor Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 235000019260 propionic acid Nutrition 0.000 description 1
- IUVKMZGDUIUOCP-BTNSXGMBSA-N quinbolone Chemical compound O([C@H]1CC[C@H]2[C@H]3[C@@H]([C@]4(C=CC(=O)C=C4CC3)C)CC[C@@]21C)C1=CCCC1 IUVKMZGDUIUOCP-BTNSXGMBSA-N 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 238000000967 suction filtration Methods 0.000 description 1
- 235000019605 sweet taste sensations Nutrition 0.000 description 1
- 239000002562 thickening agent Substances 0.000 description 1
- 238000000108 ultra-filtration Methods 0.000 description 1
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-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D209/00—Heterocyclic compounds containing five-membered rings, condensed with other rings, with one nitrogen atom as the only ring hetero atom
- C07D209/02—Heterocyclic compounds containing five-membered rings, condensed with other rings, with one nitrogen atom as the only ring hetero atom condensed with one carbocyclic ring
- C07D209/04—Indoles; Hydrogenated indoles
- C07D209/10—Indoles; Hydrogenated indoles with substituted hydrocarbon radicals attached to carbon atoms of the hetero ring
- C07D209/18—Radicals substituted by carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals
- C07D209/20—Radicals substituted by carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals substituted additionally by nitrogen atoms, e.g. tryptophane
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07B—GENERAL METHODS OF ORGANIC CHEMISTRY; APPARATUS THEREFOR
- C07B2200/00—Indexing scheme relating to specific properties of organic compounds
- C07B2200/13—Crystalline forms, e.g. polymorphs
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/10—Process efficiency
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- Chemical & Material Sciences (AREA)
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Abstract
The invention discloses a preparation method of high-purity cake-shaped L-tryptophan crystals and a product thereof, wherein the preparation method comprises three stages of high-temperature concentration, low-temperature concentration and cooling crystal growth, and the high-purity cake-shaped L-tryptophan crystals are prepared by accurately regulating and controlling the technological parameters of each step; the preparation method adopts the traditional crystallization process, does not adopt organic solvents, does not need to add extra equipment investment, and is suitable for industrial production; the L-tryptophan crystal prepared by the method is in a regular round cake shape, and has the advantages of uniform particle size, narrow distribution, high crystal purity and good crystal flowability.
Description
Technical Field
The invention relates to the field of amino acid production, in particular to a preparation method of high-purity cake-shaped L-tryptophan crystals and a product thereof.
Background
L-tryptophan is L-aminoindolyl propionic acid with a molecular formula of C 11 H 12 N 2 O 2 The molecular weight is 204.23, the appearance is white or yellowish leaf crystal or powder, and the product has no or slightly stink and sweet taste. Dissolving in dilute acid or dilute alkali, slightly dissolving in ethanol, insoluble in chloroform and diethyl ether, heating in dark with acid and stabilizing in alkali solution, and easily decomposing when coexisting with other amino acids or saccharides. L-tryptophan is one of the limiting amino acids necessary for humans and animals and is widely used as a food additive and a feed additive.
The preparation method of L-tryptophan can be largely classified into a microorganism direct fermentation method, a microorganism conversion method and an enzyme method. The direct fermentation method of microorganism for producing tryptophan is a mainstream production method with the advantages of low cost, easy popularization of industrial production and the like. The L-tryptophan is generally extracted by adopting an evaporation concentration crystallization method, a foaming and material flushing phenomenon is easy to occur in the evaporation concentration process, and the obtained crystals are flaky or powdery crystals, so that the problems of irregular shape, uneven size and poor fluidity of the crystals exist.
At present, a plurality of patents pay attention to the appearance, the size and the particle size of the L-tryptophan crystal, but all reported methods are not suitable for industrialized amplification. As disclosed in patent application publication No. CN 114773251A, a spherical crystal of L-tryptophan and a preparation method and application thereof are disclosed, the preparation method comprises dissolving L-tryptophan in an acidic solution to obtain a mixed solution, adding ethyl acetate into the mixed solution to obtain a mixed solution in which spherical droplets are dispersed, and adding alkali liquor into the mixed solution until the pH reaches around the isoelectric point of L-tryptophan to prepare spherical granular crystals. The method uses the organic solvent ethyl acetate, so that the problem that the product quality is affected by solvent residues exists, and in addition, the use of the organic solvent brings higher requirements to workshops and equipment.
In another example, patent document with application publication number CN 106986808A discloses a crystallization process for extracting L-tryptophan from fermentation broth, wherein concentrated fermentation broth after heat inactivation, microfiltration, ultrafiltration and spin steaming is continuously crystallized at 4 ℃ under 50W ultrasonic intensity, the ultrasonic action time is 15-20min, and then the fermentation broth is kept stand for 1h at constant temperature of 4 ℃, and then the finished product is obtained after suction filtration and drying. The crystals prepared by the method are tiny and uniform in particle size, but the method is not suitable for industrialized amplification due to the addition of an ultrasonic field in the crystallization process.
Disclosure of Invention
Aiming at the problems in the prior art, the invention discloses a preparation method of L-tryptophan crystals, which adopts the traditional crystallization process to prepare regular cake-shaped L-tryptophan crystals by accurately regulating and controlling each process flow; organic solvents are not adopted, extra equipment investment is not required to be added, and the method is suitable for industrial production; the L-tryptophan crystals prepared by the method have uniform particle size, narrow distribution, high crystal purity and good crystal flowability.
The specific technical scheme is as follows:
a preparation method of high-purity cake-shaped L-tryptophan crystals comprises the following steps:
(1) High-temperature concentration stage: placing the L-tryptophan decolorization solution into a concentration kettle, controlling the stirring linear speed of stirring slurry of the concentration kettle to be not lower than 3m/s, controlling the vacuum pressure in the concentration kettle to be not higher than 0.08MPa, heating the feed liquid in the concentration kettle to be not lower than 60 ℃, concentrating until the mass concentration of the L-tryptophan decolorization solution is 3-5 times of that of the added initial L-tryptophan decolorization solution, and ensuring that precipitated crystals are completely broken into fine granular crystals;
(2) Low-temperature concentration stage: regulating the stirring linear speed of stirring slurry of a concentration kettle to be not higher than 0.3m/s, regulating the vacuum pressure in the concentration kettle to be not lower than 0.094MPa, cooling the feed liquid in the concentration kettle to be not higher than 40 ℃, and concentrating until the mass concentration of the L-tryptophan decolorization solution in the concentration kettle is 6-9 times of the mass concentration of the initial L-tryptophan decolorization solution added in the step (1);
(3) And (3) a cooling and crystal growing stage: transferring the L-tryptophan crystal slurry obtained by concentrating in the step (2) into a crystallization kettle, cooling, performing constant-temperature crystal growth, and performing aftertreatment to obtain the high-purity cake-shaped L-tryptophan crystal.
The invention discloses a preparation method of an L-tryptophan crystal, which is used for accurately regulating and controlling the temperature, vacuum pressure, stirring linear speed and cooling rate in a crystal growth stage in an evaporation concentration process to prepare a cake-shaped L-tryptophan crystal.
In step (1):
the L-tryptophan decolorization solution is obtained by membrane filtration and activated carbon decolorization of escherichia coli fermentation broth, and the escherichia coli strain is preserved with the number of CCTCC M2023039 and is named as Trp429E.
Preferably:
controlling the stirring linear speed of the stirring slurry of the concentration kettle to be 3-10 m/s, controlling the vacuum pressure in the concentration kettle to be 0.07-0.08 MPa, and heating the feed liquid in the concentration kettle to 60-70 ℃.
Experiments show that the solubility of L-tryptophan is 20-25 g/L at 60-70 ℃, the feeding temperature of the decolorized solution is 60-70 ℃, if the temperature is reduced, the evaporation and concentration are carried out, the phenomenon of too fast crystallization occurs, and the primary crystallization body is difficult to break into fine particles; the stirring linear speed is set to 3-10 m/s, so that the primary-precipitation flaky crystals can be effectively broken into fine granular crystals, and the uniformity of the morphology and the particle size of the round cake-shaped crystals is ensured.
Preferably:
the mass concentration of the L-tryptophan decolorization solution which is initially added is 20-25 g/L;
the mass concentration of the L-tryptophan decolorized solution obtained after the high-temperature concentration stage treatment is 80-100 g/L.
Experiments show that the stirring linear speed is 3-10 m/s, the vacuum pressure is 0.07-0.08 MPa, the concentration is 60-70 ℃, and the concentration of decolorized liquid L-tryptophan is just about 80-100 g/L when the primary crystallization is fully broken into fine granular crystals.
In the step (2):
preferably:
the stirring linear speed of the stirring slurry of the concentration kettle is regulated to be 0.1-0.3 m/s, the vacuum pressure in the concentration kettle is regulated to be 0.094-0.1 MPa, and the feed liquid in the concentration kettle is cooled to be 20-40 ℃.
Experiments show that the degradation loss of the L-tryptophan occurs under the condition of higher temperature and the color of the crystal product deepens, and the longer the temperature is, the larger the degradation loss is, and the darker the color of the crystal is. The technological parameters in the concentration kettle are controlled within the range, so that the degradation loss of the product can be reduced to a certain extent.
Preferably:
the mass concentration of the L-tryptophan decolorized solution obtained after the low-temperature concentration stage treatment is 120-180 g/L, and more preferably 160-180 g/L.
Experiments show that too low concentration of L-tryptophan at the concentration end point can affect the crystallization yield, while too high concentration increases the viscosity of crystal slurry, and the problem of difficult material transfer can occur.
In the step (3):
preferably:
the temperature is reduced, the temperature reduction rate is 3-5 ℃/h, and the temperature of the crystal slurry is reduced to 10-15 ℃;
and the constant temperature crystal growing time is 4-6 hours.
Experiments show that if the cooling speed in the step is too high, such as 10 ℃/h, the morphology of the product is irregular, the product with the target morphology cannot be prepared, and the purity of the product is also obviously reduced.
In the step (3):
the post-treatment includes filtration and washing.
Experiments show that the crystal slurry prepared by the method has higher filtering speed in the subsequent filtering process, so that the problem of wet crystal sticking cloth is well solved, and the production efficiency is further improved.
The invention also discloses the high-purity cake-shaped L-tryptophan crystal prepared by the method, and the product has a regular cake shape, the average particle size is 45-50 mu m and the particle size distribution is concentrated through morphological characterization.
The purity of the L-tryptophan crystal is higher than 98 percent through test; and has good fluidity, and the repose angle is not higher than 36 degrees.
Compared with the prior art, the invention has the following beneficial effects:
the crystal prepared by the invention is in a regular round cake shape, has uniform grain size, narrow distribution, high crystal purity and good fluidity. In addition, the crystal slurry prepared by the invention has higher filtering speed in the subsequent filtering process, well solves the problem that wet crystals adhere to filter cloth, and further improves the production efficiency.
Drawings
FIG. 1 is an SEM image of L-tryptophan crystals prepared in example 1;
FIG. 2 is a graph showing the particle size distribution of the L-tryptophan crystals prepared in example 1;
FIG. 3 is an SEM image of the product of comparative example 1;
FIG. 4 is a graph showing the particle size distribution of the product of comparative example 1;
FIG. 5 is an SEM image of the product of comparative example 2;
FIG. 6 is a graph showing the particle size distribution of the product of comparative example 2;
FIG. 7 is an SEM image of the product of comparative example 4;
FIG. 8 is a graph showing the particle size distribution of the product of comparative example 4.
Detailed Description
The present invention will be described in further detail with reference to specific examples, but the scope of the present invention is not limited to the examples.
Example 1
(1) High-temperature concentration stage: weighing 4kg of L-tryptophan decolorization solution (20 g/L), adding 1-kgL-tryptophan decolorization solution into a concentration kettle, controlling the stirring linear speed of stirring slurry of the concentration kettle to be 3m/s, controlling the temperature of feed liquid (L-tryptophan decolorization solution) to be 60 ℃, and slowly feeding in the concentration kettle until the residual 3-kgL-tryptophan decolorization solution is fed, wherein the distilled water steaming rate is consistent with the decolorization liquid feeding rate in the whole feeding process. After the feeding is finished, the concentrated solution is sampled, and the concentration of L-tryptophan is 80g/L through testing; and detecting the appearance of the precipitated crystals by scanning through an electron microscope, if the flaky crystals are not sufficiently broken, closing a water outlet valve of condensed water, maintaining the concentration of L-tryptophan unchanged, and continuing to stir at a high speed under the evaporation concentration condition until the precipitated crystals are broken into fine granular crystals.
(2) Low-temperature concentration stage: the stirring linear speed of the stirring slurry of the concentration kettle is controlled to be 0.1m/s, the temperature of the concentrated solution is slowly reduced to 20 ℃, the vacuum degree in the concentration kettle is correspondingly increased to be 0.1MPa, and the concentration is continuously carried out under the condition until the concentration of L-tryptophan is 160g/L.
(3) And (3) a cooling and crystal growing stage: transferring the L-tryptophan crystal slurry obtained after concentration to a crystallization kettle, stirring at a low linear speed of 0.1m/s, cooling the L-tryptophan crystal slurry to 10 ℃ at a cooling rate of 3 ℃/h, and maintaining the same stirring speed for crystal growth at constant temperature for 4 hours. Filtering to obtain wet L-tryptophan crystals, and drying the wet L-tryptophan crystals in a forced air drying oven at 60 ℃ for 12 hours to obtain the L-tryptophan crystals, wherein the HPLC purity of the crystals is 98.54% and the crystallization yield is 89.88% through testing.
FIG. 1 is an SEM image of the product of this example, and the crystals were observed to be in the form of regular round cakes.
FIG. 2 is a graph showing the particle size distribution of crystals produced by this example, and it was found from the graph that the average particle size of the crystals was 47.28. Mu.m, the particle size distribution of the crystals was very concentrated, wherein the ratio of crystals having a particle size of less than 28.61 μm was 10%, the ratio of crystals having a particle size of 28.61 to 49.25 μm was 80%, and the ratio of crystals having a particle size of more than 49.25. Mu.m was 10%.
Example 2
(1) High-temperature concentration stage: weighing 5kg of L-tryptophan decolorizing solution (25 g/L), adding 1-kgL-tryptophan decolorizing solution into a concentrating kettle, controlling the stirring linear speed of stirring slurry of the concentrating kettle to be 10m/s, controlling the temperature of the L-tryptophan decolorizing solution to be 70 ℃, and slowly feeding the L-tryptophan decolorizing solution until the rest 4kg of L-tryptophan decolorizing solution is fed in the concentrating process, wherein the distilled water steaming rate is consistent with the decolorizing solution feeding rate in the whole process. After the feeding is finished, the concentrated solution is sampled, and the concentration of L-tryptophan is 100g/L through testing; and detecting the appearance of the precipitated crystals by scanning through an electron microscope, if the flaky crystals are not sufficiently broken, closing a water outlet valve of condensed water, maintaining the same concentration of L-tryptophan, and continuing to stir at a high speed under the evaporation concentration condition until the precipitated flaky crystals are broken into fine granular crystals.
(2) Low-temperature concentration stage: stirring at low linear speed of 0.3m/s, slowly lowering the temperature of the concentrated solution to 40deg.C, and correspondingly increasing the vacuum degree in the concentrating kettle to 0.094MPa, and concentrating under the condition until the concentration of L-tryptophan is 180g/L.
(3) And (3) a cooling and crystal growing stage: transferring the L-tryptophan crystal slurry obtained after concentration to a crystallization kettle, stirring at a low linear speed of 0.3m/s, cooling the crystal slurry to 15 ℃ at a cooling rate of 5 ℃/h, and maintaining the same stirring speed for constant temperature crystal growth for 6 hours. Filtering to obtain wet L-tryptophan crystals, and drying the wet L-tryptophan crystals in a forced air drying oven at 60 ℃ for 6 hours to obtain the L-tryptophan crystals, wherein the HPLC purity of the crystals is 98.18% and the crystallization yield is 91.43% through testing.
As shown by SEM characterization, the product prepared in the embodiment is in a regular cake shape; the average grain size of the crystals is 46.57 mu m, the grain size distribution of the crystals is very concentrated, wherein the crystals with the grain size smaller than 26.65 mu m account for 10%, the crystals with the grain size of 26.65-48.56 mu m account for 80%, and the crystals with the grain size larger than 48.56 mu m account for 10%.
Example 3
(1) High-temperature concentration stage: 4kg of L-tryptophan decolorization solution (20 g/L) is weighed, 1-kgL-tryptophan decolorization solution is firstly added into a concentration kettle, the stirring linear speed of stirring slurry of the concentration kettle is controlled to be 6m/s, the temperature of the L-tryptophan decolorization solution is controlled to be 65 ℃, the vacuum pressure in the concentration kettle is 0.075MPa, the concentration process is slowly carried out until the residual 3-kgL-tryptophan decolorization solution is completely fed, and the distilled water evaporation rate is kept consistent with the decolorization solution feeding rate in the whole process. After the feeding is finished, the concentrated solution is sampled, and the concentration of L-tryptophan is 80g/L through testing; and detecting the appearance of the precipitated crystals by scanning through an electron microscope, if the flaky crystals are not sufficiently broken, closing a water outlet valve of condensed water, maintaining the same concentration of L-tryptophan, and continuing to stir at a high speed under the evaporation concentration condition until the precipitated flaky crystals are broken into fine granular crystals.
(2) Low-temperature concentration stage: the stirring linear speed of the stirring slurry of the concentration kettle is changed to be 0.2m/s, the temperature of the concentrated solution is slowly reduced to 30 ℃, the vacuum degree in the concentration kettle is correspondingly increased to be 0.096MPa, and the concentration is continued until the concentration of L-tryptophan is 170g/L under the condition.
(3) And (3) a cooling and crystal growing stage: transferring the L-tryptophan crystal slurry obtained after concentration to a crystallization kettle, stirring at a low linear speed of 0.2m/s, cooling the crystal slurry to 12 ℃ at a cooling rate of 4 ℃/h, and maintaining the same stirring speed for constant temperature crystal growth for 5 hours. Filtering to obtain wet L-tryptophan crystals, drying the wet L-tryptophan crystals in a forced air drying oven at 60 ℃ for 10 hours to obtain the L-tryptophan crystals, wherein the HPLC purity of the crystals is 98.88% and the crystallization yield is 90.67% through testing.
As shown by SEM characterization, the product prepared in the embodiment is in a regular cake shape; the average grain size of the crystals is 48.42 mu m, the grain size distribution of the crystals is very concentrated, wherein the crystals with the grain size smaller than 28.85 mu m account for 10%, the crystals with the grain size of 28.85-49.86 mu m account for 80%, and the crystals with the grain size larger than 49.86 mu m account for 10%.
Example 4
The preparation process was substantially the same as in example 1, except that in step (1), step (2), the final concentration of L-tryptophan concentrate was adjusted to 120g/L under the same low temperature concentration conditions.
The crystal HPLC purity was 98.84% and the crystallization yield was 85.58% as tested.
As shown by SEM characterization, the product prepared in the embodiment is in a regular cake shape; the average grain size of the crystals is 48.87 mu m, the grain size distribution of the crystals is very concentrated, wherein the proportion of the crystals with the grain size smaller than 29.21 mu m is 10%, the proportion of the crystals with the grain size of 29.21-50.28 mu m is 80%, and the proportion of the crystals with the grain size larger than 50.28 mu m is 10%.
Comparative example 1
The preparation process was substantially the same as in example 1 except that in step (1), the stirring line speed of the thickener tank stirring paddle was controlled to be 1m/s, and the step was stopped after concentration to an L-tryptophan concentration of 80g/L. The appearance and morphology of the precipitated crystals are detected by scanning through an electron microscope, and the flaky crystals are not fully crushed into fine particles.
The crystal HPLC purity was 97.21% and the crystallization yield was 89.76% by testing.
FIG. 3 is a scanning electron microscope image of the L-tryptophan crystal prepared in this comparative example, and the product is observed to be in a sheet form; the average grain diameter of the crystal is 87.62 mu m, the grain diameter of the crystal is uneven and the distribution is wide (see figure 4), wherein the grain diameter is less than 27.24 mu m and accounts for 10%,27.24 mu m-245.5 mu m and accounts for 80%, and more than 245.5 mu m and accounts for 10%.
Comparative example 2
The preparation process was substantially the same as in example 1, except that the concentration temperature of the L-tryptophan decolorized solution in the step (1) was 40℃and the vacuum pressure was 0.094MPa.
The result shows that the crystals are subjected to the sudden analysis phenomenon, the flaky crystals are fully broken, the high-speed stirring time is required to be prolonged, the appearance and the appearance of the crystals of the final finished product are irregular, the grain size of the crystals is smaller, and the fluidity of the crystals is poor.
The test shows that the purity of the crystal by HPLC is 97.56%, and the crystallization yield is 90.05%.
FIG. 5 is a scanning electron microscope image of the L-tryptophan crystals prepared in this comparative example, and it was observed that a large number of crystals having irregular morphology were also present in the product as well as in the cake-like crystals. The average grain size of the crystal is 40.35 μm and the grain size of the crystal is uniform (see figure 6), wherein the grain size is less than 15.52 μm and 10%,15.52 μm-68.87 μm and 80%, and more than 68.87 μm and 10%.
Comparative example 3
The preparation process was substantially the same as in example 1 except that in the step (2), the stirring line speed of the stirring slurry of the concentrating tank was controlled to be 0.1m/s, but the concentration was continued to be carried out under reduced pressure while maintaining the temperature of the concentrated solution at 60℃and the vacuum degree in the concentrating tank at 0.08MPa until the concentration of L-tryptophan was 160g/L.
Through testing, the color of the crystallization product and the crystallization mother liquor are deepened, and the color and purity of the product are greatly affected. The crystal HPLC purity was 93.21% and the crystallization yield was 88.12% by testing.
It was observed that the product was in the form of a regular cake, characterized by a particle size distribution, the crystals had an average particle size of 46.65 μm and a very concentrated particle size distribution, wherein the crystals having a particle size of less than 27.25 μm accounted for 10%, the crystals having a particle size of 27.25 to 46.74 μm accounted for 80%, and the crystals having a particle size of greater than 46.74 μm accounted for 10%.
Comparative example 4
The preparation process was substantially the same as in example 1, except that in step (3), the temperature of the L-tryptophan slurry was lowered to 10℃at a temperature lowering rate of 10℃per hour.
The crystal HPLC purity was tested to be 96.56% and the crystallization yield to be 90.12%.
FIG. 7 is an SEM image of the crystals of L-tryptophan prepared in this comparative example, and it was observed that the product was an irregular crystal; as characterized by the particle size distribution of FIG. 8, the average particle size of the crystals was 47.36 μm, and the crystal particle size was very heterogeneous, wherein the particle size was less than 13.27 μm and 10%,13.27 μm to 191.1 μm and 80%, and more than 191.1 μm and 10%.
To further characterize the product properties, the filtration rate and flowability of the dry crystals of the slurries prepared in each example and comparative example, respectively, were also characterized. The properties are listed in table 1 below.
TABLE 1
a: the filtering flow rate of the crystal slurry specifically refers to the filtering speed when the wet crystal of the L-tryptophan is obtained by filtering after the crystal growth in the cooling crystal growth stage in the step (3) in the preparation process is finished;
b: dry crystals refer specifically to the products prepared separately for each example and comparative example;
c: the repose angle theta is the maximum angle formed by the free inclined surface of the powder stacking layer and the horizontal plane in a static balance state, the smaller the repose angle theta is, the smaller the friction force is, the better the fluidity is, and the calculation formula is tan theta = h/r, wherein h is the height of the powder stacking layer, and r is the radius of the stacking layer.
Claims (10)
1. The preparation method of the high-purity cake-shaped L-tryptophan crystal is characterized by comprising the following steps of:
(1) High-temperature concentration stage: placing the L-tryptophan decolorization solution into a concentration kettle, controlling the stirring linear speed of stirring slurry of the concentration kettle to be not lower than 3m/s, controlling the vacuum pressure in the concentration kettle to be not higher than 0.08MPa, heating the feed liquid in the concentration kettle to be not lower than 60 ℃, concentrating until the mass concentration of the L-tryptophan decolorization solution is 3-5 times of that of the added initial L-tryptophan decolorization solution, and ensuring that precipitated crystals are completely broken into fine granular crystals;
(2) Low-temperature concentration stage: regulating the stirring linear speed of stirring slurry of a concentration kettle to be not higher than 0.3m/s, regulating the vacuum pressure in the concentration kettle to be not lower than 0.094MPa, cooling the feed liquid in the concentration kettle to be not higher than 40 ℃, and concentrating until the mass concentration of the L-tryptophan decolorization solution in the concentration kettle is 6-9 times of the mass concentration of the initial L-tryptophan decolorization solution added in the step (1);
(3) And (3) a cooling and crystal growing stage: transferring the L-tryptophan crystal slurry obtained by concentrating in the step (2) into a crystallization kettle, cooling, performing constant-temperature crystal growth, and performing aftertreatment to obtain the high-purity cake-shaped L-tryptophan crystal.
2. The method for producing high-purity cake-shaped L-tryptophan crystals according to claim 1, wherein in step (1):
controlling the stirring linear speed of the stirring slurry of the concentration kettle to be 3-10 m/s, controlling the vacuum pressure in the concentration kettle to be 0.07-0.08 MPa, and heating the feed liquid in the concentration kettle to 60-70 ℃.
3. The method for producing high-purity cake-shaped L-tryptophan crystals according to claim 1, wherein in step (1):
the mass concentration of the L-tryptophan decolorization solution which is initially added is 20-25 g/L;
the mass concentration of the L-tryptophan decolorized solution obtained after the high-temperature concentration stage treatment is 80-100 g/L.
4. The method for producing high-purity cake-shaped L-tryptophan crystals according to claim 1, wherein in step (2):
the stirring linear speed of the stirring slurry of the concentration kettle is regulated to be 0.1-0.3 m/s, the vacuum pressure in the concentration kettle is regulated to be 0.094-0.1 MPa, and the feed liquid in the concentration kettle is cooled to be 20-40 ℃.
5. The method for producing high-purity cake-shaped L-tryptophan crystals according to claim 1, wherein in step (2):
the mass concentration of the L-tryptophan decolorized solution obtained after the low-temperature concentration stage treatment is 120-180 g/L.
6. The method for producing high-purity cake-shaped L-tryptophan crystals according to claim 1, wherein in step (2):
the mass concentration of the L-tryptophan decolorized solution obtained after the treatment in the low-temperature concentration stage is 160-180 g/L.
7. The method for producing high-purity cake-shaped L-tryptophan crystals according to claim 1, wherein in step (3):
the temperature is reduced, the temperature reduction rate is 3-5 ℃/h, and the temperature of the crystal slurry is reduced to 10-15 ℃;
and the constant temperature crystal growing time is 4-6 hours.
8. The method for producing high-purity cake-shaped L-tryptophan crystals according to claim 1, wherein in step (3):
the post-treatment includes filtration and washing.
9. A high purity cake-shaped L-tryptophan crystal prepared according to the method of any one of claims 1 to 8.
10. The high-purity cake-shaped L-tryptophan crystal according to claim 9, wherein the crystal is in a regular cake shape, has an average particle diameter of 45 to 50 μm, and has a concentrated particle size distribution ， The purity is higher than 98 percent, and the repose angle is not higher than 36 degrees.
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