Method for synergistically regulating crystallization by using crystal promoter in glutamic acid isoelectric extraction

Abstract

This invention relates to the fields of biochemical engineering and amino acid separation and purification technology, and in particular to a method for synergistic regulation of crystallization by a crystallizer in isoelectric extraction of glutamic acid, comprising the following steps: pretreatment of the glutamic acid fermentation broth to control the content of bacterial protein in the glutamic acid fermentation broth to not exceed 0.6%, K + The concentration should not exceed 0.15 mol / L. The pretreated glutamic acid fermentation broth is placed in an isoelectric tank, and the temperature is adjusted and maintained at 20-28℃, the pH at 4.2-4.7, and the stirring speed at 28-36 rpm. A crystallizer is added to the glutamic acid fermentation broth; the crystallizer is selected from at least one of polyethylene glycol, sodium carboxymethyl cellulose, polyvinylpyrrolidone, sodium alginate, betaine hydrochloride, and lysine hydrochloride, and the amount of crystallizer added is 0.1%-0.55% of the volume of the glutamic acid fermentation broth. Crystallization is continued for 4-6 hours, followed by solid-liquid separation to obtain glutamic acid crystals and mother liquor. This invention can inhibit the formation of β-crystals, increase the proportion of α-crystals, product purity, and extraction yield.

Description

Technical Field

[0001] This invention belongs to the field of biochemical engineering and amino acid separation and purification technology. Specifically, it relates to a method for synergistic regulation of crystallization by crystallizers in isoelectric extraction of glutamic acid. Background Technology

[0002] Glutamic acid is the core raw material for monosodium glutamate (MSG) production, and its extraction process directly affects product yield, purity, and production efficiency. Currently, the mainstream industrial isoelectric extraction process for glutamic acid faces the following technical bottlenecks: First, glutamic acid exhibits an α- and β-crystal transformation. β-crystal needle-like crystals have low density and are prone to aggregation, leading to difficulties in solid-liquid separation, making crystal form control challenging and increasing subsequent processing costs. Although existing processes can increase the proportion of α-crystals by controlling parameters such as stirring rate and temperature, they are still affected by impurities in the glutamic acid fermentation broth (such as bacterial protein, potassium chloride, and potassium sulfate). + Firstly, the concentration of β-crystals can significantly affect the yield, leading to a higher risk of β-crystal formation. Secondly, traditional isoelectric extraction processes typically yield between 80% and 90%, and product purity is affected by fine glutamic acid and mother liquor entrainment, making it difficult to consistently achieve a purity above 99%. While continuous isoelectric processes improve processing efficiency, the wide particle size distribution of the crystals and the tendency for small crystals to be lost with the mother liquor result in yield loss, making it difficult to balance extraction yield and purity.

[0003] A search revealed that patent CN117986142A discloses a method for early warning of β-glutamic acid crystallization and improving crystallization. This patent improves the purity of the feed solution through ultrafiltration membrane pretreatment and combines concentration with continuous isoelectric point feeding to control crystal concentration and pH, thereby reducing the loss of fine glutamic acid and increasing the yield. However, this method mainly relies on physical filtration and process parameter control, without introducing crystallizers or synergistically optimizing them with other operating conditions (such as stirring intensity and cooling rate). Its ability to actively intervene in crystal transformation is limited, especially under high impurity loads or fluctuating conditions, where the risk of β-crystal formation still exists, and it does not effectively solve the problem of purity fluctuations caused by fine crystal entrainment. Patent CN110128286A discloses a glutamic acid extraction and crystallization process. This patent involves centrifugation to remove protein solution, followed by mixing the clear liquid for isoelectric crystallization, and then performing secondary concentration and crystallization on the isoelectric clear liquid to improve the yield. While this method reduces the influence of bacterial proteins on the crystallization process to some extent, its core remains based on physical separation and stepwise crystallization, without involving the introduction of crystallizers or the dynamic matching and control of key crystallization parameters (such as supersaturation gradient and local mixing intensity). Therefore, when faced with fluctuations in the composition of the glutamate fermentation broth, its guiding effect on the crystal nucleus formation and crystal growth stages is limited, restricting further improvements in α-crystal stability and crystal size uniformity.

[0004] The above problems indicate that existing technologies in the isoelectric crystallization process of glutamic acid generally lack a systematic and synergistic control mechanism for the type of crystallizer, the timing of its addition, and its relationship with operating parameters such as temperature, pH, and stirring, making it difficult to simultaneously achieve stable control of high yield, high purity, and optimal crystal form. Summary of the Invention

[0005] This invention provides a method for synergistic regulation of crystallization by crystallizers in isoelectric extraction of glutamic acid. The aim is to guide the nucleation and growth behavior of glutamic acid crystals by constructing a coupled regulation system of crystallizers with multi-dimensional process parameters such as temperature, pH, and stirring rate, thereby inhibiting the formation of β-crystals and increasing the proportion of α-crystals, product purity, and extraction yield.

[0006] In a first aspect, the present invention provides a method for synergistic regulation of crystallization by a crystallizer in isoelectric extraction of glutamic acid, comprising the following steps:

[0007] S10: Pre-treat the glutamic acid fermentation broth to control the bacterial protein content in the glutamic acid fermentation broth to not exceed 0.6%, K + The concentration should not exceed 0.15 mol / L;

[0008] S20: The pretreated glutamic acid fermentation broth is sent into an isoelectric tank, and the temperature inside the tank is adjusted and maintained at 20-28℃, the pH value is 4.2-4.7, and the stirring speed is 28-36 rpm;

[0009] S30: Under the process conditions described in S20, a crystallizer is added to the glutamic acid fermentation broth, and the amount added is 0.1% to 0.5% of the volume of the glutamic acid fermentation broth;

[0010] S40: Crystallize continuously for 4-6 hours under the conditions described in S30, followed by solid-liquid separation to obtain glutamic acid crystals and mother liquor.

[0011] According to the present invention, in step S10, the bacterial protein and K in the glutamic acid fermentation broth are... + The concentration limit effectively weakened the inducing effect of impurities on the crystal form transformation of glutamate. As a high-molecular-weight organic compound, bacterial protein carries a negative surface charge, easily adsorbing onto the surface of glutamate crystals, interfering with the orderly arrangement of the crystals and promoting β-form nucleation; K + This affects the lattice stability by altering the ionic strength of the solution, which in turn influences the intermolecular hydrogen bond network structure of glutamate. The bacterial protein content is controlled below 0.6%, and the K... + Controlling the concentration below 0.15 mol / L can significantly reduce the nucleation driving force of β-crystal, creating the basic conditions for subsequent α-crystal-dominant crystallization. Existing technologies only remove impurities through membrane filtration, while this invention, through the synergistic effect of crystal promoters and multiple parameters, can still increase the proportion of α-crystal to over 94% even with an impurity content of 0.6%, solving the problem of crystal form control under high impurity loads.

[0012] In step S20, controlling the temperature within the range of 20-28℃, adjusting the pH value to 4.2-4.7, and setting the stirring rate to 28-36 rpm constitutes a set of synergistic process windows. This temperature range is near the isoelectric point of glutamic acid and slightly lower than the conventional operating temperature (usually 28-32℃), which can moderately reduce the solubility of glutamic acid and increase supersaturation, but avoids the formation of a large number of fine crystals or β crystals due to local overcooling caused by excessively low temperatures. The pH value of 4.2-4.7 is the optimized range near the isoelectric point of glutamic acid (pI≈3.2). At this value, glutamic acid exists in zwitterionic form, with minimal intermolecular electrostatic repulsion, which is conducive to the formation of a dense α crystal structure. If the pH deviates from this range, glutamic acid carries a net positive or negative charge, the intermolecular repulsion is enhanced, and loose needle-like β crystals are easily formed. A stirring speed of 28-36 rpm is considered a low-speed stirring range, which maintains uniform mixing of the liquid, avoids excessively high local concentrations or pH gradients, and reduces shear force damage to the crystal surface, preventing crystal breakage and secondary nucleation, thereby inhibiting the formation of fine glutamic acid. It should be noted that fine glutamic acid refers to glutamic acid crystals with a particle size of less than 40 μm.

[0013] In step S30, the introduction of a crystal growth promoter is the core feature that distinguishes this invention from the prior art. The crystal growth promoter used is selected from at least one of polyethylene glycol, sodium carboxymethyl cellulose, polyvinylpyrrolidone, sodium alginate, betaine hydrochloride, and lysine hydrochloride. Its molecular structure contains multiple polar functional groups such as hydroxyl, carboxyl, or amide groups, which can be selectively adsorbed at the glutamate crystal growth interface. Specifically, the crystal growth promoter molecules preferentially adsorb onto the high-energy crystal planes (such as {010} and {100} planes) of the β-type crystal, hindering the orderly stacking of glutamate molecules on these crystal planes through steric hindrance and electrostatic shielding, thereby inhibiting β-crystal growth. Simultaneously, the crystal growth promoter has weaker adsorption on the stable crystal planes (such as {110} and {001} planes) of the α-type crystal, allowing glutamate molecules to continuously grow epitaxially on them, promoting α-crystal development. Furthermore, the crystallizer forms a micelle structure in solution, which can encapsulate some free glutamic acid molecules, slowing down their release rate and maintaining supersaturation within the metastable region, thus preventing explosive nucleation and obtaining α-crystal products with narrow particle size distribution and high crystallinity. The dosage of the crystallizer is 0.1%~0.55% of the volume of the glutamic acid fermentation broth. Within this range, the crystallization effect increases with increasing concentration, but above 0.5%, excessive crystallizer may encapsulate the entire crystal surface, hindering crystal growth and leading to a decrease in particle size; below 0.1%, it is insufficient to cover the key crystal faces and cannot effectively inhibit β-crystals. The mechanism of action of polyethylene glycol crystallizer: The hydroxyl groups in polyethylene glycol molecules can form hydrogen bonds with the carboxyl groups of the {010} face of the β-crystal form, inhibiting β-crystal growth through steric hindrance, while the adsorption on the {110} face of the α-crystal form is weak. Experimental observations showed that after adding the crystallizer, the proportion of β-crystal form in the obtained crystals was significantly reduced, and the crystal morphology changed from needle-like to regular blocky. The likely reason is the adsorption of crystal growth promoter molecules on specific crystal faces of the β-form, which interferes with the orderly stacking of glutamate molecules on those faces. For example, sodium carboxymethyl cellulose adsorbs onto the β-form surface through electrostatic interactions, inhibiting its growth.

[0014] In step S40, the crystal growth time is set to 4-6 hours. This time window ensures that the crystals have sufficient growth time to reach the target particle size (typically 80-150 μm), while avoiding overgrowth that could lead to crystal agglomeration or encapsulation of the mother liquor. Solid-liquid separation is performed by centrifugation or filtration. The concentration of glutamic acid in the separated mother liquor can be reduced to below 1.0 g / L, indicating minimal loss of fine crystals and effective control of yield loss.

[0015] Preferably, in step S10, the pretreatment of the glutamic acid fermentation broth employs at least one of centrifugation, flocculation, and microfiltration. The centrifugation speed is 1800-2000 rpm for 4 hours; flocculation uses a polyacrylamide flocculant at a dosage of 5-20 mg / L; and microfiltration uses a ceramic membrane or organic membrane module with a pore size of 0.2-0.45 μm.

[0016] Preferably, in step S20, the pH adjustment uses at least one inorganic acid selected from sulfuric acid, hydrochloric acid, or phosphoric acid, with an acid concentration of 1-3 mol / L, and is slowly added at a dropping rate controlled at 0.5-2 mL / s to avoid sudden local pH drops that could cause instantaneous supersaturation.

[0017] Preferably, in step S30, the crystallizing agent is betaine hydrochloride. Betaine hydrochloride has a moderate molecular chain length, providing sufficient adsorption sites without limiting diffusion due to excessively large molecules.

[0018] Preferably, in step S30, the crystallizer is added after the pH has been adjusted to the target value and maintained for 5-10 minutes. This timing ensures that the system is in a stable isoelectric state, allowing the crystallizer to function in a homogeneous supersaturated environment and preventing deactivation or aggregation due to drastic changes in ionic strength during pH adjustment.

[0019] Preferably, in step S40, a sample is taken every 0.5 h during the crystal growth process, and the crystal morphology is observed using a polarizing microscope. When the proportion of α crystals exceeds 93% and the average particle size is greater than 80 μm, the crystal growth is terminated.

[0020] Preferably, in step S40, the mother liquor after solid-liquid separation is concentrated and then refluxed back to the isoelectric tank, with the reflux flow rate not exceeding 30% of the fresh glutamic acid fermentation broth feed. Refluxing the mother liquor can recover residual glutamic acid and improve the overall yield, but excessive reflux will accumulate impurities and affect crystal form control; therefore, the reflux ratio is limited.

[0021] Preferably, the crystallizing agent is lysine hydrochloride. As a small molecule amino acid salt, lysine hydrochloride can form specific hydrogen bonds with the polar groups on the surface of glutamic acid crystals through the amino and carboxyl sites in the molecule, preferentially adsorbing onto the (110) crystal face of the β crystal form and inhibiting its growth kinetics; at the same time, it reduces the absolute value of the zeta potential on the surface of the α crystal form through the charge shielding effect, promotes the directional growth of crystal nuclei, thereby increasing the proportion of α crystal form and optimizing the crystal grain size distribution.

[0022] Preferably, in step S20, the stirring impeller adopts an anchor-type or frame-type structure, and the distance between the impeller blade and the bottom of the tank is 0.1 to 0.2 times the tank diameter. This type of impeller can generate overall circulating flow, avoid bottom deposition, and at the same time, the shear force is evenly distributed, reducing crystal collision and breakage.

[0023] Preferably, in step S10, the initial concentration of glutamic acid in the glutamic acid fermentation broth is 100-120 g / L. This concentration range ensures sufficient crystallization driving force while avoiding runaway supersaturation due to excessively high concentration.

[0024] Preferably, in step S30, the crystallizer is added in the form of an aqueous solution with a concentration of 1% to 5% and an addition rate of 1 to 3 mL / min. Slow addition prevents excessively high local concentrations from forming micelles and ensures uniform dispersion of the crystallizer.

[0025] Secondly, the present invention provides a glutamic acid crystal prepared by the above method, wherein the α-crystal form accounts for not less than 94%, the purity is not less than 99.28%, the fine glutamic acid content does not exceed 0.5%, and the average particle size is 80~150μm.

[0026] According to the present invention, since the glutamic acid crystal is prepared by the method described in the first aspect, its crystal structure is complete, its morphology is regular, and its particle size is uniform, making it suitable for direct use as a raw material for monosodium glutamate production without the need for additional refining processes.

[0027] Thirdly, this invention provides the application of the above-mentioned crystallization synergistic regulation method of crystallizer in the monosodium glutamate industry, which can replace the traditional isoelectric extraction process to achieve continuous production of glutamic acid with high yield, high purity and superior crystal form.

[0028] Preferably, in the aforementioned application, the operating volume of the isoelectric tank is 10~100 m³. 3 The processing time for a single batch does not exceed 30 hours, and the annual production capacity can reach 5,000 to 20,000 tons of glutamic acid.

[0029] Preferably, in the aforementioned application, the cost of the crystallizer accounts for no more than 1.5% of the total production cost, which is more economical than existing membrane separation or secondary crystallization processes.

[0030] In summary, this invention constructs a dynamically balanced crystallization environment by limiting the impurity level of the glutamic acid fermentation broth, precisely controlling the three key elements of isoelectric crystallization (temperature, pH, and stirring), scientifically selecting the type and addition process of the crystallizer, and placing each parameter within a specific numerical range to work synergistically. The crystallizer and the low temperature of 20-28℃ synergistically inhibit the formation of β-crystal nuclei. In this environment, glutamic acid molecules preferentially grow epitaxially on the α-crystal template, β-crystal nucleation is effectively suppressed, and the formation of fine crystals is limited, ultimately yielding a glutamic acid product with a high α-crystal ratio, high purity, and high yield. This method does not rely on a complex recycling system; it achieves a performance breakthrough solely through the precise matching of process parameters and additives, demonstrating significant inventiveness, novelty, and industrial applicability. Existing processes can increase the proportion of α crystals only under low impurity conditions where the bacterial protein content is below 0.3%. However, when the impurity content rises to 0.6%, the proportion of α crystals drops to below 90%. In contrast, this invention, through the synergistic effect of crystal promoters and multiple parameters, can still increase the proportion of α crystals to over 94% under high impurity conditions where the bacterial protein content is 0.6%, thus solving the problem of crystal form control under high impurity load. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the process flow of the present invention. Detailed Implementation

[0032] The various embodiments or implementation schemes in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments.

[0033] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0034] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0035] like Figure 1 As shown, this invention provides a method for synergistic regulation of crystallization by crystallizers in isoelectric extraction of glutamic acid. By limiting the pretreatment indicators of glutamic acid fermentation broth, accurately setting the three elements of isoelectric crystallization (temperature, pH, and stirring rate), scientifically selecting the type of crystallizer and its addition process, and placing each parameter within a specific numerical range to form a coupled regulation system, a glutamic acid crystallization process with α-crystal form dominance, high purity, and high yield can be achieved.

[0036] In a first aspect, the present invention provides a method for synergistic regulation of crystallization by a crystallizer in isoelectric extraction of glutamic acid, comprising the following steps:

[0037] S10: Pre-treat the glutamic acid fermentation broth to control the bacterial protein content in the glutamic acid fermentation broth to not exceed 0.6%, K + The concentration should not exceed 0.15 mol / L;

[0038] S20: The pretreated glutamic acid fermentation broth is sent into an isoelectric tank, and the temperature inside the tank is adjusted and maintained at 20-28℃, the pH value is 4.2-4.7, and the stirring speed is 28-36 rpm;

[0039] S30: Under the process conditions described in S20, a crystallizer is added to the glutamic acid fermentation broth at a dosage of 0.1% to 0.55% of the glutamic acid fermentation broth volume;

[0040] S40: Crystallize continuously for 4-6 hours under the conditions described in S30, followed by solid-liquid separation to obtain glutamic acid crystals and mother liquor.

[0041] According to the present invention, in step S10, the pretreatment of the glutamic acid fermentation broth employs at least one of centrifugation, flocculation, or microfiltration. When centrifugation is used, the centrifuge speed is set to 1800-2000 rpm, the treatment time is 4 hours, and the supernatant is used as the raw material for subsequent isoelectric crystallization. When flocculation is used, an anionic polyacrylamide flocculant with a molecular weight of 8-12 million is used, the addition amount is 5-20 mg / L, the flocculation reaction is carried out at 25°C, the stirring rate is 60 rpm, the reaction time is 15 minutes, followed by settling for 30 minutes, and the supernatant is collected. When microfiltration is used, a ceramic membrane module with a pore size of 0.2-0.45 μm is selected, the operating pressure is 0.15-0.25 MPa, and the membrane flux is controlled at 80-120 L / (m²). 2 •h), the transmembrane pressure difference should not exceed 0.3 MPa, and the turbidity of the filtered liquid should be less than 5 NTU. After treatment by any of the above methods, the cell protein content in the glutamic acid fermentation broth should be determined by the Lowry method to ensure that it does not exceed 0.6%; K + The concentration was determined by flame atomic absorption spectrometry to ensure it did not exceed 0.15 mol / L. Meanwhile, the initial glutamic acid concentration in the fermentation broth was controlled at 100–120 g / L to ensure sufficient driving force for the subsequent crystallization process and to avoid oversaturation and runaway.

[0042] In step S20, the pretreated glutamic acid fermentation broth is pumped into an isoelectric tank. The isoelectric tank has a volume of 50 m³. 3 The inner wall is polished to Ra≤0.4 micrometers to reduce crystal adhesion. A jacketed temperature control system uses circulating cooling water and a PID controller to stabilize the tank temperature at 20-28℃ with a control accuracy of ±0.2℃. pH adjustment uses a 2 mol / L sulfuric acid solution, added dropwise at a constant rate of 1.2 mL / s by an acid metering pump. During the dropwise addition, an online pH monitoring probe provides real-time feedback to ensure the pH is accurately maintained between 4.2 and 4.7, with fluctuations not exceeding ±0.05. The stirring system uses an anchor-type impeller with a blade diameter 0.9 times the tank's inner diameter and a blade bottom distance 0.15 times the tank diameter. The motor drive speed is set to 28-36 rpm, and the frequency converter control speed error does not exceed ±1 rpm. This stirring structure creates an overall axial circulating flow, preventing bottom sedimentation, while controlling the shear rate at 15-25 s⁻¹. -1 This effectively prevents crystals from colliding and breaking.

[0043] In step S30, the crystallizer is added after pH adjustment and stabilization for 8 minutes. The crystallizer is added to the central region of the isoelectric tank as a 1% aqueous solution, with a total addition amount of 0.1%–0.55% of the glutamic acid fermentation broth volume. For example, when treating 50 cubic meters of glutamic acid fermentation broth, 50 kg of crystallizer solution is added. The stirring rate is kept constant during addition to ensure uniform dispersion of the crystallizer. The crystallizer used is selected from at least one of polyethylene glycol, sodium carboxymethyl cellulose, polyvinylpyrrolidone, sodium alginate, betaine hydrochloride, and lysine hydrochloride.

[0044] In step S40, the crystallization process lasts for 4-6 hours. Every 3 hours, 50 mL of the solution is sampled via a sampling valve, filtered through a 0.22 μm filter membrane, and a portion is used for observation under a polarizing microscope (Olympus BX53, equipped with a CCD camera), while the other portion is used for laser particle size analysis (Malvern Mastersizer 3000). Crystallization is terminated when the microscopic image shows that the proportion of α crystals exceeds 93% and the D50 particle size measured by the laser particle size analyzer is greater than 80 μm. Subsequently, a solid-liquid separation system is started, and separation is performed using a horizontal screw centrifuge (drum diameter 500 mm, length-to-diameter ratio 3.5, rotation speed 3200 rpm). The moisture content of the separated wet crystals is controlled at 30%–35%. The mother liquor was collected via pipeline to a mother liquor storage tank. The residual concentration of glutamic acid was determined by high-performance liquid chromatography (HPLC, Agilent 1260, C18 column, mobile phase: 0.01 mol / L potassium dihydrogen phosphate-methanol = 95:5, flow rate: 1.0 mL / min, detection wavelength: 210 nm) to ensure it was below 1.0 g / L. After being concentrated to 60% of its original volume under reduced pressure, the mother liquor was refluxed to the isoelectric tank at a ratio not exceeding 30% of the fresh glutamic acid fermentation broth feed. The reflux pipeline was equipped with a flow meter for precise measurement. The fresh glutamic acid fermentation broth feed rate was the volume of pretreated fermentation broth entering the isoelectric tank in a single batch.

[0045] In some implementations, the isoelectric tank is equipped with an automatic control system that integrates parameters such as temperature, pH, stirring rate, acid addition rate, and crystallizer addition acceleration rate. All data is recorded in real time and stored in the PLC system, and operators can monitor the entire process through a human-machine interface (HMI).

[0046] The following describes embodiments of the present invention. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0047] Example 1

[0048] Take 50 ml of glutamic acid fermentation broth 3 Glutamic acid concentration 110 g / L, bacterial protein content 0.8%, K + The concentration was 0.18 mol / L. Centrifugation was performed at 2000 rpm for 4 hours using a disc centrifuge, yielding 48.5 ml of supernatant. 3 The bacterial cell protein content was measured to be 0.52%, K + Concentration 0.13 mol / L. Pump the supernatant into a 50 mL aerator. 3 The isoelectric tank was activated, and the jacketed cooling system was started, setting the target temperature to 24℃. The anchor-type agitator was turned on, and the speed was adjusted to 32 rpm. 2 mol / L sulfuric acid was added dropwise at a rate of 1.5 mL / s using a metering pump. After 35 min, the pH stabilized at 4.7. Stirring continued for 8 min, and then the crystallizing agent was added. Samples were taken every 1 h during crystallization. At 4 h, polarized light microscopy showed that the α-crystal ratio reached 93%, and the laser particle size D50 was 92 μm, at which point crystallization was terminated. Centrifugation yielded 4.2 tons of wet crystals, with a glutamic acid concentration of 0.85 g / L in the mother liquor. The mother liquor was concentrated to 29 mL. 3 Then, take 14 m 3 (accounting for 48.5 m of fresh feed) 3 28.9% of the glutamic acid was refluxed to the next batch. The obtained dry glutamic acid crystals were analyzed by X-ray diffraction (XRD, Cu Kα radiation), and the α crystal form accounted for 94.0%, the HPLC purity was 99.32%, the fine glutamic acid content was 0.42%, and the average particle size was 105 μm.

[0049] Example 2

[0050] The glutamic acid fermentation broth pretreatment adopted the flocculation method: take 50 m 3 Glutamic acid fermentation broth (glutamic acid 115 g / L, bacterial protein 0.9%, K) + Add 0.20 mol / L of a 4% polyacrylamide solution to achieve a final concentration of 12 mg / L in the glutamic acid fermentation broth. A total of 150 L of this flocculant solution (0.3% of the fermentation broth volume) was added. The mixture was stirred at 60 rpm for 15 min, allowed to stand for 30 min, and 47.8 mL of the supernatant was collected. 3 The bacterial cell protein was measured to be 0.55%, K + 0.14 mol / L. The remaining operations were the same as in Example 1, except the crystallizer was replaced with a 2% lysine hydrochloride solution, added at a dosage of 250 L (0.5%). Crystallization was terminated after 5 h, with an α-crystal ratio of 98.8% and a D50 of 88 μm. The obtained crystals had an α-crystal ratio of 94%, a purity of 99.41%, a fine glutamic acid content of 0.38%, and an average particle size of 98 μm.

[0051] Example 3

[0052] The glutamic acid fermentation broth pretreatment was performed using microfiltration: 50 m 3 Glutamic acid fermentation broth (glutamic acid 105 g / L, bacterial protein 0.7%, K) + (0.17 mol / L) was filtered through a 0.3 μm ceramic membrane at an operating pressure of 0.2 MPa, yielding 49.2 m³ of filtrate. 3 Bacterial protein 0.48%, K + 0.12 mol / L. Lysine hydrochloride was used as the crystallizer. Other conditions were the same as in Example 1. Crystallization was terminated after 6 h. The crystals had an α-crystal form ratio of 94%, a purity of 99.29%, a fine glutamic acid content of 0.45%, and an average particle size of 85 μm.

[0053] Example 4

[0054] Betaine hydrochloride was used as a crystallizing agent. The pretreatment and isoelectric conditions of the glutamic acid fermentation broth were the same as in Example 1. Crystallization was terminated after 4 hours. The crystals had an α-crystal ratio of 94%, a purity of 99.35%, a fine glutamic acid content of 0.35%, and an average particle size of 110 μm.

[0055] Comparative Example 1

[0056] Traditional isoelectric process was used: the glutamic acid fermentation broth was pretreated by centrifugation (cell protein 0.53%, K...). + The isoelectric concentration was 0.13 mol / L, the isoelectric vessel temperature was set to 30℃, the pH was adjusted to 3.2 (the true isoelectric point of glutamic acid), the stirring speed was 60 rpm, no crystallizer was added, and crystallization was carried out for 4 h. The obtained crystals had an α-crystal ratio of 82.5%, a purity of 98.10%, 2.8% fine glutamic acid, and an average particle size of 65 μm.

[0057] Comparative Example 2

[0058] Based on Example 1, the timing of adding the crystallizer was advanced to be synchronized with the start of pH adjustment, while other conditions remained unchanged. As a result, the crystallizer locally aggregated during the period of drastic pH change, the proportion of α-crystal form decreased to 95.2%, and the proportion of fine glutamic acid increased to 1.1%.

[0059] The glutamic acid crystals obtained in the above examples and comparative examples were subjected to performance tests, and the results are shown in the table below:

[0060]

[0061] As shown in the table above, the embodiments of the present invention are significantly superior to the comparative examples in terms of key performance indicators of glutamic acid crystals. The α-crystal proportion of Examples 1-4 all reached 94.0% or higher, while that of Comparative Example 1 (traditional process) was only 82.5%, and that of Comparative Example 2 (improper timing of crystallizer addition) was 95.2%, indicating that adding the crystallizer when the pH is unstable will lead to its aggregation and deactivation. The purity of the products of the embodiments all exceeded 99.28%, with Example 2 reaching 99.41%, while that of Comparative Examples 1 and 2 were 98.10% and 98.75%, respectively. The fine glutamic acid content of the embodiments was ≤0.45%, while that of Comparative Example 1 was as high as 2.8%. The average particle size of the embodiments was 85~110μm, while that of Comparative Example 1 was only 65μm. The yield of the embodiments all reached 93.2%~95.8%, significantly higher than that of Comparative Example 1 (85.3%) and Comparative Example 2 (90.2%). The above results verify that the crystallization system constructed by the present invention through pretreatment of glutamic acid fermentation broth to control impurities, multi-parameter synergistic regulation (temperature 20-28℃, pH 4.2-4.7, stirring 28-36 rpm), and precise addition of crystallizer can effectively inhibit the formation of β-crystals, reduce fine crystal inclusions, and achieve a synergistic improvement in high crystal purity, high product purity, excellent particle size distribution, and high extraction yield.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for synergistic regulation of crystallization by a crystallizer in isoelectric extraction of glutamic acid, characterized in that, Includes the following steps: S10: pretreating the glutamic acid fermentation liquor, controlling the content of the cell protein in the glutamic acid fermentation liquor to be not more than 0.6%, K + concentration to be not more than 0.15 mol / L; S20: The pretreated glutamic acid fermentation broth is sent into an isoelectric tank, and the temperature inside the isoelectric tank is adjusted and maintained at 20-28℃, the pH value is 4.2-4.7, and the stirring speed is 28-36 rpm; S30: Under the process conditions of step S20, a crystallizer is added to the glutamic acid fermentation broth. The crystallizer is selected from at least one of polyethylene glycol, sodium carboxymethyl cellulose, polyvinylpyrrolidone, sodium alginate, betaine hydrochloride, and lysine hydrochloride. The amount of crystallizer added is 0.1% to 0.55% of the volume of the glutamic acid fermentation broth. S40: Under the process conditions of step S30, crystallization is continued for 4-6 hours, followed by solid-liquid separation to obtain glutamic acid crystals and mother liquor.

2. The method for synergistic regulation of crystallization by crystallizer in isoelectric extraction of glutamic acid according to claim 1, characterized in that, In step S10, the glutamic acid fermentation broth is pretreated by at least one of centrifugation, flocculation, or microfiltration; wherein the centrifugation speed is 1800~2000 rpm and the time is 4h; the flocculation uses a polyacrylamide flocculant with an addition amount of 5~20 mg / L; and the microfiltration uses a ceramic membrane or organic membrane module with a pore size of 0.2~0.45μm.

3. The method for synergistic regulation of crystallization by crystallizer in isoelectric extraction of glutamic acid according to claim 1, characterized in that, In step S20, the pH value is adjusted using at least one inorganic acid selected from sulfuric acid, hydrochloric acid, or phosphoric acid, with an acid concentration of 1-3 mol / L, added at a dropping rate of 0.5-2 mL / s.

4. The method for synergistic regulation of crystallization by crystallizer in isoelectric extraction of glutamic acid according to claim 3, characterized in that, In step S30, the crystallizer is added after the pH is adjusted to the target value and maintained for 5-10 minutes.

5. The method for synergistic regulation of crystallization by crystallizer in isoelectric extraction of glutamic acid according to claim 1, characterized in that, In step S40, the mother liquor after solid-liquid separation is concentrated and then returned to the isoelectric tank, with the return flow not exceeding 30% of the fresh glutamic acid fermentation broth feed.

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