Method for separating and extracting bio-based succinic acid from fermentation liquor

Abstract

The invention provides a method for separating and extracting bio-based succinic acid from fermentation liquor, which comprises the following steps: (1) enabling the fermentation liquor to sequentially pass through a ceramic membrane and a nanofiltration membrane, and decoloring to obtain bio-based succinic acid decolored liquor; (2) sequentially carrying out ion exchange impurity removal and concentration treatment on the bio-based succinic acid decoloring solution to obtain a bio-based succinic acid concentrated solution; and (3) carrying out multi-stage cooling crystallization on the bio-based succinic acid concentrated solution to obtain the bio-based succinic acid, the multi-stage cooling crystallization comprises first-stage crystallization, second-stage crystallization and third-stage crystallization which are carried out in sequence. Through the steps of integrated membrane filtration, decoloration, ion exchange, concentration, multi-stage crystallization and the like, thalli, proteins, pigments, inorganic ions and other impurities in fermentation liquor can be efficiently removed, so that a high-purity bio-based succinic acid product is obtained, meanwhile, the product yield is increased, and energy consumption and waste discharge are reduced.

Description

Technical Field

[0001] This invention belongs to the field of bio-fermentation engineering technology and relates to a method for separating and extracting bio-based succinic acid from fermentation broth. Background Technology

[0002] Succinic acid (C4H6O4), as an important C4 platform compound, has broad application prospects in food, medicine, chemical industry, and biodegradable plastics. With the rise of the green circular economy, the technical route of using lignocellulose such as crop straw as raw materials, through pretreatment and enzymatic hydrolysis to obtain straw sugar, and then producing bio-based succinic acid through microbial fermentation, has become an important development direction to replace petroleum-based succinic acid. However, the composition of straw sugar fermentation broth is extremely complex, containing not only the target product succinic acid, but also microbial cells, unfermented residual sugars (such as glucose and xylose), proteins, pigments, and inorganic salts (such as calcium). 2+ Mg 2+ SO4 2- The presence of impurities such as organic acids (e.g., acetic acid, lactic acid, formic acid) and byproducts poses a significant challenge to subsequent separation and purification processes.

[0003] In the existing technology, the main methods for extracting succinic acid from fermentation broth include the following: (1) Calcium salt precipitation method: Lime milk is added to the fermentation broth to form insoluble calcium succinate precipitate of succinic acid, and then succinic acid is released by acidification with sulfuric acid. This method is mature, but it has problems such as low succinic acid yield, high energy consumption, and the generation of a large amount of calcium sulfate solid waste. (2) Ion exchange method: Strong base anion exchange resin is used to adsorb succinate ions in the fermentation broth, and then eluted by acid or alkali. This method has high selectivity, but the resin exchange capacity is limited, a large amount of resin is required and regeneration is frequent, and a large amount of acid and alkali wastewater will be generated. (3) Solvent extraction method: Succinic acid is extracted with organic solvents under acidic conditions. Compared with the first two methods, the extraction method has high production capacity and low energy consumption, but traditional organic solvents are highly toxic and flammable, and the solvent needs to be distilled and recovered after extraction, which also has problems of energy consumption and solvent residue. (4) Membrane separation method: including microfiltration / ultrafiltration, nanofiltration and reverse osmosis. Membrane separation has the advantages of no phase change and low energy consumption, but a single membrane process is often difficult to achieve high-purity separation requirements and needs to be combined with other methods. (5) Electrodialysis and bipolar membrane method: The selective migration of succinate ions through ion exchange membranes under the action of an electric field can reduce acid and alkali consumption. However, impurities in the fermentation broth will contaminate the membrane and require strict pretreatment. (6) Crystallization method: Succinate is precipitated by evaporation concentration and cooling crystallization. However, impurities in the fermentation broth interfere with crystal growth, and repeated recrystallization is often required to achieve the required purity, and the yield is low.

[0004] In summary, while existing separation and purification technologies for succinic acid fermentation broth each have their advantages, they generally suffer from problems such as high cost, high energy consumption, difficulty in wastewater treatment, and unsatisfactory product purity or yield. A single separation technology cannot simultaneously achieve high yield, high purity, and environmental protection requirements. Therefore, there is an urgent need to develop an integrated, low-energy-consumption, and environmentally friendly new process to achieve efficient extraction and high purification of succinic acid from fermentation broth. Summary of the Invention

[0005] The purpose of this invention is to provide a method for separating and extracting bio-based succinic acid from fermentation broth. By integrating steps such as membrane filtration, decolorization, ion exchange, concentration and multi-stage crystallization, the method can efficiently remove bacteria, proteins, pigments, inorganic ions and other impurities from the fermentation broth, thereby obtaining a high-purity bio-based succinic acid product, while improving product yield and reducing energy consumption and waste emissions.

[0006] To achieve this objective, the present invention employs the following technical solution:

[0007] This invention provides a method for separating and extracting bio-based succinic acid from fermentation broth, the method comprising the following steps:

[0008] (1) The fermentation broth was passed through a ceramic membrane and a nanofiltration membrane in sequence, and the bio-based succinic acid decolorized solution was obtained after decolorization;

[0009] (2) The bio-based succinic acid decolorizing solution is subjected to ion exchange for impurity removal and concentration treatment in sequence to obtain a bio-based succinic acid concentrate;

[0010] (3) The bio-based succinic acid concentrate is subjected to multi-stage cooling crystallization to obtain the bio-based succinic acid;

[0011] The multi-stage cooling crystallization includes a first-stage crystallization, a second-stage crystallization, and a third-stage crystallization performed sequentially.

[0012] In this invention, the succinic acid content in the fermentation broth is 75-95 g / L, for example, it can be 76 g / L, 78 g / L, 80 g / L, 82 g / L, 85 g / L, 86 g / L, 88 g / L, 90 g / L, 92 g / L, or 94 g / L. The fermentation broth can be commercially available or prepared using conventional methods. Exemplarily, it can be a fermentation broth from non-grain sugar or starch-based grain sugar sources such as straw, agricultural and forestry waste, and sugarcane.

[0013] In this invention, the complex composition of straw sugar fermentation broth is taken as the research object, and the technical route for separating and extracting succinic acid is studied. The preparation method of straw sugar fermentation broth includes: using wheat straw as raw material, pretreatment and enzymatic separation to obtain straw syrup, and then using an engineered strain of succinic acid-producing yeast in an acidic environment to produce straw sugar fermentation broth. The fermentation culture medium components include: straw sugar 100g / L, yeast powder 6g / L, KH2PO4 1g / L, (NH4)2SO4 3g / L, MgSO4·7H2O 0.4g / L, and CaCl2 0.04g / L.

[0014] The method provided by this invention, through the integration of membrane filtration, decolorization, ion exchange, concentration and multi-stage crystallization, can efficiently remove bacteria, proteins, pigments, inorganic ions and other impurities from fermentation broth, thereby obtaining high-purity bio-based succinic acid products, while improving product yield and reducing energy consumption and waste emissions.

[0015] It should be noted that by subjecting the bio-based succinic acid concentrate to multi-stage cooling crystallization, impurities can be effectively separated, allowing succinic acid to precipitate in steps and obtaining high-purity and high-yield succinic acid crystals. After each stage of crystallization, solid-liquid separation is performed, and the succinic acid crystals are collected. The mother liquor can be used for the next stage of crystallization or returned to the previous steps to improve the yield. In summary, multi-stage cooling crystallization significantly improves the crystallization yield and purity of succinic acid.

[0016] Preferably, step (1) further includes heating the fermentation liquid to 50°C~70°C before passing it through the ceramic membrane, for example, it can be 52°C, 54°C, 55°C, 56°C, 58°C, 60°C, 62°C, 64°C, 65°C, 66°C or 68°C.

[0017] Preferably, the average pore size of the ceramic membrane in step (1) is 20nm~200nm, for example, it can be 40nm, 50nm, 60nm, 80nm, 100nm, 120nm, 140nm, 150nm, 160nm or 180nm, etc., and the operating pressure is 0.1MPa~1MPa, for example, it can be 0.2MPa, 0.3MPa, 0.4MPa, 0.5MPa, 0.6MPa, 0.7MPa, 0.8MPa or 0.9MPa, etc.

[0018] In this invention, a ceramic membrane is used to filter the fermentation broth, which removes bacterial cells and large particulate matter, resulting in a clear fermentation broth. By controlling the pore size and operating pressure parameters of the ceramic membrane, efficient filtration and removal of bacterial residues are achieved.

[0019] Preferably, the nanofiltration membrane in step (1) has a molecular weight cutoff of 200 Da to 1000 Da, such as 300 Da, 400 Da, 400 Da, 500 Da, 600 Da, 700 Da, 800 Da or 900 Da, and an operating pressure of 0.17 MPa to 2.5 MPa, such as 0.18 MPa, 0.19 MPa, 0.2 MPa, 0.21 MPa, 0.22 MPa, 0.23 MPa or 0.24 MPa.

[0020] In this invention, the clarified liquid after ceramic membrane filtration is further clarified and separated using a nanofiltration membrane to remove macromolecular impurities such as pigments, soluble proteins, and polysaccharides, resulting in a nanofiltration clarified liquid. Nanofiltration not only further improves the clarity of the filtrate but also removes some monovalent or polyvalent ions, reducing the load on subsequent treatments and protecting downstream membrane modules from contamination.

[0021] Preferably, the decolorization temperature in step (1) is 40℃~60℃, for example, it can be 42℃, 44℃, 45℃, 46℃, 48℃, 50℃, 52℃, 54℃, 55℃, 56℃ or 58℃, etc.

[0022] Preferably, the decolorization in step (1) is performed using activated carbon for decolorization and impurity removal.

[0023] In this invention, the clarified liquid after nanofiltration is decolorized to remove residual pigments and odorous substances. The color and impurity content of the decolorized solution are significantly reduced, which is beneficial for subsequent crystallization to obtain a light-colored product.

[0024] Preferably, the amount of activated carbon used, by mass-volume percentage, is 0.1% to 0.8% of the volume of the solution obtained after passing through the nanofiltration membrane, for example, it can be 0.2%, 0.3%, 0.4%, 0.5%, 0.6% or 0.7%, etc.

[0025] Preferably, after decolorization in step (1), solid-liquid separation is also performed.

[0026] Preferably, step (2) involves ion exchange purification, which includes passing the bio-based succinic acid decolorizing solution sequentially through a cation exchange resin column and an anion exchange resin column.

[0027] In this invention, the bio-based succinic acid decolorizing solution is passed sequentially through a cation exchange resin column and an anion exchange resin column to remove metal cations (such as Na) from the decolorizing solution. + Ca 2+ Mg 2+ (etc.) and anionic impurities (such as Cl) - SO4 2- (etc.). Additionally, ion exchange resins can be regenerated with acid and alkali and reused after saturation.

[0028] In this invention, the cation exchange resin column is preferably made of a strong acidic cation exchange resin (such as styrene-based sulfonic acid resin 001×7 type), and the anion exchange resin column is preferably made of a strong basic anion exchange resin (such as macroporous acrylic strong basic resin Tulsion® A-30MP).

[0029] Furthermore, ion exchange can reduce the concentration of inorganic ions in the decolorizing solution to extremely low levels (such as Ca). 2+ ≤2 ppm, Fe 3+ ≤1 ppm, SO4 2- ≤2 ppm, Cl - (≤2 ppm), thus obtaining a high-purity dilute succinic acid solution.

[0030] Preferably, the loading flow rate for ion exchange purification in step (2) is 0.5 BV / h to 4 BV / h, for example, it can be 0.6 BV / h, 0.8 BV / h, 1 BV / h, 1.2 BV / h, 1.5 BV / h, 1.6 BV / h, 1.8 BV / h, 2 BV / h, 2.2 BV / h, 2.4 BV / h, 2.5 BV / h, 2.6 BV / h, 3 BV / h, 3.2 BV / h, 3.4 BV / h, 3.5 BV / h, 3.6 BV / h or 3.8 BV / h, etc., preferably 1 BV / h to 2 BV / h.

[0031] Preferably, the feed amount for ion exchange purification in step (2) is 2% to 8% of the volume of the cation exchange resin column or the anion exchange resin column, for example, it can be 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5% or 7%, etc.

[0032] In this invention, by controlling the relevant parameter range of ion exchange for impurity removal, it is beneficial to improve the purity of succinic acid.

[0033] Preferably, the concentration process in step (2) includes reverse osmosis concentration and evaporation concentration performed sequentially.

[0034] In this invention, the succinic acid concentration is further increased to near saturation by concentrating the solution after ion exchange purification. The reverse osmosis membrane has a high rejection rate for succinic acid, allowing the succinic acid solution to be concentrated to the desired concentration with low energy consumption. The permeate water (mainly fresh water) produced by reverse osmosis concentration can be reused in the process or discharged. The resulting first concentrate then proceeds to the next evaporation concentration treatment. Multi-effect evaporation or mechanical vapor recompression (MVR) technology can be used for evaporation concentration, significantly reducing steam consumption during the concentration process.

[0035] In this invention, the mass concentration of succinic acid in the first concentrate is 200 g / L-400 g / L, for example, it can be 220 g / L, 240 g / L, 250 g / L, 260 g / L, 280 g / L, 300 g / L, 320 g / L, 340 g / L, 350 g / L, 360 g / L or 380 g / L, etc.

[0036] Preferably, the evaporation and concentration temperature is 55℃~80℃, for example, it can be 56℃, 58℃, 60℃, 62℃, 64℃, 65℃, 66℃, 68℃, 70℃, 72℃, 74℃, 75℃, 76℃ or 78℃, etc.

[0037] Preferably, the bio-based succinic acid concentration in the bio-based succinic acid concentrate in step (2) is 300 g / L to 500 g / L, for example, it can be 320 g / L, 340 g / L, 350 g / L, 360 g / L, 380 g / L, 400 g / L, 420 g / L, 440 g / L, 450 g / L, 460 g / L or 480 g / L, etc.

[0038] Preferably, in step (3) the first-stage crystallization, the initial temperature of the solution is 55℃~70℃, for example, it can be 56℃, 57℃, 58℃, 59℃, 60℃, 61℃, 62℃, 63℃, 64℃, 65℃, 66℃, 67℃, 68℃ or 69℃, etc., preferably 60℃~70℃.

[0039] Preferably, the cooling rate of the first-stage crystallization in step (3) is 10℃ / h to 25℃ / h, for example, it can be 12℃ / h, 14℃ / h, 15℃ / h, 16℃ / h, 18℃ / h, 20℃ / h, 22℃ / h or 24℃ / h, etc., preferably 10℃ / h to 20℃ / h.

[0040] Preferably, the cooling endpoint of the first-stage crystallization in step (3) is 35℃~50℃, for example, it can be 36℃, 37℃, 38℃, 39℃, 40℃, 41℃, 42℃, 43℃, 44℃, 45℃, 46℃, 47℃, 48℃ or 49℃, etc., preferably 40℃~50℃; and this temperature is maintained for 1.5h~3h, for example, it can be 1.6h, 1.8h, 2h, 2.2h, 2.4h, 2.5h, 2.6h or 2.8h.

[0041] Preferably, in the second-stage crystallization in step (3), the initial temperature of the solution is 35℃~50℃, for example, it can be 36℃, 37℃, 38℃, 39℃, 40℃, 41℃, 42℃, 43℃, 44℃, 45℃, 46℃, 47℃, 48℃ or 49℃, etc., preferably 40℃~50℃.

[0042] Preferably, the cooling rate of the second-stage crystallization in step (3) is 5℃ / h to 15℃ / h, for example, it can be 6℃ / h, 7℃ / h, 8℃ / h, 9℃ / h, 10℃ / h, 11℃ / h, 12℃ / h, 13℃ / h or 14℃ / h, etc., preferably 5℃ / h to 10℃ / h.

[0043] Preferably, the cooling endpoint of the second-stage crystallization in step (3) is 15℃~40℃, for example, it can be 16℃, 18℃, 20℃, 22℃, 24℃, 25℃, 26℃, 28℃, 30℃, 32℃, 34℃, 35℃, 36℃ or 38℃, etc., preferably 20℃~40℃; and this temperature is maintained for 1.5h~3h, for example, it can be 1.6h, 1.8h, 2h, 2.2h, 2.4h, 2.5h, 2.6h or 2.8h, etc.

[0044] In this invention, the final cooling temperature of the second-stage crystallization is lower than the initial temperature of the solution at that stage.

[0045] Preferably, in the third-stage crystallization in step (3), the initial temperature of the solution is 15℃~40℃, for example, it can be 16℃, 18℃, 20℃, 22℃, 24℃, 25℃, 26℃, 28℃, 30℃, 32℃, 34℃, 35℃, 36℃ or 38℃, etc., preferably 20℃~40℃.

[0046] Preferably, the cooling rate of the third-stage crystallization in step (3) is 2℃ / h to 8℃ / h, for example, it can be 2.5℃ / h, 3℃ / h, 3.5℃ / h, 4℃ / h, 4.5℃ / h, 5℃ / h, 5.5℃ / h, 6℃ / h, 6.5℃ / h, 7℃ / h or 7.5℃ / h, etc., preferably 2℃ / h to 5℃ / h.

[0047] Preferably, the cooling endpoint of the third-stage crystallization in step (3) is 0℃~15℃, for example, it can be 2℃, 4℃, 5℃, 6℃, 7℃, 8℃, 9℃, 10℃, 11℃, 12℃, 13℃ or 14℃, etc., preferably 5℃~15℃; and this temperature is maintained for 1.5h~3h, for example, it can be 1.6h, 1.8h, 2h, 2.2h, 2.4h, 2.5h, 2.6h or 2.8h, etc.

[0048] It should be noted that a multi-stage cooling crystallization process is adopted, in which the temperature of the solution is gradually reduced in each stage. By controlling the cooling rate and the range of the final temperature for the first, second, and third stages of crystallization, the succinic acid in the solution has sufficient time to precipitate as the cooling rate gradually decreases step by step. The slower crystallization rate also helps to reduce the entrainment of impurities, which is conducive to obtaining high-purity succinic acid. In addition, the lower final temperature helps to reduce the solubility of succinic acid, allowing for the recovery of more succinic acid.

[0049] Preferably, in step (3), solid-liquid separation is performed after the first-stage crystallization, the second-stage crystallization, and the third-stage crystallization.

[0050] Preferably, in step (3), the mother liquor obtained after solid-liquid separation following the first-stage crystallization enters the second-stage crystallization.

[0051] Preferably, the mother liquor obtained after solid-liquid separation following the second-stage crystallization in step (3) enters the third-stage crystallization.

[0052] Preferably, the mother liquor obtained after solid-liquid separation following the third-stage crystallization in step (3) is reused in the ion exchange purification process in step (2).

[0053] In this invention, the mother liquor after the third-stage crystallization still contains some succinic acid and impurities. The mother liquor after the third-stage crystallization is returned to step (2) for ion exchange purification to recover the succinic acid and remove impurities. The recovered succinic acid is then used in subsequent operations to improve the overall product yield. Finally, the treated mother liquor can be recycled or discharged in compliance with standards, minimizing wastewater discharge.

[0054] Preferably, step (3) after multi-stage cooling crystallization further includes combining the succinic acid crystals obtained after solid-liquid separation, and then washing, centrifuging and drying in sequence.

[0055] In this invention, the crude succinic acid crystals obtained from crystallization are washed with a small amount of organic solvent (such as ethanol, methanol, etc.) to remove the mother liquor and impurities adhering to the crystal surface. After washing, the crystals are centrifuged to obtain wet crystals. The wet crystals are then dried at an appropriate temperature (such as vacuum drying or forced-air drying) to remove residual solvent and moisture, thus obtaining a high-purity bio-based succinic acid product.

[0056] Preferably, the yield of the bio-based succinic acid is >98%, for example, it can be 98.2%, 98.4%, 98.5%, 98.6%, 98.8%, 99%, 99.2%, 99.5%, 99.5% or 99.8%, etc., preferably >98.5%.

[0057] Preferably, the purity of the bio-based succinic acid is >99.7%, for example, it can be 99.72%, 99.75%, 99.76%, 99.78%, 99.8%, 99.82%, 99.85%, 99.88%, or 99.9%.

[0058] In this invention, the yield of the obtained bio-based succinic acid product reaches 98%, and the purity can reach over 99.7%, meeting the requirements for polymer-grade succinic acid raw materials.

[0059] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0060] Compared with the prior art, the present invention has the following beneficial effects:

[0061] (1) The method provided by the present invention can efficiently remove bacteria, proteins, pigments, inorganic ions and other impurities from the fermentation broth by integrating membrane filtration, decolorization, ion exchange, concentration and multi-stage crystallization, thereby obtaining a high-purity bio-based succinic acid product that meets the requirements of polymer-grade succinic acid raw materials and improves the product yield.

[0062] (2) The method provided by the present invention makes full use of the low energy consumption advantage of membrane separation for clarification and pre-concentration, and then combines it with efficient evaporation and concentration to reduce the overall energy consumption; in addition, the entire process does not use reagents such as lime and sulfuric acid for precipitation, thus avoiding the generation of a large amount of solid waste; the waste liquid of ion exchange resin regeneration and the condensate of evaporation and concentration can be treated and reused.

[0063] (3) The method provided by the present invention has a highly efficient and compact process route, mature and reliable unit operations, and can be operated continuously, making it suitable for large-scale industrial production of succinic acid. Detailed Implementation

[0064] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0065] Unless otherwise defined, the technical terms used in the following embodiments and comparative examples have the same meanings as commonly understood by those skilled in the art. The raw materials, instruments, and equipment used in the following embodiments and comparative examples are all commercially available or obtainable through existing methods; the experimental methods described, unless otherwise specified, are conventional methods.

[0066] In the following examples and comparative examples, the production process of the straw sugar fermentation liquid includes: using wheat straw as raw material, pretreatment and enzymatic hydrolysis to obtain straw syrup, and then using an engineered strain of succinic acid-producing yeast to ferment in an acidic environment to obtain straw sugar fermentation liquid. The fermentation medium includes the following components at the following mass concentrations: straw sugar 100g / L, yeast powder 6g / L, KH2PO4 1g / L, (NH4)2SO4 3g / L, MgSO4·7H2O 0.4g / L, CaCl2 0.04g / L; wherein the mass concentration of succinic acid is about 85g / L, and it contains impurities such as bacterial cells, proteins, pigments and inorganic ions.

[0067] In Examples 1 and 4 below, the OD in the fermentation broth 600 The concentration of yeast cells was measured by spectrophotometry, following the method described in GB / T35882-2018, which uses a visible spectrophotometer to measure the concentration at a wavelength of 600 nm. The instrument used was a Shimadzu UV-2450 UV-Vis spectrophotometer.

[0068] Example 1

[0069] This embodiment provides a method for separating and extracting bio-based succinic acid from straw sugar fermentation broth, the method comprising the following steps:

[0070] (1) 210L of straw sugar fermentation liquid was heated to 60℃ and filtered using a ceramic membrane with an average pore size of 100nm at an operating pressure of 0.3MPa to obtain a clear fermentation liquid; then a spiral wound nanofiltration membrane with a molecular weight cutoff of 300Da was used to filter the fermentation liquid at an operating pressure of 1.5MPa to obtain a nanofiltration liquid; then activated carbon was added to the nanofiltration liquid and decolorized for 30min at a temperature of 50℃ with stirring. After filtration, a bio-based succinic acid decolorized liquid was obtained.

[0071] Among them, the OD of the fermentation broth 600 ≤2, bacterial removal rate >99%; activated carbon dosage, by mass-volume percentage, is 0.5% of the nanofiltration solution volume;

[0072] (2) The bio-based succinic acid decolorizing solution is passed sequentially through a cation exchange resin column of strong acid styrene-based sulfonic acid resin 001×7 and an anion exchange resin column of macroporous acrylic-based strong base resin Tulsion® A-30MP for ion exchange to remove impurities; then the solution with removed ions is concentrated by reverse osmosis membrane to obtain the first concentrate; then the first concentrate is sent to an MVR evaporator and concentrated by reduced pressure evaporation at a temperature of 65℃ and a pressure of -0.09MPa to obtain the bio-based succinic acid concentrate;

[0073] The loading flow rate for ion exchange purification is 1 BV / h; the feed rate for ion exchange purification is 5% of the column volume of cation exchange resin or anion exchange resin; the mass concentration of succinic acid in the first concentrate is 300 g / L; and the mass concentration of succinic acid in the bio-based succinic acid concentrate is 450 g / L.

[0074] (3) The bio-based succinic acid concentrate was subjected to first-stage crystallization, second-stage crystallization and third-stage crystallization in sequence. After the first-stage crystallization, second-stage crystallization and third-stage crystallization, centrifugation was performed. The succinic acid crystals obtained from the three centrifugation were combined, washed twice with anhydrous ethanol, and after centrifugation, the wet succinic acid crystals were vacuum dried at a temperature of 60°C to obtain the bio-based succinic acid product.

[0075] In the first-stage crystallization, the initial temperature of the solution is 60℃, the cooling rate is 10℃ / h, the cooling endpoint is 40℃, and this temperature is maintained for 2h; in the second-stage crystallization, the initial temperature of the solution is 40℃, the cooling rate is 5℃ / h, the cooling endpoint is 30℃, and this temperature is maintained for 2h; in the third-stage crystallization, the initial temperature of the solution is 30℃, the cooling rate is 4℃ / h, the cooling endpoint is 10℃, and this temperature is maintained for 2h.

[0076] The mother liquor obtained after centrifugation following the first-stage crystallization enters the second-stage crystallization; the mother liquor obtained after centrifugation following the second-stage crystallization enters the third-stage crystallization; the mother liquor obtained after centrifugation following the third-stage crystallization is reused in step (2) ion exchange for impurity removal.

[0077] Example 2

[0078] This embodiment provides a method for separating and extracting bio-based succinic acid from straw sugar fermentation broth. Except for adjusting the relevant parameters in steps (2) and (3), namely, the sample loading flow rate for ion exchange purification is 1.5 BV / h, the initial temperature of the solution in the first-stage crystallization is 60℃, the cooling rate is 15℃ / h, the cooling endpoint is 40℃ and the temperature is maintained for 2h; the initial temperature of the solution in the second-stage crystallization is 40℃, the cooling rate is 10℃ / h, the cooling endpoint is 30℃ and the temperature is maintained for 2h; the initial temperature of the solution in the third-stage crystallization is 30℃, the cooling rate is 5℃ / h, the cooling endpoint is 10℃ and the temperature is maintained for 2h; other conditions are the same as in Example 1.

[0079] Example 3

[0080] This embodiment provides a method for separating and extracting bio-based succinic acid from straw sugar fermentation broth. Except for adjusting the relevant parameters in steps (2) and (3), namely, the sample loading flow rate for ion exchange purification is 2 BV / h, the initial temperature of the solution in the first-stage crystallization is 60℃, the cooling rate is 20℃ / h, the cooling endpoint is 40℃ and the temperature is maintained for 2h; the initial temperature of the solution in the second-stage crystallization is 40℃, the cooling rate is 10℃ / h, the cooling endpoint is 30℃ and the temperature is maintained for 2h; the initial temperature of the solution in the third-stage crystallization is 30℃, the cooling rate is 5℃ / h, the cooling endpoint is 10℃ and the temperature is maintained for 2h; other conditions are the same as in Example 1.

[0081] Example 4

[0082] This embodiment provides a method for separating and extracting bio-based succinic acid from straw sugar fermentation broth, the method comprising the following steps:

[0083] (1) 210L of straw sugar fermentation liquid was heated to 70℃ and filtered using a ceramic membrane with an average pore size of 80nm at an operating pressure of 0.5MPa to obtain a clear fermentation liquid; then a spiral nanofiltration membrane with a molecular weight cutoff of 500Da was used to filter the fermentation liquid at an operating pressure of 1MPa to obtain a nanofiltration liquid; then activated carbon was added to the nanofiltration liquid and decolorized for 30min at a temperature of 55℃ with stirring. After filtration, a bio-based succinic acid decolorized liquid was obtained.

[0084] Among them, the OD of the fermentation broth 600 ≤2, bacterial removal rate >99%; activated carbon dosage, by mass-volume percentage, is 0.3% of the nanofiltration solution volume;

[0085] (2) The bio-based succinic acid decolorizing solution is passed sequentially through a cation exchange resin column of strong acid styrene-based sulfonic acid resin 001×7 and an anion exchange resin column of macroporous acrylic-based strong base resin Tulsion® A-30MP for ion exchange to remove impurities; then the solution with removed ions is concentrated by reverse osmosis membrane to obtain the first concentrate; then the first concentrate is sent to an MVR evaporator and concentrated by reduced pressure evaporation at a temperature of 60℃ and a pressure of -0.09MPa to obtain the bio-based succinic acid concentrate;

[0086] The sample loading flow rate for ion exchange purification is 2 BV / h; the feed rate for ion exchange purification is 5% of the column volume of cation exchange resin or anion exchange resin; the mass concentration of succinic acid in the first concentrate is 320 g / L; and the mass concentration of succinic acid in the bio-based succinic acid concentrate is 470 g / L.

[0087] (3) The bio-based succinic acid concentrate was subjected to first-stage crystallization, second-stage crystallization and third-stage crystallization in sequence. After the first-stage crystallization, second-stage crystallization and third-stage crystallization, centrifugation was performed. The succinic acid crystals obtained from the three centrifugation were combined, washed twice with anhydrous ethanol, and after centrifugation, the wet succinic acid crystals were vacuum dried at a temperature of 60°C to obtain the bio-based succinic acid product.

[0088] In the first-stage crystallization, the initial temperature of the solution is 60℃, the cooling rate is 10℃ / h, the cooling endpoint is 40℃, and this temperature is maintained for 2h; in the second-stage crystallization, the initial temperature of the solution is 40℃, the cooling rate is 5℃ / h, the cooling endpoint is 25℃, and this temperature is maintained for 2h; in the third-stage crystallization, the initial temperature of the solution is 25℃, the cooling rate is 4℃ / h, the cooling endpoint is 5℃, and this temperature is maintained for 2h.

[0089] The mother liquor obtained after centrifugation following the first-stage crystallization enters the second-stage crystallization; the mother liquor obtained after centrifugation following the second-stage crystallization enters the third-stage crystallization; the mother liquor obtained after centrifugation following the third-stage crystallization is reused in step (2) ion exchange for impurity removal.

[0090] Example 5

[0091] This embodiment provides a method for separating and extracting bio-based succinic acid from straw sugar fermentation broth. Except for the sample loading flow rate of 4 BV / h for ion exchange purification, all other conditions are the same as in Example 1.

[0092] Example 6

[0093] This embodiment provides a method for separating and extracting bio-based succinic acid from straw sugar fermentation broth. Except for the cooling rate of the first-stage crystallization being 25℃ / h, all other conditions are the same as in Example 1.

[0094] Example 7

[0095] This embodiment provides a method for separating and extracting bio-based succinic acid from straw sugar fermentation broth. Except for the cooling endpoint of the first-stage crystallization being 35°C and the cooling endpoint of the second-stage crystallization being 25°C, all other conditions are the same as in Example 1.

[0096] Example 8

[0097] This embodiment provides a method for separating and extracting bio-based succinic acid from straw sugar fermentation broth. Except for the cooling rate of 15℃ / h for the second-stage crystallization, all other conditions are the same as in Example 1.

[0098] Example 9

[0099] This embodiment provides a method for separating and extracting bio-based succinic acid from straw sugar fermentation broth. Except for the cooling endpoint of the second-stage crystallization being 15°C and the cooling endpoint of the third-stage crystallization being 5°C, all other conditions are the same as in Example 1.

[0100] Example 10

[0101] This embodiment provides a method for separating and extracting bio-based succinic acid from straw sugar fermentation broth. Except for the cooling rate of the third-stage crystallization being 8°C / h, all other conditions are the same as in Example 1.

[0102] Example 11

[0103] This embodiment provides a method for separating and extracting bio-based succinic acid from straw sugar fermentation broth. Except for the cooling endpoint of the third-stage crystallization being 0°C, all other conditions are the same as in Example 1.

[0104] Comparative Example 1

[0105] This comparative example provides a method for separating and extracting bio-based succinic acid from straw sugar fermentation broth. Except for step (1) where the filtration is not performed through a nanofiltration membrane, all other conditions are the same as in Example 1.

[0106] Comparative Example 2

[0107] This comparative example provides a method for separating and extracting bio-based succinic acid from straw sugar fermentation broth. Except for the absence of decolorization in step (1), all other conditions are the same as in Example 1.

[0108] Comparative Example 3

[0109] This comparative example provides a method for separating and extracting bio-based succinic acid from straw sugar fermentation broth. Except for the absence of ion exchange purification in step (2), all other conditions are the same as in Example 1.

[0110] Comparative Example 4

[0111] This comparative example provides a method for separating and extracting bio-based succinic acid from straw sugar fermentation broth. Except for step (3), where the first-stage crystallization is not performed, the initial temperature of the solution in the second-stage crystallization is 60°C, the cooling rate is 5°C / h, the cooling endpoint is 30°C and the temperature is maintained for 2h; and the initial temperature of the solution in the third-stage crystallization is 30°C, the cooling rate is 4°C / h, the cooling endpoint is 10°C and the temperature is maintained for 4h, all other conditions are the same as in Example 1.

[0112] Comparative Example 5

[0113] This comparative example provides a method for separating and extracting bio-based succinic acid from straw sugar fermentation broth. Except for step (3), which does not involve a second-stage crystallization, i.e., the initial temperature of the solution in the first-stage crystallization is 60°C, the cooling rate is 10°C / h, the cooling endpoint is 40°C and the temperature is maintained for 2h; and the initial temperature of the solution in the third-stage crystallization is 40°C, the cooling rate is 4°C / h, the cooling endpoint is 10°C and the temperature is maintained for 4h, all other conditions are the same as in Example 1.

[0114] Comparative Example 6

[0115] This comparative example provides a method for separating and extracting bio-based succinic acid from straw sugar fermentation broth. Except for step (3), which does not involve a third-stage crystallization, i.e., the initial temperature of the solution in the first-stage crystallization is 60°C, the cooling rate is 10°C / h, the cooling endpoint is 40°C and the temperature is maintained for 2h; and the initial temperature of the solution in the second-stage crystallization is 40°C, the cooling rate is 5°C / h, the cooling endpoint is 30°C and the temperature is maintained for 4h, all other conditions are the same as in Example 1.

[0116] Comparative Example 7

[0117] This comparative example provides a method for separating and extracting bio-based succinic acid from straw sugar fermentation broth. Except for step (3), which involves only one cooling crystallization step, i.e., the initial temperature of the solution is 60°C, the cooling rate is 10°C / h, and the cooling endpoint is 10°C and maintained for 6h, all other conditions are the same as in Example 1.

[0118] The bio-based succinic acid products prepared in the above embodiments and comparative examples were tested.

[0119] The formula for calculating the yield of bio-based succinic acid is as follows:

[0120] Succinic acid yield = M / (C×V)×100%

[0121] Where M is the mass of succinic acid obtained after vacuum drying in the above examples and comparative examples, in g; C and V are the concentration of succinic acid and the volume of the solution in the straw sugar fermentation broth, in g / L and L, respectively.

[0122] The purity and sugar content of the bio-based succinic acid product were determined by high-performance liquid chromatography (HPLC). The detection parameters are as follows: a 1260 Infinity II HPLC system was used, with a Bio-Rad Aminex HPX-87H column (300 × 7.8 mm) and a mobile phase of 2.43 mmol / L dilute sulfuric acid. The program settings were as follows: autosampler was set to autosample; mobile phase: 2.43 mmol / L dilute sulfuric acid; flow rate: 0.6 mL / min; detection time: 25 min; injection volume: 10 μL; column oven temperature: 40℃; RID detector temperature: 40℃, 2.31 Hz.

[0123] The moisture content of bio-based succinic acid products was determined by the Karl Fischer coulometric method according to GB / T 6283-2008; the ash content was determined by the residue on ignition method according to GB / T 9741-2008.

[0124] The results are shown in Table 1.

[0125] Table 1

[0126]

[0127] As shown in Table 1:

[0128] The methods provided in Examples 1-4 of this invention, through the integration of membrane filtration, decolorization, ion exchange, concentration, and multi-stage crystallization, can efficiently remove bacteria, proteins, pigments, inorganic ions, and other impurities from straw sugar fermentation broth, thereby obtaining a high-purity bio-based succinic acid product, while improving product yield and reducing energy consumption; wherein, the yield of bio-based succinic acid is >98.5%, purity >99.7%, sugar content as low as 0%, moisture content <0.2%, and ash content <0.04%.

[0129] A comparison of Examples 1 and 5 shows that if the sample loading flow rate for ion exchange purification is too fast, the treatment effect of the ion exchange resin will deteriorate, resulting in a certain degree of decrease in the yield and purity of bio-based succinic acid.

[0130] A comparison of Examples 1, 6, 8, and 10 shows that if the cooling rate of the first, second, or third stage crystallization is too fast, the succinic acid will precipitate too quickly due to the rapid crystallization, carrying a small amount of impurities and forming large-particle crystals, which will lead to a decrease in the yield and purity of bio-based succinic acid.

[0131] A comparison of Examples 1, 7, 9, and 11 shows that if the cooling endpoint of the first, second, or third stage crystallization is too low, it will significantly affect the cooling time of succinic acid in different stages of crystallization, which will lead to a decrease in the yield and purity of bio-based succinic acid.

[0132] As can be seen from the comparison between Example 1 and Comparative Examples 1-3, if any step such as nanofiltration, decolorization, or ion exchange is not performed during the entire process, the yield and purity of bio-based succinic acid will decrease. This demonstrates that nanofiltration, decolorization, and deep desalination via ion exchange play a crucial role in improving product purity. High-purity succinic acid is obtained through the complementary processes of membrane filtration, decolorization, ion exchange, concentration, and multi-stage crystallization.

[0133] A comparison of Example 1 and Comparative Examples 4-7 shows that performing only one-step cooling crystallization, without first-stage, second-stage, or third-stage crystallization, leads to a decrease in the yield and purity of bio-based succinic acid. This demonstrates that multi-stage cooling crystallization can effectively separate impurities, allowing succinic acid to precipitate in steps, resulting in high-purity and high-yield succinic acid crystals.

[0134] The applicant declares that the detailed structural features of the present invention are illustrated through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components selected in the present invention, additions of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for separating and extracting bio-based succinic acid from fermentation broth, characterized in that, The method includes the following steps: (1) The fermentation broth was passed through a ceramic membrane and a nanofiltration membrane in sequence, and the bio-based succinic acid decolorized solution was obtained after decolorization; (2) The bio-based succinic acid decolorizing solution is subjected to ion exchange for impurity removal and concentration treatment in sequence to obtain a bio-based succinic acid concentrate; (3) The bio-based succinic acid concentrate is subjected to multi-stage cooling crystallization to obtain the bio-based succinic acid; The multi-stage cooling crystallization includes a first-stage crystallization, a second-stage crystallization, and a third-stage crystallization performed sequentially.

2. The method according to claim 1, characterized in that, Step (1) further includes heating the fermentation broth to 50°C~70°C before passing it through the ceramic membrane; Preferably, the ceramic membrane in step (1) has an average pore size of 20 nm to 200 nm and an operating pressure of 0.1 MPa to 1 MPa.

3. The method according to claim 1, characterized in that, The nanofiltration membrane described in step (1) has a molecular weight cutoff of 200 Da to 1000 Da and an operating pressure of 0.17 MPa to 2.5 MPa. Preferably, the decolorization temperature in step (1) is 40℃~60℃; Preferably, the decolorization in step (1) is performed using activated carbon for decolorization and impurity removal; Preferably, the amount of activated carbon used, by mass-volume percentage, is 0.1% to 0.8% of the volume of the solution obtained after nanofiltration. Preferably, after decolorization in step (1), solid-liquid separation is also performed.

4. The method according to claim 1, characterized in that, Step (2) involves ion exchange purification, which includes passing the bio-based succinic acid decolorizing solution sequentially through a cation exchange resin column and an anion exchange resin column. Preferably, the sample loading flow rate for ion exchange purification in step (2) is 0.5 BV / h to 4 BV / h, and more preferably 1 BV / h to 2 BV / h; Preferably, the feed amount for ion exchange purification in step (2) is 2% to 8% of the volume of the cation exchange resin column or the volume of the anion exchange resin column.

5. The method according to claim 1, characterized in that, The concentration process in step (2) includes reverse osmosis concentration and evaporation concentration performed sequentially; Preferably, the evaporation and concentration temperature is 55℃~80℃; Preferably, the bio-based succinic acid concentration in the bio-based succinic acid concentrate in step (2) is 300g / L to 500g / L.

6. The method according to claim 1, characterized in that, In step (3), the initial temperature of the solution in the first-stage crystallization is 55℃~70℃, preferably 60℃~70℃; Preferably, the cooling rate of the first-stage crystallization in step (3) is 10℃ / h~25℃ / h, more preferably 10℃ / h~20℃ / h; Preferably, the cooling endpoint of the first-stage crystallization in step (3) is 35℃~50℃, more preferably 40℃~50℃, and this temperature is maintained for 1.5h~3h.

7. The method according to claim 1, characterized in that, In step (3), during the second-stage crystallization, the initial temperature of the solution is 35℃~50℃, preferably 40℃~50℃; Preferably, the cooling rate of the second-stage crystallization in step (3) is 5℃ / h~15℃ / h, more preferably 5℃ / h~10℃ / h; Preferably, the cooling endpoint of the second-stage crystallization in step (3) is 15℃~40℃, more preferably 20℃~40℃, and this temperature is maintained for 1.5h~3h.

8. The method according to claim 1, characterized in that, In the third-stage crystallization described in step (3), the initial temperature of the solution is 15℃~40℃, preferably 20℃~40℃; Preferably, the cooling rate of the third-stage crystallization in step (3) is 2℃ / h~8℃ / h, more preferably 2℃ / h~5℃ / h; Preferably, the cooling endpoint of the third-stage crystallization in step (3) is 0℃~15℃, more preferably 5℃~15℃, and this temperature is maintained for 1.5h~3h.

9. The method according to claim 1, characterized in that, In step (3), solid-liquid separation was performed after the first-stage crystallization, the second-stage crystallization, and the third-stage crystallization. Preferably, in step (3), the mother liquor obtained after solid-liquid separation following the first-stage crystallization enters the second-stage crystallization; Preferably, in step (3), the mother liquor obtained after solid-liquid separation following the second-stage crystallization enters the third-stage crystallization; Preferably, the mother liquor obtained after solid-liquid separation following the third-stage crystallization in step (3) is reused in the ion exchange purification process in step (2); Preferably, step (3) after multi-stage cooling crystallization further includes combining the succinic acid crystals obtained after solid-liquid separation, and then washing, centrifuging and drying in sequence.

10. The method according to claim 1, characterized in that, The yield of the bio-based succinic acid is >98%, preferably >98.5%; Preferably, the purity of the bio-based succinic acid is >99.7%.

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