Method for extracting succinic acid from fermentation liquor

Abstract

The invention provides a method for extracting succinic acid from fermentation liquor. The method comprises the following steps: (1) filtering succinic acid fermentation liquor, and performing multi-stage forward cross-flow extraction by using an extracting agent A to obtain a succinic acid loaded organic phase and a raffinate phase; and (2) carrying out multistage reverse cross-flow extraction on the succinic acid loaded organic phase by using an extracting agent B to obtain a succinic acid aqueous solution and a mixture containing an extracting agent A, and carrying out post-treatment to extract succinic acid from the fermentation liquor to obtain succinic acid crystals, the extracting agent A comprises a complexing agent with a structure shown in a formula I and a cosolvent. The method for extracting the succinic acid from the fermentation liquor has the advantages of being easy to operate, high in succinic acid extraction selectivity, high in extraction efficiency, free of acid and alkali introduction in the extraction process, free of high-salinity wastewater and the like, the method is suitable for industrial production, and the extracting agent A used for extraction can be recycled and reused after being regenerated.

Description

Technical Field

[0001] The present invention belongs to the technical field of biochemistry separation, and particularly relates to a method for extracting succinic acid from fermentation broth. Background Art

[0002] Succinic acid is an important C4 platform compound, which is widely used in the fields of food, medicine, and chemical industry, and can be used as a synthetic monomer for polybutylene succinate (PBS). The manufacturing methods of succinic acid are divided into chemical synthesis and microbial fermentation methods. Among them, the microbial fermentation method is expected to gradually replace the chemical synthesis method due to its advantages such as rich and renewable raw material resources, green and low-carbon, and low theoretical cost. The purification cost of succinic acid fermentation broth accounts for more than 60% of the total production cost, which has a great impact on whether industrialization can be achieved.

[0003] Extracting succinic acid crystals from fermentation broth includes three steps: the first step requires removing the bacteria and macromolecular insoluble solids in the fermentation broth, usually by microfiltration (microfiltration or ultrafiltration) or centrifugation; the second step requires removing a large number of impurities including inorganic salts, proteins, pigments, and residual sugars, and there are many choices for this step, including the calcium salt method, ammonium salt method, ion exchange, decolorization, and electrodialysis or a combination of the above methods to achieve; the third stage is to convert the finally obtained aqueous succinic acid solution into succinic acid crystals, usually by evaporation concentration, cooling crystallization, and centrifugal drying.

[0004] In the second stage, in the calcium salt method, calcium hydroxide or calcium chloride is added to the succinic acid fermentation broth, and after solid-liquid separation, calcium succinate is obtained, and then sulfuric acid is added for acidification to obtain succinic acid and calcium sulfate. This method has a low yield, large consumption of acids and bases, a high content of by-product calcium sulfate, and high energy consumption; in the ion exchange method, the amount of water used during elution is large, and a large amount of acids and bases are required for resin regeneration; nanofiltration will generate a large amount of wastewater, and the retention effect on impurities such as inorganic salts and pigments is not good; decolorization usually uses activated carbon as a decolorizing agent, and the regeneration of activated carbon is difficult and the treatment cost is high; the electrodialysis method has low selectivity for succinic acid, large equipment investment, high energy consumption, and cannot effectively separate divalent ions. In contrast, the solvent extraction method has the advantages of simple operation, high selectivity for product extraction, no introduction of acids and bases during the extraction process, and no generation of high-salt wastewater.

[0005] CN115417763A provides a purification method for succinic acid fermentation broth, including steps such as filtration - liquid-liquid extraction - evaporation concentration crystallization - drying, etc. Among them, amines and C6-C20 hydrocarbon solvents are used as a composite extractant for extraction. The distribution coefficient of the amine extractant in forward extraction is very high, but the complex formed with succinic acid during forward extraction has low solubility in the extractant, which may cause a certain degree of emulsification, making phase separation difficult during back extraction and resulting in a low back extraction yield. In addition, the amine extractant has high toxicity, and the application of the produced succinic acid in the food and pharmaceutical industries is limited.

[0006] CN105503578A provides a method for extracting succinic acid fermentation broth with an extractant, including steps such as microfiltration - acidification - extraction - evaporation concentration - cooling crystallization - centrifugal drying. Among them, the extractant is methyl ethyl ketone or tetrahydrofuran. These two solvents have high solubility in water, which is not conducive to extraction layering, and belong to physical extraction based on the principle of similar solubility, with low extraction efficiency.

[0007] Therefore, how to provide a method for extracting succinic acid from fermentation broth with high extraction efficiency and simple extraction method has become an urgent technical problem to be solved at present. Summary of the Invention

[0008] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a method for extracting succinic acid from fermentation broth. The present invention uses solvent extraction method to extract succinic acid crystals from fermentation broth by using a specific extractant A, omitting steps such as calcium salt method, ammonium salt method, ion exchange, decolorization and electrodialysis used in traditional purification methods. The method for extracting succinic acid from fermentation broth provided by the present invention has the advantages of simple operation, high selectivity for succinic acid extraction, high extraction efficiency, no introduction of acids and bases during the extraction process and no generation of high - salt wastewater, is suitable for industrial production, and the extractant A used in the extraction can be recycled and reused after regeneration.

[0009] To achieve this purpose, the present invention adopts the following technical solutions:

[0010] In the first aspect, the present invention provides a method for extracting succinic acid from fermentation broth, and the method includes the following steps:

[0011] (1) After filtering the succinic acid fermentation broth, perform multi - stage forward cross - flow extraction with extractant A to obtain a succinic acid - loaded organic phase and a raffinate phase;

[0012] (2) Perform multi - stage reverse cross - flow extraction on the succinic acid - loaded organic phase with extractant B to obtain a succinic acid aqueous solution and a mixture containing extractant A. After post - treatment, complete the extraction of succinic acid from the fermentation broth to obtain succinic acid crystals;

[0013] The extractant A includes a complexing agent and a co - solvent having the structure shown in Formula I below;

[0014]

[0015] Among them, R1 represents an ester group of C1 - 10;

[0016] R2 and R3 each independently represent any one of an alkyl group of C1 - C10, an ester group of C1 - 10 or a hydroxyl group;

[0017] The co - solvent is an alcohol solvent containing 7 - 10 carbon atoms.

[0018] In the present invention, by using the solvent extraction method, succinic acid crystals are extracted from the fermentation broth by using a specific extractant A, eliminating steps such as the calcium salt method, ammonium salt method, ion exchange, decolorization, and electrodialysis used in traditional purification methods. The method for extracting succinic acid from the fermentation broth provided by the present invention has the advantages of simple operation, high selectivity for succinic acid extraction, high extraction efficiency, no introduction of acids and bases during the extraction process, and no generation of high-salt wastewater, is suitable for industrial production, and the extractant A used in the extraction can be recycled and reused after regeneration.

[0019] Compared with ordinary physical extraction, in the method for extracting succinic acid from the fermentation broth provided by the present invention, by using the extractant A for complexation extraction, the extraction efficiency is greatly improved. Compared with the amine extractants commonly used in the prior art, the phosphine oxide extractant used in the present invention has more balanced forward and reverse extraction yields, further improving the total extraction yield of succinic acid; in addition, the phosphine oxide extractant has milder properties and lower toxicity and can be applied to the food and pharmaceutical industries.

[0020] In the present invention, C1-10 can be C1, C2, C3, C4, C5, C6, C7, C8, C9 or C10.

[0021] The co-solvent is an alcohol solvent containing 7-10 (for example, it can be 7, 8, 9 or 10) carbon atoms.

[0022] The following are the preferred technical solutions of the present invention, but do not limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the objectives and beneficial effects of the present invention can be better achieved and realized.

[0023] As a preferred technical solution of the present invention, the filtration method in step (1) includes filtration using an ultrafiltration membrane.

[0024] Preferably, the pore size of the ultrafiltration membrane is 20-80 nm, for example, it can be 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm or 80 nm, etc.

[0025] Preferably, the pressure difference of the filtration membrane is 0.01-0.1 MPa, for example, it can be 0.01 MPa, 0.02 MPa, 0.03 MPa, 0.04 MPa, 0.05 MPa, 0.06 MPa, 0.07 MPa, 0.08 MPa, 0.09 MPa or 0.1 MPa, etc.

[0026] It should be noted that the present invention has no special requirements for the material of the filtration membrane, and ultrafiltration membranes made of commonly used materials in the art are applicable, including but not limited to, for example: ultrafiltration membranes made of polyvinyl chloride, ultrafiltration membranes made of polypropylene, etc.; similarly, the present invention has no special requirements for the pore density of the ultrafiltration membrane, and ultrafiltration membranes with pore densities in the art are applicable, including but not limited to, for example: 10 pores / cm 2 .

[0027] In the present invention, the concentration of succinic acid in the succinic acid fermentation broth filtered using the ultrafiltration membrane is 60 - 120 g / L, for example, it can be 60 g / L, 65 g / L, 70 g / L, 75 g / L, 80 g / L, 85 g / L, 90 g / L, 95 g / L, 110 g / L, 105 g / L, 110 g / L, 115 g / L or 120 g / L, etc.

[0028] Preferably, the temperature of the filtration is 40 - 60 °C, for example, it can be 40 °C, 42 °C, 44 °C, 46 °C, 48 °C, 50 °C, 52 °C, 54 °C, 56 °C, 58 °C or 60 °C, etc.

[0029] As a preferred technical solution of the present invention, R1 represents any one of isooctyl ester group, dimethylheptyl ester group or 2 - ethylhexyl ester group.

[0030] Preferably, R2 and R3 each independently represent any one of methyl, ethyl, propyl, hydroxyl, isooctyl ester group, dimethylheptyl ester group or 2 - ethylhexyl ester group.

[0031] As a preferred technical solution of the present invention, the complexing agent is selected from any one or a combination of at least two of diisooctyl phosphate, dimethylheptyl methylphosphonate or 2 - ethylhexyl 2 - ethylhexylphosphate monoester.

[0032] In the present invention, the diisooctyl phosphate is

[0033] The dimethylheptyl methylphosphonate is

[0034] The 2 - ethylhexyl 2 - ethylhexylphosphate monoester is

[0035] In the present invention, by selecting a specific phosphate ester with a specific structural formula as a complexing agent, an extractant with excellent performance is prepared. The mechanism of complex extraction is a separation method based on the interaction between the Lewis acid (or base) functional groups of the solute and the Lewis base (or acid) functional groups in the extractant. Based on the Lewis acid-base theory, -COOH in succinic acid belongs to the Lewis acidic functional group, so succinic acid is a Lewis acid. The P=O bond in the phosphate ester belongs to the Lewis basic functional group, and the P=O base is a polar covalent bond with stable properties, large bond energy, and strong complexing ability. Therefore, using the phosphate ester as a complexing agent and combining it with a cosolvent to form a mixed extractant system can form a complex with succinic acid and improve the extraction efficiency.

[0036] Preferably, the cosolvent is selected from any one or a combination of at least two of n-heptanol, isooctanol, n-nonanol, or n-decanol.

[0037] In the present invention, by selecting an alcohol solvent with a specific number of carbon atoms as a cosolvent, an excellent succinic acid extractant is prepared. If the number of carbon atoms in the alcohol solvent is too small, the flash point is low, the flammability increases, the hydrophobicity decreases, and the solubility in water increases, which is not conducive to extraction phase separation; if the number of carbon atoms in the alcohol solvent is too large, the solubility of the complex in the cosolvent decreases significantly, which is not conducive to back extraction.

[0038] As a preferred technical solution of the present invention, the volume ratio of the complexing agent to the cosolvent is 1:(0.1 - 10), for example, it can be 1:0.1, 1:0.5, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, or 1:10, etc.

[0039] In the present invention, by controlling the volume ratio of the complexing agent to the cosolvent within a specific range, an extractant with excellent performance is prepared, balancing the yields of forward extraction and reverse extraction, and significantly improving the total recovery rate of succinic acid.

[0040] As a preferred technical solution of the present invention, the volume ratio of the extractant A to the material to be extracted A is (3 - 5):1, for example, it can be 3:1, 3.2:1, 3.4:1, 3.6:1, 3.8:1, 4:1, 4.2:1, 4.4:1, 4.6:1, 4.8:1, or 5:1, etc.

[0041] It should be noted that in the present invention, the number of stages of multi-stage forward cross-flow extraction is 2 - 3. Among them, the material to be extracted A is the filtrate or raffinate after filtration of the succinic acid fermentation broth. In the first forward cross-flow extraction, the material to be extracted A is the filtrate after filtration of the succinic acid fermentation broth. In the 2nd - 3rd forward cross-flow extractions, the material to be extracted A is the raffinate after extraction of the filtrate of the succinic acid fermentation broth.

[0042] In the first to third forward cross-current extractions, the volume ratio of extractant A to the substance to be extracted A is (3 - 5):1.

[0043] As a preferred technical solution of the present invention, the number of stages of the multi-stage forward cross-current extraction is 2 - 3 stages, for example, it can be 2 stages or 3 stages.

[0044] Preferably, the temperature of the multi-stage forward cross-current extraction is 20 - 60 °C, for example, it can be 20 °C, 25 °C, 30 °C, 35 °C, 40 °C, 45 °C, 50 °C, 55 °C or 60 °C, etc.

[0045] As a preferred technical solution of the present invention, the extractant B includes water.

[0046] Preferably, the volume ratio of extractant B to the substance to be extracted B is (3 - 5):1, for example, it can be 3:1, 3.2:1, 3.4:1, 3.6:1, 3.8:1, 4:1, 4.2:1, 4.4:1, 4.6:1, 4.8:1 or 5:1, etc.

[0047] Similarly, in the present invention, since the number of stages of the multi-stage counter-current extraction is 3 - 5 stages, therefore, in the multi-stage counter-current extraction, wherein the substance to be extracted B is the succinic acid-loaded organic phase described in step (1) or the mixture containing extractant A described in step (2). In the first counter-current extraction, the substance to be extracted B is the succinic acid-loaded organic phase obtained in step (1), and in the second to fifth counter-current extractions, the substance to be extracted B is the mixture containing extractant A obtained in step (2);

[0048] In the first to fifth counter-current extractions, the volume ratio of extractant B to the substance to be extracted is (3 - 5):1.

[0049] As a preferred technical solution of the present invention, the number of stages of the multi-stage counter-current extraction is 3 - 5 stages, for example, it can be 3 stages, 4 stages or 5 stages.

[0050] Preferably, the temperature of the multi-stage counter-current extraction is 40 - 80 °C, for example, it can be 40 °C, 45 °C, 50 °C, 55 °C, 60 °C, 65 °C, 70 °C, 75 °C or 80 °C, etc.

[0051] In the present invention, by setting the process conditions of the multi-stage forward cross-current extraction and the multi-stage counter-current extraction, the extraction efficiency of succinic acid is further improved.

[0052] As a preferred technical solution of the present invention, the method of the post-treatment includes evaporation and concentration, cooling crystallization, centrifugation and drying.

[0053] Preferably, the temperature for evaporation and concentration is 60 - 80°C (such as 60°C, 62°C, 64°C, 66°C, 68°C, 70°C, 72°C, 74°C, 76°C, 78°C or 80°C, etc.), the system pressure is 10 - 40 KPa (such as 10 KPa, 12 KPa, 15 KPa, 18 KPa, 20 KPa, 22 KPa, 24 KPa, 27 KPa, 30 KPa, 33 KPa, 36 KPa or 40 KPa, etc.), and the concentration multiple is 2 - 10 times (such as 2 times, 3 times, 4 times, 5 times, 6 times, 7 times, 8 times, 9 times or 10 times, etc.).

[0054] Preferably, the temperature for cooling and crystallization is 10 - 30°C (such as 10°C, 12°C, 14°C, 16°C, 18°C, 20°C, 22°C, 24°C, 26°C, 28°C or 30°C, etc.), and the system pressure is 60 - 80 KPa (such as 60 KPa, 62 KPa, 64 KPa, 66 KPa, 68 KPa, 70 KPa, 72 KPa, 74 KPa, 76 KPa, 78 KPa or 80 KPa, etc.).

[0055] Preferably, the temperature for drying is 75 - 85°C, such as 75°C, 76°C, 77°C, 78°C, 79°C, 80°C, 81°C, 82°C, 83°C, 84°C or 85°C, etc.

[0056] In the present invention, the method for extracting succinic acid from the fermentation broth specifically comprises the following steps:

[0057] (1) At 40 - 60°C, after filtering the succinic acid fermentation broth with an ultrafiltration membrane having a pore size of 20 - 80 nm, at 20 - 60°C, perform multi-stage forward cross-flow extraction with extractant A to obtain a succinic acid-loaded organic phase and a raffinate phase; wherein, the volume ratio of extractant A to the substance to be extracted A is (3 - 5):1, the number of stages of multi-stage forward cross-flow extraction is 2 - 3 stages, and the substance to be extracted A is the filtrate after filtering the succinic acid fermentation broth or the raffinate phase obtained in step (1);

[0058] (2) At 40 - 80 °C, use extractant B to perform multi - stage counter - current extraction on the succinic acid - loaded organic phase to obtain an aqueous solution of succinic acid and extractant A. Evaporate and concentrate the aqueous solution of succinic acid at a temperature of 60 - 80 °C and a system pressure of 10 - 40 KPa. After the concentration multiple is 2 - 10 times, perform cooling crystallization at a temperature of 10 - 30 °C and a system pressure of 60 - 80 KPa, centrifuge, and dry at 75 - 85 °C to complete the extraction of succinic acid from the fermentation broth and obtain succinic acid crystals; wherein, the volume ratio of extractant B to the substance to be extracted B is (3 - 5):1, the number of stages of multi - stage counter - current extraction is 3 - 5, and the substance to be extracted B is the succinic acid - loaded organic phase obtained in step (1) or the mixture containing extractant A obtained in step (2).

[0059] It should be noted that in the present invention, there is no special limitation on the concentration of succinic acid in the fermentation broth. Fermentation broths with conventional succinic acid concentrations in the art can all use the method provided by the present invention to extract succinic acid from the fermentation broth.

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

[0061] (1) The present invention uses the solvent extraction method to extract succinic acid crystals from the fermentation broth by using a specific extractant A, eliminating steps such as the calcium salt method, ammonium salt method, ion exchange, decolorization, and electrodialysis used in traditional purification methods.

[0062] (2) The solvent extraction method used in the present invention has the advantages of simple operation, high selectivity for the extraction of succinic acid, no need to introduce acids and bases during the extraction process, and no generation of high - salt wastewater; moreover, the complexing extraction agent system (extractant A) used in the present invention has the advantages of high selectivity, high yield, low energy consumption, and no introduction of acids and bases for the extraction of succinic acid, and balances the forward extraction yield and the reverse extraction yield during the extraction process of the fermentation broth. The forward extraction yield ≥ 96.85%, the reverse extraction yield ≥ 96.24%, the difference between the forward extraction yield and the reverse extraction yield ≤ 1.32%. After extraction, the total yield of succinic acid is 93.21 - 97.41%, and the total yield of the purified succinic acid crystals obtained is 80.1 - 85.82%, with a purity of 99.75 - 99.82%; and all the extractants used in the extraction are recycled and reused after regeneration.

[0063] (3) Compared with ordinary physical extraction, the mixed extractant provided by the present invention greatly improves the extraction efficiency through complexing extraction; compared with amine - type extractants, phosphine oxide - type extractants have more balanced forward and reverse extraction yields, so the total extraction yield is higher; in addition, the properties of phosphine oxide - type extractants are milder and less toxic, and can be applied to the food and pharmaceutical industries. Detailed implementation mode

[0064] To facilitate the understanding of the present invention, the following examples are listed. Those skilled in the art should understand that the said examples are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0065] Examples 1 - 22 and Comparative Examples 1 - 3

[0066] Examples 1 - 22 and Comparative Examples 1 - 3 respectively provide a method for extracting succinic acid from fermentation broth, which specifically includes the following steps:

[0067] (1) At 50 °C, use an ultrafiltration membrane with a pore size of 50 nm (purchased from Jiangsu Jiusihe Biotechnology Co., Ltd., with a pore density of 10 pores / cm 2 ) to filter the succinic acid fermentation broth to obtain a filtrate;

[0068] Among them, the concentration of succinic acid in the succinic acid fermentation broth used in Examples 1, 4 - 22, and Comparative Examples 1 - 3 is 78.1 g / L; the concentration of succinic acid in the succinic acid fermentation broth used in Example 2 is 68.2 g / L; the concentration of succinic acid in the succinic acid fermentation broth used in Example 3 is 62.1 g / L;

[0069] Perform multi - stage forward cross - flow extraction using extractant A and the substance to be extracted A to obtain a succinic acid - loaded organic phase and a raffinate phase (specific process parameters are shown in Tables 1 - 4);

[0070] Among them, the substance to be extracted A is the filtrate or raffinate phase after filtering the succinic acid fermentation broth. In the first forward cross - flow extraction, the substance to be extracted A is the filtrate after filtering the succinic acid fermentation broth. In the 2nd - 3rd forward cross - flow extractions, the substance to be extracted A is the raffinate phase after extraction of the filtrate of the succinic acid fermentation broth;

[0071] (2) Use extractant B to perform multi - stage reverse cross - flow extraction on the succinic acid - loaded organic phase to obtain an aqueous succinic acid solution and a mixture containing extractant A (specific process parameters are shown in Tables 1 - 4);

[0072] Among them, the substance to be extracted B is the succinic acid - loaded organic phase and the mixture containing extractant A. In the first reverse cross - flow extraction, the substance to be extracted B is the succinic acid - loaded organic phase. In the 2nd - 5th reverse cross - flow extractions, the substance to be extracted B is the mixture containing extractant A;

[0073] Then, at a temperature of 70 °C and a system pressure of 30 KPa, evaporate and concentrate the aqueous succinic acid solution. After the concentration multiple is 8 times, perform cooling crystallization at a temperature of 20 °C and a system pressure of 70 KPa, centrifuge, and dry at 80 °C to complete the extraction of succinic acid from the fermentation broth and obtain succinic acid crystals.

[0074] Table 1

[0075]

[0076]

[0077]

[0078] Table 2

[0079]

[0080]

[0081] Table 3

[0082]

[0083]

[0084] Table 4

[0085]

[0086]

[0087] Among them, the test method for the concentration of succinic acid in the filtrate is as follows: tested by HLPC, using a Bio-RAD 442864 chromatographic column, with 5 mmol / L H2SO4 as the mobile phase, a flow rate of 0.5 mL / min, a column temperature of 35 °C, a detector temperature of 35 °C, a wavelength of 210 nm, and an injection volume of 20 μL for the filtrate in the above examples and comparative examples;

[0088] The test method for the moisture content of succinic acid crystals is: tested according to GB / T 34686-2017;

[0089] The test method for the purity of succinic acid is: tested according to GB / T 34686-2017.

[0090] As can be seen from the above content, the solvent extraction method used in the present invention has the advantages of simple operation, high selectivity for the extraction of succinic acid, no need to introduce acids and bases during the extraction process, and no generation of high-salt wastewater; moreover, the complex extraction agent system (extraction agent A) used in the present invention has the advantages of high selectivity, high yield, low energy consumption, and no introduction of acids and bases for the extraction of succinic acid, and balances the forward extraction yield and the reverse extraction yield in the extraction process of the fermentation broth. The forward extraction yield ≥ 96.85%, the reverse extraction yield ≥ 96.24%, and the difference between the forward extraction yield and the reverse extraction yield ≤ 1.32%. After extraction, the total yield of succinic acid is 93.21 - 97.61%, and the total yield of the purified succinic acid crystals obtained is 80.1 - 86.06%, with a purity of 99.75 - 99.82%; and all the extraction agents used in the extraction are recycled and reused after regeneration.

[0091] As can be seen from the content of Examples 1-22, the present invention further improves the extraction effect of the extractant on the fermentation broth and balances the positive extraction yield and the counter-extraction yield in the fermentation broth extraction process by regulating process conditions such as the volume ratio of the complexing agent and the co-solvent, the number of stages of multi-stage forward cross-flow extraction, the number of stages of multi-stage reverse cross-flow extraction, and the dosages of extractant A and extractant B.

[0092] Furthermore, as can be seen from the content of Examples 1-22, the present invention can prepare succinic acid with a relatively high total extraction yield and high purity and avoid waste of raw materials by controlling the mass ratios of extractant A to the substance A to be extracted and extractant B to the substance B to be extracted within specific ranges. If the dosage of extractant A or extractant B is too small, the total extraction yield of succinic acid is relatively low; if the dosage of extractant A or extractant B is too large, there is not much improvement in the yield of succinic acid, but instead, extractant A and extractant B will be wasted.

[0093] Meanwhile, the present invention can prepare succinic acid with a relatively high total extraction yield, high purity and high production efficiency by controlling the number of stages of multi-stage forward cross-flow extraction and the number of stages of multi-stage reverse cross-flow extraction within specific ranges. If the number of stages of multi-stage forward cross-flow extraction and the number of stages of multi-stage reverse cross-flow extraction are too small, the total extraction yield of the prepared succinic acid is relatively low; if the number of stages of multi-stage forward cross-flow extraction and the number of stages of multi-stage reverse cross-flow extraction are too large, although the total extraction yield of succinic acid is slightly increased, it will cause waste of extractant A and extractant B and reduce the production efficiency.

[0094] As can be seen from the content of Example 1 and Comparative Examples 1-3, the present invention further improves the extraction effect of the extractant on the fermentation broth and balances the positive extraction yield and the counter-extraction yield in the fermentation broth extraction process through the action of specific complexing agent and co-solvent.

[0095] In summary, the present invention uses the solvent extraction method to extract succinic acid crystals from the fermentation broth by using specific extractant A, eliminating steps such as the calcium salt method, ammonium salt method, ion exchange, decolorization and electrodialysis used in traditional purification methods.

[0096] Moreover, the solvent extraction method used in the present invention has advantages such as simple operation, high selectivity for the extraction of succinic acid, no need to introduce acids and bases during the extraction process and no generation of high-salt wastewater; and the complexing extraction agent system (extractant A) used in the present invention has advantages such as high selectivity, high yield, low energy consumption and no introduction of acids and bases for the extraction of succinic acid, and balances the positive extraction yield and the counter-extraction yield in the fermentation broth extraction process; and all the extractants used in the extraction are recycled and reused after regeneration.

[0097] Compared with ordinary physical extraction, the mixed extractant provided by the present invention greatly improves the extraction efficiency through complexation extraction; compared with amine extractants, phosphine oxide extractants have more balanced forward and reverse extraction yields, so the total extraction yield is higher; in addition, the properties of phosphine oxide extractants are milder and less toxic, and can be applied to the food and pharmaceutical industries.

[0098] The applicant declares that the present invention uses the above embodiments to illustrate the detailed process flow of the present invention, but the present invention is not limited to the above detailed process flow, that is, it does not mean that the present invention must rely on the above detailed process flow to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent replacement of each raw material of the product of the present invention, the addition of auxiliary components, the selection of specific methods, etc. all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for extracting succinic acid from fermentation broth, characterized in that, The method includes the following steps: (1) After filtering the succinic acid fermentation broth, perform multi-stage forward cross-flow extraction using extractant A to obtain a succinic acid-loaded organic phase and a raffinate phase; (2) Perform multi-stage reverse cross-flow extraction on the succinic acid-loaded organic phase using extractant B to obtain an aqueous succinic acid solution and a mixture containing extractant A. After post-treatment, complete the extraction of succinic acid from the fermentation broth to obtain succinic acid crystals; The extractant A includes a complexing agent and a co-solvent having the structure shown in Formula I below; Wherein, R1 represents an ester group with 1-10 carbon atoms; R2 and R3 each independently represent any one of an alkyl group with 1-10 carbon atoms, an ester group with 1-10 carbon atoms, or a hydroxyl group; The co-solvent is an alcohol solvent containing 7-10 carbon atoms.

2. The method according to claim 1, wherein The filtration method in step (1) includes filtration using an ultrafiltration membrane; Preferably, the pore size of the ultrafiltration membrane is 20-80 nm.

3. The method according to claim 1 or 2, characterized in that, The R1 represents any one of isooctyl ester group, dimethylheptyl ester group, or 2-ethylhexyl ester group; Preferably, R2 and R3 each independently represent any one of methyl, ethyl, propyl, hydroxyl, isooctyl ester group, dimethylheptyl ester group, or 2-ethylhexyl ester group.

4. The method according to claim 1, wherein The complexing agent is selected from any one or a combination of at least two of diisooctyl phosphate, dimethylheptyl methylphosphonate, or 2-ethylhexyl 2-ethylhexyl phosphate monoester; Preferably, the co-solvent is selected from any one or a combination of at least two of n-heptanol, isooctanol, n-nonanol, or n-decanol.

5. The method according to claim 1, characterized in that The volume ratio of the complexing agent to the co-solvent is 1:(0.1-10).

6. The method according to claim 1, characterized in that, The volume ratio of the extractant A to the substance to be extracted A is (3-5):1; Wherein, the substance to be extracted A is the filtrate after filtering the succinic acid fermentation broth or the raffinate phase obtained in step (1).

7. The method according to claim 1, characterized in that, The number of stages of the multi-stage forward cross-flow extraction is 2-3 stages; Preferably, the temperature of the multi-stage forward cross-flow extraction is 20-60 °C.

8. The method according to claim 1, characterized in that The extractant B includes water; Preferably, the volume ratio of the extractant B to the substance to be extracted B is (3-5):1; Wherein, the substance to be extracted B is the succinic acid-loaded organic phase obtained in step (1) or the mixture containing extractant A obtained in step (2).

9. The method according to claim 1, wherein The number of stages of the multi-stage reverse cross-flow extraction is 3-5 stages; Preferably, the temperature of the multi-stage reverse cross-flow extraction is 40-80 °C.

10. The method according to claim 1, characterized in that The post-treatment method includes evaporation and concentration, cooling crystallization, centrifugation, and drying.

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