Potassium type neutralization regulation and control method in sebacic acid fermentation process and application

Abstract

The invention relates to a potassium type neutralization regulation and control method in a sebacic acid fermentation process and application, a potassium hydroxide solution is used as a neutralizer, sebacic acid generated by microorganisms is neutralized in situ in the fermentation process, a product is accumulated in a high-solubility sylvite form, and the problem of sodion pollution caused by use of sodium hydroxide in a traditional process is avoided. The method comprises the core steps of strain activation, seed solution preparation, fermentation culture medium preparation, fermentation starting, pH dynamic regulation and control and product extraction. By automatically controlling the pH value to be 4.5-6.8, a 20-40% potassium hydroxide solution is fed, so that the fermentation acid production concentration reaches 180g / L or above. A potassium sulfate byproduct which is easy to dissolve in water is generated through subsequent acidification and crystallization, efficient separation can be achieved through washing, and a low-sodium / sodium-free high-purity sebacic acid product is obtained. According to the method, potassium ions are used as necessary elements for microbial growth to optimize a metabolic environment, so that the viscosity of fermentation liquor is remarkably reduced, dissolved oxygen transfer is improved, the environmental protection pressure of downstream extraction is relieved, and the production efficiency and the product quality are improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of fermentation production of long-chain dicarboxylic acids, in particular to a potassium-type neutralization regulation method in a sebacic acid fermentation process and application. BACKGROUND

[0002] Long-chain dicarboxylic acids (LCDA) are key monomers for the synthesis of high-performance polyamides, polyesters, hot-melt adhesives, perfumes and plasticizers. Sebacic acid (C10) is one of the most important varieties, and is currently mainly produced by microbial fermentation, that is, using Candida tropicalis and other engineering bacteria to oxidize n-alkanes.

[0003] In the biological fermentation process, the microorganism oxidizes the alkane substrate into dicarboxylic acid, and the continuous release of protons leads to a sharp drop in the pH of the fermentation broth. In order to maintain the optimal activity of the bacteria and relieve the product inhibition, an alkaline neutralizing agent must be continuously fed in real time. The existing industrial production generally uses sodium hydroxide (NaOH) solution as the neutralizing agent, and the product exists in the form of sodium sebacate in the fermentation broth after neutralization.

[0004] However, the sodium-type process has the following fatal defects: (1) great difficulty in downstream extraction and great environmental pressure: sulfuric acid needs to be added during acidification extraction, and a large amount of sodium sulfate by-product is generated. Sodium sulfate has low value, high separation cost, and is easy to cause environmental pollution, which becomes a bottleneck restricting the sustainable development of the industry. (2) poor physical properties of the fermentation broth and low mass transfer efficiency: the solubility of sodium sebacate is relatively low (about 10 g / L at 20 DEG C), and high concentration can easily cause the viscosity of the fermentation broth to increase sharply, leading to uneven mixing, blocked oxygen transfer, inhibited bacterial growth and acid production efficiency. (3) introduction of non-essential ions: high concentration of sodium ions is not essential for microbial growth, and excessive accumulation may interfere with the cell membrane potential and the activity of key enzyme systems, limiting the fermentation conversion rate and the concentration of the final product. (4) affecting product quality: the residual sodium ions cause unstable performance of the polymer product, and especially in high molecular polymerization reactions, trace amounts of sodium salt can cause chain rupture or crosslinking side reactions.

[0005] Therefore, it is of great practical significance to develop a new neutralizing agent system that eliminates sodium ion pollution from the source, improves fermentation performance and simplifies downstream extraction, for the green upgrading of the sebacic acid industry. SUMMARY

[0006] The main purpose of the present application is to overcome the defects of serious sodium ion pollution, difficult downstream extraction, and great environmental pressure caused by using sodium hydroxide neutralizer in the existing sebacic acid fermentation process, and to provide a new potassium type neutralization regulation method and application in the sebacic acid fermentation process, so as to solve the technical problem of completely eliminating the introduction of sodium ions from the production source, converting by-products into high-solubility potassium sulfate to realize clean separation, thereby obtaining low-sodium / no-sodium high-purity sebacic acid product and reducing the burden of environmental treatment, thereby being more suitable for practical use and having industrial utilization value.

[0007] Another purpose of the present application is to provide a potassium type neutralization regulation method and application in the sebacic acid fermentation process, which solves the technical problem of optimizing the metabolic environment of the microbial body by using potassium ions as essential elements for microbial growth, significantly reducing the viscosity of the fermentation broth by improving the solubility of the product salt, improving the oxygen transfer efficiency, thereby increasing the fermentation acid concentration to more than 180g / L and shortening the fermentation cycle, thereby being more suitable for practical use.

[0008] Still another purpose of the present application is to provide a potassium type neutralization regulation method and application in the sebacic acid fermentation process, which solves the technical problem of using the huge solubility difference between potassium sulfate and sebacic acid in the terminal extraction process to realize the complete separation of by-products and target products through simple washing, simplifying the extraction process, reducing equipment investment and operating cost, thereby being more suitable for practical use.

[0009] Still another purpose of the present application is to provide a potassium type neutralization regulation method and application in the sebacic acid fermentation process, which solves the technical problem of replacing the difficult-to-handle sodium sulfate by-product in the traditional sodium type process with the resourceful potassium sulfate mother liquor that can be used or conveniently disposed of, realizing the green transformation of fermentation production, thereby being more suitable for practical use.

[0010] The purpose of the present application and the solution to the technical problem are realized by adopting the following technical scheme.

[0011] A method for potassium neutralization regulation during sebacic acid fermentation includes the following steps: (1) Strain activation and seed culture preparation: The sebacic acid producing strain is inoculated onto an agar slant medium for activation, and then transferred to a seed culture medium for cultivation until the logarithmic growth phase; (2) Fermentation medium preparation: A fermentation medium containing carbon source, nitrogen source, inorganic salts and trace elements is prepared, wherein the carbon source is n-alkanes, and no additional potassium salts are added to the medium; (3) Fermentation start-up: The seed culture is transferred into a fermenter at an inoculation rate of 5%-15%, and the temperature is controlled at 28-30℃ and the pressure at 0.05℃. -0.10MPa, stirring speed 300-600rpm, aeration rate 0.5-1.0vvm, maintain dissolved oxygen at 20-40% saturation; (4) pH dynamic regulation of acid production: when the pH of the fermentation broth drops to 4.0-5.0 due to the generation of sebacic acid, start adding 20-40wt% potassium hydroxide solution to maintain the pH in the range of 6.4-6.8, so that the generated sebacic acid dissolves and accumulates in the form of potassium salt until the acid production concentration reaches 150-220g / L; (5) Product extraction: after fermentation, add sulfuric acid to acidify to pH 1.5-3.5, so that potassium sebacic acid salt is converted into sebacic acid crystals and precipitates out, while potassium sulfate is retained in the mother liquor. Separate by centrifugation and wash and dry to obtain sebacic acid product.

[0012] The objectives of this invention and the technical problems it addresses can be further achieved through the following technical measures:

[0013] The aforementioned method and application of potassium neutralization control in the sebacic acid fermentation process, wherein the concentration of potassium hydroxide solution is 30wt%, the pH control range is 6.4-6.8, the control accuracy is ±0.2, and automatic feeding is achieved through a closed-loop feedback control system composed of a pH sensor and an alkali pump.

[0014] The aforementioned method and application of potassium neutralization regulation in the sebacic acid fermentation process, wherein the sebacic acid producing strain is Candida tropicalis or its genetically engineered strain, which is physiologically adapted to potassium ions and tolerant to high concentrations of the product.

[0015] The aforementioned method and application of potassium neutralization regulation in the sebacic acid fermentation process, wherein the carbon source is n-decane, the initial concentration of which in the fermentation medium is 10-20% (v / v), and the alkane conversion rate is greater than 90% at the end of fermentation.

[0016] The aforementioned method and application of potassium neutralization regulation in the sebacic acid fermentation process, wherein the amount of sulfuric acid added in the acidification extraction process is 1.0-1.2 times the theoretical molar amount, the acidification temperature is 80-95℃, the crystallization pH is 2.0-3.0, and the solubility of potassium sulfate by-product in the mother liquor is greater than 120g / L.

[0017] The aforementioned potassium-type neutralization control method and its application in the sebacic acid fermentation process, wherein the viscosity of the fermentation broth is maintained at 50-100 mPa·s throughout the acid production stage, which is significantly lower than the 200-300 mPa·s of the sodium-type process, and the dissolved oxygen transfer coefficient is increased by 30-50%.

[0018] The aforementioned method and application of potassium neutralization control in the sebacic acid fermentation process, wherein the final sebacic acid product has a sodium ion content of less than 100 ppm, a potassium ion residue of less than 50 ppm, and a product purity of ≥99.5%, meeting the requirements for high-performance polymer synthesis.

[0019] The objective of this invention and the technical problem it solves are further achieved by the following technical solutions. According to this invention:

[0020] A potassium-type neutralization and regulation system for sebacic acid fermentation includes: a fermenter, a potassium hydroxide storage tank, a pH sensor, a controller, and an alkali pump. The pH sensor monitors the pH value of the fermentation broth in real time and transmits the signal to the controller. The controller controls the alkali pump to add potassium hydroxide solution from the potassium hydroxide storage tank to the fermenter according to a preset pH range, forming a closed-loop feedback control circuit to achieve precise and stable pH regulation during the acid production stage.

[0021] The objectives of this invention and the technical problems it addresses can be further achieved through the following technical measures:

[0022] The aforementioned method and application of potassium neutralization regulation in the sebacic acid fermentation process, wherein the regulation system also includes a dissolved oxygen electrode, a temperature sensor and a stirring speed controller, and maintains the optimal metabolic environment of the fermentation process through multi-parameter linkage control, so as to maximize the synergistic effect of potassium ion regulation and dissolved oxygen transfer.

[0023] The aforementioned potassium neutralization control method and application in the sebacic acid fermentation process, wherein the potassium hydroxide storage tank is made of stainless steel or fiberglass and is equipped with a heating and insulation device to maintain the alkaline solution temperature at 40-60℃ to prevent crystallization. The alkaline solution pump is a metering pump or peristaltic pump resistant to strong alkali corrosion with an accuracy of ±2%.

[0024] Compared with the prior art, the present invention has significant advantages and beneficial effects. As can be seen from the above technical solution, in order to achieve the aforementioned objectives, the main technical contents of the present invention are as follows:

[0025] This invention proposes a method for potassium-based neutralization and regulation in the fermentation production of sebacic acid. The method is characterized by using potassium hydroxide as the sole neutralizing agent. During the acid-producing stage of microbial fermentation, dynamic pH control is used to dissolve and accumulate the generated sebacic acid in the form of potassium salt. After fermentation, sulfuric acid acidification causes the sebacic acid to crystallize and precipitate, simultaneously generating water-soluble potassium sulfate as a byproduct to achieve product separation. Specifically, the method includes:

[0026] Sebacic acid-producing strains were inoculated into the fermentation medium, and the fermentation conditions were controlled for cultivation.

[0027] When the pH of the fermentation broth drops due to acid production, potassium hydroxide solution is added to maintain the pH within the range most suitable for cell growth and acid production, so that sebacic acid dissolves in the fermentation broth in the form of potassium salt.

[0028] After acid production is complete, sulfuric acid is added for acidification. The byproducts are separated by utilizing the difference in solubility between potassium sulfate and sebacic acid. Sebacic acid product is obtained through solid-liquid separation and washing.

[0029] Preferably, the concentration of the potassium hydroxide solution is 20-40 wt%, and automatic feeding is achieved through a feedback control system consisting of a pH sensor and a feed pump to control the pH atmosphere.

[0030] Preferably, the sebacic acid producing strain is Candida tropicalis, and the fermentation carbon source is n-alkanes.

[0031] Preferably, the fermentation conditions include: temperature 28-32℃, dissolved oxygen saturation of 20-40%, tank pressure of 0.05-0.10MPa, and the viscosity of the culture medium during the acid production stage of fermentation is controlled below 100mPa·s.

[0032] Preferably, no additional potassium salt is needed in the fermentation medium; the potassium ions required for cell growth and metabolism are provided in situ by potassium hydroxide neutralizer.

[0033] Preferably, the sulfuric acid acidification process is controlled at a pH of 1.5-3.5, an acidification temperature of 60-95℃, and the amount of sulfuric acid added is 1.0-1.2 times the theoretical molar amount.

[0034] Preferably, the final acid concentration at the end of fermentation reaches 150-220 g / L, the alkane conversion rate is greater than 90%, and the fermentation cycle is 120-168 hours.

[0035] Preferably, the product extraction step includes: centrifuging the acidified liquid to obtain crude sebacic acid, washing it with deionized water at 50-80℃ to remove residual potassium sulfate, and drying it to obtain high-purity sebacic acid with a sodium ion content of less than 100ppm.

[0036] This invention proposes an application of a method for neutralizing and regulating potassium-type sebacic acid fermentation, which increases the solubility of product salts in the fermentation broth to over 150 g / L and reduces the viscosity of the fermentation broth to less than 1 / 3 of that in the sodium-type process.

[0037] Furthermore, the final sebacic acid product contains less than 50 ppm of potassium ions, and the potassium sulfate byproduct has a solubility of more than 100 g / L in the mother liquor, enabling resource recovery or environmentally friendly treatment.

[0038] As described above, this invention provides a potassium-based neutralization and regulation method for sebacic acid fermentation, belonging to the field of long-chain dicarboxylic acid fermentation engineering technology. This method uses potassium hydroxide solution as a neutralizing agent to neutralize the sebacic acid produced by microorganisms in situ during fermentation, accumulating the product as a highly soluble potassium salt, thus avoiding sodium ion pollution problems caused by the use of sodium hydroxide in traditional processes. The core steps include: strain activation, seed culture preparation, fermentation medium preparation, fermentation start-up, dynamic pH control, and product extraction. By automatically controlling the pH within the range of 4.5-6.8 and adding 20-40% potassium hydroxide solution, the acid concentration produced during fermentation reaches above 180 g / L. Subsequent acidification and crystallization generate water-soluble potassium sulfate byproducts, which can be efficiently separated by washing to obtain a low-sodium / sodium-free high-purity sebacic acid product. This invention utilizes potassium ions as an essential element for microbial growth to optimize the metabolic environment, significantly reducing the viscosity of the fermentation broth, improving dissolved oxygen transfer, alleviating the environmental pressure on downstream extraction, and improving production efficiency and product quality.

[0039] The core technical principle of this invention is based on a triple synergistic mechanism of "in-situ neutralization - ion regulation - terminal purification":

[0040] During the fermentation acid production stage, potassium hydroxide solution is added in real time via an automatic pH control system to react with the H+ produced by the microorganisms. + Transient reaction (KOH + H+) + →K + The fermentation broth pH is precisely stabilized within the optimal range (6.4-6.8) using H2O. Simultaneously, the generated sebacic acid is rapidly converted into highly soluble potassium sebacic acid (solubility >150g / L), completely eliminating product feedback inhibition.

[0041] K + It is a major intracellular cation and a cofactor for more than 30 key enzymes, including pyruvate kinase and ATPase, playing a crucial role in maintaining cell osmotic pressure and pH homeostasis. Compared to Na+... + K + It better meets the physiological needs of tropical Candida, optimizes the intracellular ionic environment, improves the cell's tolerance to high concentrations of products, and enables the final acid concentration of fermentation to exceed 180g / L.

[0042] After fermentation, sulfuric acid is added for acidification (R(COO-K)). + The reaction is: K₂SO₄ + H₂SO₄ → R(COOH)₂ + K₂SO₄. Potassium sulfate (K₂SO₄) has a solubility of up to 120 g / L in water at 25°C, while sebacic acid has a solubility of only 0.1 g / L. Utilizing this solubility difference, K₂SO₄ can be completely removed through simple centrifugation and washing. The mother liquor can then be directly used for potassium salt recovery or environmentally friendly treatment, yielding pure sebacic acid with a sodium content of <100 ppm.

[0043] By employing the above technical solution, the potassium neutralization regulation method and its application in the sebacic acid fermentation process of the present invention have at least the following advantages:

[0044] Significantly environmentally friendly: Sodium ion introduction is completely eliminated from the production source; the byproduct potassium sulfate has high solubility and is easy to separate, allowing for resource utilization or convenient treatment; environmental protection costs are reduced by more than 80%, achieving clean production of sebacic acid.

[0045] Fermentation efficiency is greatly improved: the solubility of potassium sebacic acid salt is more than 15 times that of sodium salt, the viscosity of fermentation broth is reduced by 60%-70%, the dissolved oxygen transfer efficiency is increased by 30%-50%, the acid production concentration exceeds 180g / L, and the fermentation cycle is shortened by 10-15%.

[0046] The product boasts superior quality: the final product contains less than 100 ppm sodium ions, less than 50 ppm potassium ions, and has a purity of ≥99.5%, fully meeting the stringent requirements for metal ion content in high-end polyamide, polyester, and other polymerization reactions.

[0047] The process is economically efficient: potassium hydroxide and sodium hydroxide have similar costs, but the improved fermentation efficiency and reduced subsequent environmental protection costs reduce the overall production cost by 15%-20%, and equipment investment is reduced due to the simplification of the extraction process.

[0048] Optimization of metabolic environment: Potassium ions, as an essential element for microbial physiology, are provided in situ to maintain the balance of intracellular and extracellular ions, enhance the tolerance of bacteria to high concentrations of products, and embody the green biomanufacturing concept of "nurturing instead of controlling".

[0049] Simple separation and purification: Taking advantage of the huge solubility difference between potassium sulfate and sebacic acid, complete separation can be achieved through simple centrifugation and washing, without the need for complex desalting equipment, and the extraction yield is increased to over 95%.

[0050] In summary, the unique potassium-based neutralization control method and its application in the sebacic acid fermentation process of this invention eliminates sodium ion pollution at the production source, optimizes the fermentation metabolic environment using potassium ions, and improves product solubility, ultimately achieving a synergistic innovation of efficient fermentation and clean separation. It possesses numerous advantages and practical value, and is truly innovative as no similar design has been publicly disclosed or used in similar methods. It represents a significant improvement in both methodological principle and function, demonstrating substantial technological advancement and producing user-friendly and practical results. Furthermore, it offers several enhanced effects compared to existing neutralization control methods in the sebacic acid fermentation process, making it more suitable for practical application and possessing broad industrial applicability. It is indeed a novel, progressive, and practical new design.

[0051] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0052] Description of the Drawings

[0053] Figure 1 Schematic diagram of the process flow for potassium neutralization regulation during sebacic acid fermentation. Detailed Implementation

[0054] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation methods, steps, structures, features, and effects of the potassium neutralization regulation method in the sebacic acid fermentation process proposed by the present invention.

[0055] Please see Figure 1 As shown in the preferred embodiment of the present invention, the method for potassium neutralization regulation in the sebacic acid fermentation process and its application mainly include the following steps:

[0056] Strain activation: Inoculate high sebacic acid-producing strains (such as Candida tropicalis NY-1) preserved at -80℃ glycerol onto YPD slant medium and incubate at 29℃ for 36-48 hours to activate them.

[0057] Seed culture: Pick a loopful of cells from the slant and transfer it to a 500mL shake flask containing 100mL of seed culture medium. The medium composition is: glucose 20g / L, yeast extract 10g / L, KH2PO4 1g / L, MgSO4·7H2O 0.5g / L, pH 6.0. Incubate at 29℃ and 200rpm for 16-24 hours until OD reaches 10 ... 600 Reaching 8-12.

[0058] Fermentation medium preparation: Add 2.5L of culture medium to a 5L fermenter. The formula is: 15% (v / v) n-decane, 3g / L urea, 1g / L ammonium sulfate, 2g / L KH₂PO₄, 1g / L MgSO₄·7H₂O, and 1mL / L trace element solution (containing Fe, Mn, Zn, and Cu). Key feature: No potassium salts are added to the culture medium; the required potassium ions are entirely provided by the subsequent neutralizing agent.

[0059] Fermentation start-up: Transfer the seed culture to the fermenter at a 10% inoculum volume (250 mL), and control the initial pH to 6.5. Set the culture conditions: temperature 29.0±0.5℃, tank pressure 0.06MPa, stirring speed 400rpm, aeration rate 0.6vvm. In the initial stage, the cells grow rapidly, consuming alkanes and nitrogen sources.

[0060] KOH neutralization control: When the pH naturally drops to 4.5, the automatic feed system of 30% (w / w) potassium hydroxide solution is started, and the pH operating range is set to 6.4-6.8. When pH ≤ 6.4, the alkali pump is started, and when pH ≥ 6.8, it is shut off to achieve precise feedback control. During this stage, acid production continues, sebacic acid dissolves in the form of potassium salt, the viscosity of the fermentation broth is maintained at 50-80 mPa·s (significantly lower than the 200-300 mPa·s of the sodium-type process), and dissolved oxygen is maintained at 30±5% saturation.

[0061] Fermentation termination: Fermentation is terminated when the alkane conversion rate is >95% (residual hydrocarbons <1%) and the acid concentration no longer increases. The total fermentation time is approximately 144-156 hours, with a final acid concentration of 185-200 g / L and a conversion rate of over 90%.

[0062] Product extraction:

[0063] Heat the fermentation broth to 85°C for 15 minutes to sterilize, then cool it to 70°C.

[0064] Slowly add 98% concentrated sulfuric acid to adjust the pH to 2.5, stir for 2 hours, and sebacic acid crystals will precipitate.

[0065] Separation was performed using a horizontal screw centrifuge to obtain sebacic acid wet cake and mother liquor containing K2SO4;

[0066] Wash the wet cake three times with 60℃ deionized water, each time using twice the mass of the wet cake, to thoroughly remove soluble salts.

[0067] The product was dried in a vacuum drying oven at 105℃ for 4 hours to obtain white sebacic acid crystals.

[0068] Example 1:

[0069] Strain activation: Candida tropicalis CGMCC No. 7306, preserved in glycerol at -80℃, was inoculated into YPD slant medium and cultured at 29℃ for 36 hours.

[0070] Seed culture: A loopful of bacterial cells was picked from the slant and inoculated into a 500 mL shake flask containing 100 mL of seed culture medium. The medium composition was: glucose 20 g / L, yeast extract 10 g / L, KH₂PO₄ 1 g / L, MgSO₄·7H₂O 0.5 g / L, pH 6.0. The culture was incubated at 29 °C and 200 rpm for 20 hours. OD₂... 600 It reached 10.2.

[0071] Fermentation medium preparation: Add 30L of culture medium to a 50L fermenter. The formula is: 15% (v / v) n-decane, 3g / L urea, 1g / L ammonium sulfate, 2g / L KH₂PO₄, 1g / L MgSO₄·7H₂O, and 1mL / L trace element solution (0.5g / L FeSO₄·7H₂O, 0.1g / L MnSO₄·H₂O, 0.1g / L ZnSO₄·7H₂O, 0.05g / L CuSO₄·5H₂O). No potassium salts were added to the culture medium.

[0072] Fermentation start-up: Transfer the seed culture to the fermenter at a 10% inoculum (3L), initial pH 6.5. Control culture conditions: temperature 29.0℃, tank pressure 0.06MPa, stirring speed 400rpm, aeration rate 0.6vvm, dissolved oxygen maintained at 30% saturation.

[0073] KOH neutralization and control: When the pH of the fermentation broth drops to 4.5 due to acid production, the automatic feeding system of 30wt% potassium hydroxide solution is activated, with the pH control range set at 6.4-6.8 (control accuracy ±0.2). The alkali pump starts when pH ≤ 6.4 and shuts off when pH ≥ 6.8, with this cycle controlled for 144 hours. During this process, the viscosity of the fermentation broth is maintained at 65-85 mPa·s, and the concentration of potassium sebacic acid salt continues to accumulate.

[0074] Fermentation termination: After 156 hours of fermentation, 0.8% of n-decane remains, the acid concentration reaches 192 g / L, and the alkane conversion rate is 96.2%. At this point, fermentation is stopped.

[0075] Product extraction: The fermentation broth was heated to 85℃ for sterilization for 15 minutes, cooled to 70℃, and concentrated sulfuric acid was slowly added to adjust the pH to 2.5 (the amount of sulfuric acid added was 1.1 times the theoretical molar amount). The mixture was stirred and crystallized for 2 hours. Separation was performed using a horizontal screw centrifuge to obtain sebacic acid wet cake and potassium sulfate mother liquor. The wet cake was washed three times with deionized water at 60℃, each time with twice the mass of the wet cake. Finally, it was vacuum dried at 105℃ for 4 hours to obtain the sebacic acid product.

[0076] Results: The product purity was 99.7%, sodium ion content was 85 ppm, potassium ion residue was 42 ppm, the total extraction yield was 95.3%, and the concentration of potassium sulfate mother liquor was 125 g / L, which can be directly recycled as potassium fertilizer.

[0077] Example 2:

[0078] The same strain and fermentation medium as in Example 1 were used, and the fermentation was carried out in a 5L fermenter (3L liquid volume). Fermentation conditions: temperature 28°C, tank pressure 0.05MPa, stirring 300rpm, aeration 0.5vvm, dissolved oxygen saturation 20%.

[0079] When the pH dropped to 5.0, a 20wt% potassium hydroxide solution was added, with the pH controlled within the range of 5.5-5.9. After 168 hours of fermentation, the acid concentration was 150 g / L, the alkane conversion rate was 90.1%, and the fermentation broth viscosity was 95 mPa·s. The fermentation broth was heated to 60℃ and acidified with sulfuric acid to pH 1.5, with the amount of sulfuric acid added being 1.0 times the theoretical molar amount. After washing twice with deionized water at 50℃ and drying, a product with a purity of 99.5% was obtained, with a sodium ion content of 98 ppm and a potassium ion residue of 48 ppm.

[0080] Example 3:

[0081] Fermentation conditions in a 50L fermenter: temperature 32℃, pressure 0.10MPa, stirring 600rpm, aeration 1.0vvm, dissolved oxygen 40% saturation.

[0082] When the pH dropped to 4.0, a 40wt% potassium hydroxide solution was added, with the pH controlled within the range of 6.6-7.0. After 120 hours of fermentation, the acid concentration was 220 g / L, the alkane conversion rate was 92.5%, and the fermentation broth viscosity was 88 mPa·s. The fermentation broth was heated to 95℃ and acidified to pH 3.5, with sulfuric acid added at 1.2 times the theoretical molar amount. After washing three times with 80℃ water, the product purity was 99.8%, sodium ion content was 72 ppm, potassium ion content was 38 ppm, and the potassium salt solubility in the fermentation broth reached 180 g / L.

[0083] Example 4:

[0084] In a 10L fermenter, a 5% inoculum was used, and the fermentation temperature was 30℃. When the pH dropped to 4.8, the pH was strictly controlled at 5.5±0.2 using a 20wt% KOH solution. After 144 hours of fermentation, the acid concentration was 165 g / L, and the alkane conversion rate was 91.3%. Despite the low pH, the viscosity of the fermentation broth was only 78 mPa·s due to the high solubility of potassium salts. After acidification, the product purity was 99.6%, with 92 ppm sodium ions and 45 ppm potassium ions.

[0085] Example 5:

[0086] In a 100L fermenter, a 15% inoculum was used, and the fermentation temperature was 31℃. When the pH dropped to 4.2, it was controlled at 7.0±0.2 using a 30wt% KOH solution. After 132 hours of fermentation, the acid concentration was 185 g / L, and the viscosity of the fermentation broth was 82 mPa·s. Due to the high pH and vigorous cell metabolism, the final product had a purity of 99.7%, with sodium ions at 80 ppm and potassium ions at 40 ppm.

[0087] Example 6:

[0088] The same process as in Example 1 was used, except that the fermentation temperature was controlled at 28°C, the stirring speed was adjusted to 300 rpm, and the dissolved oxygen was maintained at 20%. After 160 hours of fermentation, the acid concentration was 175 g / L, the conversion rate was 90.5%, and the viscosity of the fermentation broth was 92 mPa·s. The product purity was 99.5%, with sodium ions at 95 ppm and potassium ions at 46 ppm.

[0089] Example 7:

[0090] Fermentation temperature was controlled at 32℃, with other parameters the same as in Example 1. After 132 hours of fermentation, the acid concentration was 189 g / L, the conversion rate was 92.1%, and the fermentation broth viscosity was 68 mPa·s. High temperature resulted in strong cell activity, but the aeration rate needed to be increased to 0.8 vvm to maintain dissolved oxygen. The product purity was 99.6%, with sodium ions at 83 ppm and potassium ions at 41 ppm.

[0091] Example 8:

[0092] Using the 20wt% KOH and pH 5.5 control strategy from Example 2, fermentation was terminated when acid production reached 150 g / L after 120 hours. At this point, the alkane conversion rate was 90.0%, and the fermentation broth viscosity was only 55 mPa·s. Although the acid concentration was low, the advantages of the potassium-based process were fully demonstrated, with a product purity of 99.5%, sodium ion concentration of 97 ppm, and potassium ion concentration of 47 ppm.

[0093] Example 9:

[0094] Using the 40wt% KOH and high pH control strategy from Example 3, fermentation was extended to 168 hours in a 5L fermenter. By gradually increasing the feed rate, the final acid concentration reached 220 g / L, the alkane conversion rate was 93.2%, and the fermentation broth viscosity was 98 mPa·s. The product purity was 99.8%, with 68 ppm sodium ions and 35 ppm potassium ions, fully validating the advantages of the potassium-based process at high concentrations.

[0095] Example 10:

[0096] At 50m 3 The fermenter contains 30m of liquid. 3 A 12% inoculum was used. Fermentation conditions: temperature 29.5℃, tank pressure 0.08MPa, stirring power 2.8kW / m³. 3 Ventilation: 0.7 vvm; Dissolved oxygen: 25-35%.

[0097] The pH was controlled at 6.5 ± 0.2 using a 30 wt% KOH solution. After 156 hours of fermentation, the acid concentration was 188 g / L, the alkane conversion rate was 94.5%, and the viscosity of the fermentation broth was 72 mPa·s (monitored by an online viscometer). The fermentation broth was sterilized at 85°C and then pumped into an acidification tank. 98% concentrated sulfuric acid was added to bring the pH to 2.0, with the amount of sulfuric acid added being 1.15 times the theoretical amount. The crystallization temperature was maintained at 75°C. Separation was performed using a disc centrifuge to obtain a sebacic acid wet cake. The cake was washed three times with 65°C deionized water, each time with a water volume 2.5 times the mass of the wet cake. The final product was obtained by air-drying.

[0098] Results: Batch yield was 5.28 tons, product purity was 99.7%, sodium ion concentration was 75 ppm, potassium ion concentration was 38 ppm, total extraction yield was 96.1%, potassium sulfate mother liquor concentration was 118 g / L, and 1.86 tons of industrial-grade potassium sulfate were recovered by evaporation and crystallization per batch.

[0099] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the methods and techniques disclosed above without departing from the scope of the present invention to create equivalent embodiments. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for neutralizing and regulating potassium-type potassium produced by sebacic acid fermentation, characterized in that, Potassium hydroxide is used as the sole neutralizing agent. During the acid-producing stage of microbial fermentation, the generated sebacic acid is dissolved and accumulated in the form of potassium salt through dynamic pH control. After fermentation, the sebacic acid is crystallized out by acidification with sulfuric acid, and water-soluble potassium sulfate byproduct is generated to achieve product separation. The specific steps include: Sebacic acid-producing strains were inoculated into the fermentation medium, and the fermentation conditions were controlled for cultivation. When the pH of the fermentation broth drops to 4.0-5.0 due to acid production, potassium hydroxide solution is added. The pH is maintained in the range of 6.4-6.8 through feedback control, so that sebacic acid dissolves in the fermentation broth in the form of potassium salt. After acid production is complete, sulfuric acid is added for acidification. The byproducts are separated by utilizing the difference in solubility between potassium sulfate and sebacic acid. Sebacic acid product is obtained through solid-liquid separation and washing.

2. The method according to claim 1, characterized in that, The concentration of the potassium hydroxide solution is 20wt%-40wt%, and automatic feeding is achieved through a feedback control system consisting of a pH sensor and a feed pump to control the pH range.

3. The method according to claim 1, characterized in that, The sebacic acid producing strain is Candida tropicalis, and the fermentation carbon source is n-alkanes.

4. The method according to claim 1, characterized in that, The fermentation conditions include: temperature 28-32℃, dissolved oxygen saturation of 20-40%, tank pressure of 0.05-0.10MPa, and the viscosity of the culture medium during the acid production stage of fermentation is controlled below 100mPa·s.

5. The method according to claim 1, characterized in that, No additional potassium salts are needed in the fermentation medium; the potassium ions required for cell growth and metabolism are provided in situ by potassium hydroxide neutralizer.

6. The method according to claim 1, characterized in that, The sulfuric acid acidification process is controlled at a pH of 1.5-3.5, an acidification temperature of 60-95℃, and the amount of sulfuric acid added is 1.0-1.2 times the theoretical molar amount.

7. The method according to claim 1, characterized in that, The fermentation endpoint produced an acid concentration of 150-220 g / L, with an alkane conversion rate greater than 90%, and a fermentation cycle of 120-168 hours.

8. The method according to claim 1, characterized in that, The product extraction steps include: after acidification, centrifuging the liquid to obtain crude sebacic acid, washing with deionized water at 50-80℃ to remove residual potassium sulfate, and drying to obtain high-purity sebacic acid with a sodium ion content of less than 100ppm.

9. The application of the method according to any one of claims 1-8, characterized in that, The method increases the solubility of product salts in the fermentation broth to over 150 g / L and reduces the viscosity of the fermentation broth to less than 1 / 3 of that of the sodium-type process.

10. The application of the method according to any one of claims 1-8, characterized in that, The final sebacic acid product contains less than 50 ppm of potassium ions, and the potassium sulfate byproduct has a solubility of more than 100 g / L in the mother liquor, which can be recycled or treated in an environmentally friendly manner.

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