System for producing organic acid from syngas fermentation product using bipolar electrodialysis device

Abstract

The present invention relates to a system for producing an organic acid from a syngas fermentation product using a bipolar electrodialysis device. By combining syngas fermentation using microorganisms and bipolar electrodialysis, the extraction of organic acid precursors and the production of organic acids can be performed in a single process. In addition, a base produced in the bipolar electrodialysis device can be reused in the microbial fermentation process to adjust the pH of the medium, thereby improving the efficiency of microbial fermentation.

Description

Organic acid production system from synthesis gas fermentation products using a bipolar electrodialysis device

[0001] The present invention relates to a system for producing organic acids from a synthesis gas fermentation product using a bipolar electrodialysis device.

[0002] The petroleum-based energy / chemical industry occupies a leading position in the domestic industrial production rankings. However, due to the recent fluctuations in the supply and demand of petroleum and its price, which alternate between stable and unstable, the demand for securing fundamental technologies for the discovery and utilization of alternative, stable, and inexpensive raw materials is rapidly increasing. Currently, C1 gases, composed of a single carbon atom such as methane (CH4) and carbon monoxide (CO), which have vast reserves but are limited to simple combustion, are converted into various transportation fuels and chemical materials due to their molecular structure, just like petroleum, consisting of carbon and oxygen. Therefore, the successful development of technologies for converting C1 gases into transportation fuels and chemical materials has enormous ripple effects, and thus, research and development in related technologies are being competitively pursued recently.

[0003] Syngas, a representative alternative energy source, can be produced by reforming natural gas or gasifying solid feedstocks such as coal, organic waste, and biomass. Syngas offers the following advantages as an alternative energy source.

[0004] First, since synthesis gas can be converted from most hydrocarbons, there is a low risk of raw material depletion, and its price fluctuations are less than those of fossil fuels, allowing for a stable supply of raw materials.

[0005] Second, in the case of energy conversion based on synthesis gas, there is less concern about environmental pollution due to carbon dioxide emissions because carbon dioxide is used rather than emitted.

[0006] Third, since the main components are hydrogen and carbon, it can be converted into various high value-added products such as acetic acid, butyric acid, ethanol, and butanol, so it has high usability and is economical.

[0007] These syngases can be utilized through biorefinery processes using microorganisms. Anaerobic acetic acid-producing bacteria, commonly known as acetogens, are a representative example. Acetogens are characterized by their ability to convert C1 gases, such as carbon monoxide and carbon dioxide, into acetyl-CoA via the Wood-Ljungdahl metabolic pathway, converting this into organic acids such as acetic acid, thereby providing the energy necessary for cell growth.

[0008] Specifically, the synthesis gas bioconversion process using acetogen generally requires additional processes such as extracting precursors of organic acids from fermentation culture media and acid treatment to convert them into organic acids, which are the final product, in order to produce the final energy source, organic acids. However, there are problems in that the cost and yield associated with performing the additional processes are problematic.

[0009] Accordingly, various studies are being conducted on technologies for producing organic acids, which are alternative energy sources, through synthetic gas fermentation using microorganisms, to simplify the process, thereby reducing costs consumed in the process and greenhouse gas emissions, as well as to improve the production yield of organic acids.

[0010] [Prior Art Literature]

[0011] [Patent Document]

[0012] (Patent Document 1) KR 10-2020-0088818 A1

[0013] The purpose of the present invention is to provide a system for producing organic acids from a synthesis gas fermentation product using a bipolar electrodialysis device.

[0014] Another object of the present invention is to provide a system for producing organic acids from a syngas fermentation product using a bipolar electrodialysis device that can perform extraction of an organic acid precursor and production of an organic acid in a single process by combining syngas fermentation using microorganisms and bipolar electrodialysis.

[0015] Another object of the present invention is to provide a system for producing organic acids from a synthesis gas fermentation product using a bipolar electrodialysis device, which can improve microbial fermentation efficiency by reusing the base produced in the bipolar electrodialysis device in the microbial fermentation process to control the pH of the medium.

[0016] In order to achieve the above object, a system for producing organic acids from a synthesis gas fermentation product using a bipolar electrodialysis device according to one embodiment of the present invention includes a bioreactor for producing a synthesis gas fermentation product using microorganisms; and a bipolar electrodialysis device for producing an organic acid by electrodialyzing the synthesis gas fermentation product.

[0017] The above bipolar electrodialysis device comprises an anode; a first bipolar membrane; an anion exchange membrane; a cation exchange membrane; a second bipolar membrane; and a cathode arranged in that order.

[0018] The above microorganism is selected from the group comprising Moorella, Clostridium, Ruminococcus, Acetobacterium, Eubacterium, Butyribacterium, Oxobacter, Methanosarcina, Methanosarcina, and Desulfotomaculum.

[0019] The organic acid is selected from the group consisting of acetic acid, butyric acid, lactic acid, propionic acid, valeric acid, glycolic acid, sorbic acid, fumaric acid, formic acid, malic acid, tartaric acid and mixtures thereof.

[0020] The applied voltage when operating the above bipolar electrodialysis device is less than 20 V.

[0021] The above system can simultaneously perform extraction of organic acid precursors contained in a synthesis gas fermentation product and production of organic acids.

[0022] The above system can improve microbial fermentation efficiency by resupplying the base produced during the electrodialysis process to the bioreactor.

[0023] Another embodiment of the present invention provides a method for producing organic acids from a synthesis gas fermentation product using a bipolar electrodialysis device, comprising: 1) a step of injecting a gaseous substrate into a bioreactor containing microorganisms and fermenting the substrate to obtain a synthesis gas fermentation product; and 2) a step of obtaining an organic acid from the synthesis gas fermentation product using a bipolar electrodialysis device.

[0024] The above step 2) includes a step of supplying a synthesis gas fermentation product between a cation exchange membrane and an anion exchange membrane of a bipolar electrodialysis device; and a step of applying voltage to the bipolar electrodialysis device to convert an organic acid precursor contained in the synthesis gas fermentation product into an organic acid.

[0025] An organic acid according to another embodiment of the present invention is produced by the above production method.

[0026] The present invention relates to a system for producing organic acids from syngas fermentation products using a bipolar electrodialysis device. By combining syngas fermentation using microorganisms and bipolar electrodialysis, extraction of organic acid precursors and production of organic acids can be performed in a single process. Furthermore, the base produced in the bipolar electrodialysis device can be reused in the microbial fermentation process to control the pH of the medium, thereby improving microbial fermentation efficiency.

[0027] FIG. 1 is a schematic diagram of an organic acid production system from a synthesis gas fermentation product using a bipolar electrodialysis device according to one embodiment of the present invention.

[0028] Figure 2 shows the results of confirming gas fermentation performance according to one embodiment of the present invention, in which [A] confirms biomass, [B] confirms CO2 and methanol consumption rates, [C] confirms titer product and productivity, and [D] confirms the overall carbon balance.

[0029] Figure 3 shows the polarization curve of a bipolar electrodialysis system according to one embodiment of the present invention, where [A] shows the theoretical curve and [B] shows the measured curve. Meanwhile, i lim1 means the first limiting current density (first LCD), i lim2 stands for the second limiting current density (second LCD), U diss stands for water-dissociation voltage.

[0030] FIG. 4 shows changes in pH and conductivity according to voltage of a bipolar electrodialysis system according to one embodiment of the present invention.

[0031] FIG. 5 is a comparison of the BPM of a bipolar electrodialysis device according to one embodiment of the present invention before and after use using photographs and SEM images, respectively.

[0032] FIG. 6 shows changes in pH and conductivity when the driving voltage of a bipolar electrodialysis device according to one embodiment of the present invention is changed to 4 V and 20 V.

[0033] FIG. 7 is a schematic diagram of a bipolar electrodialysis device according to one embodiment of the present invention, showing the residual ratios of the [B] acid compartment, [C] fermentation broth compartment, [D] base compartment, and [E] electrode compartment, and [F] sodium concentration of each compartment.

[0034] FIG. 8 shows the growth profile of Eubacterium callanderi KIST612 in various medium conditions (recycled medium with pH adjusted with base in CBBM and BPMED) according to one embodiment of the present invention, where [A] shows biomass and [B] shows CO2 and methanol consumption.

[0035] [A] of FIG. 9 is a schematic diagram for cost and carbon emission analysis of a production system of organic acid from a synthesis gas fermentation product using a bipolar electrodialysis device according to one embodiment of the present invention, [B] and [C] are schematic diagrams of a bipolar electrodialysis device (BPMED) of the present invention and a general electrodialysis device (ED), respectively, [D] shows material cost analysis data operated by ED or BPMED, and [E] analyzes CO2 emissions by ED or BPMED.

[0036] The present invention relates to a system for producing organic acids from a synthesis gas fermentation product using a bipolar electrodialysis device, which includes a bioreactor for producing a synthesis gas fermentation product using microorganisms; and a bipolar electrodialysis device for producing an organic acid by electrodialyzing the synthesis gas fermentation product.

[0037] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0038] The term "gaseous substrate" in this specification refers to a gaseous substance containing CO, and may include waste gas itself containing CO and / or CO2, or CO, CO2, H2, or a mixture thereof separated and purified from the waste gas.

[0039] Meanwhile, the above "waste gas" may be a by-product of an industrial process or a waste gas obtained from some other source, for example, automobile exhaust fumes or biomass gasification.

[0040] Meanwhile, the term "BCR (bubble column reactor)" in this specification refers to a bioreactor in which microorganisms can produce fermentation products using the gaseous substrate.

[0041] Meanwhile, the term "IEM (ion-exchange membranes)" in this specification means ion exchange membranes, "CEM (cation exchange membranes)" means cation exchange membranes, "AEM (anion exchange membranes)" means anion exchange membranes, "ED (electrodialysis)" means electrodialysis, "BPMED (bipolar membrane electrodialysis)" means bipolar electrodialysis, and "CBBM (carbonate-buffered basal medium)" means carbonate-buffered basal medium.

[0042] The term "fermentation product" in this specification is defined as a product produced through microbial fermentation using a gaseous substrate containing CO2 of the present invention, and including the organic acid precursor of the present invention.

[0043] Meanwhile, the term "organic acid precursor" in this specification refers to a substance that can be converted into the organic acid of the present invention through a treatment process such as acid treatment. For example, if the organic acid is acetic acid, the precursor is acetate, and if the organic acid is butyric acid, the precursor is butyrate.

[0044] Syngas fermentation is a biological process that converts gaseous carbon and energy sources into valuable chemicals, making it a promising solution for achieving environmental sustainability. This process utilizes microorganisms as biocatalysts to metabolize carbon products such as CO and CO2. These carbon oxides are commonly found in syngas derived from industrial waste gases or solid waste gasification. Therefore, syngas fermentation is emerging as a powerful and efficient method for upcycling gaseous waste into valuable biochemicals, minimizing carbon emissions and promoting a circular economy.

[0045] Despite these advantages, there are several limitations to using this process to produce chemicals. C1 gas typically exhibits insufficient energy density to produce high concentrations of large products, compared to carbohydrate-based biological pathways and thermochemical conversions using chemical catalysts. For example, acetic acid, an essential platform chemical, is synthesized via the acetyl-CoA pathway of acetogens, through the reduction of CO and H2 / CO2. However, conventional techniques have shown that acetate production by microbial species ranges from 0.1% to 4.4%, highlighting the need to increase productivity and extraction efficiency.

[0046] In particular, gas fermentation, which primarily uses CO2 as a substrate, generally has low productivity, and active research has been conducted to optimize various parameters to improve productivity. However, as awareness of the need to reduce CO2 emissions to mitigate global warming spreads, experiments are focusing on simultaneously improving productivity and reducing CO2. Furthermore, as carbon capture, utilization, and storage (CCUS) technology using CO2 is developing into a commercial business in addition to reducing CO2 emissions, research is primarily focused on CO2 reduction. In particular, as part of the global carbon neutrality scenario, which aims to achieve net-zero greenhouse gas emissions by 2050 to meet the 1.5°C target set by the Intergovernmental Panel on Climate Change (IPCC), research efforts are focused on achieving carbon neutrality. Therefore, biological upcycling processes using carbon dioxide as a substrate are emerging as important technologies.

[0047] In syngas fermentation, H2 and CO2 are used together, especially in the absence of CO. However, with CO acting as an intermittent reactant, relying solely on CO2 and H2 results in a process with limited energy density. This low energy profile leads to reduced cell production and reduced conversion of C1 compounds. To overcome these limitations and promote CO2 consumption, an additional carbon source is needed.

[0048] Methanol can be used as a supplemental carbon source, as acetogen-producing strains possess a methyl branch, allowing it to be used in conjunction with CO2. However, despite concerted efforts to increase productivity through combined fermentation of CO2 and methanol, yield improvements have been limited. Meanwhile, the introduction of syngas or other C1 chemicals has been designed to increase biomass concentration and accelerate the process, but the anticipated rapid increase in product yield has proven difficult to achieve.

[0049] Nonetheless, existing industrial methods such as distillation and solvent extraction suitable for high-concentration products have low yields in the carbon dioxide fermentation process, so an appropriate extraction process capable of solubilizing chemicals upcycled from carbon dioxide is needed.

[0050] A promising solution for the above extraction process is the application of electrodialysis (ED) technology, which has been proven to be superior to the traditional method of electrodialysis (ED) in terms of cost-effectiveness, operational stability, and efficiency of chemical extraction.

[0051] However, the overall system configuration, from gas fermentation to organic acid purification, contains some inconsistencies due to a lack of understanding of the independent processes. Conventional technologies have successfully developed integrated systems by applying CO fermentation and ED while extracting acetate. However, for practical use in the chemical industry, a post-processing process is required to convert the acetate into high-value-added acetic acid.

[0052] Accordingly, in the present invention, a technology utilizing bipolar membrane electrodialysis (BPMED) for generating acidic and alkaline electrolytes is intended to be used to reduce additional costs and additional post-treatment processes.

[0053] From an environmental perspective, the application of the BPMED system is one of the eco-friendly technologies that considers efficient energy utilization without generating gases or by-products. Referring to Fig. 1, in principle, the core of the BPMED system is to use a bipolar membrane (BPM) with a sandwich structure of a cation exchange membrane (CEM) and an anion exchange membrane (AEM).

[0054] BPM generates protons and hydroxyl ions in each layer under an external electric field. Therefore, while the ED system can only extract acetate produced through gaseous fermentation, the BPMED system can not only extract the acetate but also effectively convert it into high-concentration acetic acid. Furthermore, the generated alkaline solution can be reused to maintain culture conditions for microbial growth and fermentation.

[0055] Accordingly, the present invention attempted to construct a reciprocal circulation system by combining the advantages of gas fermentation and BPMED systems, and specifically, focused on recycling of the medium and optimization of the ion exchange membrane, and studied the integration of gas fermentation and bipolar electrodialysis (BPMED) for sustainable production of acetic acid and base.

[0056] Gas fermentation was performed in a bioreactor using Eubacterium callanderi KIST612, an acetic acid fish strain, and the BPMED system was operated under specific voltage conditions to evaluate the production, ion concentration, and residue ratio of protons and hydroxyl ions.

[0057] Specifically, gas fermentation has a stable CO2 consumption rate (0.167 mmol g cell -1) and methanol, consistently producing acetate as the rate of conversion of carbon to biochemicals increased. Meanwhile, the BPMED system efficiently produced acetic acid (acetate extraction yield of 99.72% to 99.82%) and hydroxide ions (8 to 18 V), although system operation issues were identified at high voltages above 20 V. The BPMED process, which included an additional membrane configuration and exhibited a lower acetate flux than the ED process, demonstrated cost-effectiveness that outperformed the ED-integrated process by 17.6%, and this economic advantage also translated into environmental benefits, as the BPMED process was found to reduce carbon dioxide emissions by approximately 7.4% compared to the ED process.

[0058] Accordingly, the present invention aims to provide an integrated system that can increase the extraction efficiency of organic acid precursors by improving microbial fermentation efficiency by combining gas fermentation and BPMED systems, while simultaneously performing the organic acid conversion process from the organic acid precursor within a single system.

[0059] A system for producing organic acids from a synthesis gas fermentation product using a bipolar electrodialysis device according to one embodiment of the present invention includes a bioreactor for producing a synthesis gas fermentation product using microorganisms; and a bipolar electrodialysis device for producing an organic acid by electrodialyzing the synthesis gas fermentation product.

[0060] Specifically, a synthesis gas fermentation product, defined as a fermentation liquid or fermentation medium containing an organic acid precursor, can be produced through the fermentation action of microorganisms contained within the bioreactor, and the fermentation product can be supplied to a bipolar electrodialysis device. Thereafter, the fermentation product can be electrodialyzed through the bipolar electrodialysis device so that the organic acid precursor can be ultimately converted into an organic acid.

[0061] Meanwhile, the pH condition inside the bioreactor is preferably in the range of 6.8 to 7.2, and the fermentation efficiency of the microorganisms can be maximized within the above range. Meanwhile, the base produced through the bipolar electrodialysis device is characterized in that it can be re-supplied to the bioreactor to control the pH inside the bioreactor within the above range, thereby maximizing the microbial fermentation efficiency.

[0062] In addition, methanol can be supplied together with CO2, which is one of the gaseous substrates in the gas fermentation process inside the bioreactor, and is characterized in that methanol is additionally supplied and cultured whenever the methanol concentration decreases to 5 mmol or less, thereby increasing the cell concentration inside the bioreactor to 1.5 to 2.0 g L. -1 in the range of , more preferably 1.5 to 1.6 g L -1 can be maintained within the range of .

[0063] Meanwhile, the CO2 consumption rate inside the bioreactor is 0.160 mmol g cell -1 0.180 mmol g cell -1 , more preferably 0.167 mmol g cell -1 It is.

[0064] That is, when the cell concentration and CO2 consumption rate inside the bioreactor satisfy the above range, the fermentation efficiency can be further maximized, and the synthesis gas fermentation product containing the organic acid precursor can be produced more efficiently. After 5 days of fermentation in the range satisfying the above conditions, the average productivity of the organic acid precursor contained in the fermentation product is 0.50 mmol L. -1 h -1 0.60 mmol L -1 h -1 can satisfy the range of

[0065] Meanwhile, the bipolar electrodialysis device is configured such that an anode; a first bipolar membrane; an anion exchange membrane; a cation exchange membrane; a second bipolar membrane; and a cathode are arranged in sequence.

[0066] Specifically, referring to the bipolar electrodialysis device disclosed in FIG. 1, the bipolar electrodialysis device is configured such that an anode; a first bipolar membrane; an anion exchange membrane; a cation exchange membrane; a second bipolar membrane; and a cathode are arranged in that order, and a compartment between the first bipolar membrane and the anion exchange membrane (AEM) can be defined as an acid compartment or a concentrated compartment, a compartment between the anion exchange membrane (AEM) and the cation exchange membrane (CEM) can be defined as a fermentation broth compartment containing a fermentation product, and a compartment between the cation exchange membrane (CEM) and the second bipolar membrane can be defined as a base compartment.

[0067] Meanwhile, the first bipolar membrane and the second bipolar membrane convert water (H2O) into hydroxyl ions (OH - ) and hydrogen ions (H + ) can be dissociated into each.

[0068] Looking at the process of producing the organic acid of the present invention by driving the bipolar electrodialysis device, the fermented fermentation liquid can be supplied to the fermentation liquid compartment through the bioreactor. Then, by driving the bipolar electrodialysis device, the organic acid precursor contained in the fermentation liquid can pass through the anion exchange membrane and move to the acid compartment or the concentrated compartment, and then, the hydrogen ions (H) produced in the first bipolar membrane + ) can be converted into organic acids.

[0069] Meanwhile, Na contained in the above fermentation solution +Cations such as these can pass through the cation exchange membrane (CEM) to the base compartment, and on the base compartment, hydroxyl ions (OH) generated in the second bipolar membrane - ) can be combined with NaOH to produce salts. Thereafter, the produced salts can be re-supplied to the bioreactor and used to control the pH of the fermentation medium, thereby maximizing the microbial fermentation efficiency within the bioreactor.

[0070] Additionally, residual components of the fermentation broth previously supplied to the fermentation broth compartment can also be re-supplied to the bioreactor and recycled as a fermentation medium.

[0071] The above microorganism is selected from the group comprising Moorella, Clostridium, Ruminococcus, Acetobacterium, Eubacterium, Butyribacterium, Oxobacter, Methanosarcina, Methanosarcina, and Desulfotomaculum.

[0072] However, it is not limited to the types of microorganisms exemplified above, and is defined to include all types of microorganisms capable of producing a fermentation product using the gaseous substrate containing CO2 of the present invention.

[0073] Specifically, the microorganism of the present invention is preferably Eubacterium, and more preferably Eubacterium callanderi KIST612 strain.

[0074] The organic acid is selected from the group consisting of acetic acid, butyric acid, lactic acid, propionic acid, valeric acid, glycolic acid, sorbic acid, fumaric acid, formic acid, malic acid, tartaric acid and mixtures thereof.

[0075] More specifically, the organic acid may be acetic acid or butyric acid.

[0076] The applied voltage when operating the above bipolar electrodialysis device is less than 20 V.

[0077] When the applied voltage is 20 V or higher, the phenomenon of the intermediate layer of BPM being peeled off due to the limitation of water dissociation (see Fig. 5) may occur, and the conversion efficiency of the organic acid precursor into the organic acid may be reduced. Therefore, it is preferable that the applied voltage be less than 20 V when operating the bipolar electrodialysis device.

[0078] Meanwhile, it is preferable that the applied voltage when operating the bipolar electrodialysis device is 8 V to 18 V, and in the voltage range, the extraction efficiency of the organic acid precursor present in the fermentation product and the conversion efficiency of the precursor into the organic acid can be maximized. However, if it is below the range, the extraction efficiency and conversion efficiency may decrease, and it may take a long time to produce the final organic acid, and if it exceeds the range, as mentioned above, the intermediate layer of the BPM may be peeled off due to the limitation of water dissociation.

[0079] More preferably, the applied voltage when operating the bipolar electrodialysis device is preferably 12 V. When a voltage exceeding 12 V is applied, the extraction speed of acetate may increase, but the pH change may be significantly reduced, which may lower the overall process efficiency. Therefore, considering the acetate extraction speed, pH reduction, etc., an applied voltage of 12 V is most preferable.

[0080] Specifically, within the above-mentioned applied voltage range, the time required for producing the organic acid of the present invention may be within 5 hours.

[0081] More specifically, within the above applied voltage range, the acetate flux of the present invention system is 0.43 to 8.67 mol m -2 h -1 It can be. Meanwhile, within the above-mentioned applied voltage range, the acetate extraction rate of the system of the present invention can be 99.72 to 99.82%. In addition, within the above-mentioned applied voltage range, the current efficiency of the system of the present invention is 9.48 to 22.57%.

[0082] The above system can simultaneously perform extraction of organic acid precursors contained in a synthesis gas fermentation product and production of organic acids.

[0083] As mentioned above, in the case of the existing electrodialysis device, the organic acid precursor was extracted from the fermentation product, and then the organic acid precursor was subjected to a separate post-process to finally obtain the organic acid, which was cumbersome because an independent, separate process was required. Therefore, the present invention is characterized in that the extraction process of the organic acid precursor contained in the fermentation product obtained from the bioreactor and the conversion process of the extracted precursor into an organic acid can be performed in a single system by combining a bipolar membrane electrodialysis device and a bioreactor.

[0084] In addition, the above system can improve microbial fermentation efficiency by resupplying the base produced in the electrodialysis process to the bioreactor.

[0085] That is, while an organic acid is produced in the electrodialysis device of the present invention, a base (NaOH) is produced in the base compartment, and the base component is resupplied to the bioreactor, thereby controlling the pH inside the bioreactor to 6.8 to 7.2, thereby providing an optimal environment for microbial fermentation, thereby maximizing fermentation efficiency.

[0086] Another embodiment of the present invention provides a method for producing organic acids from a synthesis gas fermentation product using a bipolar electrodialysis device, comprising: 1) a step of injecting a gaseous substrate into a bioreactor containing microorganisms and fermenting the substrate to obtain a synthesis gas fermentation product; and 2) a step of obtaining an organic acid from the synthesis gas fermentation product using a bipolar electrodialysis device.

[0087] The above step 2) includes a step of supplying a synthesis gas fermentation product between a cation exchange membrane and an anion exchange membrane of a bipolar electrodialysis device; and a step of applying voltage to the bipolar electrodialysis device to convert an organic acid precursor contained in the synthesis gas fermentation product into an organic acid.

[0088] Specifically, the fermentation product produced through a microbial fermentation process using a gaseous substrate inside the bioreactor can be supplied to the fermentation liquid compartment between the cation exchange membrane and the anion exchange membrane of the bipolar electrodialysis device. Meanwhile, among the fermentation products supplied to the fermentation liquid compartment, the organic acid precursor having an anion can pass through the anion exchange membrane to move to the acid compartment, and the cation can move through the cation exchange membrane to the base compartment.

[0089] Meanwhile, when voltage is applied to the bipolar electrodialysis device, dissociation of water molecules occurs in the first and second bipolar membranes, resulting in H + and OH - are generated respectively, and in the mountain section, the above H +It can react with an organic acid precursor to convert the organic acid precursor into an organic acid. Meanwhile, in base harvesting, the OH - It can combine with cations to form a salt, which can be re-supplied to the bioreactor to adjust the pH of the fermentation medium in the bioreactor to 6.8 to 7.2.

[0090] Furthermore, the fermentation products remaining in the fermentation liquid compartment can also be re-supplied to the bioreactor and recycled as a fermentation medium.

[0091] An organic acid according to another embodiment of the present invention is produced by the above production method.

[0092] [Experimental Materials Preparation and Methods]

[0093] Cultivation and growth conditions of microbial strains

[0094] Eubacterium callanderi KIST612 was cultured in a 60-ml vial with 1 atm of CO2 and N2 for inoculation. Cells were cultured using carbonate-buffered basal medium (CBBM) consisting of yeast extract, L-cysteine, NaHCO3, basal medium, trace element solution, and 0.1% resazurin solution. In addition, 1% sodium phosphate (prepared with 1 M NaH2PO44 and 0.5 M Na2HPO4) and 1% vitamin solution were added to the culture vial.

[0095] Bioreactor setup, operating conditions, and analysis

[0096] A bubble column reactor (BCR) with a capacity of 500 mL (working volume of 350 mL) developed in the laboratory was used for gas fermentation. CO2 and N2 gases (80:20) supplied by Daedeok Gas, Korea, were fed to the reactor using a sintered gas filter (Daihan Science, Korea) with a pore size range of 10–16 μm.

[0097] Meanwhile, 5 mL min at atmospheric pressure -1 The gas flow maintained at 0 was controlled using a digital mass flow controller (MFC, Korea Instruments Total Solution). The pH was adjusted to 7 by adding 2 N NaOH through a control box (R3610, Consort, Belgium). The fermentation broth was extracted using a hollow fiber membrane cartridge (CFP-2-E-3MA, Ge Healthcare, USA) attached to the main reactor. The feed growth medium for the fermentation process was prepared in a 5 L glass vessel. Gas components were analyzed using a gas chromatograph equipped with a thermal conductivity detector (ACME 6100, YoungIn Chromass, Korea), and inductively coupled plasma-mass spectrometry (ICP-MS, Agilent Technologies, USA), inductively coupled plasma-optical emission spectrometry (ICP-OES, Thermo Scientific, USA), and ion chromatography (IC, Thermo Scientific, USA) were used to analyze the elements in the liquid medium.

[0098] Measurement of limiting current density and operation of the BPMED (Bipolar Membrane Electrodialysis) system

[0099] To measure the limiting current density (LCD) of the BPMED system, the stack was composed of three compartments, as shown in Figure 1. CMS was selected as a monoselective cation exchange membrane (CEM) that blocks divalent ions, and AMX was selected as an anion exchange membrane (AEM). Meanwhile, BP-1 BPM was used for acid and base production.

[0100] 0.05 M Na2SO4 electrolyte solution was placed in the electrode chamber (platinum-coated titanium electrode, effective area: 4Х6 cm 2) and connected to a power supply (PWS4602, Tektronix, USA). The LCD values ​​of the fermentation broth in the fermentation broth compartment and 0.01 M CH3COONa in the concentrated compartment were measured. To satisfy the LCD measurement conditions, the flow rate of each compartment was 5 mL min. -1 at 20 mL min -1 The LCD was determined according to the flow rate by increasing the flow rate.

[0101] Meanwhile, to observe changes in pH and conductivity during electrodialysis (ED), a pH (InPro3030, Mettler Toledo, USA) meter and a conductivity meter (LCT1, Sensortechnik, Germany) were installed in the fermentation broth and concentrated compartment, respectively. Prior to the experiment, each compartment of the BPMED system was washed with the fermentation broth, and the fermentation broth compartment and concentrated compartment were each washed with 0.01 M CH3COONa.

[0102] Meanwhile, after operating the BPMED system, the membrane was analyzed using SEM images to investigate surface morphological changes. This process involved freezing the membrane in liquid nitrogen and then slicing it with an SEM blade to highlight differences between the original and used BPM membranes.

[0103] Integrated process modeling of syngas fermentation and BPMED

[0104] A kinetic simulation was performed to evaluate the integrated gas fermentation and BPMED process. Furthermore, the cell concentration throughout the bioreactor was compared using the specific growth rate (μ), determined using Equations 1 and 2 below:

[0105] [Formula 1]

[0106]

[0107] [Formula 2]

[0108]

[0109] Here,

[0110] X is biomass concentration (g L -1 ) and

[0111] D is the dilution rate (h -1 ) and

[0112] C t is the product concentration (g L) at time t -1 ) and

[0113] P is productivity (g L -1 h -1 )am.

[0114] Meanwhile, the concentration of dissolved gas can be expressed by the following equation 3:

[0115] [Formula 3]

[0116]

[0117] Here,

[0118] q gas is the specific gas uptake rate (mol·gDCW) -1 ·h -1 ) and

[0119] k L a is the mass transfer coefficient,

[0120] X is the concentration of biomass (g·L -1 )am.

[0121] C L , gasCalculations revealed that certain gases would act as limiting factors for the cell during operation. All other relevant data were obtained directly using analytical equipment, and a model was developed to simulate product inhibition kinetics and gas circulation dynamics. Meanwhile, the specific CO2 consumption rate was determined using Equation 4 below:

[0122] [Formula 4]

[0123]

[0124] BPMED model

[0125] The acetate flux through the membrane was predicted using Equation 5 with previous data:

[0126] [Formula 5]

[0127]

[0128] Here,

[0129] J A , A and m represent the membrane flux of acetate, the membrane surface area and the amount of transported acetate, respectively.

[0130] Meanwhile, the current efficiency (θ) was estimated using Equation 6 below:

[0131] [Formula 6]

[0132]

[0133] Here

[0134] ΔNa, i and F represent the change in the molar concentration of acetate, current density and Faraday constant, respectively.

[0135] Meanwhile, the amount of energy consumed in the BPMED process was estimated using Equation 7 below:

[0136] [Formula 7]

[0137]

[0138] Here,

[0139] U, I, and t represent the voltage, current intensity (A), and operating time of the BMPED process, respectively. Meanwhile, from an environmental perspective, to convert energy consumption into CO2 emissions, 0.233 kg CO2kWh -1 A conversion factor of 0.131 $ kWh was applied. Energy cost was 0.131 $ kWh -1 was calculated based on the price.

[0140] Carbon emissions model

[0141] The environmental impacts of the bipolar membrane electrodialysis (BPMED) and electrodialysis (ED) systems were assessed by calculating greenhouse gas emissions using Equation 8 below. Specifically, the carbon dioxide equivalent (CO2) measurement method, also known as the greenhouse gas factor (GHG factor), can be used as a key metric to determine the environmental impact of implemented technologies:

[0142] [Formula 8]

[0143]

[0144] The amount of CO2 emissions generated when producing or processing a specific material (M) in a virtual process was determined.

[0145] [Experimental Results]

[0146] Check gas fermentation performance

[0147] Gas fermentation was performed using Eubacterium callandari KIST612, yielding a fermentation product (fermentation medium) containing acetate. The strain was cultured and concentrated in a custom-designed gas bioreactor. Specifically, the headspace gas composition was controlled using a digital mass flow controller (MFC, Korea Instruments Total Solution) by adjusting the CO2 and N2 supply ratios. Meanwhile, methanol (75 mmol) was used as the carbon and electron source.

[0148] The culture of the above strain reached a steady state on the 12th day, and the cell concentration was 1.5 to 1.6 g L -1 It was confirmed that it was within the range.

[0149] Meanwhile, during the fermentation process, methanol was added to the medium whenever the residual methanol concentration decreased below 5 mmol, as shown in Fig. 2 [A]. Mass transfer limitations are a common problem in many gas fermentation processes, and these limitations are generally caused by the characteristics of gaseous substrates, in which only dissolved gases can be absorbed by microorganisms. However, in the present invention, the Henry's law constant of CO2 is higher than that of other gaseous substances such as CO and H2, and the supply ratio is also high, so mass transfer limitations did not occur.

[0150] Throughout the experiment, the CO2 consumption rate was 0.080 to 0.095 mmol h, as can be seen in Fig. 2 [B]. -1 This was maintained between the cells, which may be the result of continuous absorption by the microbial consortium. Meanwhile, the initial low CO2 and methanol consumption rates were due to the low cell concentration. The results for the specific consumption rate showed that the average specific consumption rate during the early stage of fermentation (day 1) was 1.291 mmol g cell. -1 h -1 It was confirmed to be 0.167 mmol gcell, which is the normal state rate. -1 h -1 It can be confirmed that the consumption rate exceeds 0.50 mmol h for methanol. -1 was measured as , and the average specific consumption rate was 2.065 mmol gcell -1 h -1 It was confirmed that.

[0151] The main biochemical substance produced through fermentation of the above strain was acetate, and after 5 days of fermentation, the average productivity of acetate was 0. 58 mmol L. -1 h -1 was maintained. Meanwhile, the total carbon balance confirmed that a significant amount of carbon was allocated to the produced biochemicals (Fig. 2 [D]). A 95% carbon balance was confirmed in S1, which was initially injected with carbon substrate and grew stably. Meanwhile, an increase in carbon conversion to acetate and butyrate was confirmed over time, which is consistent with the observed increase in titer (81 to 90% of the carbon balance in S2 to S4). Meanwhile, the carbon balance indicates the efficiency of the gas fermentation process that converts carbon into biochemicals, and suggests that the fermentation process using CO2 as a carbon substrate in the present invention was successfully performed.

[0152] Polarization curve of the BPMED system

[0153] To generate protons and hydroxyl ions, it is essential to establish appropriate operating conditions for the BPMED system. Therefore, the polarization curve of the BPMED system was analyzed. The polarization curve of the BPMED system differs from that of the ED system. As shown in Figure 3 [A], due to the unique characteristics of the BPM, the polarization curve can theoretically be divided into several regions.

[0154] i lim1 Below, salt ions can move through each layer of the BPM. After that, the electrical resistance increases significantly because the salt ions are removed from the intermediate layer (IL) of the BPM. Meanwhile, i lim1 The size of varies depending on the BPM unit characteristics. i lim1The most important area above is water dissociation, which determines the water decomposition performance and operating conditions. This is U diss Below, it means that the water dissociation reaction is difficult. Meanwhile, i lim2 In the above, it was confirmed that although the voltage increased, the water diffusion within the BPM was mainly limited, and thus the water dissociation reaction was limited.

[0155] Referring to Fig. 3 [B], i lim1 The degree of co-ion transport was the same regardless of the flow rate below U diss The value was measured to be approximately 3 V, which dissociates water molecules, regardless of the flow rate. As expected, the measured current density increased with increasing flow rate, as the concentration polarization in each compartment was minimized, while the current density i lim2 The results showed that the water dissociation and ion transport in the BPMED system increased with increasing current. Limited water dissociation was observed in the BPMED system above approximately 18 V. Based on the current-voltage relationship, the BPMED was operated under various applied voltages in subsequent experiments.

[0156] Verifying the effectiveness of the BPMED system under low-voltage and high-voltage conditions.

[0157] The purpose of the BPMED system is to produce acetic acid and hydroxyl ions from the fermentation product (fermentation broth). During operation, it is important to monitor the pH and conductivity of the compartment. As shown in Figure 4, changes in pH and conductivity were measured according to polarization curves under various potential conditions.

[0158] The pH values ​​of the acid and base compartments rapidly decreased and increased, respectively, across the entire applied voltage range. This suggests that BPM stably generated protons and hydroxyl ions through water dissociation.

[0159] The pH change in the fermentation solution showed different trends depending on the applied potential. The pH value was maintained at the minimum applied voltage, except for a slight increase. Meanwhile, the pH change in the fermentation solution compartment decreased significantly above 12 V. This phenomenon can be attributed to the overproduction of protons in the desalinated fermentation solution, leading to proton leakage through the AEM.

[0160] Meanwhile, while BPMED is operating, the conductivity of the fermentation compartment is affected by the movement of acetate ions through the AEM and Na through the CEM. + , which decreases due to the movement of acetate ions. This would indicate that the conductivity of the acidic compartment increases with the concentration of acetate ions and the production of protons.

[0161] Additionally, the conductivity decreased rapidly due to the rapid movement of acetate ions and the generation of protons depending on the applied voltage intensity. During the operation of the BPMED system, it was confirmed that at the maximum voltage intensity, the production of protons / hydroxyl ions was rapid and the extraction of acetate ions was rapid, depending on the changes in pH and conductivity. Meanwhile, the contamination of the fermentation broth due to proton leakage could be minimized at 12 V for the first 3 hours. At the lowest applied voltage (8 V), it was confirmed that it took a long time (8 hours) to extract acetic acid from the conductivity value due to the low water dissociation rate (Figs. 4 and 6).

[0162] Meanwhile, when the BPMED system was operated at 20 V or higher, it was confirmed that there was difficulty in generating acetic acid. As can be seen in Fig. 5 [A], the BPM before operating the BPMED had a uniform surface, but after operating the BPMED, a convex portion was observed on the surface of the BPM (Fig. 5 [B]). A striking contrast is observed in the cross-sectional SEM image between the initial BPM and the BPM after use. Referring to Fig. 5 [C], the intermediate layer (IL) between the cation exchange layer (CEL) and the anion exchange layer (AEL) was confirmed to be densely packed without any voids, whereas the BPM used to operate the BPMED system at 20 V showed a gap between the cation exchange layer (CEL) and the anion exchange layer (AEL) (Fig. 5 [D]). This is attributed to the ballooning phenomenon or peeling phenomenon caused by the excessive electric field in the IL of the BPM.

[0163] As a result, as water molecules with high resistance accumulate in the intermediate layer (IL), the distance of the water splitting region increases, inhibiting the production of protons / hydroxyl ions, and causing pH and conductivity to become unstable over time.

[0164] More specifically, referring to Fig. 6, it was confirmed that the values ​​of pH and conductivity fluctuate significantly compared to the voltage range of the present invention when the driving voltage range is outside of 8 to 18 V. Meanwhile, in the case of BPMED using the fermentation liquid of the present invention, i lim2 It was confirmed that it does not work under current conditions slightly exceeding 20V.

[0165] Ion migration and retention rate of the BPMED system

[0166] The residual percentages in each compartment were calculated for various ion concentrations as shown in Tables 1 and 2 below. Table 1 shows the residual mineral concentrations in the fermentation broth compartment, and Table 2 shows the residual mineral concentrations in the base compartment.

[0167] Minerals8 V (mM)12 V (mM)16 V (mM)18 V (mM)Na + 7.18184.47624.16823.1623Mg 2+ 0.50800.22210.09450.1004Cu 2+ 0.24730.16210.07230.0988Ca 2+ 0.18350.03190.07560.0078Mn 2+ 0.01330.00710.00350.0020Zn 2+ 0.21200.12160.10930.0880Ni 2+ 0.03140.02790.02860.0244Co 2+ 0.15740.14680.08610.0783Fe 2+ 0.00670.00590.00580.0047

[0168] Minerals8 V (mM)12 V (mM)16 V (mM)18 V (mM)Na + 110.8716124.3165126.9768130.5236Mg 2+ 0.10960.11450.13110.0228Cu 2+ 0.05020.08030.06130.0627Ca 2+ 3.39723.59583.58373.6685Mn 2+ 0.00130.00320.00370.0039Zn 2+ 0.01120.04330.03020.0285Ni 2+ 0.00020.00060.00020.0001Co 2+ 0.00000.00090.00000.0000Fe 2+ 0.00020.00000.00050.0009

[0169] Specifically, although the role of the AEM is to exclude cations from the acid compartment, multivalent ions were measured in the acid compartment (Fig. 7 [B]). In particular, it can be confirmed that the concentration of divalent ions increases with the strength of the applied electric field. On the one hand, it can be assumed that the movement of divalent cations through the AEM, together with the enhanced acetate flux at high electric fields, is caused by diffusion, and on the other hand, because the different retention ratios of cations lead to different ion sizes and membrane mobility.

[0170] Meanwhile, in the base compartment, calcium ions were extracted at the highest concentration, even though monovalent CEM was applied to the BPMED system (Fig. 7 [D]). In the electrode compartment, it was confirmed that a small number of divalent ions affected the acid compartment (Figs. 7 [B] and [E]).

[0171] This phenomenon suggests that the residual ions leaked through the AEL of the BPM due to the strong electric field, and thus, the effect of the electric field was clearly observed in the fermentation solution (Fig. 7 [C]). The BPMED system required the longest time to terminate operation under the 8 V condition, but showed the highest percentage of residual divalent ions among the conditions investigated. When the highest voltage was applied in BPMED, the termination time was the shortest, but the residual divalent ions were the lowest.

[0172] In the BPMED process, the transport of acetate ions is essential for acetic acid production. However, due to the use of a monovalent cation exchange membrane, the transport of polyvalent cations is limited. To overcome this limitation and maintain an appropriate ion balance, the initial concentrations of the acid and base compartments were strategically changed during the BPMED operation. During the observation, an increase in the concentration in the base compartment was observed. This change was attributed to the Na from the fermentation broth. + It means the movement of ions, and it was confirmed that these ions passed through the electrode compartment (Fig. 7[F]). When an electric field is applied, the polarity is strengthened, and Na+ The concentration of ions increases, particularly at high voltage levels. Specifically, the extraction efficiency of acetate ions in the acid compartment was confirmed to be over 99.72% over the applied voltage range.

[0173] Meanwhile, for the acetate content, the ratio was found to slightly increase depending on the applied electric field strength (see Table 3 below). Current efficiency and energy consumption showed decreasing and increasing trends, respectively, depending on the applied voltage strength of the current density. This phenomenon is related to ion leakage and the driving force of the electric field. Since it is difficult to approach 100% in an actual system, ion leakage occurs due to the ion selectivity of the IEM. Proton leakage is a dominant factor compared to hydroxyl ion leakage. The intrinsic mobility of protons is faster than that of hydroxyl ions. Meanwhile, with respect to BPM, co-ion leakage can occur, which reduces current efficiency and increases energy consumption. In particular, ion movement due to ion leakage is accelerated by the higher driving force of increasing current density.

[0174] Meanwhile, Table 3 below shows the flux, current efficiency, and ion balance of acetate at the applied voltage (8 to 18 V) of the present invention.

[0175] Applied voltage(V)Acetate Flux(mol m -2 h -1 )Acetate Extraction rate (%)Current efficiency (%)Ion balance (%)80.4399.7222.5795.6121.7399.7814.8992.2162.6099.8110.6090.6188.6799.829.4889.1

[0176] Evaluation of the growth performance of the BPMED process

[0177] Since unknown chemicals that cannot be analyzed or detected may remain in the medium and limit cell growth, the recycled medium whose pH was adjusted according to the BPMED process was compared with CBBM (Fig. 8). To prepare a medium with an appropriate pH level, the pH was adjusted using the base generated in the BPMED process. During the extraction of the fermentation medium, small particles including microorganisms were pre-filtered using a hollow fiber membrane (HFM) cartridge. Afterwards, only the necessary nutrients were supplemented to the remaining medium and it was utilized without further treatment. Referring to Fig. 8, the cell growth amount using CBBM was 0.162 g L -1 reached, which is the growth of the recycled medium (0.158 g L -1 ) were similar to those in other growth media and recycled chemicals. However, cells cultured in different growth media consumed similar amounts of CO2 and methanol.

[0178] These results suggest that the BPMED system is superior to conventional methods because it not only allows for the reuse of media, but also allows for pH control through the base generated during the BPMED process. Therefore, it has the advantage of eliminating the need for additional treatment systems to recycle media during microbial culture.

[0179] In previous studies, there have been studies on media reuse in the purification step through the ED process, but these studies generally did not provide detailed analyses of the media components recycled after further processing, and often lacked real-world examples of culture growth.

[0180] Accordingly, the reusability of growth media combined with residual component analysis can lead to a more efficient recycling system, and more specifically, the BPMED system has the advantage of significantly improving the recycling process by reusing residual components and controlling pH.

[0181] Case Studies for Cost and Carbon Emissions Analysis

[0182] ED can provide more efficient treatment than distillation or solvent processes. Meanwhile, the BPMED system offers the advantage of simplified base supply during fermentation for pH adjustment and the ability to directly convert acetate ions into acetic acid by supplying protons (Figure 9 [A]). However, BPM is more expensive than the CEM and AEM used in ED, and its increased number of membranes can increase system resistance and lower acetate flux per unit area.

[0183] Meanwhile, a comparative analysis was conducted to evaluate the cost-effectiveness and environmental impact of BPMED and ED. Growth media recycled from ED and BPMED were used for gas fermentation. Operational data included gas fermentation. Energy costs and greenhouse gas emissions were calculated by planning scenarios using pump and tank electricity and the applied current.

[0184] Specifically, both processes were simulated using the same gas fermentation system with a single-channel configuration, a single-stack ED device, designed to extract acetate produced through gas fermentation for 100 days and convert it into acetic acid. Energy consumption was calculated separately for the fermentation and ED processes, and the costs including the electricity for the pump, the water tank, and the electricity input to the ED device, as well as the greenhouse gas emissions, were evaluated. The applied voltage was set to 12 V, and the acetate flux was 2.02 mol m for the ED process. -2 h -1 , 1.73 mol m for the BPMED process -2 h -1 was calculated as

[0185] The specific results are shown in Table 4 below.

[0186] Gas fermentationOperating period(d)100Working volume(L)4Growth medium(L)520Substrate_CO2(L h -1 )0.1q max _CO2(mol gcell -1 h -1 )0.001Substrate_methanol (mol)10q max _methanol (mol gcell -1 h -1 )0.003Product_acetate (mmol L -1 h -1 )0.73Product_butyrate (mmol L -1 h -1 )0.63NaOH for pH adjustment (L)1Energy (MJ)427Purification processEDBPMEDMembrane (CEM:AEM:BPM)1:1:01:1:1Acetate flux (mol m -2 h -1 )2.021.73Operating period (d)100100Applied voltage1212Membrane area (cm 2 )4.755.55Energy(MJ)497471Base production(L)1-2.6H3PO3for acetic acid(L)0.2 (additional process for acetic acid production)Direct acetic acid productionCost and carbon footprint analysisEDBPMEDMaterial cost analysis ($)159131GHG emission (kg)10.669.87

[0187] Because the ED process had a higher acetate extraction flux, all extractions were completed within 85.5% of the membrane area required for the BPMED process. However, ED requires additional base for the fermentation process and an additional post-treatment process to convert acetate to acetic acid. This scenario considered a treatment process using H3PO4, but did not include the additional heating energy for acetic acid production. Consequently, the ED process required more energy input for the applied voltage and pump operation (497 MJ) than the BPMED process (471 MJ) to extract the same amount of acetate. Despite the larger membrane area and higher membrane cost, the BPMED process is simpler and has 17.6% lower operating costs than the ED process (Figure 9[D] and Table 5).

[0188] These cost savings are due to the elimination of the acid treatment process required to convert acetate to acetic acid and the base generated during the BPMED process. As the productivity of the gas fermentation process increases, the cost-effectiveness of acid recovery also becomes a significant cost factor. In this scenario, the BPMED process is clearly more efficient than the ED process, as the acetate conversion process is minimized.

[0189] Cost Analysis Data for Acetate Production via CO2 Fermentation with ED / BPMED Materials Purification process Unit ED BPMED Growth medium 131.29 131.29 $ pH adjustment 10-16 Acetic acid production 2.0 30 Electricity (CO2 fermentation / Purification process / Acetic acid production) 7.81 (6.46 / 0.97 / 0.38) 9.66 (6.46 / 3.20 / 0) Membrane 13.66 21.34

[0190] For greenhouse gas emissions, an analysis was conducted in a manner similar to the cost analysis. The integrated process utilizing the BPMED system reduced greenhouse gas (CO2) emissions by 7.4% compared to the ED system. Compared to the cost analysis, this small difference indicates a significant environmental cost related to the energy input during process operation, particularly with respect to the acetate extraction rate. The energy requirement for the BPMED system's purification process was approximately three times that of the ED system, but total CO2 emissions were lower. This is due to the elimination of the additional process required to convert acetate to acetic acid and the inclusion of base production for gas fermentation. Calculating the acetic acid production process using the ED system, assuming minimal chemical and pump inputs, confirmed that the BPMED process was more efficient.

[0191] The present invention relates to an integrated system that integrates gas fermentation and BPMED. In gas fermentation, CO2 and methanol are supplied as the main substrates to Eubacterium callanderi KIST612, and then CO2 is converted to acetate (carbon balance, 85% to 95%) to produce 0.167 mmol gcell. -1 h -1 The specific CO2 consumption rate was confirmed.

[0192] Meanwhile, in the subsequent process, acetic acid was produced from microbial fermentation products using a BPMED system. To optimize process conditions, the polarization curve of the BPMED system was measured, and the results confirmed that water dissociation occurred between 8 V and 18 V, depending on the pH and conductivity of each compartment. Specifically, high-purity acetic acid (99.72%) with the lowest divalent ion content was obtained at 8 V. Current efficiency and energy consumption showed decreasing and increasing trends, respectively, depending on the applied potential. This phenomenon was caused by ion leakage at higher electric fields, along with the imperfect ion selectivity of the IEM. In particular, at extremely high voltages, the intermediate layer (IL) or bonding layer of the BPM deteriorated, limiting water dissociation. Consequently, the generated alkaline solution was returned to the gas fermentation system and used to enhance microbial growth through pH adjustment.

[0193] Consequently, cost and carbon emissions were analyzed within the system boundary, including the integrated process, and the BPMED and ED processes were compared. Despite its high-cost membrane, BPMED achieved a 17.6% and 7.4% reduction in cost and CO2 emissions, respectively, compared to ED. Based on these results, BPM was found to be more advantageous in terms of cost and energy savings.

[0194] Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims also fall within the scope of the present invention.

[0195] The present invention relates to a system for producing organic acids from a synthesis gas fermentation product using a bipolar electrodialysis device.

Claims

1. A bioreactor that produces synthetic gas fermentation products using microorganisms; and A bipolar electrodialysis device comprising an electrodialysis device for producing organic acids by electrodialyzing the above-mentioned synthesis gas fermentation product. Organic acid production system from synthesis gas fermentation product using bipolar electrodialysis device.

2. In paragraph 1, The above bipolar electrodialysis device comprises an anode; a first bipolar membrane; an anion exchange membrane; a cation exchange membrane; a second bipolar membrane; and a cathode arranged in sequence. Organic acid production system from synthesis gas fermentation product using bipolar electrodialysis device.

3. In paragraph 1, The above microorganism is selected from the group consisting of Moorella, Clostridium, Ruminococcus, Acetobacterium, Eubacterium, Butyribacterium, Oxobacter, Methanosarcina, Methanosarcina, and Desulfotomaculum. Organic acid production system from synthesis gas fermentation product using bipolar electrodialysis device.

4. In paragraph 1, The organic acid is selected from the group consisting of acetic acid, butyric acid, lactic acid, propionic acid, valeric acid, glycolic acid, sorbic acid, fumaric acid, formic acid, malic acid, tartaric acid and mixtures thereof. Organic acid production system from synthesis gas fermentation product using bipolar electrodialysis device.

5. In paragraph 1, The applied voltage when operating the above bipolar electrodialysis device is less than 20 V. Organic acid production system from synthesis gas fermentation product using bipolar electrodialysis device.

6. In paragraph 1, The above system can simultaneously perform extraction of organic acid precursors contained in synthesis gas fermentation products and production of organic acids. Organic acid production system from synthesis gas fermentation product using bipolar electrodialysis device.

7. In paragraph 1, The above system can improve the microbial fermentation efficiency by resupplying the base produced during the electrodialysis process to the bioreactor. Organic acid production system from synthesis gas fermentation product using bipolar electrodialysis device. 8.1) A step of injecting and fermenting a gaseous substrate into a bioreactor containing microorganisms to obtain a synthesis gas fermentation product; and 2) A step of obtaining an organic acid from the above-mentioned synthesis gas fermentation product using a bipolar electrodialysis device. Method for producing organic acids from synthesis gas fermentation products using a bipolar electrodialysis device.

9. In paragraph 8, Step 2) above is a step of supplying a synthesis gas fermentation product between a cation exchange membrane and an anion exchange membrane of a bipolar electrodialysis device; and A step of applying voltage to the above bipolar electrodialysis device to convert an organic acid precursor contained in a synthesis gas fermentation product into an organic acid. Method for producing organic acids from synthesis gas fermentation products using a bipolar electrodialysis device.

10. Organic acid produced by the production method according to Article 8 or 9.

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