Efficient method for generating organic matters by catalyzing and fixing CO2 through typical mode microbial cathode

Abstract

The invention belongs to the technical field of CO2 resource utilization, and discloses an efficient method for generating organic matters by catalyzing and fixing CO2 through a typical mode microbial cathode, the working principle of the method is as follows: CO2 reduction is realized by driving a microbial carbon sequestration pathway through the extracellular electron uptake effect of microorganisms, and the carbon sequestration pathway of the microorganisms is activated under the condition of applying voltage. Microorganisms absorb electrons from the cathode to obtain energy, and CO2 is converted into organic matters under the carbon sequestration action of the microorganisms; the method comprises the following steps: preparing a biological cathode in a microbial electrosynthesis system, introducing CO2 into a cathode chamber, and setting the polarization potential range of the cathode to be-0.6 V to 1V (vs.SHE); a typical mode microorganism Shewanella oneidensis MR-1 cultured on the cathode directly obtains electrons from the electrode to fix CO2, and an organic matter is synthesized; the biological cathode is high in current density, the speed of reducing CO2 to synthesize organic matter is high, and the biological cathode has important application value on microbial electrochemical CO2 recycling.

Description

Technical Field

[0001] The present invention relates to the technical field of CO2 resource utilization, and mainly to a method for reducing CO2 to produce organic matter by using a microbial electrosynthesis system. Background Art

[0002] The reduction and utilization of CO2 is one of the greatest challenges in the contemporary response to global climate change. So far, a consensus has been reached on reducing CO2 emissions by partially replacing fossil fuels with renewable energy. However, developing new technologies to reduce CO2 concentrations in the atmosphere and thus achieve "negative" carbon emissions remains a huge challenge. Carbon capture and utilization (CCU) technology through catalytic or biological CO2 conversion at large industrial sites is becoming an attractive solution in the global circular carbon economy. Currently, the thermal / electrocatalytic CO2 reduction based on metal-based catalysts is mainly studied to convert CO2 into single-carbon compounds (mainly CO or CH4). Although long-chain hydrocarbons can be produced through CO and / or methanol media, the long-term stability of the catalyst and new technologies to further reduce energy are still under investigation. In order to effectively reduce human dependence on fossil fuels, the bioconversion of CO2 into value-added chemicals is considered to be a highly promising method for CO2 utilization.

[0003] Microbial electrosynthesis (MES) is a new technology that can use electroactive microorganisms as biocatalysts to convert CO2 into fuels and chemicals that are easy to store and transport under the drive of renewable electricity. In MES, electrotrophic microorganisms are able to accept electrons from a solid cathode and use inorganic carbon as the only carbon source for their metabolism and growth. This technology shows many advantages in CO2 utilization and renewable energy development: MES has mild operating conditions, flexible expansion, does not require additional land use, and is easy to efficiently couple with other biological systems (e.g., water treatment, anaerobic digestion, etc.).

[0004] In summary, the application of microbial electrosynthesis in CO2 resource utilization has good research value and application prospects.

[0005] In this regard, Chinese Patent [202010840878.1] discloses a method for electrosynthesis of organic matter by microbial cathode catalytic reduction of CO2. A biological cathode is prepared in a microbial electrosynthesis system, CO2 is introduced into the cathode chamber for cyclic aeration, and the polarization potential range is set to -0.8V~1.2V (vs.Ag / AgC1). The domesticated and cultured microorganisms Ruminococcaceae, Clostridiaceae, and Lachnospiraceae on the cathode obtain electrons from the electrode or the hydrogen generated by the electrode to reduce CO2 and synthesize organic matter. However, this method has two shortcomings. First, since the microorganisms grown at the cathode are anaerobic bacteria, anaerobic sludge with acid-producing ability needs to be domesticated in advance, and microporous aeration is required to ensure the anaerobic environment of the cathode chamber, which is more complicated to operate; second, this method does not detect the yield and yield of the reaction products, and the CO2 conversion efficiency is unclear. Summary of the invention

[0006] The purpose of the present invention is to invent a method for catalytically reducing CO2 to generate organic matter using a typical model microbial electrosynthesis system. The method is characterized by: Shewanella oneidensis MR-1 is enriched at the cathode of the microbial electrosynthesis system and CO2 is synthesized into organic matter through a microbial electrochemical pathway. The organic matter mainly includes acetic acid and ethanol. The present invention overcomes the shortcomings of the prior art, such as complex operating conditions, high energy consumption and high cost.

[0007] A typical model microbial cathode catalytic fixation of CO2 to produce organic matter is an efficient method, the working principle of which is that the CO2 reduction is driven by the microbial carbon fixation pathway through the extracellular electron uptake of the microorganism. When a voltage is applied, the microorganism absorbs electrons from the cathode to obtain energy, and CO2 is simultaneously converted into organic matter by the microbial carbon fixation. The method mainly includes the following steps: (1) Construction of microbial electrosynthesis reaction device: S1. Place the proton exchange membrane at 0.4~0.8 mol·L -1 Soak in NaCl solution for 45-50 h, then rinse with deionized water to allow the proton exchange membrane to be fully soaked; Preferably, the NaCl solution is 0.4 mol·L -1 , 0.6 mol·L -1 or 0.8 mol·L -1 , the soaking time is 45h, 48h or 50h; S2. Use 0.1~0.3 mm titanium wire as conductor, carbon cloth as cathode placed in cathode chamber, titanium plate as anode placed in anode chamber, and Ag / AgCl as reference electrode placed in cathode chamber; Preferably, the titanium wire is 0.1 mm, 0.2 mm or 0.3 mm; S3. inserting a proton exchange membrane between the cathode chamber and the anode chamber; (2) Operation of microbial electrochemical reactor S1. Place the reactor in a dry place and expose it to the sun to remove harmful mold species; S2. Activation of microorganisms: Shewanella oneidensis The initial inoculum of MR-1 was activated in aerobic LB broth medium and shaken at 120-180 rpm for 15-25 h at 28-32 °C; Preferably, the temperature is 28°C, 30°C or 32°C; the shaking speed is 120 rpm, 150 rpm or 180 rpm; the duration is 15h, 20h or 25h; S3. Collect the bacterial cells by centrifugation at 7000-9000 rpm for 3-5 min and wash 3-5 times with fresh cathode electrolyte. Preferably, the centrifugal speed is 7000 rpm, 8000 rpm or 9000 rpm, the time is 3 min, 4 min or 5 min, and the number of washes is 3 times, 4 times or 5 times; S4. Transfer the resuspended bacterial cells to the cathode chamber of the sterile microbial electrosynthesis device and add 70-90 mL of cathode electrolyte to make the final OD600 1. At the same time, add 70-90 mL of anode electrolyte to the anode chamber. Preferably, the anolyte is 70 mL, 80 mL or 90 mL; S5. Microbial cathode enrichment: The potential of the electrode where the microorganisms are located is set to 0.1~0.3 V vs. SHE, and it is run for 10~15 hours to allow the microorganisms to combine with the electrode to form a biofilm; then, the electrode potential of the microbial cathode is set to -0.5 V ~-1 V vs. SHE for microbial electrosynthesis reaction, and CO2 with a purity greater than 99.999% is introduced into the bottom of the cathode chamber; Preferably, 0.1 V vs. SHE, 0.2 V vs. SHE or 0.3 V vs. SHE; the operation time is 10 h, 12 h or 15 h; the potential is set to -0.5 V vs. SHE, -0.8 V vs. SHE or -1 V vs. SHE; S6. Perform microporous aeration. The microbial electrosynthesis cycle is 4 to 6 days. After each cycle, replace 75 to 85% of the cathode liquid and start the next cycle.

[0008] Preferably, the cycle is 4 days, 5 days or 6 days; and the cathode liquid is replaced by 75%, 80% or 85%.

[0009] In some embodiments, the microbial electrosynthesis system is a dual-chamber microbial electrochemical reactor.

[0010] In some embodiments, the cathode electrolyte is a microbial liquid culture solution, comprising 0.25 ~ 2 mM NH4Cl, 80 ~ 120 mM NaCl, 1.5 ~ 2.5 mM K2HPO4, 1.5 ~ 2.5 mM KH2PO4, 1.1.3 ~ 1.4 mM KCl, 35 ~ 45 mM NaHCO3, 2 ~ 3 mM CaCl2, 1.5 ~ 2.5 mM gSO4·7H2O, 0.8 ~ 1.2 mL·L - ¹Trace element solution and 0.8~1.2 mL·L - ¹ Vitamin solution.

[0011] Preferably, the microbial liquid culture medium is 0.25 ~ 2 mM NH4Cl, 2 mM K2HPO4, 1 mL·L - ¹Trace element solution.

[0012] In some embodiments, the active ingredient of the aerobic LB broth medium is 9-11 g L tryptone. -1 , yeast extract 4~ 6 g·L -1 and NaCl 9~11 g·L -1 .

[0013] Preferably, tryptone is 9 g·L -1 , 10 g·L -1 or 11 g L -1 .

[0014] In some of the embodiments, the anolyte is a phosphate buffer solution comprising 40-60 mM KH2PO4 and 20-25 mM NaOH, with a pH of 6.7-6.9.

[0015] Preferably, the pH is 6.7, 6.8 or 6.9.

[0016] In some embodiments, the gas inlet of the cathode chamber is connected to a gas flow meter, and microporous aeration is performed by CO2 aeration, with a flow rate of 1-3 mL·min - ¹, aeration for 1~3 hours, stop for 6~10 hours.

[0017] Preferably, the flow rate is 1 mL min - ¹、2 mL·min - ¹ or 3 mL min -¹, aeration for 1h, 2h or 3h, stop for 6h, 8h or 10h.

[0018] In some embodiments, the organic matter mainly includes acetic acid and ethanol.

[0019] In some of the embodiments, the reaction temperature of the microbial electrosynthesis system is 30 ± 1 °C.

[0020] In some of the embodiments, the cathode current density and the production and yield of reaction products are detected to evaluate the CO2 conversion efficiency.

[0021] (1) No need for anaerobic operation: The present invention adopts Shewanella oneidensis MR-1 microorganisms do not require a special anaerobic environment, which simplifies the operation process and experimental conditions and reduces equipment and operation costs; (2) Strong electron transfer ability: The microorganism has excellent electron transfer ability and can efficiently use electrical energy to reduce CO2, significantly improving the CO2 conversion efficiency; (3) Mature genetic manipulation technology: Shewanella oneidensis The genetic manipulation technology of MR-1 has matured, and its metabolic pathway can be optimized through genetic engineering to further enhance the ability to convert CO2 into high value-added organic matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the microbial electrosynthesis system; Figure 2 is the acetic acid production rate of different microorganisms reported in unmodified microbial electrosynthesis system; Figure 3 The current density generated by different microbial cathodes reported; Figure 4 is the acetic acid production in four microbial electrosynthetic reaction cycles; Figure 5 is the acetic acid production in 24 h under different applied voltage conditions; Figure 6 is the change of cathode current density under different applied voltage conditions; Figure 7 Effects of different nitrogen source addition amounts on acetic acid production. DETAILED DESCRIPTION

[0023] In order to facilitate the understanding of the technical implementation method of the present invention, the technical scheme in the embodiment of the present invention will be clearly and completely described below in combination with the technical process steps, specific implementation conditions and materials in the embodiment of the present invention. Obviously, the described embodiment is only a part of the embodiment of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Example

[0024] like Figure 1 As shown, the proton exchange membrane was placed in 0.4 mol·L -1 Soak in NaCl solution for 45 h, then clean with deionized water to fully infiltrate the proton exchange membrane; then use 0.1 mm titanium wire as the conductor, carbon cloth as the cathode placed in the cathode chamber, titanium plate as the anode placed in the anode chamber, and Ag / AgCl as the reference electrode placed in the cathode chamber; then insert the proton exchange membrane between the cathode chamber and the anode chamber to construct the microbial electrosynthesis reaction device. Then place the reaction device in a dry place for exposure to the sun to remove bad mold strains; Shewanella oneidensis The initial inoculum of MR-1 was grown in aerobic LB broth (tryptone 9 g L -1 , yeast extract 4 g·L -1 and NaCl 9 g·L -1 ) and activated at 120 rpm for 15 h at 25 ℃; the bacterial cells were collected by centrifugation at 7000 rpm for 3 min and washed with 0.25 mM NH4Cl, 90 mM NaCl, 1.5 mM K2HPO4, 1.5 mM KH2PO4, 1.25 mM KCl, 30 mM NaHCO3, 2.0 mM CaCl2, 1.5 mM MgSO4·7H2O, 0.8 mL·L - ¹Trace element solution and 0.8 mL·L - The cells were washed three times with fresh cathode electrolyte consisting of ¹vitamin solution, and then the resuspended bacterial cells were transferred to the cathode chamber of the sterile microbial electrosynthesis device with 70 mL cathode electrolyte added to make the final OD600 1. At the same time, 70 mL of anolyte consisting of 40 mM KH2PO4 and 20 mM NaOH was added to the anode chamber; finally, the potential of the electrode where the microorganisms were located was set to 0.1 V vs. SHE, and the operation was carried out for 10 h to allow the microorganisms to combine with the electrode to form a biofilm; subsequently, the electrode potential of the microbial cathode was set to -0.6 V vs. SHE for microbial electrosynthesis reaction, and CO2 with a purity greater than 99.999% was introduced at the bottom of the cathode chamber at a gas flow rate of 1 mL min-1 ; Finally, microporous aeration was carried out, the microbial electrosynthesis cycle was 4 days, and the acetic acid production in one reaction cycle reached 3.15 mM. Example

[0025] like Figure 1 As shown, the proton exchange membrane was placed in 0.6 mol·L - ¹ NaCl solution for 48 h, then cleaned with deionized water to fully infiltrate the proton exchange membrane; 0.2 mm titanium wire was used as the conductor, carbon cloth was placed in the cathode chamber as the cathode, titanium plate was placed in the anode chamber as the anode, and Ag / AgCl was used as the reference electrode and placed in the cathode chamber; then the proton exchange membrane was inserted between the cathode chamber and the anode chamber to construct a microbial electrosynthesis reaction device. The device was placed in a dry place and exposed to the sun to remove bad mold species; Shewanella oneidensis The initial inoculum of MR-1 was grown in aerobic LB broth (tryptone 10 g L - ¹, yeast extract 5 g·L - , - ¹, NaCl 10 g·L - ¹) and activated at 35 °C with shaking at 150 rpm for 20 h; the bacterial cells were collected by centrifugation at 8000 rpm for 4 min and washed with 0.5 mM NH4Cl, 100 mM NaCl, 2.0 mM K2HPO4, 2.0 mM KH2PO4, 1.35 mM KCl, 35 mM NaHCO3, 2.5 mM CaCl2, 2.0 mM MgSO4·7H2O, 1 mL·L - ¹Trace element solution and 1 mL·L - ¹ The fresh cathode electrolyte of the vitamin solution was washed 4 times; then the resuspended bacterial cells were transferred to the cathode chamber of the sterile microbial electrosynthesis device with 80 mL of cathode electrolyte, so that the final OD600 was 1, and 80 mL of anolyte composed of 50 mM KH2PO4 and 22 mM NaOH was added to the anode chamber. The potential of the electrode where the microorganisms were located was set to 0.2 V vs. SHE, and it was run for 12 h to allow the microorganisms to combine with the electrode to form a biofilm; then, the electrode potential of the microbial cathode was set to -0.8 V vs. SHE for microbial electrosynthesis reaction, and CO2 with a purity greater than 99.999% was introduced at the bottom of the cathode chamber at a gas flow rate of 2 mL min - ¹; Finally, microporous aeration was carried out, the microbial electrosynthesis cycle was 5 days, and the acetic acid production in one reaction cycle reached 4.28 mM. Example

[0026] like Figure 1As shown, the proton exchange membrane was placed in 0.8 mol·L - ¹ NaCl solution for 50 h, then cleaned with deionized water to fully infiltrate the proton exchange membrane; 0.3 mm titanium wire was used as the conductor, carbon cloth was placed in the cathode chamber as the cathode, titanium plate was placed in the anode chamber as the anode, and Ag / AgCl was used as the reference electrode and placed in the cathode chamber; then the proton exchange membrane was inserted between the cathode chamber and the anode chamber to construct a microbial electrosynthesis reaction device. The device was placed in a dry place and exposed to the sun to remove bad mold species; Shewanella oneidensis The initial inoculum of MR-1 was grown in aerobic LB broth (tryptone 11 g L - ¹, yeast extract 6 g·L - ¹, NaCl 11 g L - ¹) and activated at 30 ℃ with shaking at 180 rpm for 25 h; the bacterial cells were collected by centrifugation at 9000 rpm for 5 min and washed with 1.0 mM NH4Cl, 110 mM NaCl, 2.5 mM K2HPO4, 2.5 mM KH2PO4, 1.5 mM KCl, 40 mM NaHCO3, 3.0 mM CaCl2, 2.5 mMMgSO4·7H2O, 1.2 mL·L - ¹Trace element solution and 1.2 mL·L - ¹ The fresh cathode electrolyte of the vitamin solution was washed 5 times; then the resuspended bacterial cells were transferred to the cathode chamber of the sterile microbial electrosynthesis device with 90 mL of cathode electrolyte, so that the final OD600 was 1, and 90 mL of anolyte composed of 60 mM KH2PO4 and 25 mM NaOH was added to the anode chamber. The potential of the electrode where the microorganisms were located was set to 0.3 V vs. SHE, and it was run for 15 h to allow the microorganisms to combine with the electrode to form a biofilm; then, the electrode potential of the microbial cathode was set to -0.8 V vs. SHE for microbial electrosynthesis reaction, and CO2 with a purity greater than 99.999% was introduced at the bottom of the cathode chamber at a gas flow rate of 3 mL min - ¹; Finally, microporous aeration was performed, and the microbial electrosynthesis cycle was 6 days. The acetic acid production rate in one reaction cycle reached 78.6 mmol·m - ²·day - The acetic acid production rate of this example was compared with that of the unmodified MES using pure bacteria reported in the current literature, and the results are as follows: Figure 2 As shown in Figure 2, MR-1 showed the highest acetic acid production rate. Since the rate-limiting step of microbial electrosynthesis is the electron transfer from the electrode to the microorganism, the cathode current density generated by these microorganisms was further compared, as shown in Figure 2. Figure 3The results showed that the high acetate production rate of MR-1 may be mainly attributed to the strong electron transfer ability of this strain. Example

[0027] like Figure 1 As shown, the proton exchange membrane was placed in 1.0 mol·L - ¹ NaCl solution for 52 h, then cleaned with deionized water to fully infiltrate the proton exchange membrane; 0.2 mm titanium wire was used as the conductor, carbon cloth was placed in the cathode chamber as the cathode, titanium plate was placed in the anode chamber as the anode, and Ag / AgCl was used as the reference electrode and placed in the cathode chamber; then the proton exchange membrane was inserted between the cathode chamber and the anode chamber to construct a microbial electrosynthesis reaction device. The device was placed in a dry place and exposed to the sun to remove bad mold species; Shewanella oneidensis The initial inoculum of MR-1 was grown in aerobic LB broth (tryptone 12 g L - ¹, yeast extract 7 g·L - ¹, NaCl 12 g·L - ¹) and activated at 200 rpm at 30 ℃ for 18 h; the bacterial cells were collected by centrifugation at 8500 rpm for 4 min and washed with 1.2 mM NH4Cl, 120 mM NaCl, 3.0 mM K2HPO4, 3.0 mM KH2PO4, 1.7 mM KCl, 45 mM NaHCO3, 3.5 mM CaCl2, 3.0 mMMgSO4·7H2O, 1.5 mL·L - ¹Trace element solution and 1.5 mL·L - ¹ The fresh cathode electrolyte of the vitamin solution was washed three times; then the resuspended bacterial cells were transferred to the cathode chamber of the sterile microbial electrosynthesis device with 100 mL of cathode electrolyte added to make the final OD600 1, and 100 mL of anolyte composed of 70 mM KH2PO4 and 28 mM NaOH was added to the anode chamber. The potential of the electrode where the microorganisms were located was set to 0.25 V vs. SHE, and it was run for 10 h to allow the microorganisms to combine with the electrode to form a biofilm; then, the electrode potential of the microbial cathode was set to -0.8 V vs. SHE for microbial electrosynthesis reaction, and CO2 with a purity greater than 99.999% was introduced at the bottom of the cathode chamber at a gas flow rate of 4 mL min - ¹; Finally, microporous aeration was performed, and the microbial electrosynthesis cycle was 5 days. The acetic acid production rate in one reaction cycle reached 80.2 mmol·m - ²·day - ¹. After four reaction cycles, the acetic acid production did not significantly decrease. Figure 4As shown, it is indicated that the microbial cathode of the present invention has good stability and can carry out CO2 reduction sustainably. Example

[0028] like Figure 1 As shown, the proton exchange membrane was placed in 0.5 mol·L - ¹ KCl solution for 40 h, then cleaned with deionized water to fully infiltrate the proton exchange membrane; 0.15 mm titanium wire was used as the conductor, carbon cloth was placed in the cathode chamber as the cathode, titanium plate was placed in the anode chamber as the anode, and Ag / AgCl was used as the reference electrode and placed in the cathode chamber; then the proton exchange membrane was inserted between the cathode chamber and the anode chamber to construct a microbial electrosynthesis reaction device. The device was placed in a dry place and exposed to the sun to remove bad mold species; Shewanella oneidensis The initial inoculum of MR-1 was grown in aerobic LB broth (tryptone 8 g L - ¹, yeast extract 5 g·L - ¹, KCl 8 g·L - ¹) and activated at 26 °C with shaking at 170 rpm for 16 h; the bacterial cells were collected by centrifugation at 7000 rpm for 3 min and washed with 1.0 mM NH4Cl, 85 mM KCl, 2.0 mM K2HPO4, 2.0 mM KH2PO4, 1.2 mM KCl, 38 mM NaHCO3, 2.0 mM CaCl2, 1.8 mMMgSO4·7H2O, 1 mL·L - ¹Trace element solution and 1 mL·L - ¹ The fresh cathode electrolyte of the vitamin solution was washed 5 times; then the resuspended bacterial cells were transferred to the cathode chamber of the sterile microbial electrosynthesis device with 85 mL of cathode electrolyte, so that the final OD600 was 1, and 85 mL of anolyte composed of 45 mM KH2PO4 and 25 mM KOH was added to the anode chamber. The potential of the electrode where the microorganisms were located was set to 0.15 V vs. SHE, and it was run for 9 h to allow the microorganisms to combine with the electrode to form a biofilm; then, the electrode potential of the microbial cathode was set to -0.9 V vs. SHE for microbial electrosynthesis reaction, and CO2 with a purity greater than 99.999% was introduced at the bottom of the cathode chamber at a gas flow rate of 2 mL min - ¹; Finally, microporous aeration was performed, and the microbial electrosynthesis cycle was 4 days. The acetic acid production rate in one reaction cycle reached 72.5 mmol·m - ²·day - ¹. Example

[0029] like Figure 1As shown, the proton exchange membrane was placed in 0.3 mol·L - ¹ NaBr solution for 36 h, then cleaned with deionized water to fully infiltrate the proton exchange membrane; 0.25 mm titanium wire was used as the conductor, carbon cloth was placed in the cathode chamber as the cathode, titanium plate was placed in the anode chamber as the anode, and Ag / AgCl was used as the reference electrode and placed in the cathode chamber; then the proton exchange membrane was inserted between the cathode chamber and the anode chamber to construct a microbial electrosynthesis reaction device. The device was placed in a dry place and exposed to the sun to remove bad mold species; Shewanella oneidensis The initial inoculum of MR-1 was grown in aerobic LB broth (tryptone 9 g L - ¹, yeast extract 4 g·L - ¹, NaBr 9 g·L - ¹) and activated at 32 °C with shaking at 180 rpm for 22 h; the bacterial cells were collected by centrifugation at 7500 rpm for 4 min and washed with 1.5 mM NH4Cl, 95 mMNaBr, 3.5 mM K2HPO4, 3.5 mM KH2PO4, 1.6 mM KCl, 50 mM NaHCO3, 2.8 mM CaCl2, 2.5 mMMgSO4·7H2O, 1.3 mL·L - ¹Trace element solution and 1.3 mL·L - ¹ The fresh cathode electrolyte of the vitamin solution was washed 4 times; then the resuspended bacterial cells were transferred to the cathode chamber of the sterile microbial electrosynthesis device with 75 mL of cathode electrolyte added to make the final OD600 1, and 75 mL of anolyte composed of 55 mM KH2PO4 and 30 mM NaOH was added to the anode chamber. The potential of the electrode where the microorganisms were located was set to 0.18 V vs. SHE, and it was run for 11 h to allow the microorganisms to combine with the electrode to form a biofilm; then, the electrode potential of the microbial cathode was set to -1.0 V vs. SHE for microbial electrosynthesis reaction, and CO2 with a purity greater than 99.999% was introduced at the bottom of the cathode chamber at a gas flow rate of 3 mL min - ¹; Finally, microporous aeration was performed, and the microbial electrosynthesis cycle was 6 days. The acetic acid production rate in one reaction cycle reached 76.8 mmol·m - ²·day - ¹.

[0030] Comparative Example 1 In the microbial electrosynthesis system of the present invention, when the reaction temperature is controlled at 35°C and the cathode potential is controlled at -0.5~-1.4 V vs. SHE, the acetic acid production gradually increases with the increase of the potential, but the acetic acid production reaches a plateau after the voltage is higher than -1.1 V. Figure 5 By comparing the total current density of the cathode and the current density used for acetic acid production at different voltages, it is found that when the voltage is higher than -0.9 V, the proportion of current density used for acetic acid production gradually decreases, as shown in Figure 6 As shown, it is speculated that too high a voltage will cause water electrolysis, resulting in electrons being lost through the production of H2 instead of being absorbed by microorganisms for CO2 reduction. Therefore, the applied electrode potential should not be too high to avoid energy loss.

[0031] Comparative Example 2 In the microbial electrosynthesis system of the present invention, when the reaction temperature was controlled at 30°C, the cathode potential was controlled at -0.9V vs. SHE, no nitrogen source was added or 0-2 mM NH4Cl was added as a nitrogen source. Figure 7 As shown, acetic acid can be produced within the nitrogen source addition concentration range of the present invention. However, when no nitrogen source is added, no acetic acid is detected during the entire reaction cycle, indicating that nitrogen source is essential for CO2 conversion of MR-1.

[0032] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An efficient method for producing organic matter by cathode catalytic fixation of CO2 by typical model microorganisms, characterized in that: The working principle of the method is that the CO2 reduction is achieved by the microbial carbon fixation pathway driven by the extracellular electron uptake of the microorganism. When a voltage is applied, the microorganism absorbs electrons from the cathode to obtain energy, and CO2 is simultaneously converted into organic matter by the microbial carbon fixation. The method mainly includes the following steps: (1) Construction of microbial electrosynthesis reaction device: S1. Place the proton exchange membrane at 0.4~0.8 mol·L -1 Soak in NaCl solution for 45-50 h, then rinse with deionized water to allow the proton exchange membrane to be fully soaked; S2. Use 0.1~0.3 mm titanium wire as conductor, carbon cloth as cathode placed in cathode chamber, titanium plate as anode placed in anode chamber, and Ag / AgCl as reference electrode placed in cathode chamber; S3. inserting a proton exchange membrane between the cathode chamber and the anode chamber; (2) Operation of microbial electrochemical reactor: S1. Place the reactor in a dry place and expose it to the sun to remove harmful mold species; S2. Activation of microorganisms: Shewanella oneidensis The initial inoculum of MR-1 was activated in aerobic LB broth medium and shaken at 120-180 rpm for 15-25 h at 28-32 °C; S3. Collect the bacterial cells by centrifugation at 7000-9000 rpm for 3-5 min and wash 3-5 times with fresh cathode electrolyte. S4. Transfer the resuspended bacterial cells to the cathode chamber of the sterile microbial electrosynthesis device and add 70-90 mL of cathode electrolyte to make the final OD600 1. At the same time, add 70-90 mL of anode electrolyte to the anode chamber. S5. Microbial cathode enrichment: The potential of the electrode where the microorganisms are located is set to 0.1~0.3 V vs. SHE, and it is run for 10~15 hours to allow the microorganisms to combine with the electrode to form a biofilm; then, the electrode potential of the microbial cathode is set to -0.5 V ~ -1 V vs. SHE for microbial electrosynthesis reaction, and CO2 with a purity greater than 99.999% is introduced into the bottom of the cathode chamber; S6. Perform microporous aeration, and the microbial electrosynthesis cycle is 4 to 6 days. After each cycle, replace 75 to 85% of the cathode liquid and start the next cycle.

2. According to claim 1, a highly efficient method for producing organic matter by cathode catalytic fixation of CO2 using typical model microorganisms is characterized in that: The microbial electrosynthesis system is a double-chamber microbial electrochemical reactor.

3. The efficient method for producing organic matter by cathode catalytic fixation of CO2 by typical model microorganisms according to claim 1, characterized in that: The cathode electrolyte is a microbial liquid culture solution, comprising 0.25 ~ 2 mM NH4Cl, 80 ~ 120 mM NaCl, 1.5 ~ 2.5 mM K2HPO4, 1.5 ~ 2.5 mM KH2PO4, 1.1.3 ~ 1.4 mM ~ KCl, 35 ~ 45 mM NaHCO3, 2 ~ 3 mM CaCl2, 1.5 ~ 2.5 mM gSO4·7H2O, 0.8 ~ 1.2 mL·L - ¹Trace element solution and 0.8~1.2mL·L - ¹ Vitamin solution.

4. The highly efficient method for producing organic matter by cathode catalytic fixation of CO2 by typical model microorganisms according to claim 1, characterized in that: The active ingredient of the aerobic LB broth medium is 9-11 g·L tryptone. -1 , yeast extract 4~6 g·L -1 and NaCl 9~11 g·L -1 .

5. The efficient method for producing organic matter by cathode catalytic fixation of CO2 by typical model microorganisms according to claim 1, characterized in that: The anode electrolyte is a phosphate buffer solution containing 40-60 mM KH2PO4 and 20-25 mM NaOH, with a pH of 6.7-6.

9.

6. The highly efficient method for producing organic matter by cathode catalytic fixation of CO2 by typical model microorganisms according to claim 1, characterized in that: The gas inlet of the cathode chamber is connected to a gas flow meter, and microporous aeration is performed by CO2 aeration, with a flow rate of 1-3 mL·min - ¹, aeration for 1~3 hours, stop for 6~10 hours.

7. The highly efficient method for producing organic matter by cathode catalytic fixation of CO2 by typical model microorganisms according to claim 1, characterized in that: The organic matter mainly includes acetic acid and ethanol.

8. The highly efficient method for producing organic matter by cathode catalytic fixation of CO2 by typical model microorganisms according to claim 1, characterized in that: The reaction temperature of the microbial electrosynthesis system is 30 ± 1 °C.

9. The highly efficient method for producing organic matter by cathode catalytic fixation of CO2 by typical model microorganisms according to claim 1, characterized in that: It also includes testing the cathode current density and the production and yield of reaction products to evaluate the CO2 conversion efficiency.

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