A microbial electrochemical system device and method for realizing in-situ synthesis of wastewater treatment, co2 fixation and microbial protein

Abstract

The application discloses a microbial electrochemical system device and method for realizing wastewater treatment, CO2 fixation and in-situ synthesis of microbial protein synchronously, which comprises an anode chamber, a cathode chamber, a protein production chamber, a power supply, a mixed gas tank and a peristaltic pump; the anode chamber, the cathode chamber and the protein production chamber are sequentially arranged from left to right; a cation exchange membrane is arranged between the anode chamber and the cathode chamber; a cation exchange membrane is also arranged between the cathode chamber and the protein production chamber; an anode is arranged in the anode chamber and connected with the positive pole of the power supply through a wire, and a resistor is arranged on the wire connecting the anode and the positive pole of the power supply. The microbial electrochemical system and the protein production system are coupled to form an ammonia-nitrogen recovery-in-situ protein synthesis microbial electrochemical system, the system can convert active nitrogen into high-value protein products in-situ, the system can synchronously treat wastewater, recover ammonia-nitrogen and fix carbon dioxide, and has excellent environmental benefits.

Description

Technical Field

[0001] This invention relates to the field of microbial protein synthesis technology. More specifically, it relates to a microbial electrochemical system device and method that simultaneously realizes wastewater treatment, CO2 fixation, and in-situ synthesis of microbial proteins. Background Technology

[0002] The advent of the Haber-Bosch process in 1900 led to a rapid increase in industrial nitrogen fertilizer production, resulting in a historic rise in crop yields. Nitrogen fertilizer altered the nitrogen cycle; 30% of nitrogen is now generated by human activities (primarily the production and use of nitrogen fertilizer), and this figure is projected to rise further. This has led to numerous environmental problems, such as eutrophication and ecosystem degradation caused by the discharge of wastewater into the natural environment.

[0003] It is reported that the world's population is projected to reach 10 billion by 2050, increasing food demand by 30%-60%. This rapid population growth leads to a surge in protein demand, but in traditional protein cycles, protein loss during livestock and agricultural production reaches as high as 72%, and during pasture farming, the loss reaches as high as 82%. Recent research predicts that the efficiency of the nitrogen cycle in nature is only 16%. Traditional protein production methods require large amounts of arable land and have adverse environmental impacts, such as greenhouse gas emissions, water pollution, and soil erosion. It is reported that agriculture alone accounts for 10%-12% of global greenhouse gas emissions. Therefore, it is necessary to seek new protein supply methods that reduce reactive nitrogen loss and increase protein supply.

[0004] The greenhouse effect has become one of the limiting factors for sustainable human development, leading to global warming and even disrupting the ecological balance. Carbon dioxide is a major greenhouse gas; therefore, the CO2 problem urgently needs to be addressed, requiring a solution for carbon dioxide fixation.

[0005] Microbial protein, also known as biological protein or single-cell protein, can be produced by algae, yeast, bacteria, and fungi. It is a high-value-added product that can be used as a protein supplement in animal feed. The advantages of producing microbial protein from high-ammonia nitrogen wastewater using hydroxide bacteria include: 1) reduced wastewater treatment operating costs; 2) lower dependence on land use, reducing pressure on arable land; and 3) CO2 fixation capacity, thus mitigating the greenhouse effect.

[0006] With a growing global population and increasing food crises, research on recycling waste into high-value products is on the rise, such as studies on nitrogen-containing wastewater and the production of microbial proteins from various related microorganisms. This year, many scholars both domestically and internationally have focused on researching the production of microbial proteins from ammonia nitrogen recovered through electrochemical systems, aiming to address the problem of insufficient supply from traditional protein production methods.

[0007] Currently, many researchers use electrochemical methods to recover ammonia nitrogen for microbial protein production, but this simply involves transferring the recovered ammonia nitrogen to another reactor for protein production. This transfer process incurs losses and setbacks. Furthermore, protein production requires diluting the recovered ammonia nitrogen to achieve a suitable concentration for protein-producing microorganisms. These processes significantly increase losses and energy consumption.

[0008] In summary, there is a need for a novel method for microbial protein synthesis that can simultaneously treat wastewater, fix carbon dioxide, convert reactive nitrogen in the system into high-protein products in situ, and reduce losses and energy consumption. Summary of the Invention

[0009] The first technical problem to be solved by the present invention is to provide a microbial electrochemical system device that simultaneously realizes wastewater treatment, CO2 fixation and in-situ synthesis of microbial proteins.

[0010] The second technical problem to be solved by the present invention is to provide a method for simultaneously realizing wastewater treatment, CO2 fixation and in-situ synthesis of microbial proteins using the above-mentioned microbial electrochemical system device.

[0011] This invention couples a microbial chemical system and a protein production system to form a "ammonia nitrogen recovery-in-situ protein synthesis" microbial electrochemical system. This system can convert active nitrogen into high-value-added protein products in situ. This system can simultaneously treat wastewater, recover ammonia nitrogen, and fix carbon dioxide, and has excellent environmental benefits.

[0012] To solve the first technical problem mentioned above, the invention adopts the following technical solution:

[0013] A microbial electrochemical system device that simultaneously realizes wastewater treatment, CO2 fixation and in-situ synthesis of microbial proteins includes an anode chamber, a cathode chamber, a protein production chamber, a power supply, a mixing gas tank, and a peristaltic pump;

[0014] The anode chamber, cathode chamber, and protein production chamber are arranged sequentially from left to right;

[0015] A cation exchange membrane is located between the anode chamber and the cathode chamber.

[0016] A cation exchange membrane is also used between the cathode chamber and the protein production chamber.

[0017] The anode chamber is provided with an anode, which is connected to the positive terminal of the power supply via a wire, and a resistor is provided on the wire connecting the anode and the positive terminal of the power supply;

[0018] The cathode chamber contains a cathode, which is connected to the negative terminal of a power source via a wire;

[0019] The protein production chamber is connected to the mixed gas tank through an air inlet pipe and an air outlet pipe to form a circulation loop, and the peristaltic pump is installed on the air inlet pipe.

[0020] Preferably, the anode chamber is connected to a first storage gas bag via a pipe, and the cathode chamber is connected to a second storage gas bag via a pipe.

[0021] Preferably, both the anode chamber and the cathode chamber are directly connected to the mixed gas tank via pipelines.

[0022] Preferably, the anode is made of carbon brush; the cathode is made of graphite plate.

[0023] To solve the second technical problem mentioned above, the invention adopts the following technical solution:

[0024] A method for simultaneously achieving wastewater treatment, CO2 fixation, and in-situ synthesis of microbial proteins using a microbial electrochemical system includes the following steps:

[0025] S1. Fabricate the anode carbon brush and cathode electrode required for the microbial electrochemical system, and perform pretreatment;

[0026] S2. Inoculate the anode chamber with anaerobic sludge, add nutrient solution, and introduce nitrogen gas to maintain a strictly anaerobic environment; add potassium ferricyanide solution to the cathode chamber; cultivate and acclimate the anaerobic sludge to enrich the anode with electrogenic microorganisms.

[0027] S3. After the electrogenic microorganisms in the anode chamber have been cultured and domesticated, the potassium ferricyanide solution in the cathode chamber is replaced with a phosphate buffer solution; at the same time, protein-producing culture medium is added to the protein-producing chamber to form a three-chamber microbial electrochemical system.

[0028] S4. At different temperatures, different voltages are applied to the power supply. The domesticated protein-producing microorganisms are inoculated into the protein-producing chamber and a mixture of carbon dioxide, hydrogen and oxygen is introduced to carry out protein production culture, thus obtaining the "ammonia nitrogen recovery-in-situ protein synthesis" microbial electrochemical system.

[0029] S5. Process the culture products in the protein production chamber to obtain microbial protein.

[0030] As a further improvement to the technical solution, step S1 includes the following preprocessing steps:

[0031] S1-1, Process carbon fiber filaments and titanium wires with a diameter of 0.8-1.2mm into carbon brushes;

[0032] S1-2, Use 0.9-1.1 mol·L⁻¹ on the carbon brush. -1 Soak in NaOH solution for 5-7 hours to remove impurity ions;

[0033] S1-3, using 0.9-1.1 mol·L -1 Soak in HCl for 5-7 hours, then ultrasonically clean with deionized water until neutral.

[0034] S1-4. Boil in deionized water for 2.5-3.5 hours, changing the water every 25-35 minutes.

[0035] S1-5. Heat the carbon brushes in a muffle furnace to obtain the carbon brushes required for the experiment.

[0036] S1-6. Cut the graphite plate into cubes of 4cm*4cm*0.5cm;

[0037] S1-7. Soak in 0.9-1.1 mol·L-1 NaOH solution for 4-6 hours to remove impurity ions;

[0038] S1-8: Soak in 0.9-1.1 mol·L-1 HCl for 5-7 hours, then ultrasonically clean with deionized water until neutral to obtain the graphite plate required for the cathode.

[0039] Preferably, in step S1-1, the carbon brush is 5-7 cm long and 3-5 cm in diameter.

[0040] Preferably, in steps S1-5, the temperature of the muffle furnace heating treatment is 480-520℃, and the treatment time is 9-11 minutes.

[0041] As a further improvement to the technical solution, step S2 includes the following specific steps:

[0042] S2-1. Use anaerobic sludge from the thickening tank of the sewage treatment plant as inoculum. After the anaerobic sludge is settled, pour off the supernatant.

[0043] S2-2. Anaerobic sludge and nutrient solution are added to an anode chamber with a carbon brush to form an anolyte.

[0044] S2-3. Nitrogen gas is continuously introduced into the anode chamber to remove oxygen and maintain a strictly anaerobic environment.

[0045] S2-4. Add potassium ferricyanide solution to the cathode chamber as the cathode solution;

[0046] S2-5. The anode, resistor and cathode are connected in series to form a microbial fuel cell. At a suitable temperature of 25-32℃, electrogenic microorganisms derived from anaerobic sludge are cultivated and domesticated on the anode carbon brush, so that electrogenic microorganisms are enriched on the anode.

[0047] Preferably, in step S2-2, the nutrient solution is formulated to contain the following substances per liter of solution: 3 mg magnesium sulfate, 0.13 mg zinc chloride, 0.005 mg zinc sulfate heptahydrate, 1.5 mg nitric acid, 0.5 mg manganese sulfate monohydrate, 310 mg ammonium chloride, 130 mg potassium chloride, 0.01 mg boric acid, 0.01 mg cobalt chloride hexahydrate, 5 mg nicotinic acid, 2 mg folic acid, 0.01 mg copper sulfate pentahydrate, 0.024 mg nickel chloride hexahydrate, 0.024 mg sodium tungstate dihydrate, 0.1 mg B-12, 5 mg vitamin B1, 6 mg vitamin B2, 10 mg vitamin B6, 6 mg para-aminobenzoic acid, and 2000 mg sodium acetate.

[0048] Preferably, in step S2-2, the pH of the anolyte in the anode chamber is 6.5-7.5.

[0049] Preferably, in step S2-2, the volume ratio of anaerobic sludge to nutrient solution is 1:1.

[0050] Preferably, in steps S2-3, the nitrogen gas is introduced for 9-11 minutes.

[0051] Preferably, in steps S2-4, the concentration of the potassium ferricyanide solution is 15-17 g / L.

[0052] Preferably, in steps S2-5, the resistance is 950-1050Ω.

[0053] As a further improvement to the technical solution, step S3 includes the following specific steps:

[0054] S3-1. After the electrogenic microorganisms in the anode chamber have been cultured, replace the solution in the anode chamber with fresh nutrient solution.

[0055] S3-2. Prepare a phosphate buffer solution for recovering ammonia nitrogen as the catholyte;

[0056] S3-3, Inject cathodic liquid into the cathode chamber;

[0057] S3-4. Connect the anode, resistor, power supply and cathode in series;

[0058] S3-5. Simultaneously, protein-producing culture medium is added to the protein-producing chamber to form a three-chambered microbial electrochemical system device.

[0059] Preferably, in step S3-1, the fresh nutrient solution is formulated to contain the following substances per liter of solution: 3 mg magnesium sulfate, 0.13 mg zinc chloride, 0.005 mg zinc sulfate heptahydrate, 1.5 mg nitric acid, 0.5 mg manganese sulfate monohydrate, 310 mg ammonium chloride, 130 mg potassium chloride, 0.01 mg boric acid, 0.01 mg cobalt chloride hexahydrate, 5 mg nicotinic acid, 2 mg folic acid, 0.01 mg copper sulfate pentahydrate, 0.024 mg nickel chloride hexahydrate, 0.024 mg sodium tungstate dihydrate, 0.1 mg B-12, 5 mg vitamin B1, 6 mg vitamin B2, 10 mg vitamin B6, 6 mg para-aminobenzoic acid, 1462 mg (1560 mg COD) glucose or 2000 mg sodium acetate (1560 mg COD) or 1820 mg sodium lactate (1560 mg COD);

[0060] Preferably, in step S3-2, each liter of the catholyte comprises the following substances: 140-11400 mg of dipotassium hydrogen phosphate and 1340-6000 mg of sodium dihydrogen phosphate.

[0061] Preferably, in steps S3-4, the resistance is 8-12Ω.

[0062] Preferably, in steps S3-5, the protein-producing culture medium is formulated to contain the following substances per liter of solution: 2.3g potassium dihydrogen phosphate, 2.9g disodium hydrogen phosphate, 0.5g magnesium sulfate, 0.5g sodium carbonate, 0.01g calcium chloride, 0.05g ferric ammonium citrate, 0.6mg boric acid, 0.4mg cobalt chloride, 0.2mg zinc sulfate, 0.06mg manganese chloride, 0.06mg sodium molybdate, 0.04mg nickel chloride, and 0.02mg copper sulfate.

[0063] Preferably, in steps S3-5, the protein-producing medium needs to be sterilized at 120-122℃ for 18-22 minutes and cooled to room temperature before use. The added organic carbon source is sodium acetate, and no additional nitrogen source is added to the prepared protein-producing medium.

[0064] As a further improvement to the technical solution, step S4 includes the following specific steps:

[0065] S4-1. Inoculate the domesticated protein-producing microorganisms into the protein-producing chamber;

[0066] S4-2, The mixed gas cylinder is filled with a mixture of hydrogen, oxygen and carbon dioxide;

[0067] S4-3. Start the peristaltic pump to deliver the mixed gas to the protein production chamber;

[0068] S4-4. Apply a suitable voltage to form a "ammonia nitrogen recovery-in-situ protein synthesis" microbial electrochemical system.

[0069] Preferably, in step S4-1, the domestication process of the protein-producing microorganisms includes the following specific steps:

[0070] ① After preparing the protein production medium, sterilize it at 120-122℃ for 18-22 min, cool it to room temperature, and then add 15 g / L agar to obtain the acclimatization medium;

[0071] ② The blue-capped bottle used for acclimatization was 500 mL, the working volume was 200 mL, the headspace volume was 415 mL, and the inoculum consisted of 10% aerobic sludge and 10% anaerobic sludge.

[0072] ③ Inject the mixed gas into the headspace of the blue-capped bottle. The volume ratio of the mixed gas components is H2:O2:CO2 = 60:25:15. After the mixed gas is continuously purged into the headspace of the blue-capped bottle for 8-12 minutes, seal the reactor.

[0073] ④ The mixed gas sealed in the blue-capped bottle is replaced every 12 hours; the pH is controlled at 7.0±0.2 during the cultivation process; the reactor temperature is controlled at 20-40℃ and the rotation speed is 150 rpm;

[0074] ⑤ When the consumption rate of the mixed gas and hydrogen is stable and reaches more than 60%, the domestication is complete and a protein-producing microbial system is obtained.

[0075] The domestication method of the above-mentioned protein-producing microbial system is derived from the application publication number CN 112725397 A, a method for producing single-cell protein by microbial fermentation.

[0076] Preferably, in step S4-2, the volume ratio of the mixed gas is H2:O2:CO2 = 50:35:15 to 70:20:10.

[0077] Preferably, in step S4-3, the rotational speed of the peristaltic pump is 5-50 rpm.

[0078] Preferably, in step S4-4, the pH of each chamber in the "ammonia nitrogen recovery-in situ protein synthesis" microbial electrochemical system is 5.0-9.0.

[0079] Preferably, in step S4-4, the suitable voltage range is 0.01-1.0V; the temperature range is 20-40℃.

[0080] Preferably, in step S4-4, the "ammonia nitrogen recovery-in-situ protein synthesis" microbial electrochemical system can achieve a wastewater COD removal rate of >90%, a CO2 consumption rate of >1.0L / d per liter of solution, and an ammonia nitrogen conversion rate of >15%.

[0081] As a further improvement to the technical solution, step S5 includes the following steps:

[0082] S5-1. Centrifuge the product at 9000-11000 rpm for 10-15 min and discard the supernatant.

[0083] S5-2. After centrifugation, wash the product with deionized water and centrifuge again, repeating 1-3 times.

[0084] S5-3. After centrifugation and washing, the product is baked at 100-110℃ for 20-30 hours to obtain microbial protein.

[0085] Preferably, in step S5-3, the standard for the formation of microbial protein is one or more of the following methods: 1) crude protein content in the product > 30%; 2) crude protein yield in the product > 1 g / L.

[0086] Any range described in this invention includes the endpoint, any value between the endpoints, and any subrange consisting of the endpoint or any value between the endpoints.

[0087] Unless otherwise specified, all raw materials used in this invention can be obtained commercially, and the equipment used in this invention can be conventional equipment in the relevant field or refer to existing technology in the relevant field.

[0088] Compared with the prior art, the present invention has the following beneficial effects. :

[0089] 1) Currently, physicochemical methods for treating ammonia nitrogen have drawbacks such as requiring the addition of large amounts of chemicals and high costs, while traditional biological methods have long start-up times, high energy consumption, and may generate N2O. Compared with traditional denitrification processes, microbial electrochemical systems can degrade organic pollutants while generating electricity or energy, resulting in higher treatment efficiency and stronger adaptability to wastewater. This invention provides a method for simultaneously achieving wastewater treatment, CO2 fixation, and in-situ synthesis of microbial proteins, with low energy consumption, generating energy while degrading organic pollutants, and converting ammonia nitrogen into microbial proteins.

[0090] 2) Current research on electrochemical recovery of ammonia nitrogen to produce microbial protein involves transferring the recovered ammonia nitrogen "extra-situ" to another reactor. However, this transfer process incurs significant losses and energy consumption, and requires dilution. The present invention provides a method for simultaneously achieving wastewater treatment, CO2 fixation, and in-situ synthesis of microbial protein. This method offers mild reaction conditions, enables in-situ production of microbial protein, and reduces losses and energy consumption.

[0091] 3) In contrast to single microbial electrochemical systems and single protein-producing systems, this system couples the two, driving the diffusion and migration of ammonia nitrogen at the cathode through a cation exchange membrane and electron transfer from the anode to the cathode generated by the BES. Driven by the concentration gradient and the continuous consumption of ammonia nitrogen in the protein-producing chamber, microbial protein is generated in situ within the chamber. This synergistic system enables in-situ microbial protein production without the need for ammonia nitrogen transportation and dilution, simultaneously achieving wastewater treatment, ammonia nitrogen recovery, and CO2 fixation, resulting in excellent environmental benefits. Attached Figure Description

[0092] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0093] Figure 1 This is a schematic diagram of one embodiment of the microbial electrochemical system device of the present invention;

[0094] Figure 2 This is a schematic diagram of another embodiment of the microbial electrochemical system device of the present invention. Detailed Implementation

[0095] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments and accompanying drawings, further explains the invention. Similar components in the drawings are indicated by the same reference numerals. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.

[0096] Various cross-sectional views of embodiments of the present invention are shown in the accompanying drawings. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0097] Currently, many researchers use electrochemical methods to recover ammonia nitrogen to produce microbial proteins, which simply involves transferring the recovered ammonia nitrogen to another reactor for protein production. During the transfer process, losses and damages occur. Furthermore, protein production requires diluting the recovered ammonia nitrogen to achieve a suitable concentration for protein-producing microorganisms. These processes significantly increase losses and energy consumption.

[0098] Based on this, see Figure 1As shown, as one aspect of the present invention, a microbial electrochemical system device for simultaneously realizing wastewater treatment, CO2 fixation and in-situ synthesis of microbial proteins includes an anode chamber 10, a cathode chamber 11, a protein production chamber 12, a power supply 4, a mixed gas tank 6, and a peristaltic pump 5.

[0099] The anode chamber 10, cathode chamber 11 and protein production chamber 12 are arranged sequentially from left to right;

[0100] A cation exchange membrane 13 is located between the anode chamber 10 and the cathode chamber 11.

[0101] A cation exchange membrane 13 is also located between the cathode chamber 11 and the protein production chamber 12.

[0102] The anode chamber 10 is provided with an anode 1, which is connected to the positive terminal of the power supply 4 through a wire, and a resistor 3 is provided on the wire connecting the anode 1 and the positive terminal of the power supply 4.

[0103] The cathode chamber 11 is provided with a cathode 2, which is connected to the negative terminal of the power supply 4 via a wire;

[0104] The protein production chamber 12 is connected to the mixed gas tank 6 through an air inlet pipe 121 and an air outlet pipe 122 to form a circulation loop, and the peristaltic pump 5 is installed on the air inlet pipe 121.

[0105] The device of the present invention enables ammonium ions to be smoothly recovered from the anode chamber through the cathode chamber for ammonia nitrogen recovery and smoothly enter the protein production chamber to complete the function of in-situ microbial protein production.

[0106] See Figure 1 As shown, in some embodiments of the present invention, the anode chamber 10 is connected to a first storage gas bag 101 via a pipe, and the cathode chamber 11 is connected to a second storage gas bag 111 via a pipe. It can be understood that the first storage gas bag 101 is used to store carbon dioxide generated in the anode chamber 10 during wastewater treatment; the second storage gas bag 111 is used to store hydrogen generated in the cathode chamber 11 during the recovery of ammonia nitrogen and the transport of ammonia nitrogen to the protein production chamber.

[0107] See Figure 2As shown, in some embodiments of the present invention, both the anode chamber 10 and the cathode chamber 11 are directly connected to the mixed gas tank 6 via pipelines. It is understood that the anode chamber 10 generates carbon dioxide during wastewater treatment, and the cathode chamber 11 generates hydrogen during the recovery of ammonia nitrogen and the transport of ammonia nitrogen to the protein production chamber. Since both carbon dioxide and hydrogen are components of the mixed gas tank, directly connecting both the anode chamber 10 and the cathode chamber 11 to the mixed gas tank 6 via pipelines can serve as a supplementary gas source, allowing for external supplementation to meet any insufficient gas components.

[0108] In some embodiments of the present invention, the anode 1 is made of carbon brush; the cathode 2 is made of graphite plate.

[0109] In another aspect, the present invention provides a method for simultaneously achieving wastewater treatment, CO2 fixation, and in-situ synthesis of microbial proteins using the aforementioned microbial electrochemical system, comprising the following steps:

[0110] S1. Fabricate the anode carbon brush and cathode electrode required for the microbial electrochemical system, and perform pretreatment;

[0111] S2. Inoculate the anode chamber with anaerobic sludge, add nutrient solution, and introduce nitrogen gas to maintain a strictly anaerobic environment; add potassium ferricyanide solution to the cathode chamber; cultivate and acclimate the anaerobic sludge to enrich the anode with electrogenic microorganisms.

[0112] S3. After the electrogenic microorganisms in the anode chamber have been cultured and domesticated, the potassium ferricyanide solution in the cathode chamber is replaced with a phosphate buffer solution; at the same time, protein-producing culture medium is added to the protein-producing chamber to form a three-chamber microbial electrochemical system.

[0113] S4. At different temperatures, different voltages are applied to the power supply. The domesticated protein-producing microorganisms are inoculated into the protein-producing chamber and a mixture of carbon dioxide, hydrogen and oxygen is introduced to carry out protein production culture, thus obtaining the "ammonia nitrogen recovery-in-situ protein synthesis" microbial electrochemical system.

[0114] S5. Process the culture products in the protein production chamber to obtain microbial protein.

[0115] In this invention, the term "domesticated protein-producing microorganisms" belongs to the prior art. For example, domesticated protein-producing microorganisms are disclosed in the specification of "A method for producing single-cell protein by microbial fermentation" published in application CN 112725397A, such as the "domesticated microorganisms" obtained in paragraph 0054 of the specification; specifically, such "domesticated microorganisms" are the "microorganisms that can be used to produce single-cell proteins" described in paragraph 0090 of the specification of the patent document.

[0116] In this invention, the term "microbial electrochemistry" refers to a system that utilizes electrochemically active microorganisms with extracellular electron transfer capabilities, with a bioanode as a catalyst, to remove substances from waste or wastewater and recover energy and chemical products. At the anode in the anode chamber, electrogenic microorganisms first degrade organic matter (e.g., domestic wastewater) to generate electrons and protons, which are then transferred to the cathode chamber via an external circuit and a proton exchange membrane, respectively.

[0117] In this invention, the term "anaerobic sludge" refers to sludge that has undergone anaerobic cultivation in an anaerobic reactor, resulting in anaerobic bacterial communities and thus achieving good organic matter settling properties. It is mainly used for wastewater treatment, capable of degrading various organic pollutants in raw wastewater, and is more economical in cost.

[0118] In this invention, the term "electrogenetic microorganisms" mainly refers to those belonging to the phyla Proteobacteria and Firmicutes, such as Bacillus, Pseudomonas, Rubia, Shewanella, Lactococcus, and Escherichia coli. Electrogenetic microorganisms generate electrons during the metabolism of organic matter and, through an electron transport chain, these electron-generating microorganisms on the anode can be considered a mixture of cells with different functions. They serve as the power source for the cells and can be used for power generation and proliferation.

[0119] In this invention, the term "protein production system" refers to a system capable of producing microbial proteins, which has the following functions: 1) using a mixed gas and organic carbon source as substrates for growth; 2) converting reactive nitrogen into microbial proteins.

[0120] In some embodiments of the present invention, step S1, the preprocessing includes the following steps:

[0121] S1-1, Process carbon fiber filaments and titanium wires with a diameter of 0.8-1.2mm into carbon brushes;

[0122] S1-2, Use 0.9-1.1 mol·L⁻¹ on the carbon brush. -1 Soak in NaOH solution for 5-7 hours to remove impurity ions;

[0123] S1-3, using 0.9-1.1 mol·L -1 Soak in HCl for 5-7 hours, then ultrasonically clean with deionized water until neutral.

[0124] S1-4. Boil in deionized water for 2.5-3.5 hours, changing the water every 25-35 minutes.

[0125] S1-5. Heat the carbon brushes in a muffle furnace to obtain the carbon brushes required for the experiment.

[0126] S1-6. Cut the graphite plate into cubes of 4cm*4cm*0.5cm;

[0127] S1-7. Soak in 0.9-1.1 mol·L-1 NaOH solution for 4-6 hours to remove impurity ions;

[0128] S1-8: Soak in 0.9-1.1 mol·L-1 HCl for 5-7 hours, then ultrasonically clean with deionized water until neutral to obtain the graphite plate required for the cathode.

[0129] In some embodiments of the present invention, in step S1-1, the carbon brush is 5-7 cm long and 3-5 cm in diameter.

[0130] In some embodiments of the present invention, in steps S1-5, the temperature of the muffle furnace heating treatment is 480-520°C, and the treatment time is 9-11 minutes.

[0131] In some embodiments of the present invention, step S2 includes the following specific steps:

[0132] S2-1. Use anaerobic sludge from the thickening tank of the sewage treatment plant as inoculum. After the anaerobic sludge is settled, pour off the supernatant.

[0133] S2-2. Anaerobic sludge and nutrient solution are added to an anode chamber with a carbon brush to form an anolyte.

[0134] S2-3. Nitrogen gas is continuously introduced into the anode chamber to remove oxygen and maintain a strictly anaerobic environment.

[0135] S2-4. Add potassium ferricyanide solution to the cathode chamber as the cathode solution;

[0136] S2-5. The anode, resistor and cathode are connected in series to form a microbial fuel cell. At a suitable temperature of 25-32℃, electrogenic microorganisms derived from anaerobic sludge are cultivated and domesticated on the anode carbon brush, so that electrogenic microorganisms are enriched on the anode.

[0137] In some embodiments of the present invention, in step S2-2, the nutrient solution is formulated to contain the following substances per liter of solution: 3 mg magnesium sulfate, 0.13 mg zinc chloride, 0.005 mg zinc sulfate heptahydrate, 1.5 mg nitric acid, 0.5 mg manganese sulfate monohydrate, 310 mg ammonium chloride, 130 mg potassium chloride, 0.01 mg boric acid, 0.01 mg cobalt chloride hexahydrate, 5 mg nicotinic acid, 2 mg folic acid, 0.01 mg copper sulfate pentahydrate, 0.024 mg nickel chloride hexahydrate, 0.024 mg sodium tungstate dihydrate, 0.1 mg B-12, 5 mg vitamin B1, 6 mg vitamin B2, 10 mg vitamin B6, 6 mg para-aminobenzoic acid, and 2000 mg sodium acetate.

[0138] In some embodiments of the present invention, in step S2-2, the pH of the anolyte in the anode chamber is 6.5-7.5.

[0139] In some embodiments of the present invention, in step S2-2, the volume ratio of anaerobic sludge to nutrient solution is 1:1.

[0140] In some embodiments of the present invention, in steps S2-3, the nitrogen gas is introduced for 9-11 minutes.

[0141] In some embodiments of the present invention, in steps S2-4, the concentration of the potassium ferricyanide solution is 15-17 g / L.

[0142] In some embodiments of the present invention, in steps S2-5, the resistance is 950-1050Ω.

[0143] In some embodiments of the present invention, step S3 includes the following specific steps:

[0144] S3-1. After the electrogenic microorganisms in the anode chamber have been cultured, replace the solution in the anode chamber with fresh nutrient solution.

[0145] S3-2. Prepare a phosphate buffer solution for recovering ammonia nitrogen as the catholyte;

[0146] S3-3, Inject cathodic liquid into the cathode chamber;

[0147] S3-4. Connect the anode, resistor, power supply and cathode in series;

[0148] S3-5. Simultaneously, protein-producing culture medium is added to the protein-producing chamber to form a three-chambered microbial electrochemical system device.

[0149] In some embodiments of the present invention, in step S3-1, the nutrient solution is formulated to contain the following substances per liter of solution: 3 mg magnesium sulfate, 0.13 mg zinc chloride, 0.005 mg zinc sulfate heptahydrate, 1.5 mg nitric acid, 0.5 mg manganese sulfate monohydrate, 310 mg ammonium chloride, 130 mg potassium chloride, 0.01 mg boric acid, 0.01 mg cobalt chloride hexahydrate, 5 mg nicotinic acid, 2 mg folic acid, 0.01 mg copper sulfate pentahydrate, 0.024 mg nickel chloride hexahydrate, 0.024 mg sodium tungstate dihydrate, 0.1 mg B-12, 5 mg vitamin B1, 6 mg vitamin B2, 10 mg vitamin B6, 6 mg para-aminobenzoic acid, 1462 mg (1560 mg COD) glucose or 2000 mg sodium acetate (1560 mg COD) or 1820 mg sodium lactate (1560 mg COD).

[0150] In some embodiments of the present invention, in step S3-2, the catholyte comprises per liter of the following substances: 140-11400 mg of dipotassium hydrogen phosphate and 1340-6000 mg of sodium dihydrogen phosphate.

[0151] In some embodiments of the present invention, in steps S3-5, the protein-producing culture medium is formulated to contain the following substances per liter of solution: 2.3g potassium dihydrogen phosphate, 2.9g disodium hydrogen phosphate, 0.5g magnesium sulfate, 0.5g sodium carbonate, 0.01g calcium chloride, 0.05g ferric ammonium citrate, 0.6mg boric acid, 0.4mg cobalt chloride, 0.2mg zinc sulfate, 0.06mg manganese chloride, 0.06mg sodium molybdate, 0.04mg nickel chloride, and 0.02mg copper sulfate.

[0152] In some embodiments of the present invention, in steps S3-5, the protein-producing medium needs to be sterilized at 120-122°C for 18-22 min and cooled to room temperature before use. The added organic carbon source is sodium acetate, and no additional nitrogen source is added to the prepared protein-producing medium.

[0153] In some embodiments of the present invention, step S4 includes the following specific steps:

[0154] In step S4-1, the domestication process of the protein-producing microorganisms includes the following specific steps:

[0155] ① After preparing the protein production medium, sterilize it at 120-122℃ for 18-22 min, cool it to room temperature, and then add 15 g / L agar to obtain the acclimatization medium;

[0156] ② The blue-capped bottle used for acclimatization was 500 mL, the working volume was 200 mL, the headspace volume was 415 mL, and the inoculum consisted of 10% aerobic sludge and 10% anaerobic sludge.

[0157] ③ Inject the mixed gas into the headspace of the blue-capped bottle. The volume ratio of the mixed gas components is H2:O2:CO2 = 60:25:15. After the mixed gas is continuously purged into the headspace of the blue-capped bottle for 8-12 minutes, seal the reactor.

[0158] ④ The mixed gas sealed in the blue-capped bottle is replaced every 12 hours; the pH is controlled at 7.0±0.2 during the cultivation process; the reactor temperature is controlled at 20-40℃ and the rotation speed is 150 rpm;

[0159] ⑤ When the consumption rate of the mixed gas and hydrogen is stable and reaches more than 60%, the domestication is complete and protein-producing microorganisms are obtained.

[0160] The domestication method of the above-mentioned protein-producing microbial system is derived from the application publication number CN 112725397 A, a method for producing single-cell protein by microbial fermentation.

[0161] In some embodiments of the present invention, in step S4-2, the volume ratio of the mixed gas is H2:O2:CO2 = 50:35:15 to 70:20:10.

[0162] In some embodiments of the present invention, in step S4-3, the rotational speed of the peristaltic pump is 5-50 rpm.

[0163] In some embodiments of the present invention, in steps S4-4, the pH of each chamber in the "ammonia nitrogen recovery-in situ protein synthesis" microbial electrochemical system is 5.0-9.0.

[0164] In some embodiments of the present invention, in steps S4-4, the suitable voltage range is 0.01-1.0V; the temperature range is 20-40℃.

[0165] In some embodiments of the present invention, in step S4-4, the "ammonia nitrogen recovery-in-situ protein synthesis" microbial electrochemical system can achieve a wastewater COD removal rate of >90%, a CO2 consumption rate of >1.0L / d per liter of solution, and an ammonia nitrogen conversion rate of >15%.

[0166] In some embodiments of the present invention, step S5 includes the following steps:

[0167] S5-1. Centrifuge the product at 9000-11000 rpm for 10-15 min and discard the supernatant.

[0168] S5-2. After centrifugation, wash the product with deionized water and centrifuge again, repeating 1-3 times.

[0169] S5-3. After centrifugation and washing, the product is baked at 100-110℃ for 20-30 hours to obtain microbial protein.

[0170] In some embodiments of the present invention, in step S5-3, the standard for the formation of microbial protein is one or more of the following methods: 1) crude protein content in the product > 30%; 2) crude protein yield in the product > 1 g / L.

[0171] Example 1

[0172] A method for simultaneously achieving wastewater treatment, CO2 fixation, and in-situ synthesis of microbial proteins using a microbial electrochemical system includes the following steps:

[0173] 1) Carbon fiber filaments and titanium wire with a diameter of 1mm are processed into carbon brushes. The carbon brushes are 6cm long and 4cm in diameter.

[0174] 2) Use 1 mol·L⁻¹ carbon brushes to heat the prepared carbon brushes. -1Soak in NaOH solution for 6 hours to remove impurity ions;

[0175] 3) The carbon brush treated in step 2) is rinsed with 1 mol·L⁻¹ water. -1 Soak in HCl for 6 hours, then ultrasonically clean with deionized water until neutral.

[0176] 4) Boil the carbon brushes treated in step 3) in deionized water for 3 hours, changing the water every 30 minutes.

[0177] 5) Heat the carbon brush processed in step 4) in a muffle furnace at 500°C for 10 minutes to obtain the carbon brush.

[0178] 6) Cut the graphite plate into cubes of 4cm*4cm*0.5cm. First, use 1mol·L⁻¹ -1 Soak in NaOH solution for 5 hours to remove impurity ions; then soak in 1 mol·L⁻¹ solution. -1 The carbon brush was soaked in HCl for 6 hours and then ultrasonically cleaned with deionized water until neutral to obtain a graphite plate cathode. The carbon brush was installed as the anode in the anode chamber and the graphite plate was installed as the cathode in the cathode chamber.

[0179] 7) Anaerobic sludge and nutrient solution are added to the anode chamber, and nitrogen gas is introduced. The cathode chamber contains potassium ferricyanide solution to cultivate and acclimate the electrogenic microorganisms. The nutrient solution is formulated to contain the following substances per liter: 3 mg magnesium sulfate, 0.13 mg zinc chloride, 0.005 mg zinc sulfate heptahydrate, 1.5 mg nitric acid, 0.5 mg manganese sulfate monohydrate, 310 mg ammonium chloride, 130 mg potassium chloride, 0.01 mg boric acid, 0.01 mg cobalt chloride hexahydrate, 5 mg nicotinic acid, 2 mg folic acid, 0.01 mg copper sulfate pentahydrate, 0.024 mg nickel chloride hexahydrate, 0.024 mg sodium tungstate dihydrate, 0.1 mg B-12, 5 mg vitamin B1, 6 mg vitamin B2, 10 mg vitamin B6, and 6 mg para-aminobenzoic acid.

[0180] Furthermore, in this step, ammonium chloride is added to the nutrient solution until the initial ammonia nitrogen content in the anode chamber is 2000 mg N / L, and the organic carbon source is 2000 mg sodium acetate;

[0181] 8) After the anodic electrogenic microorganisms have been domesticated in step 7), the solution in the cathode chamber is replaced with phosphate buffer solution to increase the domesticated protein production system, i.e., the protein production chamber, and protein production culture medium is added to build a three-chamber microbial electrochemical system device.

[0182] In this step, the protein-producing culture medium is formulated to contain the following substances per liter of solution: 2.3g potassium dihydrogen phosphate, 2.9g disodium hydrogen phosphate, 0.5g magnesium sulfate, 0.5g sodium carbonate, 0.01g calcium chloride, 0.05g ferric ammonium citrate, 0.6mg boric acid, 0.4mg cobalt chloride, 0.2mg zinc sulfate, 0.06mg manganese chloride, 0.06mg sodium molybdate, 0.04mg nickel chloride, and 0.02mg copper sulfate;

[0183] In this step, the phosphate buffer solution comprises the following substances per liter: 140-11400 mg dipotassium hydrogen phosphate and 1340-6000 mg sodium dihydrogen phosphate;

[0184] 9) At 30℃, a voltage of 0.6V is applied to the power supply. The existing domesticated protein-producing microbial system is inoculated into the protein-producing chamber and a mixed gas containing carbon dioxide, hydrogen and oxygen is introduced to carry out protein production culture, and the "ammonia nitrogen recovery-in situ protein synthesis" microbial electrochemical system is obtained.

[0185] In this step, the volume ratio of the mixed gas of carbon dioxide, hydrogen, and oxygen is H2:O2:CO2 = 60:25:15;

[0186] 10) After culturing the "ammonia nitrogen recovery-in situ protein synthesis" microbial electrochemical system for 14 days, the reaction was stopped;

[0187] 11) Centrifuge the fermentation product at 10,000 rpm for 10 min and discard the supernatant; wash the centrifuged fermentation product with deionized water and centrifuge again, repeating twice.

[0188] 12) The fermentation product after three centrifugations was baked at 105°C for 24 hours to obtain microbial protein.

[0189] This embodiment describes a method for simultaneously achieving wastewater treatment, CO2 fixation, and in-situ synthesis of microbial proteins. The analysis results of COD removal rate, CO2 consumption rate, ammonia nitrogen conversion rate, and microbial protein yield are shown in Table 1 below.

[0190] Table 1: Analysis results of COD removal rate, CO2 consumption rate, ammonia nitrogen conversion rate, and microbial protein production.

[0191]

[0192] In this embodiment, a voltage of 0.6V is applied to the "ammonia nitrogen recovery-in situ protein synthesis" microbial electrochemical system.

[0193] As shown in Table 1, after 14 days of system operation, the anode COD removal rate of the system is higher than 90%, the CO2 consumption rate is higher than 1.5 L / L / d, the ammonia nitrogen conversion rate in the system is higher than 25%, and the microbial protein yield in the product is higher than 1 g / L. This shows that the system can generate microbial protein in situ without the need for transportation and dilution of ammonia nitrogen, and simultaneously achieve functions such as wastewater treatment and CO2 fixation.

[0194] Example 2

[0195] Example 1 is repeated, except that in step 9), the voltage is 0.8V. This example describes a method for simultaneously achieving wastewater treatment, CO2 fixation, and in-situ synthesis of microbial proteins. The analysis results of COD removal rate, CO2 consumption rate, ammonia nitrogen conversion rate, and microbial protein yield are shown in Table 2 below.

[0196] Table 2: Analysis results of COD removal rate, CO2 consumption rate, ammonia nitrogen conversion rate, and microbial protein production.

[0197]

[0198] In this embodiment, a voltage of 0.8V is applied to the "ammonia nitrogen recovery-in situ protein synthesis" microbial electrochemical system.

[0199] As shown in Table 1, after 14 days of system operation, the anode COD removal rate, ammonia nitrogen conversion rate, and microbial protein yield of the system were higher than those in Example 1. This indicates that increasing the voltage can improve the anode COD removal rate, and through electromigration, it can improve the ammonia nitrogen conversion rate of the system and further increase the microbial protein yield.

[0200] Example 3

[0201] Example 1 is repeated, except that in step 9), the voltage is 1.0V. This example describes a method for simultaneously achieving wastewater treatment, CO2 fixation, and in-situ synthesis of microbial proteins. The analysis results of COD removal rate, CO2 consumption rate, ammonia nitrogen conversion rate, and microbial protein yield are shown in Table 3 below.

[0202] Table 3: Analysis results of COD removal rate, CO2 consumption rate, ammonia nitrogen conversion rate, and microbial protein production.

[0203]

[0204] In this embodiment, a voltage of 1.0V is applied to the "ammonia nitrogen recovery-in situ protein synthesis" microbial electrochemical system.

[0205] As shown in Table 3, after 14 days of system operation, the anode COD removal rate, CO2 consumption rate, and microbial protein yield of the system are higher than those in Example 2. When the voltage is increased to 1.0V, the system can not only further improve the anode microbial COD removal rate, but also increase the microbial protein yield.

[0206] Example 4

[0207] Repeat Example 3, except that the temperature in step 9) is 20°C.

[0208] The analysis results of COD removal rate, CO2 consumption rate, ammonia nitrogen conversion rate, and microbial protein yield in this embodiment are shown in Table 4 below.

[0209] Table 4: Analysis results of COD removal rate, CO2 consumption rate, ammonia nitrogen conversion rate, and microbial protein yield.

[0210]

[0211] In this embodiment, the voltage applied to the "ammonia nitrogen recovery-in situ protein synthesis" microbial electrochemical system is still 1.0V, but the temperature is 20℃.

[0212] Table 4 shows that after 14 days of system operation, the anode COD removal rate, CO2 consumption rate, and ammonia nitrogen conversion rate of the system were lower than those of Example 3, but the microbial protein yield in the product was higher than that of Example 4. This indicates that the system can produce more microbial protein in situ at 20°C, and can also simultaneously achieve wastewater treatment and CO2 fixation.

[0213] Example 5

[0214] Example 4 was repeated, except that in step 9), the temperature was 40°C. The analysis results of COD removal rate, CO2 consumption rate, ammonia nitrogen conversion rate, and microbial protein yield in this example are shown in Table 5 below.

[0215] Table 5: Analysis results of COD removal rate, CO2 consumption rate, ammonia nitrogen conversion rate, and microbial protein production.

[0216]

[0217] In this embodiment, the voltage applied to the "ammonia nitrogen recovery-in situ protein synthesis" microbial electrochemical system is still 1.0V, but the temperature is 40℃.

[0218] Table 5 shows that after 14 days of system operation, the system's CO2 consumption rate, ammonia nitrogen conversion rate, and microbial protein yield in the product were all lower than in Example 4. This is because the activity of protein-producing microorganisms was inhibited when the temperature rose to 40°C, leading to a decrease in ammonia nitrogen conversion rate and microbial protein yield in the product.

[0219] Example 6

[0220] Repeat Example 3, except that in step 7), the organic carbon source is 2000 mg of glucose.

[0221] The results of the analysis of COD removal rate, CO2 consumption rate, ammonia nitrogen conversion rate and microbial protein yield in this embodiment are shown in Table 6 below.

[0222] Table 6: Analysis results of COD removal rate, CO2 consumption rate, ammonia nitrogen conversion rate, and microbial protein production.

[0223]

[0224] In this embodiment, the "ammonia nitrogen recovery-in situ protein synthesis" microbial electrochemical system is applied with a voltage of 1.0V and a temperature of 30℃, and uses glucose as the anode organic carbon source.

[0225] As can be seen from Table 6, after 14 days of system operation, the anode COD removal rate, CO2 consumption rate, ammonia nitrogen conversion rate, and microbial protein yield in the product of the system are all lower than those of Example 3. However, it can still be seen that the system can achieve in-situ production of microbial protein without the need for transportation and dilution of ammonia nitrogen, and simultaneously realize functions such as wastewater treatment and CO2 fixation.

[0226] Example 7

[0227] Example 6 was repeated, except that in step 7), the organic carbon source was sodium lactate.

[0228] The analysis results of COD removal rate, CO2 consumption rate, ammonia nitrogen conversion rate, and microbial protein yield in this embodiment are shown in Table 7 below.

[0229] Table 7: Analysis results of COD removal rate, CO2 consumption rate, ammonia nitrogen conversion rate, and microbial protein production.

[0230]

[0231] In this embodiment, the "ammonia nitrogen recovery-in-situ protein synthesis" microbial electrochemical system is applied with a voltage of 1.0V and a temperature of 30℃, and sodium lactate is used as the anode organic carbon source.

[0232] As can be seen from Table 7, after 14 days of system operation, the anode COD removal rate, CO2 consumption rate, ammonia nitrogen conversion rate, and microbial protein yield in the product of the system are all lower than those of Example 3. However, it can still be seen that the system can achieve in-situ production of microbial protein without the need for transportation and dilution of ammonia nitrogen, and simultaneously realize functions such as wastewater treatment and CO2 fixation.

[0233] Example 8

[0234] A method for simultaneously achieving wastewater treatment, CO2 fixation, and in-situ synthesis of microbial proteins using a microbial electrochemical system includes the following steps:

[0235] 1) Carbon fiber filaments and titanium wire with a diameter of 1mm are processed into carbon fiber brushes. The carbon fiber brushes are 6cm long and 4cm in diameter.

[0236] 2) The prepared carbon fiber brush is heated with 1 mol·L⁻¹ water. -1 Soak in NaOH solution for 6 hours to remove impurity ions;

[0237] 3) The carbon brush treated in step 2) is rinsed with 1 mol·L⁻¹ water. -1 Soak in HCl for 6 hours, then ultrasonically clean with deionized water until neutral.

[0238] 4) Boil the carbon brushes treated in step 3) in deionized water for 3 hours, changing the water every 30 minutes.

[0239] 5) Heat the carbon brush treated in step 4) in a muffle furnace at 500°C for 10 minutes to obtain the carbon brush for the experiment.

[0240] 6) Cut the graphite plate into cubes of 4cm*4cm*0.5cm. First, use 1mol·L⁻¹ -1 Soak in NaOH solution for 5 hours to remove impurity ions; then soak in 1 mol·L⁻¹ solution. -1 The carbon brush was soaked in HCl for 6 hours and then ultrasonically cleaned with deionized water until neutral to obtain the graphite plate cathode required for the experiment. The carbon brush was installed as the anode in the anode chamber and the graphite plate was installed as the cathode in the cathode chamber.

[0241] 7) Anaerobic sludge and nutrient solution are added to the anode chamber, and nitrogen gas is introduced. The cathode chamber contains potassium ferricyanide solution to cultivate and acclimate the electrogenic microorganisms. The nutrient solution is formulated with the following substances per liter: 3 mg magnesium sulfate, 0.13 mg zinc chloride, 0.005 mg zinc sulfate heptahydrate, 1.5 mg nitric acid, 0.5 mg manganese sulfate monohydrate, 310 mg ammonium chloride, 130 mg potassium chloride, 0.01 mg boric acid, 0.01 mg cobalt chloride hexahydrate, 5 mg nicotinic acid, 2 mg folic acid, 0.01 mg copper sulfate pentahydrate, 0.024 mg nickel chloride hexahydrate, 0.024 mg sodium tungstate dihydrate, 0.1 mg B-12, 5 mg vitamin B1, 6 mg vitamin B2, 10 mg vitamin B6, 6 mg para-aminobenzoic acid, and 2000 mg sodium acetate.

[0242] 8) Replace the solution in the anode chamber of the anodic electrogenic microorganisms that have been domesticated in step 7) with actual wastewater (i.e., wastewater taken from a sewage treatment plant), replace the cathode solution with phosphate buffer solution, add the domesticated protein production system, i.e. the protein production chamber, and add protein production culture medium to build a three-chamber microbial electrochemical system device.

[0243] In this step, the properties of the actual wastewater are as follows:

[0244] pH = 8.2 ± 0.10; SCOD (mg / L): 1253 ± 65; TCOD (mg / L): 2819 ± 185; Ammonia nitrogen concentration: 1028 ± 13; TKN: 1141 ± 10.

[0245] In this step, the protein-producing culture medium is formulated to contain the following substances per liter of solution: 2.3g potassium dihydrogen phosphate, 2.9g disodium hydrogen phosphate, 0.5g magnesium sulfate, 0.5g sodium carbonate, 0.01g calcium chloride, 0.05g ferric ammonium citrate, 0.6mg boric acid, 0.4mg cobalt chloride, 0.2mg zinc sulfate, 0.06mg manganese chloride, 0.06mg sodium molybdate, 0.04mg nickel chloride, and 0.02mg copper sulfate;

[0246] In this step, the phosphate buffer solution comprises the following substances per liter: 140-11400 mg dipotassium hydrogen phosphate and 1340-6000 mg sodium dihydrogen phosphate;

[0247] 9) At 30℃, a voltage of 1.0V is applied to the power supply. The domesticated microbial system is inoculated into the product chamber and a mixed gas containing carbon dioxide, hydrogen and oxygen is introduced to carry out protein production culture, and the "ammonia nitrogen recovery-in situ protein synthesis" microbial electrochemical system is obtained.

[0248] The volume ratio of the mixture of carbon dioxide, hydrogen, and oxygen is H2:O2:CO2 = 60:25:15;

[0249] 10) After culturing the system for 14 days, stop the reaction;

[0250] 11) Centrifuge the fermentation product at 10,000 rpm for 10 min and discard the supernatant; wash the centrifuged fermentation product with deionized water and centrifuge again, repeating twice.

[0251] 12) The fermentation product after three centrifugations was baked at 105°C for 24 hours to obtain microbial protein.

[0252] The analysis results of COD removal rate, CO2 consumption rate, ammonia nitrogen conversion rate, and microbial protein yield in this embodiment are shown in Table 8 below.

[0253] Table 8: Analysis results of COD removal rate, CO2 consumption rate, ammonia nitrogen conversion rate, and microbial protein production.

[0254]

[0255] In this embodiment, the "ammonia nitrogen recovery-in-situ protein synthesis" microbial electrochemical system applies a voltage of 1.0V and a temperature of 30℃, using actual wastewater as the anode feed.

[0256] As shown in Table 6, after 14 days of system operation, the anode COD removal rate of the system is higher than 90%, the CO2 consumption rate is higher than 1.5 L / L / d, the ammonia nitrogen conversion rate in the system is higher than 20%, and the microbial protein yield in the product is higher than 1 g / L. This shows that the system can still achieve in-situ generation of microbial protein without the need for transportation and dilution of ammonia nitrogen using actual wastewater, and simultaneously realize functions such as wastewater treatment and CO2 fixation.

[0257] Comparative Example 1

[0258] Repeat Example 3, except that in step 9), the voltage in the microbial reactor is 0V.

[0259] This embodiment describes an apparatus and method for simultaneously achieving wastewater treatment, CO2 fixation, and in-situ synthesis of microbial proteins. The analysis results of COD removal rate, CO2 consumption rate, ammonia nitrogen conversion rate, and microbial protein yield are shown in Table 9 below.

[0260] Table 9: Analysis results of COD removal rate, CO2 consumption rate, ammonia nitrogen conversion rate, and microbial protein production.

[0261]

[0262] As shown in Table 9, this comparative system cannot achieve wastewater treatment, and the CO2 consumption rate is below 1.0 L / L / d, the ammonia nitrogen conversion rate is below 15%, and the crude protein yield in the product is below 1 g / L. Therefore, it cannot simultaneously achieve the functions of wastewater treatment and CO2 fixation as described in this invention. The reason is that the applied voltage is 0V, which cannot drive the anodic microorganisms to degrade organic matter. Simultaneously, there is no electromigration to propel ammonia nitrogen towards the catholyte, thus preventing it from entering the third chamber (protein production chamber) through concentration difference. This results in a low ammonia nitrogen conversion rate, making in-situ protein production impossible.

[0263] Comparative Example 2

[0264] A method for producing microbial protein includes the following steps:

[0265] 1) Process the purchased carbon fiber filaments and titanium wire with a diameter of 1mm into a carbon fiber brush. The carbon fiber brush is 6cm long and 4cm in diameter.

[0266] 2) The prepared carbon fiber brush is heated with 1 mol·L⁻¹ water. -1 Soak in NaOH solution for 6 hours to remove impurity ions;

[0267] 3) The carbon brush treated in step 2) is rinsed with 1 mol·L⁻¹ water. -1 Soak in HCl for 6 hours, then ultrasonically clean with deionized water until neutral.

[0268] 4) Boil the carbon brushes treated in step 3) in deionized water for 3 hours, changing the water every 30 minutes.

[0269] 5) Heat the carbon brush treated in step 4) in a muffle furnace at 500°C for 10 minutes to obtain the carbon brush for the experiment.

[0270] 6) Cut the graphite plate into cubes of 4cm*4cm*0.5cm. First, use 1mol·L⁻¹ -1 Soak in NaOH solution for 5 hours to remove impurity ions; then use 1 mol·L⁻¹ water. -1 The graphite cathode was soaked in HCl for 6 hours and then ultrasonically cleaned with deionized water until neutral to obtain the experimental graphite cathode.

[0271] 7) Add nutrient solution to the anode chamber (without sludge, microbial enrichment is impossible) and purge with nitrogen. The nutrient solution is formulated to contain the following substances per liter: 3 mg magnesium sulfate, 0.13 mg zinc chloride, 0.005 mg zinc sulfate heptahydrate, 1.5 mg nitric acid, 0.5 mg manganese sulfate monohydrate, 310 mg ammonium chloride, 130 mg potassium chloride, 0.01 mg boric acid, 0.01 mg cobalt chloride hexahydrate, 5 mg nicotinic acid, 2 mg folic acid, 0.01 mg copper sulfate pentahydrate, 0.024 mg nickel chloride hexahydrate, 0.024 mg sodium tungstate dihydrate, 0.1 mg B-12, 5 mg vitamin B1, 6 mg vitamin B2, 10 mg vitamin B6, and 6 mg para-aminobenzoic acid.

[0272] In step 7), ammonium chloride is added to the nutrient solution to the anode chamber, resulting in an initial nitrogen content of 2000 mg N / L and an organic carbon source of 2000 mg sodium acetate.

[0273] 8) Replace the cathode solution in the reactor in step 7) with a phosphate buffer solution. At a certain temperature, apply voltage to the reactor to recover ammonia nitrogen.

[0274] In step 8), the voltage is 1.0V and the temperature is 30℃.

[0275] In step 8), each liter of the catholy solution comprises the following substances: 140-11400 mg dipotassium hydrogen phosphate and 1340-6000 mg sodium dihydrogen phosphate;

[0276] 9) Dilute the ammonia nitrogen recovered in step 8) and add it to the protein production medium. Inoculate the domesticated microbial system into the product chamber and introduce a mixed gas containing carbon dioxide, hydrogen and oxygen to carry out protein production culture.

[0277] In this step, the protein-producing culture medium is formulated to contain the following substances per liter of solution: 2.3g potassium dihydrogen phosphate, 2.9g disodium hydrogen phosphate, 0.5g magnesium sulfate, 0.5g sodium carbonate, 0.01g calcium chloride, 0.05g ferric ammonium citrate, 0.6mg boric acid, 0.4mg cobalt chloride, 0.2mg zinc sulfate, 0.06mg manganese chloride, 0.06mg sodium molybdate, 0.04mg nickel chloride, and 0.02mg copper sulfate;

[0278] In this step, the volume ratio of the mixed gas of carbon dioxide, hydrogen, and oxygen is H2:O2:CO2 = 60:25:15;

[0279] 10) After culturing the system for 14 days, stop the reaction;

[0280] 11) Centrifuge the fermentation product at 10,000 rpm for 10 min and discard the supernatant; wash the centrifuged fermentation product with deionized water and centrifuge again, repeating twice.

[0281] 12) The fermentation product after three centrifugations was baked at 105°C for 24 hours to obtain microbial protein.

[0282] The results of the comparative analysis of COD removal rate, CO2 consumption rate, ammonia nitrogen conversion rate, and microbial protein production are shown in Table 10 below.

[0283] Table 10: Analysis results of COD removal rate, CO2 consumption rate, ammonia nitrogen conversion rate, and microbial protein production.

[0284]

[0285] As can be seen from Table 10, the comparative system uses an anode carbon brush that has not been enriched with microorganisms. The system cannot achieve wastewater treatment by microbial degradation of organic wastewater, and the CO2 consumption rate is less than 1.5 L / L / d and the crude protein yield in the product is less than 1 g / L. Therefore, it cannot achieve the functions of simultaneous wastewater treatment, CO2 fixation, and in-situ protein production as described in this invention.

[0286] Comparative Example 3

[0287] A method for producing microbial protein includes the following steps:

[0288] 1) Carbon fiber filaments and titanium wire with a diameter of 1mm are processed into carbon fiber brushes. The carbon fiber brushes are 6cm long and 4cm in diameter.

[0289] 2) The prepared carbon fiber brush is heated with 1 mol·L⁻¹ water. -1 Soak in NaOH solution for 6 hours to remove impurity ions;

[0290] 3) The carbon brush treated in step 2) is rinsed with 1 mol·L⁻¹ water. -1 Soak in HCl for 6 hours, then ultrasonically clean with deionized water until neutral.

[0291] 4) Boil the carbon brushes treated in step 3) in deionized water for 3 hours, changing the water every 30 minutes.

[0292] 5) Heat the carbon brush treated in step 4) in a muffle furnace at 500°C for 10 minutes to obtain the carbon brush for the experiment.

[0293] 6) Cut the graphite plate into cubes of 4cm*4cm*0.5cm. First, use 1mol·L⁻¹ -1 Soak in NaOH solution for 5 hours to remove impurity ions; then use 1 mol·L⁻¹ water. -1The graphite cathode was soaked in HCl for 6 hours and then ultrasonically cleaned with deionized water until neutral to obtain the experimental graphite cathode.

[0294] 7) Anaerobic sludge and nutrient solution are added to the anode chamber, and nitrogen gas is introduced. The cathode chamber contains potassium ferricyanide solution to cultivate and acclimate the electrogenic microorganisms. The nutrient solution is formulated to contain the following substances per liter: 3 mg magnesium sulfate, 0.13 mg zinc chloride, 0.005 mg zinc sulfate heptahydrate, 1.5 mg nitric acid, 0.5 mg manganese sulfate monohydrate, 310 mg ammonium chloride, 130 mg potassium chloride, 0.01 mg boric acid, 0.01 mg cobalt chloride hexahydrate, 5 mg nicotinic acid, 2 mg folic acid, 0.01 mg copper sulfate pentahydrate, 0.024 mg nickel chloride hexahydrate, 0.024 mg sodium tungstate dihydrate, 0.1 mg B-12, 5 mg vitamin B1, 6 mg vitamin B2, 10 mg vitamin B6, and 6 mg para-aminobenzoic acid.

[0295] In this step, ammonium chloride is added to the nutrient solution to the anode chamber to initially achieve a nitrogen content of 2000 mg N / L, and the organic carbon source is 2000 mg sodium acetate.

[0296] 8) Replace the cathode solution of the reactor after the anodic electrogenic microorganisms have been domesticated in step 7) with a phosphate buffer solution. Apply voltage to the reactor at a certain temperature to recover ammonia nitrogen.

[0297] In this step, the voltage is 1.0V and the temperature is 30℃.

[0298] In this step, each liter of the catholy solution includes the following substances: 140-11400 mg dipotassium hydrogen phosphate and 1340-6000 mg sodium dihydrogen phosphate;

[0299] 9) Dilute the ammonia nitrogen recovered in step 8) and add it to the protein production medium. Inoculate the domesticated microbial system into the product chamber and introduce a mixed gas containing carbon dioxide, hydrogen and oxygen to carry out protein production culture.

[0300] In this step, the protein-producing culture medium is formulated to contain the following substances per liter of solution: 2.3g potassium dihydrogen phosphate, 2.9g disodium hydrogen phosphate, 0.5g magnesium sulfate, 0.5g sodium carbonate, 0.01g calcium chloride, 0.05g ferric ammonium citrate, 0.6mg boric acid, 0.4mg cobalt chloride, 0.2mg zinc sulfate, 0.06mg manganese chloride, 0.06mg sodium molybdate, 0.04mg nickel chloride, and 0.02mg copper sulfate;

[0301] In this step, the volume ratio of the mixed gas of carbon dioxide, hydrogen, and oxygen is H2:O2:CO2 = 60:25:15;

[0302] 10) After culturing the system for 14 days, stop the reaction;

[0303] 11) Centrifuge the fermentation product at 10,000 rpm for 10 min and discard the supernatant; wash the centrifuged fermentation product with deionized water and centrifuge again, repeating twice.

[0304] 12) The fermentation product after three centrifugations was baked at 105°C for 24 hours to obtain microbial protein.

[0305] The results of the comparative analysis of COD removal rate, CO2 consumption rate, ammonia nitrogen conversion rate, and microbial protein yield are shown in Table 11 below.

[0306] Table 11: Analysis results of COD removal rate, CO2 consumption rate, ammonia nitrogen conversion rate, and microbial protein production.

[0307]

[0308] As can be seen from Table 11, the comparative system in this case cannot achieve wastewater treatment, and the CO2 consumption rate is less than 1.5 L / L / d and the crude protein yield in the product is less than 1 g / L. Therefore, it cannot achieve the functions of simultaneously achieving wastewater treatment, CO2 fixation, and in-situ protein production as described in this invention.

[0309] Based on the results of Comparative Examples 1, 2, 3 and Example 3:

[0310] The reactor system in Example 3 can simultaneously achieve wastewater treatment, ammonia nitrogen recovery, CO2 fixation, and in-situ protein production. However, as shown in Tables 9 and 10, if the system is not subjected to voltage or if a carbon brush without microbial enrichment is used, wastewater treatment cannot be achieved, and the CO2 consumption rate, ammonia nitrogen conversion rate, and microbial protein yield are all lower than those of the "ammonia nitrogen recovery-in-situ protein synthesis" microbial electrochemical system. While a single microbial electrochemical system recovers ammonia nitrogen as a nitrogen source for protein production cultivation, achieving wastewater treatment, its CO2 consumption rate, ammonia nitrogen conversion rate, and microbial protein yield are also lower than those of the "ammonia nitrogen recovery-in-situ protein synthesis" microbial electrochemical system. Therefore, compared to a single microbial electrochemical system and a single protein production system, coupling the two allows for in-situ microbial protein production without the need for ammonia nitrogen transportation and dilution, simultaneously achieving wastewater treatment, ammonia nitrogen recovery, and CO2 fixation.

[0311] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is impossible to exhaustively list all embodiments here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A microbial electrochemical system device that simultaneously realizes wastewater treatment, CO2 fixation, and in-situ synthesis of microbial proteins, characterized in that: The system includes an anode chamber, a cathode chamber, a protein production chamber, a power supply, a mixed gas tank, and a peristaltic pump. The anode chamber, cathode chamber, and protein production chamber are arranged sequentially from left to right. A cation exchange membrane connects the anode chamber and the cathode chamber. A cation exchange membrane also connects the cathode chamber and the protein production chamber. An anode is located within the anode chamber, connected to the positive terminal of the power supply via a wire, and a resistor is installed on the wire connecting the anode and the positive terminal of the power supply. A cathode is located within the cathode chamber, connected to the negative terminal of the power supply via a wire. The protein production chamber is connected to the mixed gas tank via an inlet pipe and an outlet pipe, forming a circulation loop. The peristaltic pump is located on the inlet pipe.

2. The microbial electrochemical system device according to claim 1, characterized in that: The anode chamber is connected to a first storage gas bag via a pipe, and the cathode chamber is connected to a second storage gas bag via a pipe.

3. The microbial electrochemical system device according to claim 1, characterized in that: Both the anode chamber and the cathode chamber are directly connected to the mixed gas tank via pipelines.

4. The microbial electrochemical system device according to claim 1, characterized in that: The anode is made of carbon brush; the cathode is made of graphite plate.

5. A method for simultaneously achieving wastewater treatment, CO2 fixation, and in-situ synthesis of microbial proteins using a microbial electrochemical system device as described in any one of claims 1-4, characterized in that, Includes the following steps: S1. Fabricate the anode carbon brush and cathode electrode required for the microbial electrochemical system, and perform pretreatment; S2. Inoculate the anode chamber with anaerobic sludge, add nutrient solution, and purge with nitrogen to maintain a strictly anaerobic environment; add potassium ferricyanide solution to the cathode chamber. Anaerobic sludge is cultivated and acclimatized to enrich electrogenic microorganisms on the anode; S3. After the electrogenic microorganisms in the anode chamber have been cultured and domesticated, the potassium ferricyanide solution in the cathode chamber is replaced with a phosphate buffer solution; at the same time, protein-producing culture medium is added to the protein-producing chamber to form a three-chamber microbial electrochemical system. S4. At different temperatures, different voltages are applied to the power supply. The domesticated protein-producing microorganisms are inoculated into the protein-producing chamber and a mixture of carbon dioxide, hydrogen and oxygen is introduced to carry out protein production culture, thus obtaining the "ammonia nitrogen recovery-in-situ protein synthesis" microbial electrochemical system. S5. Process the culture products in the protein production chamber to obtain microbial protein.

6. The method for simultaneously achieving wastewater treatment, CO2 fixation, and in-situ synthesis of microbial proteins according to claim 5, characterized in that, In step S1, the preprocessing includes the following steps: S1-1, Process carbon fiber filaments and titanium wires with a diameter of 0.8-1.2mm into carbon brushes; S1-2, Use 0.9-1.1 mol·L⁻¹ on the carbon brush. -1 Soak in NaOH solution for 5-7 hours to remove impurity ions; S1-3, using 0.9-1.1 mol·L -1 Soak in HCl for 5-7 hours, then ultrasonically clean with deionized water until neutral. S1-4. Boil in deionized water for 2.5-3.5 hours, changing the water every 25-35 minutes. S1-5. Heat the carbon brushes in a muffle furnace to obtain the carbon brushes required for the experiment. S1-6. Cut the graphite plate into cubes of 4cm*4cm*0.5cm; S1-7, using 0.9-1.1 mol·L -1 Soak in NaOH solution for 4-6 hours to remove impurity ions; S1-8, using 0.9-1.1 mol·L -1 Soak in HCl for 5-7 hours, then ultrasonically clean with deionized water until neutral to obtain the graphite plate required for the cathode; In step S1-1, the carbon brush is 5-7cm long and 3-5cm in diameter; In steps S1-5, the temperature of the muffle furnace heating treatment is 480-520℃, and the treatment time is 9-11 minutes.

7. The method for simultaneously achieving wastewater treatment, CO2 fixation, and in-situ synthesis of microbial proteins according to claim 5, characterized in that, Step S2 includes the following specific steps: S2-1. Use anaerobic sludge from the thickening tank of the sewage treatment plant as inoculum. After the anaerobic sludge is settled, pour off the supernatant. S2-2. Anaerobic sludge and nutrient solution are added to an anode chamber with a carbon brush to form an anolyte. S2-3. Nitrogen gas is continuously introduced into the anode chamber to remove oxygen and maintain a strictly anaerobic environment. S2-4. Add potassium ferricyanide solution to the cathode chamber as the cathode solution; S2-5. The anode, resistor, power supply and cathode are connected in series to form a microbial fuel cell. At a suitable temperature of 25-32℃, electrogenic microorganisms from anaerobic sludge are cultivated and domesticated on the anode carbon brush, so that electrogenic microorganisms are enriched on the anode. In step S2-2, the nutrient solution is formulated to contain the following substances per liter: 3 mg magnesium sulfate, 0.13 mg zinc chloride, 0.005 mg zinc sulfate heptahydrate, 1.5 mg nitric acid, 0.5 mg manganese sulfate monohydrate, 310 mg ammonium chloride, 130 mg potassium chloride, 0.01 mg boric acid, 0.01 mg cobalt chloride hexahydrate, 5 mg nicotinic acid, 2 mg folic acid, 0.01 mg copper sulfate pentahydrate, 0.024 mg nickel chloride hexahydrate, 0.024 mg sodium tungstate dihydrate, 0.1 mg B-12, 5 mg vitamin B1, 6 mg vitamin B2, 10 mg vitamin B6, 6 mg para-aminobenzoic acid, and 2000 mg sodium acetate; In step S2-2, the pH of the anolyte in the anode chamber is 6.5-7.5; In step S2-2, the volume ratio of anaerobic sludge to nutrient solution is 1:1; In steps S2-3, the nitrogen gas is introduced for 9-11 minutes; In steps S2-4, the concentration of the potassium ferricyanide solution is 15-17 g / L; In steps S2-5, the resistor is 950-1050Ω.

8. The method for simultaneously achieving wastewater treatment, CO2 fixation, and in-situ synthesis of microbial proteins according to claim 5, characterized in that, Step S3 includes the following specific steps: S3-1. After the electrogenic microorganisms in the anode chamber have been cultured, replace the solution in the anode chamber with fresh nutrient solution. S3-2. Prepare a phosphate buffer solution for ammonia nitrogen recovery as the catholyte; S3-3. Inject the catholyte into the cathode chamber; S3-4. Connect the anode, resistor, power supply and cathode in series; S3-5. Simultaneously, protein-producing culture medium is added to the protein-producing chamber to form a three-chambered microbial electrochemical system device. In step S3-1, the fresh nutrient solution is formulated to contain the following substances per liter of solution: 3 mg magnesium sulfate, 0.13 mg zinc chloride, 0.005 mg zinc sulfate heptahydrate, 1.5 mg nitric acid, 0.5 mg manganese sulfate monohydrate, 310 mg ammonium chloride, 130 mg potassium chloride, 0.01 mg boric acid, 0.01 mg cobalt chloride hexahydrate, 5 mg niacin, 2 mg folic acid, 0.01 mg copper sulfate pentahydrate, 0.024 mg nickel chloride hexahydrate, 0.024 mg sodium tungstate dihydrate, 0.1 mg B-12, 5 mg vitamin B1, 6 mg vitamin B2, 10 mg vitamin B6, 6 mg para-aminobenzoic acid, 1462 mg glucose or 2000 mg sodium acetate or 1820 mg sodium lactate; In step S3-2, each liter of the catholyte comprises the following substances: 140-11400 mg of dipotassium hydrogen phosphate and 1340-6000 mg of sodium dihydrogen phosphate; In steps S3-4, the resistance is 8-12Ω; In steps S3-5, the protein-producing culture medium is formulated to contain the following substances per liter of solution: 2.3g potassium dihydrogen phosphate, 2.9g disodium hydrogen phosphate, 0.5g magnesium sulfate, 0.5g sodium carbonate, 0.01g calcium chloride, 0.05g ferric ammonium citrate, 0.6mg boric acid, 0.4mg cobalt chloride, 0.2mg zinc sulfate, 0.06mg manganese chloride, 0.06mg sodium molybdate, 0.04mg nickel chloride, and 0.02mg copper sulfate; In steps S3-5, the protein-producing medium needs to be sterilized at 120-122℃ for 18-22 minutes and cooled to room temperature before use. The added organic carbon source is sodium acetate, and no additional nitrogen source is added to the prepared protein-producing medium.

9. The method for simultaneously achieving wastewater treatment, CO2 fixation, and in-situ synthesis of microbial proteins according to claim 5, characterized in that, Step S4 includes the following specific steps: S4-1. Inoculate the domesticated protein-producing microorganisms into the protein-producing chamber; S4-2, The mixed gas cylinder is filled with a mixture of hydrogen, oxygen and carbon dioxide; S4-3. Start the peristaltic pump to deliver the mixed gas to the protein production chamber; S4-4. Apply a suitable voltage to form a "ammonia nitrogen recovery-in-situ protein synthesis" microbial electrochemical system; In step S4-1, the acclimatization process of the protein-producing microorganisms includes the following specific steps: ① After preparing the protein-producing culture medium, sterilize it at 120-122℃ for 18-22 min, cool it to room temperature, and add 15 g / L agar to obtain the acclimatization culture medium; ② The blue-capped bottle used for acclimatization is 500 mL, the working volume is 200 mL, the headspace volume is 415 mL, and the inoculum is 10% aerobic sludge and 10% anaerobic sludge; ③ Inject mixed gas into the headspace of the blue-capped bottle. The volume ratio of the mixed gas components is H2:O2:CO2 = 60:25:

15. After continuously purging the headspace of the blue-capped bottle with mixed gas for 8-12 min, seal the reactor; ④ Replace the mixed gas sealed in the blue-capped bottle every 12 h; During the cultivation process, the pH is controlled at 7.0±0.2; the reactor temperature is controlled at 20-40℃, and the rotation speed is 150 rpm; ⑤ When the consumption rate of the mixed gas and hydrogen is stable and reaches more than 60%, the domestication is complete and protein-producing microorganisms are obtained. In step S4-2, the volume ratio of the mixed gas is H2:O2:CO2 = 50:35:15 to 70:20:10; In step S4-3, the rotational speed of the peristaltic pump is 5-50 rpm; In step S4-4, the pH of each chamber in the "ammonia nitrogen recovery-in-situ protein synthesis" microbial electrochemical system is 5.0-9.0; In step S4-4, the suitable voltage range is 0.01-1.0V; the temperature range is 20-40℃. In step S4-4, the "ammonia nitrogen recovery-in-situ protein synthesis" microbial electrochemical system can achieve a COD removal rate of >90%, a CO2 consumption rate of >100mL / d, and an ammonia nitrogen conversion rate of >15% in wastewater treatment.

10. The method for simultaneously achieving wastewater treatment, CO2 fixation, and in-situ synthesis of microbial proteins according to claim 5, characterized in that, In step S5, the process includes the following steps: S5-1. Centrifuge the product at 9000-11000 rpm for 10-15 min and discard the supernatant; S5-2. After centrifugation, wash the product with deionized water and centrifuge again, repeating 1-3 times. S5-3. The product after centrifugation and washing is baked at 100-110℃ for 20-30 hours to obtain microbial protein; In step S5-3, the standard for the formation of microbial protein is one or more of the following methods: 1) crude protein content in the product > 30%; 2) crude protein yield in the product > 1g / L.

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