Microalgae and hydrogen oxidizing bacteria two-phase coupling air protein production device and method

Abstract

The application discloses a kind of microalgae and hydrogen oxidation bacteria dual-phase coupling air protein production device and method, it is related to biological engineering and new energy utilization technical field.The device includes microalgae photobioreactor, hydrogen oxidation bacteria reactor, gas circulation pipeline system connecting two reactors, hydrogen production system by electrolytic water driven by renewable energy waste electricity, and protein collection and separation system.The gas circulation pipeline system transports the oxygen-rich gas phase generated by the microalgae photobioreactor photosynthesis to the hydrogen oxidation bacteria reactor as the electron acceptor oxygen source of hydrogen oxidation bacteria, and the carbon dioxide-rich gas phase released by the hydrogen oxidation bacteria reactor respiratory metabolism is backflowed to the microalgae photobioreactor as the photosynthesis carbon source, to form carbon-oxygen cycle coupling of gas phase between two reactors;The hydrogen production system by electrolytic water supplies hydrogen gas energy substrate to hydrogen oxidation bacteria reactor;Two reactor culture solutions are obtained after harvesting, solid-liquid separation and protein extraction mixed mixed protein product with complementary amino acid composition.The application utilizes the mutual coupling of gas exchange between reactors to reduce the supplement demand of external carbon source and oxygen source, and utilizes renewable energy waste electricity to drive hydrogen oxidation bacteria chemotrophic autotrophic growth, while the nutritional value of product is improved through the amino acid complementation of microalgae protein and bacterial protein.

Description

Technical Field

[0001] This invention relates to the fields of bioengineering and microbial protein production technology, specifically to a protein production device and method that utilizes a microalgae photobioreactor and a hydrogen-oxidizing bacteria reactor in gas phase coupling, and integrates renewable energy wastewater electrolysis to produce hydrogen. It belongs to the interdisciplinary technical field of single-cell protein (SCP) production and gas resource utilization. Background Technology

[0002] With global population growth and continuously rising demand for protein, traditional animal husbandry and crop cultivation face problems such as scarce arable land resources, high water consumption, and high greenhouse gas emissions. Utilizing microorganisms to produce single-cell protein (SCP) is considered one of the important ways to alleviate protein supply pressure.

[0003] Microalgae, as photoautotrophic microorganisms, can convert carbon dioxide into protein and biomass through photosynthesis, offering advantages such as rapid growth, high protein content, and no need for arable land. However, microalgae cultivation requires a continuous supply of carbon dioxide as a carbon source, and excessive accumulation of oxygen can inhibit photosynthetic efficiency. Furthermore, microalgae proteins are relatively low in certain essential amino acids (such as methionine and lysine), limiting their nutritional value as a single protein source.

[0004] Hydrogen-oxidizing bacteria (HOBs) are a class of microorganisms that obtain energy through chemoautotrophic respiration using hydrogen (H2) as an electron donor and oxygen (O2) as an electron acceptor, and synthesize cellular biomass through the Calvin cycle using carbon dioxide (CO2) as a carbon source (see, for example: Malavasi et al., Bioresource Technology, 2024; Esquivel-Plennel et al., Microbial Cell Factories, 2021). These bacteria can utilize hydrogen generated from the electrolysis of water using surplus renewable energy as an energy substrate to convert CO2 into single-cell proteins, with a protein content reaching 60%–70%, and an amino acid composition that is somewhat complementary to microalgal proteins (rich in sulfur-containing amino acids). However, their cultivation process requires a continuous supply of O2 and necessitates control of the explosion risk of H2 / O2 mixtures, and some essential amino acids in single HOB proteins still deviate from the ideal protein profile of FAOs.

[0005] At present, microalgae protein production and hydroxyl bacteria protein production are mostly carried out in independent systems, which have the following technical problems: (1) Microalgae cultivation requires a continuous external supply of carbon dioxide, and hydroxyl bacteria cultivation requires an external supply of oxygen and hydrogen. The system operation depends on the external gas input, resulting in high operating costs; (2) The oxygen and carbon dioxide generated by the two types of reactors are directly emitted, and carbon and oxygen resources are not fully utilized; (3) Renewable energy waste (such as intermittent surplus electricity from wind power and photovoltaics) has not been effectively integrated into the protein production system, resulting in low energy utilization efficiency; (4) The amino acid composition of single microbial proteins is not balanced enough, and the nutritional value is limited.

[0006] Therefore, there is an urgent need to develop a new type of air protein production device and method that can realize the internal recycling of carbon and oxygen resources, integrate the waste electricity from renewable energy sources, and produce nutritionally balanced protein. Summary of the Invention

[0007] Technical problems to be solved

[0008] The purpose of this invention is to provide an air protein production apparatus and method that uses a dual-phase coupling of microalgae and hydroxyl bacteria, in order to solve the following problems existing in the prior art: (1) The microalgae photobioreactor and the hydroxide bacteria reactor operate independently, and the carbon and oxygen sources depend on external supplementation, resulting in high operating costs; (2) The carbon dioxide and oxygen produced by the reactor are directly emitted, resulting in a waste of carbon and oxygen resources and a low carbon and oxygen utilization rate in the system; (3) The curtailment of renewable energy has not been effectively coupled to the protein production system, resulting in insufficient utilization efficiency of new energy sources; (4) The amino acid composition of single microbial proteins is unbalanced, and their nutritional value needs to be improved. Technical solution To achieve the above objectives, the present invention provides the following technical solution:

[0009] A gas-phase circulating protein production device with microalgae and hydroxyl-oxidizing bacteria in a dual-phase coupling process includes: a microalgae photobioreactor (100) for cultivating microalgae and performing photosynthesis under illumination, wherein the microalgae absorb carbon dioxide (CO2) to synthesize biomass and release oxygen (O2), and the oxygen-containing phase produced is collected in the gas phase space at the top of the reactor and discharged through a first gas outlet; and a hydroxyl-oxidizing bacteria reactor (200) for cultivating hydroxyl-oxidizing bacteria. The HOB (Hydrogen-Algae Photobioreactor) describes aerobic autotrophic respiration in which the hydrogen-absorbing bacteria (H2) use hydrogen (H2) as an electron donor and oxygen (O2) as an electron acceptor to generate energy. The bacteria also fix carbon dioxide into cellular biomass via the Calvin cycle. During aerobic respiration, the bacteria produce carbon dioxide, which is released into the reactor's gas phase. This carbon dioxide-containing gas phase collects at the top of the reactor and is discharged through a second outlet. A gas circulation pipeline system (300) connects the first outlet of the microalgae photobioreactor to the second inlet of the hydrogen-absorbing bacteria reactor, and connects the second outlet to the first inlet, thereby allowing oxygen produced by microalgae photosynthesis to be transported to the hydrogen-absorbing bacteria reactor as an electron acceptor and oxygen source. The reactor comprises a photobioreactor that allows carbon dioxide released by the respiration and metabolism of the hydroxyl bacteria to be recycled back to the microalgae photobioreactor as a carbon source for microalgae photosynthesis, forming a carbon-oxygen cycle coupling between the two reactors with gas exchange as the carrier; an electrolysis water hydrogen production system (400), driven by renewable energy waste electricity, is used to electrolyze water to produce hydrogen, which is then buffered and stored before being transported to the hydroxyl bacteria reactor as an energy substrate for the hydroxyl bacteria; and a protein collection and separation system (500), connected to the culture medium outlets of the microalgae photobioreactor and the hydroxyl bacteria reactor respectively, for harvesting the culture medium, separating biomass, extracting proteins, and mixing microalgae proteins with bacterial proteins to obtain a mixed protein product with a balanced amino acid composition. In this specification, the term "air protein" refers to a single-cell protein product obtained through microbial autotrophic transformation using inorganic carbon from air components (CO2, N2) and / or water bodies, as well as H2 converted from water and renewable energy sources, as the substantial carbon / energy source, and its production process does not depend on the planting of crops on arable land.

[0010] A microalgae and hydroxide bacteria biphase coupling air protein production device includes: a microalgae photobioreactor for cultivating microalgae and performing photosynthesis, absorbing carbon dioxide and releasing oxygen; a hydroxide bacteria reactor for cultivating hydroxide bacteria and performing chemoautotrophic growth using hydrogen and oxygen as substrates, absorbing carbon dioxide and releasing oxygen; a gas circulation pipeline system connecting the microalgae photobioreactor and the hydroxide bacteria reactor for transporting oxygen generated by the microalgae photobioreactor to the hydroxide bacteria reactor and returning carbon dioxide generated by the metabolism of the hydroxide bacteria reactor to the microalgae photobioreactor, forming a carbon-oxygen biphase closed-loop cycle; an electrolysis water hydrogen production system driven by renewable energy waste electricity for electrolyzing water to produce hydrogen and oxygen, wherein the hydrogen is transported to the hydroxide bacteria reactor as an energy substrate for the hydroxide bacteria; and a protein collection and separation system connected to the microalgae photobioreactor and the hydroxide bacteria reactor respectively for collecting the culture medium in the two reactors and performing protein separation and mixing to obtain a mixed protein product.

[0011] Preferably, the gas circulation pipeline system includes: an oxygen delivery pipeline connecting the outlet of the microalgae photobioreactor to the inlet of the hydroxide bacteria reactor, wherein an oxygen buffer tank and a gas flow control valve are provided on the oxygen delivery pipeline; a carbon dioxide return pipeline connecting the outlet of the hydroxide bacteria reactor to the inlet of the microalgae photobioreactor, wherein a carbon dioxide buffer tank, a gas flow control valve and a carbon dioxide concentration sensor are provided on the carbon dioxide return pipeline; and a gas circulation pump, disposed on the oxygen delivery pipeline and / or the carbon dioxide return pipeline, for driving gas circulation.

[0012] Preferably, the water electrolysis hydrogen production system includes: an electrolyzer for electrolyzing water to produce hydrogen and oxygen; a renewable energy power generation device electrically connected to the electrolyzer for providing electrical energy; a power waste storage and control unit for monitoring the output power of the renewable energy power generation device and directing excess power (wasted power) to the electrolyzer when the output power exceeds the grid absorption capacity or electricity load demand; a hydrogen buffer tank connected to the hydrogen outlet of the electrolyzer and the air inlet of the hydrogen hydroxide bacterial reactor for storing and stabilizing the supply of hydrogen; and an oxygen discharge or replenishment pipeline connected to the oxygen outlet of the electrolyzer for discharging the oxygen generated by electrolysis into the atmosphere or replenishing the microalgae photobioreactor.

[0013] Preferably, the protein collection and separation system includes: a microalgae harvesting unit connected to the microalgae photobioreactor, used to harvest microalgae culture medium and perform solid-liquid separation to obtain microalgae biomass; a bacteria harvesting unit connected to the hydroxide bacteria reactor, used to harvest hydroxide bacteria culture medium and perform solid-liquid separation to obtain bacterial biomass; a protein extraction unit connected to both the microalgae harvesting unit and the bacteria harvesting unit, used to extract proteins from the microalgae biomass and bacterial biomass; and a protein mixing and blending unit connected to the protein extraction unit, used to mix microalgae protein and bacterial protein in a preset ratio to obtain a mixed protein product with a balanced amino acid composition.

[0014] Preferably, the microalgae photobioreactor is a closed photobioreactor, selected from one or more combinations of tubular photobioreactors, flat-plate photobioreactors, or airlift photobioreactors, and is equipped with a temperature control device, a pH monitoring and regulation device, a light system, and a nutrient replenishment device.

[0015] Preferably, the hydroxide bacteria reactor is a stirred fermenter, an airlift bioreactor, or a membrane bioreactor, and the reactor is equipped with a temperature control device, a pH monitoring and regulation device, a dissolved oxygen sensor, a dissolved hydrogen sensor, and a nutrient supplementation device.

[0016] Preferably, the device further includes: an air carbon dioxide capture unit connected to the air inlet of the microalgae photobioreactor, used to capture carbon dioxide from the ambient air and replenish it to the microalgae photobioreactor to balance carbon loss in the system's carbon cycle; and an exhaust gas treatment unit connected to the exhaust port of the gas circulation pipeline system, used to treat nitrogen or other inert gases enriched in the system to maintain a stable gas composition in the system.

[0017] This invention also provides a method for producing air protein through a two-phase coupling of microalgae and hydroxide bacteria, comprising the following steps: S1: Microalgae culture medium is inoculated into a microalgae photobioreactor, and photosynthesis is carried out under light conditions. The microalgae absorb carbon dioxide and release oxygen. S2: The oxygen generated in step S1 is transported to the hydroxide bacteria reactor through the gas circulation pipeline to provide oxygen for the hydroxide bacteria; S3: Utilize renewable energy waste to drive a water electrolysis hydrogen production system to generate hydrogen, and transport the hydrogen to a hydrogen-oxidizing bacteria reactor to provide hydrogen energy substrate for the hydrogen-oxidizing bacteria; S4: In the hydroxide bacteria reactor, hydroxide bacteria use hydrogen as an electron donor and oxygen as an electron acceptor to carry out chemoautotrophic growth and produce carbon dioxide through metabolism. S5: The carbon dioxide generated in step S4 is returned to the microalgae photobioreactor through the gas circulation pipeline to provide a carbon source for microalgae photosynthesis. S6: Collect the culture medium from the microalgae photobioreactor and the hydroxide bacteria reactor respectively, obtain microalgae protein and bacterial protein through the protein collection and separation system, and mix the two in a preset ratio to obtain a mixed protein product.

[0018] Preferably, in step S1, the microalgae are selected from one or more of Chlorella vulgaris, Spirulina platensis, Scenedesmus obliquus, or Dunaliella salina.

[0019] Preferably, in step S4, the hydroxide bacteria are selected from one or more of the following: *Hydrogenophagapseudoflava*, *Paracoccus denitrificans*, *Alcaligeneseutrophus* (now renamed *Cupriavidus necator*), or *Hydrogenobacter thermophilus*.

[0020] Preferably, in step S6, the mixing ratio of the microalgal protein to the bacterial protein is 1:3 to 3:1 (mass ratio), and more preferably 1:1 to 2:1.

[0021] Preferably, the method further includes: monitoring the concentration and flow rate of carbon dioxide and oxygen in the gas circulation pipeline system, and dynamically adjusting the gas circulation flow rate according to the photosynthetic rate of microalgae and the metabolic rate of hydroxide bacteria to maintain the balance of carbon-oxygen two-phase closed-loop circulation.

[0022] Preferably, the method further includes: when the renewable energy power generation device generates abandoned electricity, starting or increasing the operating power of the water electrolysis hydrogen production system to convert the abandoned electricity into hydrogen and store it in a hydrogen buffer tank; when renewable energy power generation is insufficient, using the hydrogen stored in the hydrogen buffer tank to maintain the continuous operation of the hydroxide bacteria reactor. Beneficial effects

[0023] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention couples the microalgae photobioreactor and the hydroxide bacteria reactor through a gas circulation pipeline to form a carbon-oxygen biphase closed-loop cycle. The oxygen produced by microalgae photosynthesis is directly supplied to the hydroxide bacteria as an electron acceptor, and the carbon dioxide produced by the metabolism of the hydroxide bacteria is directly returned to the microalgae reactor as a photosynthetic carbon source, which greatly reduces the need for external carbon sources (such as industrial carbon dioxide) and oxygen sources, and lowers the system operating cost. (2) This invention realizes the internal recycling of carbon and oxygen resources between reactors, improving the overall carbon and oxygen utilization rate of the system. Compared with independently operating microalgae cultivation systems and hydroxide bacteria cultivation systems, the carbon and oxygen losses of this invention are significantly reduced, and the resource utilization efficiency is greatly improved. (3) This invention integrates renewable energy waste-driven water electrolysis to produce hydrogen into a protein production system, transforming intermittent and fluctuating waste electricity into a stable hydrogen energy substrate. This not only solves the problem of renewable energy consumption, but also provides a clean hydrogen source for hydrogen-oxidizing bacteria, realizing a deep coupling between new energy and biomanufacturing. (4) This invention achieves complementary optimization of amino acid composition by mixing microalgae protein and hydroxyl bacteria protein. Microalgae protein is rich in amino acids such as lysine and leucine, while hydroxyl bacteria protein is rich in sulfur-containing amino acids such as methionine and cysteine. After mixing the two, the essential amino acid composition of the protein product is more balanced, the nutritional value is significantly improved, and it is more suitable as a protein source for food or feed. (5) This invention uses carbon dioxide in the air as an indirect carbon source (with optional air carbon dioxide capture unit to supplement carbon balance) and hydrogen generated by electrolysis of water using renewable energy as energy input, so that the actual carbon flow and energy flow of protein synthesis are separated from the arable land agricultural system, providing an integrated technical solution for protein supply through the "non-arable land and non-grain" pathway. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall structure of the present invention (dashed arrows indicate the gas flow direction, and solid arrows indicate the culture medium / biomass flow direction).

[0025] Figure 2 This is a schematic diagram of the gas circulation pipeline system;

[0026] Figure 3 This is a schematic diagram of a water electrolysis hydrogen production system;

[0027] Figure 4 A schematic diagram of the structural flow of a protein collection and separation system;

[0028] Figure 5 This is a flowchart of the production process of the present invention.

[0029] Figure reference numerals: 100 - Microalgae photobioreactor; 200 - Hydroxyhydric bacteria reactor; 300 - Gas circulation pipeline system; 310 - Oxygen delivery pipeline; 311 - Oxygen buffer tank; 312 - Gas flow control valve; 313 - Gas circulation pump; 320 - Carbon dioxide reflux pipeline; 321 - Carbon dioxide buffer tank; 322 - Gas flow control valve; 323 - Carbon dioxide concentration sensor; 324 - Gas circulation pump; 400 - Electrolysis water hydrogen production system; 410 - Electrolyzer; 420 - Renewable energy power generation device; 430 - Waste electricity storage and control unit; 440 - Hydrogen buffer tank; 450 - Oxygen discharge or replenishment pipeline; 451 - Hydrogen supply pipeline; 452 - Oxygen discharge pipeline; 453 - Oxygen replenishment pipeline; 500 - Protein collection and separation system; 510 - Microalgae harvesting unit; 520 - Bacterial harvesting unit; 530 - Protein extraction unit; 540 - Protein mixing and blending unit. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in further detail below with reference to the accompanying drawings. Example 1: Overall Structure of the Device

[0031] like Figure 1 As shown, the present invention provides an air protein production device with dual-phase coupling of microalgae and hydroxyl bacteria, mainly including a microalgae photobioreactor (100), a hydroxyl bacteria reactor (200), a gas circulation pipeline system (300), an electrolysis water hydrogen production system (400), and a protein collection and separation system (500).

[0032] The microalgae photobioreactor (100) is a closed tubular photobioreactor made of transparent materials (such as glass or plexiglass). Internally, it is equipped with a temperature control device (such as a cooling jacket or heating coil), a pH monitoring and control device (pH electrode and acid / base dosing pump), an LED lighting system, and a nutrient replenishment device. The reactor contains a culture medium of *Chlorella vulgaris* with an initial algal cell density of approximately 0.5 g / L. The culture temperature is controlled at 25±2℃, the pH at 7.0±0.5, the light intensity at 5000-10000 lux, and the light-dark cycle is 16:8 (16 hours of light, 8 hours of darkness).

[0033] The hydroxide bacteria reactor (200) is a stirred fermenter equipped with a temperature control jacket, pH monitoring and control device, dissolved oxygen sensor, dissolved hydrogen sensor, and nutrient replenishment device. The reactor contains a culture of *Hydrogenophaga pseudoflava*, with the culture temperature controlled at 30±1℃, pH controlled at 7.2±0.3, and the stirring speed controlled at 200-400 rpm.

[0034] A gas circulation piping system (300) connects the microalgae photobioreactor (100) to the hydroxide bacteria reactor (200). For example... Figure 2 As shown, the gas circulation pipeline system (300) includes an oxygen delivery pipeline (310) and a carbon dioxide return pipeline (320). The oxygen delivery pipeline (310) connects the outlet at the top of the microalgae photobioreactor (100) to the inlet at the bottom of the hydroxide bacteria reactor (200), and is equipped with an oxygen buffer tank (311), a gas flow control valve (312), and a gas circulation pump (313) in sequence. The carbon dioxide return pipeline (320) connects the outlet at the top of the hydroxide bacteria reactor (200) to the inlet at the bottom of the microalgae photobioreactor (100), and is equipped with a carbon dioxide buffer tank (321), a gas flow control valve (322), a carbon dioxide concentration sensor (323), and a gas circulation pump (324) in sequence.

[0035] Electrolysis water hydrogen production system (400) such as Figure 3 As shown, the system includes an electrolyzer (410), a renewable energy power generation device (420) (such as a wind turbine or photovoltaic array), a power waste storage and control unit (430), a hydrogen buffer tank (440), and an oxygen discharge or replenishment pipeline (450). The power waste storage and control unit (430) monitors the output power of the renewable energy power generation device (420) and the grid load demand in real time. When power waste is detected, it directs excess power to the electrolyzer (410). The electrolyzer (410) uses alkaline water electrolysis or proton exchange membrane (PEM) water electrolysis technology to decompose water into hydrogen and oxygen. The purified hydrogen is stored in the hydrogen buffer tank (440) and then transported to the hydroxide bacteria reactor (200) via the hydrogen supply pipeline (451) as an energy substrate for the hydroxide bacteria. The oxygen generated by electrolysis can be discharged to the atmosphere via the oxygen discharge pipeline (452) or replenished to the microalgae reactor via the oxygen replenishment pipeline (453) when the oxygen in the microalgae photobioreactor (100) is insufficient.

[0036] Protein collection and separation system (500) such as Figure 4As shown, the system includes a microalgae harvesting unit (510), a bacteria harvesting unit (520), a protein extraction unit (530), and a protein mixing and blending unit (540). The microalgae harvesting unit (510) harvests the microalgae culture medium from the microalgae photobioreactor (100) by centrifugation or membrane filtration to obtain microalgae biomass. The bacteria harvesting unit (520) harvests the bacterial culture medium from the hydroxide bacteria reactor (200) by centrifugation or membrane filtration to obtain bacterial biomass. The protein extraction unit (530) extracts proteins from the microalgae biomass and bacterial biomass using alkali-soluble acid precipitation or enzymatic hydrolysis, respectively. The protein mixing and blending unit (540) mixes microalgae protein and bacterial protein at a mass ratio of 2:1 to obtain a mixed protein product with a balanced amino acid composition. Example 2: Air Protein Production Method

[0037] like Figure 5 As shown, the present invention also provides a method for producing air protein based on the above-described device, the specific steps of which are as follows:

[0038] Step S1: Microalgae Cultivation and Oxygen Production. Chlorella culture medium was inoculated into the microalgae photobioreactor (100) at an initial inoculation density of 0.5 g / L. Under light conditions (light intensity 8000 lux, light-dark cycle 16:8), the microalgae performed photosynthesis, absorbing carbon dioxide and releasing oxygen. During cultivation, algal cell density, culture medium pH, and dissolved oxygen concentration were monitored regularly, and nutrients (such as nitrates, phosphates, and trace elements) were supplemented as needed. After 7 days of cultivation, the algal cell density increased to 3-4 g / L, and the dissolved oxygen saturation in the culture medium reached 150%-200%.

[0039] Step S2: Oxygen Delivery. Oxygen-rich gas (approximately 30%-50% oxygen content) generated in the microalgae photobioreactor (100) is delivered to the hydroxide bacteria reactor (200) via an oxygen delivery pipeline (310) driven by a gas circulation pump (313). The gas flow rate is regulated by a gas flow control valve (312), maintaining a flow rate between 0.5-2.0 vvm (gas volume / culture medium volume / minute). An oxygen buffer tank (311) is used to balance fluctuations in the gas flow rate, ensuring a stable oxygen supply to the hydroxide bacteria reactor (200).

[0040] Step S3: Waste Power to Hydrogen Production. The waste power storage and control unit (430) monitors the output power of the wind turbine generator in real time. When the wind power output exceeds the grid's absorption capacity (such as during low-load periods at night), the waste power storage and control unit (430) directs the excess power (waste power) to the electrolyzer (410). The electrolyzer (410) operates in an alkaline water electrolysis mode with an electrolysis efficiency of approximately 60%-70%, producing 1 Nm³ of hydrogen for every 5-6 kWh of electricity consumed. The produced hydrogen is dried and purified before being stored in a hydrogen buffer tank (440), achieving a hydrogen purity of over 99.9%.

[0041] Step S4: Hydroxyhydric bacteria culture and carbon dioxide production. In the hydroxyhydric bacteria reactor (200), *Pseudomonas saccharophilus* grows using hydrogen as an electron donor and oxygen as an electron acceptor through the following chemoautotrophic reaction: 2H₂ + O₂ + 2CO₂ → 2CH₂O + 2H₂O (Simplified formula) In the actual metabolic process, hydroxyl bacteria oxidize H2 to produce electrons and protons through membrane-bound hydrogenase. ATP and reducing power (NAD(P)H) are then generated via the electron transport chain with O2 as the terminal electron acceptor. CO2 is fixed via the Calvin cycle to synthesize cellular biomass (CH2O represents the biomass reduction unit). At the same time, the respiration process that sustains metabolism releases CO2 into the gas phase, which is then returned to the microalgae reactor by the airflow for reuse.

[0042] Step S5: Carbon Dioxide Recirculation. Carbon dioxide-rich gas from the top of the hydroxide bacteria reactor (200) is circulated back to the microalgae photobioreactor (100) via a carbon dioxide recirculation pipeline (320) driven by a gas circulation pump (324). A carbon dioxide concentration sensor (323) monitors the carbon dioxide concentration in the recirculated gas in real time, and a gas flow control valve (322) adjusts the recirculation flow rate according to the microalgae photosynthetic rate and the system's carbon balance requirements. The carbon dioxide in the recirculated gas is absorbed and utilized by the microalgae through photosynthesis, forming a closed-loop carbon source cycle.

[0043] Step S6: Protein Harvesting and Mixing. After the microalgae and hydroxide bacteria have reached the target density, the culture medium is harvested using the microalgae harvesting unit (510) and the bacteria harvesting unit (520), respectively. The microalgae culture medium is centrifuged (8000 rpm, 10 minutes) to obtain microalgae biomass, and the bacterial culture medium is centrifuged (10000 rpm, 15 minutes) to obtain bacterial biomass. The protein content of the microalgae biomass is approximately 50%-60% (dry weight), and the protein content of the bacterial biomass is approximately 60%-70% (dry weight).

[0044] The protein extraction unit (530) uses the alkaline dissolution and acid precipitation method to extract proteins: microalgal biomass and bacterial biomass are suspended in an alkaline solution with pH 10-11, stirred and extracted for 2 hours, and centrifuged to remove insoluble matter; the pH of the supernatant is adjusted to 4.5-5.0 to precipitate the protein, the protein precipitate is collected by centrifugation, washed and freeze-dried to obtain microalgal protein powder and bacterial protein powder respectively.

[0045] The protein mixing and blending unit (540) mixes microalgae protein powder and bacterial protein powder at a mass ratio of 2:1 to obtain a mixed protein product. Amino acid analysis shows that the mixed protein product has a balanced composition of essential amino acids, with methionine content approximately 40% higher than that of single microalgae protein and lysine content approximately 25% higher than that of single bacterial protein. The protein digestibility corrected amino acid score (PDCAAS) reaches over 0.85, indicating significantly superior nutritional value compared to single microbial protein. Example 3: System Operation Optimization

[0046] To further improve system operating efficiency, this embodiment optimizes gas circulation and energy management.

[0047] In terms of gas circulation, a central control unit (not shown) is configured to work in conjunction with a carbon dioxide concentration sensor (323), a dissolved oxygen sensor (located in the hydroxide bacteria reactor (200)), gas flow control valves (312) and (322), and gas circulation pumps (313) and (324). The central control unit dynamically adjusts the gas circulation according to the following logic: (1) When the dissolved oxygen concentration in the microalgae photobioreactor (100) exceeds the set upper limit (e.g., 200% saturation), increase the speed of the gas circulation pump (313) to accelerate the delivery of oxygen to the hydroxide bacteria reactor (200); (2) When the dissolved oxygen concentration in the hydroxide bacteria reactor (200) is lower than the set lower limit (e.g., 2 mg / L), increase the speed of the gas circulation pump (313) or start the oxygen supply pipeline (453) to supplement the oxygen supply. (3) When the carbon dioxide concentration in the carbon dioxide return pipeline (320) is lower than the set lower limit (e.g., 5%), the air carbon dioxide capture unit (not shown) is started to capture carbon dioxide from the ambient air and replenish it to the microalgae photobioreactor (100) to maintain the carbon balance of the system.

[0048] In terms of energy management, the curtailment storage and control unit (430) communicates with the grid dispatch system to obtain real-time electricity prices and grid load forecast information. When a curtailment period is predicted to occur within the next 2-4 hours, the hydrogen output flow rate of the hydrogen buffer tank (440) is reduced in advance to increase hydrogen reserves. When curtailment actually occurs, the electrolyzer (410) operates at maximum power to convert the curtailment into hydrogen for storage. When renewable energy generation is insufficient and there is no curtailment, the hydrogen buffer tank (440) releases the stored hydrogen to maintain the continuous operation of the hydroxide bacterial reactor (200). Through the above energy management strategies, the system can increase the curtailment utilization rate to over 80%, and the hydrogen supply stability of the hydroxide bacterial reactor is significantly improved. Example 4: Combinations of different microalgae and hydroxide-oxidizing bacteria

[0049] This embodiment verifies the effect of different combinations of microalgae and hydroxide bacteria on the nutritional value of mixed protein products.

[0050] Combination A: The microalgae is *Arthrospira platensis*, and the alkaloid bacteria is *Cupriavidus necator*. *Arthrospira platensis* protein is rich in gamma-linolenic acid and phycocyanin, while *Cupriavidus necator* protein is rich in branched-chain amino acids. When the two are mixed at a 1:1 mass ratio, the essential amino acid index (EAAI) of the mixed protein reaches 0.92.

[0051] Combination B: The microalgae is *Scenedesmus obliquus*, and the hydroxide-oxidizing bacteria is *Paracoccus denitrificans*. *Scenedesmus obliquus* has a thinner cell wall, resulting in a higher protein extraction rate; *Paracoccus denitrificans* grows rapidly under aerobic conditions, producing a higher carbon dioxide yield. When the two are mixed at a mass ratio of 3:1, the PDCAAS of the mixed protein reaches 0.88.

[0052] Combination C: The microalgae is Dunaliella salina, and the hydroxide-oxidizing bacteria is Hydrogenobacter thermophilus. Dunaliella salina is rich in β-carotene, and Hydrogenobacter thermophilus is a thermophilic bacterium that can grow at high temperatures (50-70℃) and has a rapid metabolic rate. When the two are mixed at a mass ratio of 1:2, the antioxidant activity of the mixed protein is significantly enhanced, making it suitable as a protein raw material for functional foods.

[0053] The above results indicate that by selecting different combinations of microalgae and hydroxyl bacteria and optimizing the mixing ratio, mixed protein products with different nutritional and functional properties can be obtained to meet the needs of different application scenarios. Example 5: Large-scale production application

[0054] This embodiment describes the application configuration of the device of the present invention in large-scale production.

[0055] In the 10-ton-class air protein production unit, the microalgae photobioreactor (100) adopts a modular tubular photobioreactor array with a total optical path area of ​​approximately 500 m², a culture medium volume of 10 m³, and an initial inoculation density of Chlorella vulgaris of 0.3 g / L. The hydroxide bacteria reactor (200) adopts a 50 m³ stirred fermenter, with an initial inoculation density of Pseudomonas saccharophilus of 1.0 g / L. The gas circulation pipeline system (300) has a pipeline diameter of 100 mm, and the flow rates of the gas circulation pumps (313) and (324) are both 100 m³ / h.

[0056] The renewable energy generation unit (420) is a 1 MW wind turbine generator set, and the curtailment storage and control unit (430) is equipped with a 500 kW electrolyzer (410) and a 2000 Nm³ hydrogen buffer tank (440). When the curtailed wind power reaches 300 kW, the electrolyzer (410) operates at its rated power and can generate about 60 Nm³ of hydrogen per hour, which meets the hydrogen demand of the hydrogen hydroxide bacterial reactor (200).

[0057] After 30 days of continuous operation, the algal cell density in the microalgae photobioreactor (100) stabilized at 4-5 g / L, with a daily harvest of approximately 500 kg of microalgae biomass (wet weight); the bacterial cell density in the hydroxide bacteria reactor (200) stabilized at 6-8 g / L, with a daily harvest of approximately 800 kg of bacterial biomass (wet weight). After protein extraction and mixing, approximately 150-200 kg (dry weight) of mixed protein product was produced daily, with a protein content of approximately 80%-85%.

[0058] According to calculations, for every ton of mixed protein product produced by this large-scale facility, approximately 15-20 MWh of renewable energy is consumed and approximately 2-3 tons of carbon dioxide are captured. Compared with traditional soybean protein production (which requires approximately 3-5 mu of arable land) and animal protein production (which requires approximately 10-15 mu of feed arable land), it has significant resource and environmental advantages.

Claims

1. A gas-phase circulating protein production device with biphase coupling of microalgae and hydroxyl bacteria, characterized in that, include: A microalgae photobioreactor (100) is provided with a first air inlet, a first air outlet, and a light-enhanced culture chamber containing microalgae culture medium. The microalgae photobioreactor is used to carry out microalgae photosynthesis under light conditions in the light-enhanced culture chamber, so that the microalgae absorb carbon dioxide and release oxygen. A hydroxide bacteria reactor (200) is provided with a second air inlet, a second air outlet, and a fermentation chamber containing hydroxide bacteria culture medium. The hydroxide bacteria reactor is used to cultivate hydroxide bacteria in the fermentation chamber. The hydroxide bacteria use hydrogen as an electron donor and oxygen as an electron acceptor for chemoautotrophic growth and release carbon dioxide produced by respiratory metabolism into the gas phase of the reactor. A gas circulation pipeline system (300) includes an oxygen delivery pipeline (310) and a carbon dioxide return pipeline (320), wherein: one end of the oxygen delivery pipeline (310) is connected to the first air outlet. The system includes a gas inlet and a second gas inlet, which are used to transport oxygen-containing gas generated by the microalgae photobioreactor to the hydroxide bacteria reactor; a carbon dioxide reflux pipeline (320) with one end connected to the second gas outlet and the other end connected to the first gas inlet, which is used to reflux carbon dioxide-containing gas discharged from the hydroxide bacteria reactor back to the microalgae photobioreactor; an electrolysis water hydrogen production system (400), which is provided with a hydrogen outlet pipeline connected to the second gas inlet or connected to the oxygen delivery pipeline, for electrolyzing water to generate hydrogen under the drive of renewable energy curtailment and supplying hydrogen substrate to the hydroxide bacteria reactor; and a protein collection and separation system (500), which is connected to the culture medium outlet of the microalgae photobioreactor and the hydroxide bacteria reactor respectively, for collecting biomass in the two reactors and performing protein separation and mixing to obtain a mixed protein product.

2. The apparatus according to claim 1, characterized in that, The oxygen delivery pipeline (310) is equipped with an oxygen buffer tank (311) and a gas flow control valve (312); the carbon dioxide return pipeline (320) is equipped with a carbon dioxide buffer tank (321), a gas flow control valve (322), and a carbon dioxide concentration sensor (323); the gas circulation pipeline system is also equipped with a gas circulation pump, which is located on the oxygen delivery pipeline or on the carbon dioxide return pipeline, or one gas circulation pump is installed on each of the two pipelines.

3. The apparatus according to claim 1, characterized in that, The water electrolysis hydrogen production system (400) includes: an electrolyzer (410) for electrolyzing water to produce hydrogen and oxygen; a renewable energy power generation device (420) with a DC power input terminal electrically connected to the electrolyzer; a power curtailment monitoring and control unit (430) for monitoring the difference between the output power of the renewable energy power generation device and the grid absorption capacity, and directing excess power to the electrolyzer when the output power exceeds the absorption capacity; a hydrogen buffer tank (440) with its inlet connected to the hydrogen outlet of the electrolyzer and its outlet connected to the second air inlet of the hydrogen hydroxide bacterial reactor via a hydrogen supply pipeline (451); and an oxygen discharge or replenishment pipeline (450) connected to the oxygen outlet of the electrolyzer for discharging the oxygen generated by electrolysis to the atmosphere or replenishing it to the first air inlet of the microalgae photobioreactor via a branch.

4. The apparatus according to claim 1, characterized in that, The protein collection and separation system (500) includes: a microalgae harvesting unit (510), connected to the drain outlet of the microalgae photobioreactor, for harvesting microalgae culture medium and performing solid-liquid separation on microalgae biomass; a bacteria harvesting unit (520), connected to the drain outlet of the hydroxide bacteria reactor, for harvesting bacterial culture medium and performing solid-liquid separation on hydroxide bacteria biomass; a protein extraction unit (530), for receiving the microalgae biomass and the bacterial biomass respectively, for extracting protein from both; and a protein mixing and blending unit (540), for mixing the extracted microalgae protein and bacterial protein at a preset mass ratio to obtain a mixed protein product.

5. The apparatus according to claim 1, characterized in that, The microalgae photobioreactor is a closed photobioreactor, selected from one or more combinations of tubular photobioreactors, flat-plate photobioreactors, or airlift photobioreactors; the reactor is equipped with a temperature control device, a pH monitoring and regulation device, a light system, and a nutrient replenishment device.

6. The apparatus according to claim 1, characterized in that, The hydroxide bacteria reactor is a stirred fermenter, an airlift bioreactor, or a membrane bioreactor; the reactor is equipped with a temperature control device, a pH monitoring and regulation device, a dissolved oxygen sensor, a dissolved hydrogen sensor, and a nutrient supplementation device.

7. The apparatus according to claim 1, characterized in that, Also includes: An air carbon dioxide capture unit, connected to the first air inlet of the microalgae photobioreactor, is used to selectively capture carbon dioxide from the ambient air and replenish it to the microalgae photobioreactor to compensate for carbon loss in the system; and / or an exhaust gas treatment unit, connected to the vent of the gas circulation pipeline system, is used to treat the nitrogen or inert gas enriched in the system to maintain the stability of the system gas composition.

8. A gas-phase circulating protein production method using a two-phase coupling of microalgae and hydroxyl-oxidizing bacteria, characterized in that, Includes the following steps: S1: Microalgae are inoculated in the microalgae photobioreactor and photosynthesize under light conditions. The microalgae absorb carbon dioxide to grow and release oxygen into the gas phase of the reactor. S2: The oxygen-containing gas discharged from the first outlet of the microalgae photobioreactor is transported to the second inlet of the hydroxide bacteria reactor through the oxygen delivery pipeline to provide oxygen electron acceptors for the hydroxide bacteria. S3: Utilize renewable energy waste electricity to drive a water electrolysis hydrogen production system to generate hydrogen, and transport the hydrogen to the hydroxide bacteria reactor as an energy substrate for the hydroxide bacteria; S4: In the hydrogen hydroxide bacteria reactor, hydrogen hydroxide bacteria use hydrogen as an electron donor and oxygen as an electron acceptor for chemoautotrophic growth, fix carbon dioxide through the Calvin cycle to synthesize cellular biomass, and release carbon dioxide into the gas phase of the reactor during respiratory metabolism. S5: The carbon dioxide-containing gas discharged from the second outlet of the hydroxide bacteria reactor is returned to the first inlet of the microalgae photobioreactor through the carbon dioxide return pipeline, providing a carbon source for microalgae photosynthesis. S6: Collect the culture medium from the two reactors respectively, and obtain microalgal biomass and bacterial biomass through solid-liquid separation. After extracting the protein, mix the microalgal protein and bacterial protein at a preset mass ratio to obtain a mixed protein product with complementary amino acid composition.

9. The method according to claim 8, characterized in that, The microalgae mentioned in step S1 are selected from one or more of Chlorella vulgaris, Arthrospira platensis, Scenedesmus obliquus, or Dunaliella salina.

10. The method according to claim 8, characterized in that, The hydroxide bacteria mentioned in step S4 are selected from one or more of the following: Hydrogenophaga pseudoflava, Paracoccus denitrificans, Alcaligenes eutrophus (now classified as Cupriavidus necator), or Hydrogenobacter thermophilus.

Images