System and method for co-metabolizing biogas to produce single cell protein by methanotrophs and microalgae

Abstract

The present invention belongs to the technical field of environmental protection, and specifically relates to a system and method for the co-metabolism of methane-oxidizing bacteria and microalgae to produce microbial protein from biogas, including a methane-oxidizing bacteria culture system, a microalgae culture system, and a first-stage microbial protein cultivation system, a second-stage microbial protein cultivation system, a microbial protein nanofilm filtration system, and a microbial protein vacuum drying system that are sequentially connected. The methane-oxidizing bacteria culture system is connected to the first-stage microbial protein cultivation system through the first methane-oxidizing bacteria liquid discharging system and to the second-stage microbial protein cultivation system through the second methane-oxidizing bacteria liquid discharging system. The microalgae culture system is connected to the first-stage microbial protein cultivation system through the first microalgae culture liquid discharging system and to the second-stage microbial protein cultivation system through the second microalgae culture liquid discharging system. In the present invention, methane and carbon dioxide in the biogas generated by the anaerobic fermentation of food waste are metabolized by methane-oxidizing bacteria and microalgae, thereby producing microbial protein.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental protection, and specifically relates to a system and method for the co-metabolism of methane-oxidizing bacteria and microalgae to produce microbial protein from biogas. Food waste is anaerobically fermented, and the biogas produced is co-metabolized by methane-oxidizing bacteria and microalgae to produce microbial protein, reducing environmental pollution. Background Technique

[0002] Food waste is rich in organic matter, has a high water content, a large amount of oil, a high salinity, and is prone to spoilage. Anaerobic fermentation is an effective way to resourcefully utilize food waste. Through dry fermentation technology, food waste can be converted into new energy biogas. However, during the utilization of biogas, the leakage and combustion of methane have a huge impact on the greenhouse effect of the air. Therefore, under the background of carbon peaking and carbon neutrality, how to reduce the carbon emissions generated by anaerobic fermentation is particularly important.

[0003] Microbial protein, also known as microbial protein or single-cell protein, is microbial protein obtained by culturing cells or filamentous microorganisms individually using a substrate under special environmental conditions. Microbial protein is not a simple protein, but a cytoplasmic mass rich in various nutrients (such as protein, vitamins, fat, carbohydrates, etc.). With the continuous development of China's animal husbandry and aquaculture, there is a serious shortage of feed, and nutritional feed with microbial protein as a protein supplement has gradually attracted the attention of scholars. Adding this microbial protein rich in nutrients to feed can largely make up for the problems of feed shortage and single nutritional components.

[0004] Methanotrophs are Gram-negative bacteria that use methane as a carbon source. It has been several years since using methanotrophs as the strain to produce microbial protein. This method of producing microbial protein has many advantages. First, methane is the main component of greenhouse gases, and methanotrophs can use methane as a carbon source and energy source and convert it into microbial protein with economic benefits. Second, the carbon source required for the growth of methanotrophs is a gaseous carbon source, which is non-toxic and non-allergenic, and has a very low probability of being infected by pathogenic bacteria such as Salmonella. Third, the nutritional components of the microbial protein produced by using methanotrophs are almost the same as those of natural protein, and the content of tryptophan is more abundant (compared with fish meal). Finally, the industrialization of microbial protein completely simulates the fermentation process of microorganisms, and the operation is simple and easy.

[0005] Microalgae refer to those tiny algal populations that can only be distinguished under a microscope. Microalgae generally refer to the general term for microorganisms containing chlorophyll a and capable of photosynthesis, belonging to a type of protist. They can convert inorganic carbon source carbon dioxide into organic carbon source through autotrophic action. Microalgae cells contain high-value nutritional components and chemical raw materials such as proteins, lipids, algal polysaccharides, β-carotene, and various inorganic elements. The protein content of microalgae is very high and is an important source of single-cell protein. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention provides a system and method for the co-metabolism of methane-oxidizing bacteria and microalgae to produce microbial protein from biogas.

[0007] The present invention is realized as follows. A system for the co-metabolism of methane-oxidizing bacteria and microalgae to produce microbial protein from biogas is provided, including a methane-oxidizing bacteria culture system, a microalgae culture system, and a primary microbial protein cultivation system, a secondary microbial protein cultivation system, a microbial protein nanofilm filtration system, and a microbial protein vacuum drying system connected in sequence. A biogas inlet pipe is provided on the primary microbial protein cultivation system. The methane-oxidizing bacteria culture system is connected to the primary microbial protein cultivation system through a first methane-oxidizing bacteria liquid discharge system and to the secondary microbial protein cultivation system through a second methane-oxidizing bacteria liquid discharge system. The microalgae culture system is connected to the primary microbial protein cultivation system through a first microalgae culture liquid discharge system and to the secondary microbial protein cultivation system through a second microalgae culture liquid discharge system.

[0008] Preferably, it further includes a control system, a first on-line gas detector, and a second on-line gas detector. The first on-line gas detector is arranged on the biogas inlet pipe of the primary microbial protein cultivation system. The second on-line gas detector is arranged on the connecting pipeline between the primary microbial protein cultivation system and the secondary microbial protein cultivation system. The control system is respectively connected to the first on-line gas detector, the first methane-oxidizing bacteria liquid discharge system, the second methane-oxidizing bacteria liquid discharge system, the second on-line gas detector, the first microalgae culture liquid discharge system, and the second microalgae culture liquid discharge system.

[0009] Further preferably, it further includes a kitchen waste anaerobic reaction system and a biogas storage system. The gas outlet of the kitchen waste anaerobic reaction system is connected to the biogas storage system, and the biogas storage system is connected to the primary microbial protein cultivation system through the biogas inlet pipe.

[0010] Further preferably, the microbial protein vacuum drying system is connected to the microalgae culture system.

[0011] Further preferably, in the microalgae culture system, the cultivated microalgae are modified high-lipid Chlorella vulgaris.

[0012] Further preferably, the culture medium for the modified high-lipid Chlorella is: 2.86 mg / L of H3BO3, 1.81 mg / L of MnCl2·4H2O, 0.22 mg / L of ZnSO4·7H2O, 0.39 mg / L of Na2MoO4·2H2O, 0.08 mg / L of CuSO4·5H2O, 0.05 mg / L of Co(NO3)2·6H2O, and 0.2 mg / L of the antibiotic CTC.

[0013] Further preferably, the culture conditions for the modified high-lipid Chlorella are: the culture temperature is 28 ± 1 °C, the light intensity is 5000 Lux, the light time is continuous illumination for 24 hours throughout the day, and it is stirred twice a day at regular intervals, with each stirring for 1 minute.

[0014] Further preferably, in the methanotroph culture system, the selected methanotroph culture medium is an inorganic salt liquid medium.

[0015] The present invention also provides a method for the co-metabolism of biogas by methanotrophs and microalgae to produce microbial protein. Based on the above-mentioned system for the co-metabolism of biogas by methanotrophs and microalgae to produce microbial protein, the method includes the following steps:

[0016] Step 1: The anaerobic digestion system for food waste produces biogas through anaerobic dry fermentation, and the biogas is stored in the biogas storage system. Methanotrophs and microalgae are respectively cultivated in the methanotroph culture system and the microalgae culture system according to specific culture media.

[0017] Step 2: According to the gas concentration ratio of methane and carbon dioxide in the biogas storage system, the first methanotroph bacterial liquid discharging system and the first microalgae culture medium discharging system are opened, and the cultivated methanotrophs and microalgae enter the primary microbial protein cultivation system.

[0018] Step 3: The biogas in the biogas storage system enters the primary microbial protein cultivation system, and methanotrophs and microalgae use methane and carbon dioxide in the biogas to reproduce in the primary microbial protein cultivation system, producing microbial protein.

[0019] Step 4: According to the gas concentration ratio of uncompletely metabolized methane and carbon dioxide in the primary microbial protein cultivation system, the second methanotroph bacterial liquid discharging system and the second microalgae culture medium discharging system are opened, and the cultivated methanotrophs and microalgae enter the secondary microbial protein cultivation system.

[0020] Step 5: The unmetabolized methane and carbon dioxide in the primary microbial protein cultivation system and the produced microbial protein enter the secondary microbial protein cultivation system. Methanotrophs and microalgae utilize the unmetabolized methane and carbon dioxide in the secondary microbial protein cultivation system for reproduction, completely metabolize the methane and carbon dioxide, and produce microbial protein.

[0021] Step 6: The microbial protein produced in the primary microbial protein cultivation system and the secondary microbial protein cultivation system is filtered and collected through the microbial protein nanofilm filtration system. The collected microbial protein enters the microbial protein vacuum drying system for drying and then is collected for standby.

[0022] Compared with the prior art, the advantages of the present invention are as follows:

[0023] The present invention provides a system and method for co-metabolizing biogas by methanotrophs and microalgae to produce microbial protein. The microalgae are modified to have a higher lipid content, so that the produced microbial protein has higher nutritional value. Methane and carbon dioxide in the biogas produced by anaerobic fermentation of food waste are metabolized by methanotrophs and microalgae, thereby producing microbial protein, which is applied to animal husbandry and aquaculture, etc., turning waste into treasure and reducing the harm to the environment. Brief Description of the Drawings

[0024] Figure 1 It is a schematic diagram of the system for co-metabolizing biogas by methanotrophs and microalgae to produce microbial protein provided by the present invention;

[0025] Figure 2 It is the influence of different exogenous additives on the lipid content of Chlorella. Detailed Embodiments

[0026] The present invention will be further explained below in combination with specific implementation embodiments, but the present invention is not limited thereto.

[0027] Refer to Figure 1 , the present invention provides a system for co-metabolizing biogas by methanotrophs and microalgae to produce microbial protein, including a methanotroph cultivation system 7, a microalgae cultivation system 10, and a primary microbial protein cultivation system 3, a secondary microbial protein cultivation system 4, a microbial protein nanofilm filtration system 5, and a microbial protein vacuum drying system 6 that are connected in sequence. A biogas inlet pipe is provided on the primary microbial protein cultivation system 3. The methanotroph cultivation system 7 is connected to the primary microbial protein cultivation system 3 through a first methanotroph bacterial liquid discharging system 8 and is connected to the secondary microbial protein cultivation system 4 through a second methanotroph bacterial liquid discharging system 9. The microalgae cultivation system 10 is connected to the primary microbial protein cultivation system 3 through a first microalgae culture solution discharging system 11 and is connected to the secondary microbial protein cultivation system 4 through a second microalgae culture solution discharging system 12.

[0028] In this embodiment, it further includes an anaerobic reaction system 1 for kitchen waste and a biogas storage system 2. The gas outlet of the anaerobic reaction system 1 for kitchen waste is connected to the biogas storage system 2, and the biogas storage system 2 is connected to the first-stage microbial protein cultivation system 3 through the biogas inlet pipe.

[0029] The method for producing microbial protein using the above system for the co-metabolism of biogas by methanotrophic bacteria and microalgae to produce microbial protein includes the following steps:

[0030] Step 1: The anaerobic reaction system 1 for kitchen waste produces biogas through anaerobic dry fermentation, and the biogas is stored in the biogas storage system 2. Methanotrophic bacteria and microalgae are respectively cultivated in the methanotrophic bacteria cultivation system 7 and the microalgae cultivation system 10 according to specific culture media.

[0031] Step 2: According to the gas concentration ratio of methane and carbon dioxide in the biogas storage system 2, the first methanotrophic bacteria liquid discharging system 8 and the first microalgae culture medium discharging system 11 are opened, and the cultivated methanotrophic bacteria and microalgae enter the first-stage microbial protein cultivation system 3.

[0032] Step 3: The biogas in the biogas storage system 2 enters the first-stage microbial protein cultivation system 3. Methanotrophic bacteria and microalgae reproduce in the first-stage microbial protein cultivation system 3 using methane and carbon dioxide in the biogas to produce microbial protein.

[0033] Step 4: According to the gas concentration ratio of uncompletely metabolized methane and carbon dioxide in the first-stage microbial protein cultivation system 3, the second methanotrophic bacteria liquid discharging system 9 and the second microalgae culture medium discharging system 12 are opened, and the cultivated methanotrophic bacteria and microalgae enter the second-stage microbial protein cultivation system 4.

[0034] Step 5: The uncompletely metabolized methane and carbon dioxide and the produced microbial protein in the first-stage microbial protein cultivation system 3 enter the second-stage microbial protein cultivation system 4. Methanotrophic bacteria and microalgae reproduce in the second-stage microbial protein cultivation system 4 using the uncompletely metabolized methane and carbon dioxide to completely metabolize methane and carbon dioxide and produce microbial protein.

[0035] Step 6: The microbial protein produced in the first-stage microbial protein cultivation system 3 and the second-stage microbial protein cultivation system 4 is filtered and collected through the microbial protein nano-filtration system 5, and the collected microbial protein enters the microbial protein vacuum drying system 6 for drying and then is collected for standby.

[0036] The microbial protein nano-filtration system 5 is a super-nano microfiltration device with about 1000 meshes.

[0037] For realizing automatic control, as an improvement of the technical solution, it further includes a control system 15, a first on-line gas detector 13 and a second on-line gas detector 14. The first on-line gas detector 13 is arranged on the biogas inlet pipe of the primary single-cell protein cultivation system 3, and the second on-line gas detector 14 is arranged on the connecting pipeline between the primary single-cell protein cultivation system 3 and the secondary single-cell protein cultivation system 4. The control system 15 is respectively connected with the first on-line gas detector 13, the first methane-oxidizing bacteria liquid discharging system 8, the second methane-oxidizing bacteria liquid discharging system 9, the second on-line gas detector 14, the first microalgae culture solution discharging system 11 and the second microalgae culture solution discharging system 12.

[0038] In this embodiment, the control system 15 is further connected with the kitchen waste anaerobic reaction system 1. During the anaerobic reaction of kitchen waste, the control system 15 first detects the biogas content generated in the kitchen waste anaerobic reaction system 1. After reaching a certain level, the biogas is then allowed to enter the biogas storage system 2. The first on-line gas detector 13 detects the concentration ratio of methane and biogas in the biogas storage system 2 and feeds it back to the control system 15. The control system 15 controls to open the first methane-oxidizing bacteria liquid discharging system 8 and the first microalgae culture solution discharging system 11. The second on-line gas detector 14 detects the concentration ratio of residual methane and carbon dioxide in the primary single-cell protein cultivation system 3 and feeds it back to the control system 15. The control system 15 controls to open the second methane-oxidizing bacteria liquid discharging system 9 and the second microalgae culture solution discharging system 12.

[0039] In order to recycle the wastewater, waste gas, etc. generated in the single-cell protein vacuum drying system 6, as an improvement, the single-cell protein vacuum drying system 6 is connected with the microalgae culture system 10.

[0040] In the microalgae culture system 10, the cultivated microalgae is modified high-lipid Chlorella vulgaris. The single-cell protein finally produced by high-lipid Chlorella vulgaris has high nutritional value and can provide more nutrition for animals as feed for livestock and poultry breeding.

[0041] Preferably, the culture solution of the modified high-lipid Chlorella vulgaris is: 2.86 mg / L of H3BO3, 1.81 mg / L of MnCl2·4H2O, 0.22 mg / L of ZnSO4·7H2O, 0.39 mg / L of Na2MoO4·2H2O, 0.08 mg / L of CuSO4·5H2O, 0.05 mg / L of Co(NO3)2·6H2O and 0.2 mg / L of the antibiotic CTC. It is necessary to wait until the first on-line gas detector 13 detects that the ratio of methane and carbon dioxide is 5.5:4.5, and then add the antibiotic CTC to the microalgae culture system 10.

[0042] ReferenceFigure 2 , which shows the effects of different exogenous additives on the lipid content of Chlorella. It can be seen that the addition of the antibiotic CTC increased the lipid content in Chlorella. This is because the stress caused by exogenous stimuli induced a stress response in Chlorella, thereby changing the metabolic pathway of lipid production and promoting the accumulation of lipids in cells. After treatment with 0.2 mg / L CTC, the lipid content of Chlorella reached as high as 16.3%, which was 1.5 times that of the control group.

[0043] Preferably, the culture conditions for the modified high-lipid Chlorella are as follows: the culture temperature is 28 ± 1 °C, the light intensity is 5000 Lux, the light time is continuous illumination for 24 hours throughout the day, and it is stirred twice a day at regular intervals, with each stirring for 1 minute.

[0044] Through the above culture, the shortest lag phase of the cells was 14.3 h, and the lipid content of Chlorella reached as high as 16.3%, an increase of 50%.

[0045] Preferably, in the methane oxidizing bacteria culture system 7, the selected methane oxidizing bacteria culture medium is an inorganic salt liquid medium.

[0046] The inorganic salt liquid medium is composed of solution A and solution B. Among them, 1 L of solution A contains 3.0 g of NaCl, 7.4 g of Na2HPO4·12H2O, 5.0 g of NH4Cl, 0.04 g of FeSO4·7H2O, 3.0 g of MgSO4·7H2O, 2.62 g of KH2PO4, 10.0 g of KNO3, 0.0167 g of FeCl3·6H2O, 0.2 g of CaCl2·2H2O, 5.24 g of K2HPO4·3H2O, and 0.0125 g of CuSO4·5H2O. 1 L of solution B contains 0.3 g of MnSO4·H2O, 0.24 g of NaMoO4·H2O, and 0.34 g of ZnSO4·7H2O. Before use, take 100 mL of solution A and 1 mL of solution B, and make up the volume to 1 L with deionized water.

Claims

1. A system for the co-metabolism of biogas by methanotrophs and microalgae to produce single cell protein, characterized in that, It includes a methane-oxidizing bacteria culture system (7), a microalgae culture system (10), and a primary single-cell protein cultivation system (3), a secondary single-cell protein cultivation system (14), a single-cell protein nanofilm filtration system (5), and a single-cell protein vacuum drying system (6) connected in sequence. A biogas inlet pipe is provided on the primary single-cell protein cultivation system (3). The methane-oxidizing bacteria culture system (7) is connected to the primary single-cell protein cultivation system (3) through a first methane-oxidizing bacteria liquid discharging system (8), and is connected to the secondary single-cell protein cultivation system (14) through a second methane-oxidizing bacteria liquid discharging system (9). The microalgae culture system (10) is connected to the primary single-cell protein cultivation system (3) through a first microalgae culture solution discharging system (11), and is connected to the secondary single-cell protein cultivation system (14) through a second microalgae culture solution discharging system (12); It also includes a control system (15), a first on-line gas detector (13), and a second on-line gas detector (4). The first on-line gas detector (13) is arranged on the biogas inlet pipe of the primary single-cell protein cultivation system (3). The second on-line gas detector (4) is arranged on the connecting pipeline between the primary single-cell protein cultivation system (3) and the secondary single-cell protein cultivation system (14). The control system (15) is respectively connected to the first on-line gas detector (13), the first methane-oxidizing bacteria liquid discharging system (8), the second methane-oxidizing bacteria liquid discharging system (9), the second on-line gas detector (4), the first microalgae culture solution discharging system (11), and the second microalgae culture solution discharging system (12); In the microalgae culture system (10), the cultivated microalgae is modified high-lipid Chlorella vulgaris; The culture solution of the modified high-lipid Chlorella vulgaris is: 2.86 mg / L of H3BO3, 1.81 mg / L of MnCl2·4H2O, 0.22 mg / L of ZnSO4·7H2O, 0.39 mg / L of Na2MoO4·2H2O, 0.08 mg / L of CuSO4·5H2O, 0.05 mg / L of Co(NO3)2·6H2O, and 0.2 mg / L of the antibiotic CTC.

2. The system for co-metabolizing biogas by methanotrophs and microalgae to produce single cell protein according to claim 1, wherein It also includes a food waste anaerobic reaction system (1) and a biogas storage system (2). The gas outlet of the food waste anaerobic reaction system (1) is connected to the biogas storage system (2), and the biogas storage system (2) is connected to the primary single-cell protein cultivation system (3) through the biogas inlet pipe.

3. The system for co-metabolizing biogas by methanotrophs and microalgae to produce single cell protein according to claim 1, wherein The single-cell protein vacuum drying system (6) is connected to the microalgae culture system (10).

4. The system for co-metabolizing biogas by methanotrophs and microalgae to produce single cell protein according to claim 1, wherein The culture conditions of the modified high-lipid Chlorella vulgaris are: the culture temperature is 28 ± 1 °C, the light intensity is 5000 Lux, the light time is continuous illumination for 24 hours throughout the day, and it is stirred regularly twice a day, with each stirring for 1 minute.

5. The system for co-metabolizing biogas to produce single cell protein by methanotrophs and microalgae according to claim 1, characterized in that, In the methane-oxidizing bacteria culture system (7), the selected methane-oxidizing bacteria culture solution is an inorganic salt liquid medium.

6. A method for co-metabolizing biogas to produce microbial protein by methanotrophs and microalgae, characterized in that, Based on the system for co-metabolizing biogas to produce single-cell protein by methane-oxidizing bacteria and microalgae according to claim 2, the method includes the following steps: Step 1: The anaerobic reaction system (1) of food waste produces biogas through anaerobic dry fermentation, and the biogas is stored in the biogas storage system (2). Methane-oxidizing bacteria and microalgae are respectively cultivated in the methane-oxidizing bacteria culture system (7) and the microalgae culture system (10) according to specific culture media. Step 2: According to the gas concentration ratio of methane and carbon dioxide in the biogas storage system (2), the first methane-oxidizing bacteria liquid discharging system (8) and the first microalgae culture medium discharging system (11) are opened, and the cultivated methane-oxidizing bacteria and microalgae enter the primary single-cell protein cultivation system (3). Step 3: The biogas in the biogas storage system (2) enters the primary single-cell protein cultivation system (3). Methane-oxidizing bacteria and microalgae use methane and carbon dioxide in the biogas to reproduce in the primary single-cell protein cultivation system (3), producing single-cell protein. Step 4: According to the gas concentration ratio of the uncompletely metabolized methane and carbon dioxide in the primary single-cell protein cultivation system (3), the second methane-oxidizing bacteria liquid discharging system (9) and the second microalgae culture medium discharging system (12) are opened, and the cultivated methane-oxidizing bacteria and microalgae enter the secondary single-cell protein cultivation system (14). Step 5: The uncompletely metabolized methane and carbon dioxide and the produced single-cell protein in the primary single-cell protein cultivation system (3) enter the secondary single-cell protein cultivation system (14). Methane-oxidizing bacteria and microalgae use the uncompletely metabolized methane and carbon dioxide to reproduce in the secondary single-cell protein cultivation system (14), completely metabolize methane and carbon dioxide, and produce single-cell protein. Step 6: The single-cell protein produced in the primary single-cell protein cultivation system (3) and the secondary single-cell protein cultivation system (14) is filtered and collected through the single-cell protein nanofilm filtration system (5). The collected single-cell protein enters the single-cell protein vacuum drying system (6) for drying and then is collected for standby.

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