Preparation method and application of polyvinyl alcohol-based shape memory film

Abstract

The invention discloses a preparation method and application of a polyvinyl alcohol-based shape memory film, and relates to the field of single-cell protein production, in particular to a preparation method of a polyvinyl alcohol-based shape memory film and application of the polyvinyl alcohol-based shape memory film. The method aims at solving the problem that the existing method for producing single-cell protein by fixing CO2 through bacteria is low in single-cell protein production efficiency. The method comprises the following steps: 1, preparing a PVA solution; spinning the PVA solution on a glass substrate; after spin-coating is finished, curing, and stripping from the glass substrate to obtain a polyvinyl alcohol film; 2, etching a micro-nano-scale cylindrical array on the surface of the silicon wafer to serve as an impressing and re-etching template; the polyvinyl alcohol film is placed on a template, hot pressing and demolding are conducted, and the polyvinyl alcohol-based shape memory film is obtained. The method provided by the invention can improve the single-cell protein production efficiency. The polyvinyl alcohol-based shape memory membrane is used for fixing carbon dioxide produced single cell protein.

Description

Technical Field

[0001] The present invention relates to the field of single cell protein production, and particularly relates to a preparation method of a polyvinyl alcohol-based shape memory membrane and the use of the membrane. Background Art

[0002] Since the mid-18th century, due to the influence of human activities, the concentration of CO2 in the atmosphere has been increasing. In order to reduce global CO2 emissions to 80% of the 1990 level by 2050, it is necessary to achieve the fixation and storage of 4200 tons of CO2 per year. To address this challenge, carbon capture and storage and carbon capture and utilization technologies are needed. CO2 capture technologies include chemical absorption, physical absorption, physicochemical absorption, and biological fixation, etc. The cost required for capturing CO2 using physical and chemical technologies is relatively high, and the difficulties in long-term storage technologies limit their use. The biological fixation and storage of CO2 technology with low cost, sustainability, and the ability to produce single cell protein simultaneously has obvious advantages.

[0003] Single cell protein (microbial protein) is a protein produced by microorganisms, including bacterial protein, fungal protein, etc. Bacterial single cell protein is also a source of B vitamins and some important lipids. The single cell protein produced by bacteria has the advantages of wide source, short production cycle, high yield, and small floor area required for large-scale production. For strains that can fix CO2 to produce single cell protein, establishing technical methods to improve their CO2 fixation amount and strengthen their production of single cell protein has broad application prospects. However, the existing methods have low efficiency in producing single cell protein and cannot meet the production requirements of single cell protein. Summary of the Invention

[0004] The present invention aims to solve the problem of low efficiency in producing single cell protein by the existing method of using bacteria to fix CO2, and provides a preparation method of a polyvinyl alcohol-based shape memory membrane and its application.

[0005] The preparation method of the polyvinyl alcohol-based shape memory membrane of the present invention includes the following steps:

[0006] First, dissolve polyvinyl alcohol (PVA) particles in pure water, gradually raise the temperature from room temperature to 95 - 100 °C, stir at a constant speed, the stirring rate is 300 r / min, the stirring time is 3 - 5 h, adjust the pH value of the solution to 3.5, add glutaraldehyde under acidic conditions, stir for 2 - 3 h, and remove bubbles in a vacuum drying oven to obtain a PVA solution;

[0007] Clean the glass substrate, place the cleaned glass substrate on the tray of a spin coater, drop the PVA solution onto the glass substrate, and perform spin coating;

[0008] After spin coating is completed, take out the glass substrate and let it stand at room temperature for 48 - 72 h, then cure it in an oven at 60 - 70 °C for 24 - 48 h, then adjust the oven temperature to 50 - 60 °C and cure for 3 - 5 h, and then peel it off from the glass substrate to obtain a smooth-surface polyvinyl alcohol film;

[0009] II. Etch a micro-nano scale cylindrical array on the surface of the silicon wafer as an imprint replication template; place the polyvinyl alcohol film prepared in step I on the template, perform hot embossing using the hot embossing method, and demold to obtain a polyvinyl alcohol-based shape memory film with a micro-nano structure pattern.

[0010] Furthermore, the dimensions of the micro-nano scale cylindrical array in step II are: diameter 500 nm - 1000 nm, height 100 - 200 nm, and pitch 100 - 300 nm.

[0011] Furthermore, the conditions of the hot embossing method in step II are: pressure 50 - 70 bar, temperature 90 - 100 °C, and hot embossing time 1 - 3 min.

[0012] Furthermore, the micro-nano structure on the surface of the polyvinyl alcohol-based shape memory film can be erased and redesigned by heating the surface of the ITO glass.

[0013] The specific method is to cut the prepared polyvinyl alcohol-based shape memory film sample into a 5×3 cm rectangle, fix both ends of the film on the same-sized transparent ITO conductive glass (resistance 55 Ω) with conductive aluminum electrodes, and apply a 15 V voltage to heat the film for 20 s to raise the film temperature to 70 °C.

[0014] The present invention also provides the application of the polyvinyl alcohol-based shape memory film in fixing single-cell protein produced from carbon dioxide.

[0015] Furthermore, the method for the polyvinyl alcohol-based shape memory film to fix single-cell protein produced from carbon dioxide includes the following steps:

[0016] I. Inoculate Pseudomonas proteolytica Y24 - 6 into a solid enrichment medium and activate it at 25 °C for 24 - 72 h;

[0017] II. Collect the activated Pseudomonas proteolytica Y24 - 6 from the solid enrichment medium in step I and prepare it into a seed solution with sterile deionized water;

[0018] III. Add a culture solution for producing single-cell protein to the device and inoculate the seed solution at 1‰ - 3‰ of the volume of the main reactor of the device;

[0019] IV. Introduce a mixed gas into the device. The mixed gas is composed of CO2 and air in a volume ratio of 1:1, and maintain the pH value in the photocatalytic device at 7.0 ± 0.2;

[0020] V. Repeat steps III to IV to keep the photocatalytic device running stably until a biofilm is formed on the flat membrane module in the device. The thickness of the biofilm is 0.1 - 0.2 mm; the device is for removing high-concentration nitrate in low-temperature groundwater, and the flat membrane module in the device is a polyvinyl alcohol-based shape memory membrane.

[0021] Furthermore, the Pseudomonas proteinensis Y24-6 is preserved in the General Microbiological Center of the China Committee for Culture Collection of Microorganisms. The preservation address is No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing. The preservation date is December 16, 2020, and the preservation number is CGMCC No. 21380.

[0022] Furthermore, the formula of the solid enrichment medium in step I is: nitrogen source 0.3 - 0.5 g / L, carbon source 0.1 - 0.2 g / L, iron salt 0.05 g / L, NaCl 0.1 - 0.5 g / L, MgSO4·7H2O 0.05 - 0.1 g / L, MnSO4 0.01 - 0.1 g / L, CaCl2 0.1 g / L, Na2HPO4 0.1 - 0.2 g / L, agar 1.8 g / L, pH value 7.0, where the carbon source is Na2CO3 or NaHCO3, the nitrogen source is NaNO3 or KNO3, and the iron salt is (NH4)2Fe(SO4)2·6H2O or FeSO4.

[0023] Furthermore, the concentration of the seed liquid in step II is not less than 10 8 cells / mL.

[0024] Furthermore, the formula of the culture solution in step III is: nitrogen source 0.3 - 0.5 g / L, carbon source 0.1 - 0.2 g / L, iron salt 0.05 g / L, NaCl 0.1 - 0.5 g / L, MgSO4·7H2O 0.05 - 0.1 g / L, MnSO4 0.01 - 0.1 g / L, CaCl2 0.1 g / L, Na2HPO4 0.1 - 0.2 g / L, pH value 7.0, where the carbon source is Na2CO3 or NaHCO3, the nitrogen source is NaNO3 or KNO3, and the iron salt is (NH4)2Fe(SO4)2·6H2O or FeSO4.

[0025] Furthermore, in step IV, Na2CO3 / NaHCO3 is used to adjust the pH value of the solution.

[0026] Advantages of the present invention:

[0027] In the device of the present invention, Pseudomonas proteolytica Y24-6 is inoculated. During the operation of the device, a biofilm containing Pseudomonas proteolytica Y24-6 is formed on its membrane module. Pseudomonas proteolytica Y24-6 can live a facultative autotrophic life and can utilize Fe 2+ as an electron donor to assimilate NO3 - -N to produce single-cell protein.

[0028] The ultraviolet lamp in the device can promote the advanced oxidation reaction of the polyvinyl alcohol-based shape memory membrane, generating free radicals such as O· and HO·. These free radicals stimulate the membrane fluidity of Pseudomonas proteolytica Y24-6 and promote the transport of NO3 - -N from outside the cell membrane into the cell membrane, accelerating the formation of single-cell protein inside the cell, improving the efficiency of single-cell protein production, and the protein yield can reach 0.42 g protein / g cell dry weight.

[0029] The polyvinyl alcohol-based shape memory membrane can effectively intercept bacteria and prevent the overflow and loss of single-cell protein-producing bacteria. The single-cell protein can be recovered through backwashing, which is convenient and fast. Through erasing and re-designing, the efficient recovery and recycling of the polyvinyl alcohol-based shape memory membrane can be achieved, which is beneficial to cost savings. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is the microscopic surface structure of the polyvinyl alcohol-based shape memory membrane;

[0031] Figure 2 is the physical form of the polyvinyl alcohol-based shape memory membrane;

[0032] Figure 3 is the structural schematic diagram of the device for removing high-concentration nitrate in low-temperature groundwater;

[0033] Figure 4 is the top view of the photocatalytic device in the main reactor of the device for removing high-concentration nitrate in low-temperature groundwater. DETAILED DESCRIPTION OF THE INVENTION

[0034] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination among the specific embodiments.

[0035] Specific Embodiment 1: The preparation method of the polyvinyl alcohol-based shape memory membrane in this embodiment includes the following steps:

[0036] 1. Dissolve polyvinyl alcohol (PVA) particles in pure water. Gradually increase the temperature from room temperature to 95 - 100 °C, stir at a constant speed, with a stirring rate of 300 r / min and a stirring time of 3 - 5 h. Adjust the pH value of the solution to 3.5, add glutaraldehyde under acidic conditions, stir for 2 - 3 h, and defoam in a vacuum drying oven to obtain a PVA solution;

[0037] Clean the glass substrate, place the cleaned glass substrate on the tray of a spin coater, drop the PVA solution onto the glass substrate, and perform spin coating;

[0038] After spin coating is completed, take out the glass substrate and place it at room temperature for 48 - 72 h, then cure it in an oven at 60 - 70 °C for 24 - 48 h, then adjust the oven temperature to 50 - 60 °C and cure for 3 - 5 h, and then peel it off from the glass substrate to obtain a smooth - surfaced polyvinyl alcohol film;

[0039] 2. Etch a micro - and nano - scale cylindrical array on the surface of a silicon wafer as an imprint replication template; place the polyvinyl alcohol film prepared in step 1 on the template, and perform hot embossing using the hot embossing method, and then demold to obtain a polyvinyl alcohol - based shape - memory film with a micro - and nano - structure pattern.

[0040] Specific Embodiment 2: The difference between this embodiment and Specific Embodiment 1 is that: the size of the micro - and nano - scale cylindrical array described in step 2 is: diameter 500 nm - 1000 nm, height 100 - 200 nm, and spacing 100 - 300 nm. Others are the same as Specific Embodiment 1.

[0041] Specific Embodiment 3: The difference between this embodiment and Specific Embodiment 1 or 2 is that: the conditions of the hot embossing method described in step 2 are: pressure 50 - 70 bar, temperature 90 - 100 °C, and hot embossing time 1 - 3 min. Others are the same as Specific Embodiment 1 or 2.

[0042] Specific Embodiment 4: The difference between this embodiment and Specific Embodiment 1 or 2 is that: the micro - and nano - structure on the surface of the polyvinyl alcohol - based shape - memory film can be erased and redesigned by heating the surface of ITO glass. Others are the same as Specific Embodiment 1 or 2.

[0043] The specific method is to cut the prepared polyvinyl alcohol - based shape - memory film sample into a 5×3 cm rectangle, fix both ends of the film on the same - sized transparent ITO conductive glass (resistance is 55 Ω) with conductive aluminum electrodes, and apply a voltage of 15 V to heat the film for 20 s to raise the film temperature to 70 °C

[0044] Specific Embodiment 5: The application of the polyvinyl alcohol - based shape - memory film in fixing carbon dioxide - producing single - cell protein.

[0045] Specific Embodiment Six: The method for fixing carbon dioxide to produce single-cell protein with a polyvinyl alcohol-based shape memory membrane described in this embodiment includes the following steps:

[0046] 1. Inoculate Pseudomonas proteinensis Y24-6 into a solid enrichment medium and activate it at 25°C for 24 to 72 hours.

[0047] 2. Collect the activated Pseudomonas proteinensis Y24-6 from the solid enrichment medium in Step 1 and prepare it into a seed solution with sterile deionized water.

[0048] 3. Add a culture solution for producing single-cell protein to the device and inoculate the seed solution at 1‰ to 3‰ of the volume of the main reactor of the device.

[0049] 4. Pass a mixed gas into the device. The mixed gas is composed of CO2 and air in a volume ratio of 1:1, and maintain the pH value in the photocatalytic device at 7.0 ± 0.2.

[0050] 5. Repeat Steps 3 to 4 to keep the photocatalytic device running stably until a biofilm is formed on the flat membrane module. The thickness of the biofilm is 0.1 to 0.2 mm. The device is a device for removing high-concentration nitrate in low-temperature groundwater, and the flat membrane module in the device is a polyvinyl alcohol-based shape memory membrane. Others are the same as in Specific Embodiment Five.

[0051] Specific Embodiment Seven: The difference between this embodiment and Specific Embodiment Six is that the Pseudomonas proteinensis Y24-6 is preserved in the China General Microbiological Culture Collection Center, with the preservation address being No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing, the preservation date being December 16, 2020, and the preservation number being CGMCC No. 21380. Others are the same as in Specific Embodiment Six.

[0052] Specific Embodiment Eight: The difference between this embodiment and Specific Embodiment Six is that the formula of the solid enrichment medium in Step 1 is as follows: nitrogen source 0.3 to 0.5 g / L, carbon source 0.1 to 0.2 g / L, iron salt 0.05 g / L, NaCl 0.1 to 0.5 g / L, MgSO4·7H2O 0.05 to 0.1 g / L, MnSO4 0.01 to 0.1 g / L, CaCl2 0.1 g / L, Na2HPO4 0.1 to 0.2 g / L, agar 1.8 g / L, pH value 7.0, where the carbon source is Na2CO3 or NaHCO3, the nitrogen source is NaNO3 or KNO3, and the iron salt is (NH4)2Fe(SO4)2·6H2O or FeSO4. Others are the same as in Specific Embodiment Six.

[0053] Specific Embodiment Nine: The difference between this embodiment and Specific Embodiment Six is that in Step 2, the concentration of the seed solution is not less than 10 8 cells / mL. Others are the same as Specific Embodiment Six.

[0054] Specific Embodiment Ten: The difference between this embodiment and Specific Embodiment Six is that in Step 3, the formula of the culture solution is as follows: nitrogen source 0.3 - 0.5 g / L, carbon source 0.1 - 0.2 g / L, iron salt 0.05 g / L, NaCl 0.1 - 0.5 g / L, MgSO4·7H2O 0.05 - 0.1 g / L, MnSO4 0.01 - 0.1 g / L, CaCl2 0.1 g / L, Na2HPO4 0.1 - 0.2 g / L, pH value 7.0, where the carbon source is Na2CO3 or NaHCO3, the nitrogen source is NaNO3 or KNO3, and the iron salt is (NH4)2Fe(SO4)2·6H2O or FeSO4. Others are the same as Specific Embodiment Six.

[0055] Specific Embodiment Eleven: The difference between this embodiment and Specific Embodiment Six is that in Step 4, Na2CO3 / NaHCO3 is used to adjust the pH value of the solution. Others are the same as Specific Embodiment Six.

[0056] The following will describe the embodiments of the present invention in detail. The following embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation schemes and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0057] Example 1: A method for preparing a polyvinyl alcohol-based shape memory film, comprising the following steps:

[0058] I. Dissolve 10 g of polyvinyl alcohol (PVA) particles in 100 mL of pure water, gradually increase the temperature from room temperature to 100 °C, stir at a constant speed, the stirring rate is 300 r / min, and the stirring time is 3 h until it is fully dissolved to a clear and transparent solution. Adjust the pH value of the solution to 3.5 with acetic acid, add 5 mL of glutaraldehyde under acidic conditions, stir for 3 h, and remove bubbles in a vacuum drying oven to obtain a PVA solution;

[0059] Clean the glass substrate. The specific method is as follows: soak the glass substrate in anhydrous ethanol and acetone for 30 min in sequence, then ultrasonically wash it with deionized water for 20 min, and dry it for standby;

[0060] Place the cleaned glass substrate on the tray of the spin coater, turn on the vacuum pump and the control switch of the spin coater to stably adsorb the substrate on the tray, drop 1 mL of the PVA solution onto the glass substrate, set the spin coating speed: low speed 500 rpm, 9 s; high speed 2000 rpm, 20 s, and then start the spin coater to start spin coating;

[0061] After spin coating is completed, take out the glass slide and place it at room temperature for 55 h, then cure it in an oven at 70 °C for 48 h, then adjust the oven temperature to 60 °C and cure for 5 h, and then peel off the glass substrate to obtain a smooth-surface polyvinyl alcohol film;

[0062] Second, use photolithography to etch micro-nano scale cylindrical arrays with different diameters, different heights, and different spacings on the surface of the silicon wafer as an imprint replication template; place the smooth-surface polyvinyl alcohol film prepared in the first step on the template, and use hot embossing at a pressure of 70 bar and hot press at 100 °C for 3 min, and demold to obtain a polyvinyl alcohol-based shape memory film with a micro-nano structure pattern; the diameter range is 500 nm to 1000 nm, the height range is 100 to 200 nm, and the spacing range is 100 to 300 nm;

[0063] The micro-nano structure on the surface of the polyvinyl alcohol-based shape memory film can be erased and redesigned by rapidly heating the ITO glass surface, thereby realizing the efficient recycling and reuse of the film. The specific method is to cut the prepared polyvinyl alcohol-based shape memory film sample into a 5×3 cm rectangle, fix both ends of the film on the same-size transparent ITO conductive glass (resistance is 55 Ω) with conductive aluminum electrodes, and apply a 15 V voltage to heat the film for 20 s to raise the film temperature to 70 °C.

[0064] Example 2: A method for fixing carbon dioxide to produce single-cell protein using the polyvinyl alcohol-based shape memory film prepared in Example 1, comprising the following steps:

[0065] The device used in this method is the device for removing high-concentration nitrate in low-temperature groundwater in the patent with the publication number CN209411899U. The structural schematic diagram of this device is as Figure 3 shown.

[0066] The device for removing high-concentration nitrate in low-temperature groundwater includes a water inlet tank 1, a microorganism inoculation pool 31, a water inlet pump 2, a main reactor 7, an air pump 5, a backwashing device 8, a lift pump 9, a peristaltic pump 20, a secondary sedimentation tank 16, and a water outlet tank 17,

[0067] A reactor water inlet 3 is provided at the lower part of one side wall of the main reactor 7, a reactor water outlet 15 is provided at the lower part of the other side wall of the main reactor 7, an air diffuser pipe 14 is provided at the bottom inside the main reactor 7, the air pump 5 is connected to the air diffuser pipe 14 through a pipe passing through the bottom of the main reactor 7, and the connection between the air pump 5 and the main reactor 7 is sealed;

[0068] A photocatalytic device 6 is provided in the middle of the main reactor 7. The photocatalytic device 6 includes a left support frame 62, a right support frame 63, a flat membrane module 61, a photocatalyst-coated glass 10, and an ultraviolet lamp group 21. A flat membrane module 61, a photocatalyst-coated glass 10, and an ultraviolet lamp group 21 are vertically arranged between the left support frame 62 and the right support frame 63. Among them, the flat membrane module 61 is perpendicular to the left support frame 62 and the right support frame 63. Two pieces of photocatalyst-coated glass 10 are respectively arranged on both sides of the flat membrane module 61 and are parallel to the flat membrane module 61. Two ultraviolet lamp groups 21 are respectively arranged outside the two pieces of photocatalyst-coated glass 10 and are parallel to the photocatalyst-coated glass 10;

[0069] The flat membrane module 61 in the photocatalytic device 6 is connected to the water outlet of the backwashing device 8 through a backwashing pipe 12, and a lift pump 9 is arranged on the backwashing pipe 12;

[0070] The water inlet tank 1 is connected to the reactor water inlet 3 of the main reactor 7 through a water inlet pump 2. The microbial inoculation pool 31 is connected to the pipeline between the water inlet tank 1 and the water inlet pump 2. The reactor water outlet 15 of the main reactor 7 is connected to the water inlet of the secondary sedimentation tank 16 through a peristaltic pump 20, and the water outlet of the secondary sedimentation tank 16 is connected to the water outlet tank 17 through a pipeline;

[0071] A water inlet valve 4 is arranged at the outlet of the water inlet tank 1, and an inoculation pool valve 11 is arranged at the outlet of the microbial inoculation pool 31.

[0072] Further, the photocatalyst-coated glass 10 is prepared by a coating method of plating a photocatalyst on the glass surface to form a photocatalyst-coated glass. For the specific coating method, refer to "Preparation and Sterilization Performance Research of Glass-based Nano-composite TiO2 Photocatalytic Film" (Wang Xun. Wuhan University of Technology, 2008.). The catalyst is TiO2, ZnO, CdS, WO3, SnO2 or BiVO4.

[0073] Further, the coating of the photocatalyst-coated glass 10 is only arranged on the side close to the ultraviolet lamp group 21, aiming to enhance the photocatalytic reaction effect; the photocatalyst coating is not arranged on the side of the photocatalyst-coated glass 10 close to the flat membrane module 61, aiming to prevent the photocatalytic oxidation from affecting the microorganisms on the membrane.

[0074] Further, valves are arranged on the pipeline between the air pump 5 and the aeration pipe 14, on the pipeline between the reactor water outlet 15 and the peristaltic pump 20, on the pipeline between the backwashing device 8 and the lift pump 9, and on the pipeline between the secondary sedimentation tank 16 and the water outlet tank 17. The arrangement of the valves facilitates the opening and closing control of each part of the device.

[0075] Further, a first flowmeter 30 is provided at the water inlet 3 of the reactor, and a second flowmeter 32 is provided on the backwash pipe 12. The setting of the flowmeter facilitates the monitoring of the influent and effluent flow rates in the device.

[0076] I. Inoculate Pseudomonas proteinensis Y24-6 into a solid enrichment medium and activate it at 25 °C for 48 h;

[0077] The Pseudomonas proteinensis Y24-6 is preserved in the China General Microbiological Culture Collection Center, with the preservation address being No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing. The preservation date is December 16, 2020, and the preservation number is CGMCC No. 21380.

[0078] The formula of the solid enrichment medium is as follows: nitrogen source 0.3 g / L, carbon source 0.1 g / L, iron salt 0.05 g / L, NaCl 0.3 g / L, MgSO4·7H2O 0.05 g / L, MnSO4 0.05 g / L, CaCl2 0.1 g / L, Na2HPO4 0.1 g / L, agar 1.8 g / L, pH value 7.0. Among them, the carbon source is Na2CO3, the nitrogen source is NaNO3, and the iron salt is (NH4)2Fe(SO4)2·6H2O.

[0079] II. Collect the activated Pseudomonas proteinensis Y24-6 from the solid enrichment medium in Step I and prepare it into a seed solution with a concentration of 10 8 cells / mL.

[0080] III. Add the culture solution for producing single-cell protein to the microbial inoculation pool 31 of the device. Inoculate the seed solution into the microbial inoculation pool 31 at 3‰ of the volume of the main reactor 7. Close the influent valve 4, open the inoculation pool valve 11 and the feed pump 2, and the culture solution for producing single-cell protein enters the main reactor 7 through the microbial inoculation pool 31.

[0081] The formula of the culture solution in Step III is as follows: nitrogen source 0.3 g / L, carbon source 0.1 g / L, iron salt 0.05 g / L, NaCl 0.3 g / L, MgSO4·7H2O 0.05 g / L, MnSO4 0.05 g / L, CaCl2 0.1 g / L, Na2HPO4 0.1 g / L, pH value 7.0. Among them, the carbon source is Na2CO3, the nitrogen source is NaNO3, and the iron salt is (NH4)2Fe(SO4)2·6H2O.

[0082] IV. Turn on the air pump 5 and the aeration pipe 14, and introduce the mixed gas into the device. The mixed gas is composed of CO2 and air in a volume ratio of 1:1. Keep the pH value in the single-cell protein production device at 7.0 (adjust the pH value of the solution with Na2CO3 / NaHCO3 buffer solution); stop aeration after 12 hours of aeration, let it stand and precipitate for 4 hours, and then discharge the clarified water through the secondary sedimentation tank 16.

[0083] V. Repeat steps III to IV to keep the device running stably until a biofilm is formed on the flat membrane module 61, and the thickness of the biofilm is 0.1 mm.

[0084] VI. Then close the inoculation tank valve 11, turn on the influent valve 4 and the influent pump 2. The groundwater in the influent tank 1 enters the main reactor 7 through the reactor inlet 3 under the lifting action of the influent pump 2. Turn on the air pump 5 and the aeration device 14, and at the same time turn on the ultraviolet lamp. The hydraulic retention time is 4 hours. Then the treated groundwater enters the secondary sedimentation tank 16 through the reactor outlet 15 and is discharged to the effluent tank 17.

[0085] Using the groundwater contaminated by high-concentration nitrate as the influent, with a nitrate concentration of 50 mg / L, use this device to operate stably. Monitor the nitrate and nitrite concentrations in the influent and effluent every day, and regularly measure the biomass and total protein on the membrane module. When the biomass on the membrane module exceeds 1 g dry weight / cm 2 membrane, recover the bacteria on the membrane module by backwashing and measure the total protein. During the 30-day operation of the photocatalytic device, the removal rate of nitrate is above 80%, and a total of 1500 L of CO2 gas is used. The membrane module in the device is backwashed 5 times within 30 days, and a total of 1440 g of dry weight of bacteria is recovered, and the total amount of protein produced is 604.8 g.

[0086] Taking the bacterial single-cell protein cultured by the ordinary fermentation culture method as a control, the protein production of the ordinary fermentation culture method is 0.37 g protein / g bacterial dry weight. Compared with the ordinary fermentation culture method, the single-cell protein production rate of the present invention is increased by 13.5%.

[0087] In actual production, if the waste CO2 generated by food fermentation and brewing enterprises is used as the carbon source, it helps to achieve the fixation and storage of CO2 in industrial production, that is, it saves the production cost of single-cell protein and also contributes to carbon neutrality.

Claims

1. A preparation method of a polyvinyl alcohol-based shape memory film, characterized in that The method includes the following steps: I. Dissolve polyvinyl alcohol particles in pure water, gradually increase the temperature from room temperature to 95 - 100 °C, stir at a constant speed with a stirring rate of 300 r / min for 3 - 5 h, adjust the pH value of the solution to 3.5, add glutaraldehyde under acidic conditions, stir for 2 - 3 h, and remove bubbles in a vacuum drying oven to obtain a PVA solution; Clean the glass substrate, place the cleaned glass substrate on the tray of a spin coater, drop the PVA solution onto the glass substrate, and perform spin coating; After spin coating is completed, take out the glass substrate and place it at room temperature for 48 - 72 h, then cure it in an oven at 60 - 70 °C for 24 - 48 h, then adjust the oven temperature to 50 - 60 °C and cure for 3 - 5 h, and then peel it off from the glass substrate to obtain a smooth polyvinyl alcohol film; II. Etch a micro - nano - scale cylindrical array on the surface of the silicon wafer as an imprint replication template; place the polyvinyl alcohol film prepared in step I on the template, and perform hot embossing using the hot embossing method and then demold to obtain a polyvinyl alcohol - based shape - memory film with a micro - nano - structure pattern.

2. The preparation method of a polyvinyl alcohol-based shape memory film according to claim 1, wherein The size of the micro - nano - scale cylindrical array described in step II is: diameter 500 - 1000 nm, height 100 - 200 nm, and spacing 100 - 300 nm.

3. The preparation method of a polyvinyl alcohol-based shape memory film according to claim 1 or 2, characterized in that The conditions of the hot embossing method described in step II are: pressure 50 - 70 bar, temperature 90 - 100 °C, and hot embossing time 1 - 3 min.

4. The preparation method of a polyvinyl alcohol-based shape memory film according to claim 1, characterized in that The micro - nano structure on the surface of the polyvinyl alcohol - based shape - memory film can be erased and redesigned by heating the surface of the ITO glass.

5. The application of the polyvinyl alcohol - based shape - memory film as described in claim 1 in fixing carbon dioxide to produce single - cell protein.

6. The application according to claim 5, wherein The method for the polyvinyl alcohol - based shape - memory film to fix carbon dioxide to produce single - cell protein includes the following steps: I. Inoculate Pseudomonas proteinensis Y24 - 6 in a solid enrichment medium and activate it at 25 °C for 24 - 72 h; II. Collect the activated Pseudomonas proteinensis Y24 - 6 from the solid enrichment medium in step I and prepare it into a seed solution with sterile deionized water; III. Add a culture solution for producing single - cell protein to the device and inoculate the seed solution at 1‰ - 3‰ of the volume of the main reactor of the device; IV. Introduce a mixed gas into the device, where the mixed gas is composed of CO2 and air in a volume ratio of 1:1, and keep the pH value in the photocatalytic device at 7.0 ± 0.2; V. Repeat steps III to IV to keep the photocatalytic device running stably until a biofilm is formed on the flat - plate membrane module in the device, and the thickness of the biofilm is 0.1 - 0.2 mm; the device is a device for removing high - concentration nitrate in low - temperature groundwater, and the flat - plate membrane module in the device is a polyvinyl alcohol - based shape - memory film.

7. The application according to claim 6, wherein The Pseudomonas proteinensis Y24 - 6 is preserved in the General Microbiology Center of the China Committee for Culture Collection of Microorganisms. The preservation address is No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing. The preservation date is December 16, 2020, and the preservation number is CGMCC No. 21380.

8. The application according to claim 6 or 7, characterized in that The formula of the solid enrichment medium described in Step 1 is: nitrogen source 0.3 - 0.5 g / L, carbon source 0.1 - 0.2 g / L, iron salt 0.05 g / L, NaCl 0.1 - 0.5 g / L, MgSO4·7H2O 0.05 - 0.1 g / L, MnSO4 0.01 - 0.1 g / L, CaCl2 0.1 g / L, Na2HPO4 0.1 - 0.2 g / L, agar 1.8 g / L, pH value 7.

0. The carbon source is Na2CO3 or NaHCO3, the nitrogen source is NaNO3 or KNO3, and the iron salt is (NH4)2Fe(SO4)2·6H2O or FeSO4.

9. The application according to claim 8, characterized in that In step two, the concentration of the seed solution is not less than 10 8 cells / mL.

10. The application according to claim 9, characterized in that The formula of the culture solution described in Step 3 is: nitrogen source 0.3 - 0.5 g / L, carbon source 0.1 - 0.2 g / L, iron salt 0.05 g / L, NaCl 0.1 - 0.5 g / L, MgSO4·7H2O 0.05 - 0.1 g / L, MnSO4 0.01 - 0.1 g / L, CaCl2 0.1 g / L, Na2HPO4 0.1 - 0.2 g / L, pH value 7.

0. The carbon source is Na2CO3 or NaHCO3, the nitrogen source is NaNO3 or KNO3, and the iron salt is (NH4)2Fe(SO4)2·6H2O or FeSO4.

Images