A biocarrier membrane for sustained-release folic acid, its preparation method and application

Abstract

This invention discloses a slow-release folic acid bio-carrier membrane, its preparation method, and its application. This microbial carrier membrane is a core-shell structured nanofiber produced by coaxial electrospinning. The outer shell uses polycaprolactone as a rigid framework, while the core encapsulates folic acid. When applied to an anaerobic ammonia oxidation denitrification system, the outer shell protects the internal folic acid from being immediately washed away by the water flow, while utilizing the concentration gradient to release the folic acid extremely slowly. This invention solves the industry pain points of slow growth and difficult start-up of anaerobic ammonia oxidizing bacteria, thus improving denitrification activity. This microbial carrier membrane directly provides targeted nutritional intervention for anaerobic ammonia oxidizing bacteria, has a simple preparation method, and possesses strong application prospects.

Description

Technical Field

[0001] This invention relates to the field of microbial immobilization materials and wastewater biological treatment technology, specifically to a slow-release folic acid biocarrier membrane, its preparation method, and its application. Background Technology

[0002] Anaerobic ammonia oxidation (AAO) has attracted widespread attention in wastewater denitrification due to its advantages such as not requiring external organic carbon sources and low operating energy consumption. However, in practical applications, this process still faces challenges such as long start-up periods, slow bacterial growth, and sensitivity to environmental conditions like oxygen and temperature, limiting its further promotion. Genomic studies have shown that AAO bacteria are folic acid synthesis-deficient microorganisms, unable to synthesize folic acid themselves and requiring symbiotic bacteria to provide it. Therefore, AAO bacteria typically exist in the form of bacterial communities, maintaining complex metabolic intertrophic relationships with other microorganisms within the system. Some growth-related substances and metabolic precursors cannot be synthesized independently by a single species and require synergistic supply from the community, with folic acid being a particularly noteworthy intertrophic factor.

[0003] Existing carrier materials for microbial immobilization and culture primarily focus on providing specific surface area, pore structure, mechanical support, or a certain degree of hydrophilicity to improve cell adhesion and mass transfer conditions. CN105236568B discloses a method for operating anaerobic ammonium oxidation using a microbial immobilized membrane bioreactor. This method uses a cubic modified polyurethane foam carrier, which exhibits good affinity with microbial cells, high water retention, and resistance to biodegradation, effectively retaining anaerobic ammonium oxidation sludge. However, the carrier design is still relatively inadequate for the continuous supply of metabolites in the anaerobic ammonium oxidation system. Directly adding folic acid to the reaction system typically results in problems such as easy diffusion and loss, short release duration, and significant susceptibility to environmental factors, making it difficult to meet the needs of early microbial initiation and stable acclimatization.

[0004] Electrospinning technology can construct nano / micron-scale fiber membranes and achieve the encapsulation and sustained release of active substances through coaxial structures, enabling the carrier material to simultaneously perform the functions of bacterial cell attachment and active substance supply. CN116856115B discloses a rapidly attaching electrospinned carrier, its preparation method, and its application, solving the technical problem that existing methods cannot achieve sustained release by directly adding N-acylhomoserine lactone or simply fixing N-acylhomoserine lactone to the carrier surface. CN117702362B discloses a rapidly attaching electrospinned carrier, its preparation method, and its application, employing a core-shell structure fiber design. The shell layer is made of biodegradable polymer material, and the core layer is a bacterial quorum response signal molecule. As the shell layer biodegrades, the bacterial quorum response signal molecule is gradually released, achieving the sustained release effect of the core-shell fiber. However, in the above-mentioned existing technologies, the degradation of the core substance relies on the degradation of the shell layer for release, making the release rate extremely difficult to control. Furthermore, the substances released in both existing technologies are bacterial quorum response signals, not microbial nutrients.

[0005] To address the above issues, there is an urgent need for a microbial carrier membrane that can slow-release folic acid while also ensuring bacterial adhesion and culture stability. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the first objective of this invention is to provide a microbial carrier membrane for slow-release folic acid. This membrane is constructed by coaxial electrospinning to create a shell-core structure fiber membrane, which stably encapsulates folic acid within the carrier and enables its slow release. Simultaneously, it enhances the attachment and cultivation capabilities of the carrier membrane for anaerobic ammonia-oxidizing bacteria.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A microbial carrier membrane for sustained-release folic acid is provided. This microbial carrier membrane is a shell-core structured nanofiber membrane fabricated using coaxial electrospinning technology. The nanofiber membrane includes an outer shell layer and an inner core layer. The outer shell layer is a polymer, and the polymer can be any one of polycaprolactone or polylactic acid. The inner core layer includes a water-soluble polymer and folic acid or folate grafted / embedded therein. The water-soluble polymer can be any one of polyvinyl alcohol, polyethylene glycol, or polyvinylpyrrolidone.

[0009] When the above-mentioned microbial membrane carrier is applied to the anaerobic ammonia oxidation denitrification system, folic acid or folate in the core layer can be slowly released in the aquatic environment.

[0010] Furthermore, the fiber diameter of the aforementioned microbial carrier membrane is 300-600 nm, and the pore size is 50-3000 nm.

[0011] Furthermore, the thickness of the aforementioned microbial carrier membrane is greater than or equal to 13 μm.

[0012] The second objective of this invention is to provide a method for preparing a microbial carrier membrane for sustained-release folic acid, specifically comprising the following steps:

[0013] The first step is to dissolve polycaprolactone in an organic solvent to obtain the outer shell spinning solution; and to dissolve the water-soluble polymer, folic acid and tin tetrachloride in water to prepare the inner core spinning solution.

[0014] The second step is to pass the outer shell spinning solution and the inner core spinning solution into the outer shell channel and the core channel of the coaxial electrospinning device, respectively, to perform coaxial electrospinning and collect the resulting fiber membrane.

[0015] The third step is to dry the obtained fiber membrane to obtain the finished microbial carrier membrane.

[0016] Furthermore, the organic solvent in the first step includes one or a mixture of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), and dichloromethane (DCM).

[0017] Furthermore, the water-soluble polymer in the first step includes any one of polyvinyl alcohol, polyethylene glycol, and polyvinylpyrrolidone.

[0018] Furthermore, in the first step, the concentration of polycaprolactone is 10wt% - 20wt%, the concentration of water-soluble polymer is 5wt% - 15wt%, and the concentration of folic acid is 5wt% - 15wt%.

[0019] Furthermore, in the second step of coaxial electrospinning, the outer shell injection speed must be greater than or equal to the core injection speed, the positive voltage must be greater than 10 kV, and the negative voltage must be less than -4 kV.

[0020] It should be noted that tin tetrachloride is used as a catalyst in the first step.

[0021] The second objective of this invention is to apply the microbial carrier membrane prepared above to an anaerobic ammonia oxidation reactor.

[0022] A third objective of this invention is to provide an anaerobic ammonia oxidation biofilm reactor in which a microbial carrier membrane for slow-release folic acid is added.

[0023] The beneficial effects of this invention are:

[0024] 1. The slow-release folic acid microbial carrier membrane of this invention can form a shell-core structure through coaxial electrospinning, stably embedding folic acid within the fiber, thereby slowing down the diffusion and loss of folic acid in the environment, achieving continuous slow release, and providing a more stable supply of metabolic nutrients for anaerobic ammonia-oxidizing bacteria. Furthermore, experimental verification shows that the fully embedded structure can effectively delay folic acid release, the hydrophilicity of the carrier membrane is improved after shell modification, and the carrier membrane with added folic acid and shell modification has a more significant effect on improving the activity of anaerobic ammonia-oxidizing bacteria, with an activity increase of up to 27.8%. This indicates that this invention has the application potential to promote bacterial adhesion, growth, and denitrification performance.

[0025] 2. Existing inert carrier materials are typically highly hydrophobic, which is detrimental to the initial adhesion of bacteria. This invention constructs a microbial carrier membrane that combines structural support, surface hydrophilicity regulation, and folic acid slow-release supply functions. This significantly reduces the surface contact angle of the fibrous membrane and forms a surface hydrogel layer. This not only improves the wettability of the carrier in water but also provides excellent initial adhesion sites for anaerobic ammonia-oxidizing bacteria. It can alleviate the problem of insufficient metabolites in the initiation stage of anaerobic ammonia oxidation systems to a certain extent, improve the carrier's adaptability to bacterial culture, and has a well-defined preparation process and mature material system, showing good prospects for engineering applications. Attached Figure Description

[0026] Figure 1 The application of microbial carriers for slow-release folic acid in wastewater treatment plants and a schematic diagram of the fiber structure of the curtain-type carrier (1-wastewater treatment plant, 2-curtain-type carrier, 3-folic acid, 4-polycaprolactone).

[0027] Figure 2 A graph showing the relationship between the thickness of the microbial carrier membrane for sustained-release folic acid and its UV blocking ability.

[0028] Figure 3 Schematic diagram of the morphology and microstructure of fully embedded and semi-embedded carrier membranes in microbial carrier membranes for sustained-release folic acid.

[0029] Figure 4 Cumulative folic acid release curve of microbial carrier membrane for sustained folic acid release;

[0030] Figure 5 Infrared spectra of fully embedded carrier membranes, semi-embedded carrier membranes, and nuclear-modified carrier membranes for sustained-release folic acid microbial carrier membranes;

[0031] Figure 6 X-ray diffraction patterns of fully embedded carrier membranes in microbial carrier membranes and fully embedded carrier membranes after acid treatment;

[0032] Figure 7 Images showing the contact angles of different carrier membranes in microbial carrier membranes;

[0033] Figure 8 NH4 in different carrier membranes of microbial carrier membranes + -N and NO2 - -N concentration changes and corresponding removal rates;

[0034] Figure 9 A schematic diagram showing the extracellular polymer composition and cell adhesion of fully embedded carrier membranes and shell-modified carrier membranes in microbial carrier membranes for sustained-release folic acid.

[0035] Figure 10 A graph showing the changes in anaerobic ammonia oxidation transcriptional activity in fully embedded carrier membranes and shell-modified carrier membranes for sustained-release folic acid microbial carrier membranes. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this invention are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, all other embodiments not described in this invention obtained by those skilled in the art based on the embodiments described in this invention without creative effort should fall within the protection scope of this invention.

[0037] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0038] Figure 1 This is a schematic diagram illustrating the application of a slow-release folic acid microbial carrier in a wastewater treatment plant and its curtain-type carrier fiber structure. (See diagram below.) Figure 1 As shown, multiple sets of curtain-type carriers are suspended inside the sewage tank. The curtain-type carriers are composed of slow-release folic acid microbial carriers prepared in this invention. They can provide an interface for microorganisms to attach and accumulate in the sewage environment, and continuously release folic acid during operation to maintain the metabolic mutual-trophic conditions required for the growth of the microbial community.

[0039] To clearly demonstrate the microstructure of the curtain-type carrier, Figure 1 The right side shows a magnified view of a single fiber. The fiber contains folic acid embedded within it, and a polycaprolactone layer forms its outer layer. This structure creates a shell-core fiber carrier, which provides good formability and mechanical support while enabling stable encapsulation and slow release of folic acid, thereby improving the carrier's stability and biocompatibility in wastewater systems.

[0040] Preparation of basic solution:

[0041] 1. Preparation of spinning solution: First, take 12 mL of N,N-dimethylformamide and 18 mL of dichloromethane and mix them evenly as a solvent. Add 4 g of polycaprolactone and stir for 2 h to obtain a polymer solution with a polycaprolactone mass fraction of 13 wt%.

[0042] The polymer solution was then divided into two portions. One portion was stored and used for the subsequent preparation of the matrix solution for the semi-embedded carrier membrane and the outer shell channel spinning solution for the fully embedded carrier membrane.

[0043] Another portion was mixed with 0.2 g of polyethylene oxide and stirred thoroughly to dissolve, resulting in a shell-modified spinning solution with a polycaprolactone content of 13 wt% and a polyethylene oxide content of 1 wt%.

[0044] 2. Preparation of folic acid solution: Add 2.22 g folic acid and 0.4 g sodium hydroxide to 50 mL water and stir for 12 h. After complete dissolution, adjust the pH to 6–8 with a small amount of hydrochloric acid to obtain a folic acid solution with a concentration of 0.1 mol / L.

[0045] 3. Preparation of nucleomodified spinning solution: Take 2.5 g folic acid, 2.5 g polyvinyl alcohol and 60 mg tin tetrachloride and add them to 25 mL of water. Stir in a fume hood for 12 h to obtain a folic acid grafted polymer solution with a polyvinyl alcohol mass fraction of 10 wt%, which is used as the nucleomodified spinning solution.

[0046] All solutions should be prepared and used immediately. For temporary storage, they should be placed in a light-protected environment at 4 ℃.

[0047] Example 1: Preparation of a semi-embedded carrier membrane

[0048] Mix 1 mL of folic acid solution with 14 mL of polymer solution, stir magnetically for 4 h, centrifuge (10000 rpm, 15 min), remove the supernatant, and take the turbid organic phase in the middle as the emulsion spinning solution.

[0049] Subsequently, the spinning distance was adjusted to 10 cm, the injection speed to 0.017 mL / min, the positive voltage to 11.63 kV, the negative voltage to -4.37 kV, the roller speed to 80 r / min, the nozzle translation speed to 100 mm / min, and the translation distance to 100 mm. The emulsion spinning solution was directly spun through a single-needle electrospinning device. After continuous spinning for 20 h, a semi-embedded carrier membrane was obtained.

[0050] Example 2: Preparation of a fully encapsulated carrier membrane

[0051] Mix 1 mL of folic acid solution with 14 mL of polymer solution, stir magnetically for 4 h, centrifuge (10000 rpm, 15 min), remove the supernatant, and take the turbid organic phase in the middle as the emulsion spinning solution.

[0052] 15 mL of the above emulsion spinning solution was placed in the core channel of the coaxial electrospinning needle, and 15 mL of polymer solution was placed in the outer shell channel. The spinning distance was adjusted to 15 cm, the outer shell injection speed was 0.1 mL / min, the core injection speed was 0.07 mL / min, the positive voltage was 14 kV, the negative voltage was -4 kV, the roller speed was 40 r / min, the nozzle translation speed was 200 mm / min, and the translation distance was 100 mm. After continuous spinning for 4 h, a fully embedded carrier membrane was obtained.

[0053] Example 3: Preparation of acid-treated fully embedded carrier membrane

[0054] The fully embedded carrier membrane prepared in Example 2 was fully immersed in 18 wt% hydrochloric acid, sonicated for 2 h, placed in the dark for 12 h, and finally dried at 65 ℃ for 4 h to obtain the acid-treated fully embedded carrier membrane.

[0055] Example 4: Preparation of shell-modified carrier membrane

[0056] Using a coaxial electrospinning process, the emulsion spinning solution prepared in Example 1 was placed in the core channel of the coaxial electrospinning needle, and the shell-modified spinning solution was placed in the outer shell channel. The spinning distance was adjusted to 15 cm, the outer shell injection speed was 0.1 mL / min, the core injection speed was 0.07 mL / min, the positive voltage was 14 kV, the negative voltage was -4 kV, the roller speed was 40 r / min, the nozzle translation speed was 200 mm / min, and the translation distance was 100 mm. After continuous spinning for 4 h, the shell-modified carrier membrane was obtained.

[0057] Example 5: Nuclear-modified carrier membrane

[0058] A coaxial electrospinning process was adopted. 15 mL of core-modified spinning solution was placed in the core channel of the coaxial electrospinning needle, and 15 mL of polymer solution was placed in the outer shell channel. The spinning distance was adjusted to 15 cm, the outer shell injection speed was 0.1 mL / min, the core injection speed was 0.07 mL / min, the positive voltage was 14 kV, the negative voltage was -4 kV, the roller speed was 40 r / min, the nozzle translation speed was 200 mm / min, and the translation distance was 100 mm. After continuous spinning for 4 h, the core-modified carrier membrane was obtained.

[0059] Material property analysis:

[0060] Materials characterization of the carrier films prepared in the above embodiments revealed that the thickness of the carrier film is closely related to its ultraviolet light blocking ability, such as... Figure 2The test results for the semi-embedded carrier membrane are shown. When the thickness reaches 13 μm or more, the UV blocking ability can reach over 97%; when the thickness reaches 38 μm or more, the UV blocking rate can exceed 99%. The prepared carrier membranes are all 120 μm or more thick, exhibiting strong UV protection for encapsulated folic acid, ensuring that over 90% of the encapsulated folic acid is essentially unaffected by UV decomposition. These results demonstrate that polycaprolactone-based fiber membranes can serve not only as a structural support layer but also as a protective layer for encapsulating active substances.

[0061] like Figure 3 (A) Macroscopic morphology of the fully embedded carrier membrane; (B) Macroscopic morphology of the semi-embedded carrier membrane; (C) Scanning electron microscope (SEM) image of the fully embedded carrier membrane; (D) Transmission electron microscope (TEM) image of the fully embedded carrier membrane; (E, F) Energy dispersive X-ray spectroscopy (EDS) images of the fully embedded carrier membrane. As shown, both the semi-embedded and fully embedded carrier membranes exhibit a nanofiber network structure. The fully embedded carrier membrane has a smoother surface. TEM further confirms its clear "shell-core" structure, indicating that coaxial electrospinning successfully achieved the core embedding of folic acid. The fiber diameter of this carrier membrane is approximately 300–600 nm, and the pore size is approximately 50–3000 nm, providing a porous support interface for bacterial attachment. EDS results showed that the C and O content in the fully embedded carrier membrane was relatively high, at 71.97 wt% and 27.99 wt% respectively, while the Na content was extremely low, at 0.04 wt%. This further indicates that sodium folic acid underwent a form transformation during spinning and embedding and mainly existed in the fiber as folic acid embedded in the fiber.

[0062] like Figure 4 As shown, different encapsulation methods directly affect the sustained-release behavior of folic acid. Both fully encapsulated and partially encapsulated carrier membranes reached their peak release in the first 9 hours, with the partially encapsulated carrier membrane releasing 0.023 mg / cm³ of folic acid in the first 9 hours. 2 The concentration was higher than 0.016 mg / cm³ of the fully embedded carrier membrane. 2 This indicates that the fully encapsulated structure has a stronger retention and delayed release effect on folic acid. After 66 hours of sustained release, 60.3% and 37.5% of the encapsulated folic acid remained unreleased in the fully encapsulated and semi-encapsulated carrier membranes, respectively, indicating that the system can maintain a continuous supply of folic acid for a relatively long period. In the nuclear-modified carrier membrane, folic acid and PVA are linked by ester bonds, and the infrared spectrum can be observed at 1720 cm⁻¹. -1 and 1226 cm -1 The presence of ester bond characteristic peaks at the PVA long chain confirms that folic acid was successfully grafted onto the PVA long chain. Meanwhile, the slow release rate of the core-modified carrier membrane was the slowest, reaching equilibrium only after about 10 h, indicating that chemical bond grafting can further enhance the slow release stability of folic acid.

[0063] Table 1. Folic acid content of the two carrier membranes before and after sustained release.

[0064] <![CDATA[fully embedded carrier membrane (mg / cm 2 )]]>< <![CDATA[Semi-embedded carrier membrane (mg / cm 2 )]]> Pre-release 0.063 0.040 After sustained release 0.038 0.015

[0065] like Figure 5 As shown, a 2954 cm⁻¹ can be observed in the infrared spectra of both sides of the semi-embedded carrier membrane and the fully embedded carrier membrane. -1 and 1290 cm -1 The characteristic absorption peaks in the vicinity indicate that the effective components of folic acid were successfully introduced into the carrier membrane; the relevant peak intensity of the semi-embedded carrier membrane is slightly higher than that of the fully embedded carrier membrane, indicating that its embedding degree is relatively weak.

[0066] Figure 6 The XRD results show that the fully embedded carrier membrane has obvious diffraction peaks at 2θ / ° = 21.38° and 23.64°, and the peak intensity decreases after acid treatment, indicating that acid washing will cause some folic acid to be lost. However, the peak position does not change, indicating that the folic acid embedded in the carrier still maintains its original crystal form.

[0067] Figure 7 The contact angle results show that the pure polycaprolactone carrier membrane has a contact angle of over 120°, exhibiting strong hydrophobicity; the contact angles of the fully embedded and semi-embedded carrier membranes are still close to 120°; while the contact angle of the shell-modified carrier membrane after adding polyethylene oxide drops to 82.5°, indicating that its hydrophilicity is significantly improved, which is conducive to the formation of hydrogels in the aqueous phase and improves the bacterial attachment environment.

[0068] In terms of biological efficacy, such as Figure 8 As shown, after the carrier membrane is placed in an anaerobic batch system, NH4 + -N and NO2 - -N concentrations decreased over time, with the shell-modified carrier membrane showing the best effect on NO2 concentration. - The -N removal effect was optimal, with the endpoint concentration reduced to 17.49 mg / L, which was better than the 21-23 mg / L of other groups; at the same time, the nitrite removal rate of this group was also higher. Figure 9 The EPS results shown indicate that the hydrogel material generated on the surface of the shell-modified carrier membrane can, to some extent, replace some of the functions of the bacterial community's own EPS, thereby promoting bacterial adhesion and implantation. Figure 10 The qRT-PCR results showed that the abundance of key genes related to anaerobic ammonia oxidation activity was increased in all vector groups, with a 12.2% increase in the fully embedded vector membrane group and a 27.8% increase in the shell-modified vector membrane group, significantly higher than the 5.1% increase in the control group. These results indicate that folic acid slow release and shell modification have a synergistic effect, which can more effectively promote the enhancement of anaerobic ammonia oxidizing bacteria activity.

[0069] In summary, this invention constructs a shell-core structured microbial carrier membrane through coaxial electrospinning, and combines it with designs such as polycaprolactone backbone, folic acid sustained release, PEO shell modification, and PVA-folic acid grafting to give the carrier membrane structural stability, continuous folic acid supply capacity, and microbial attachment promotion effect. At the same time, this carrier membrane can be used for the attachment culture and acclimatization culture of anaerobic ammonia-oxidizing bacteria, and has a promoting effect on nitrogen removal activity.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A microbial carrier membrane for sustained-release folic acid, characterized in that, Microbial carrier membranes are prepared by coaxial electrospinning to obtain nanofibers with a shell-core structure, wherein the nanofibers include an outer shell layer and an inner core layer; The outer shell layer is a polymer, and the polymer can be either polycaprolactone or polylactic acid. The core layer is composed of a water-soluble polymer and folic acid or folic acid salt grafted / embedded therein. The water-soluble polymer can be any one of polyvinyl alcohol, polyethylene glycol, or polyvinylpyrrolidone. The microbial carrier membrane is used in the anaerobic ammonia oxidation denitrification system.

2. The microbial carrier membrane according to claim 1, characterized in that, The microbial carrier membrane has a fiber diameter of 300-600 nm and a pore size of 50-3000 nm.

3. The microbial carrier membrane according to claim 1, characterized in that, The thickness of the microbial carrier membrane is greater than or equal to 13 μm.

4. A method for preparing a microbial carrier membrane for sustained-release folic acid, characterized in that, Includes the following steps: S101. Polycaprolactone is dissolved in an organic solvent to obtain the outer shell spinning solution; water-soluble polymer, folic acid and tin tetrachloride are dissolved in water to prepare the inner core spinning solution. S102. The outer shell spinning solution and the inner core spinning solution are respectively introduced into the outer shell channel and the core channel of the coaxial electrospinning device to perform coaxial electrospinning and collect the resulting fiber membrane. S103. The obtained fiber membrane is dried to obtain the finished microbial carrier membrane.

5. The method for preparing a microbial carrier membrane according to claim 4, characterized in that, The organic solvent in step S101 includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide, and dichloromethane, or a mixture thereof.

6. The method for preparing a microbial carrier membrane according to claim 4, characterized in that, The water-soluble polymer in step S101 includes any one of polyvinyl alcohol, polyethylene glycol, and polyvinylpyrrolidone.

7. The method for preparing a microbial carrier membrane according to claim 4, characterized in that, In step S101, the concentration of polycaprolactone is 10wt% - 20wt%, the concentration of water-soluble polymer is 5wt% - 15wt%, and the concentration of folic acid is 5wt% - 15wt%.

8. The method for preparing a microbial carrier membrane according to claim 4, characterized in that, In step S102, during the coaxial electrospinning process, the outer shell injection speed must be greater than or equal to the core injection speed, the positive voltage must be greater than 10 kV, and the negative voltage must be less than -4 kV.

9. The application of the microbial carrier membrane as described in any one of claims 1-3 in an anaerobic ammonia oxidation reactor.

10. An anaerobic ammonia oxidation biofilm reactor, characterized in that, The reactor was fed with a microbial carrier membrane as described in any one of claims 1-3.

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