Catalyst for acrylamide production and preparation method thereof

Abstract

The application relates to the technical field of biological catalysis, and particularly discloses a catalyst for acrylamide production and a preparation method thereof. The preparation method comprises the following steps: selecting a nitrile hydratase producing bacterium to perform fed-batch fermentation culture, and centrifuging to obtain wet sludge; sodium alginate and nano-titanium dioxide modified by a silane coupling agent are prepared into a composite carrier colloid; a bacterium suspension and the carrier colloid are mixed at a ratio of 1:3, and then are dropped into a calcium chloride solution containing glutaraldehyde to form; cross-linking is performed at low temperature by using glutaraldehyde; after washing, surface activation is performed in two steps; and finally, freeze-drying is performed to obtain solid catalyst particles. The method optimizes the whole process, the prepared catalyst has high reusability and high stability, is easy to separate from a product, and is suitable for continuous operation, solves the core defects of a traditional free bacterium catalyst, and takes into account the catalytic performance and industrial production efficiency.

Description

Technical Field

[0001] This invention relates to the field of biocatalysis technology, and in particular to a catalyst for acrylamide production and its preparation method. Background Technology

[0002] In the production of acrylamide, the microbial method has become a key research and application area due to its environmental friendliness and mild reaction conditions. The core of this process lies in using bacterial cells containing nitrile hydratase (NHase) as a biocatalyst to promote the hydration of acrylonitrile to acrylamide. However, the currently prevalent method of directly using fermentation broth or simply microfiltration-washed wet bacterial cells as catalysts has revealed several significant drawbacks.

[0003] While traditional free bacterial catalysts have the advantage of simple preparation processes and can meet basic production needs to a certain extent, their disadvantages are significant from the perspective of overall production efficiency and quality control.

[0004] First, the stability is poor. The spatial structure of enzymes in free bacterial cells is easily disrupted by the high temperatures and high concentrations of acrylonitrile in the reaction system, leading to rapid enzyme inactivation. This not only significantly shortens the catalyst's single-use lifespan, increasing the time and cost losses due to frequent catalyst replacements, but also poses a serious challenge to the continuity and stability of production. For example, in actual production scenarios, when the reaction temperature rises to 40°C and the acrylonitrile concentration reaches 25%, the activity of the free bacterial catalyst drops sharply within just a few hours, severely impacting production efficiency and product quality.

[0005] Secondly, they have poor operational tolerance. The bacterial cells themselves have limited strength and are easily ruptured under the mechanical shear forces generated by routine production operations such as stirring and material circulation. Once the cells rupture, the internal enzymes leak out, and enzyme activity is significantly reduced, severely interfering with the stability of the reaction system. This makes it difficult for the reaction process to proceed stably and continuously, increasing the uncertainty and risk in the production process.

[0006] Furthermore, separation presents a significant challenge. Completely separating the bacterial catalyst from the acrylamide solution after each batch of reaction is extremely difficult. Traditional separation methods are ineffective, resulting not only in substantial catalyst loss and unnecessary increases in production costs, but also in product contamination, severely impacting product quality and market competitiveness. For example, conventional filtration methods often fail to completely separate the bacterial cells from the acrylamide solution, leaving a certain amount of bacterial impurities in the product and reducing its purity.

[0007] Furthermore, reusability is poor. Constrained by both stability and separation challenges, the number of times free bacterial catalysts can be reused is severely limited, typically not exceeding five times. This undoubtedly significantly increases the production cost of acrylamide, weakens the cost control advantage of the microbial method, and reduces the economic viability and market competitiveness of the production process.

[0008] Finally, reaction control is challenging. The free bacterial catalyst has poor heat dissipation, easily leading to localized overheating during the highly exothermic acrylonitrile hydration reaction. This localized overheating further exacerbates enzyme inactivation, making it difficult to increase the reactor's production intensity and severely restricting efficiency, thus becoming a bottleneck in the development of microbial acrylamide production processes.

[0009] In view of the above-mentioned prior art, the applicant believes that there is a need to develop an immobilized nitrile hydratase catalyst that has high reusability, high stability, easy separation and adaptability to continuous operation. Summary of the Invention

[0010] To address the technical deficiencies of existing technologies, this application provides a catalyst for acrylamide production and a method for preparing the same.

[0011] In a first aspect, this application provides a method for preparing a catalyst for acrylamide production, employing the following technical solution: A method for preparing a catalyst for acrylamide production includes the following steps: S1: Nitrile hydratase producing bacteria that have undergone high-density fermentation culture are selected as the production strain for fermentation culture. After fermentation, the bacterial cells are collected by centrifugation to obtain wet bacterial mud. S2: Dissolve sodium alginate in deionized water to prepare a 5-6 wt% solution, add 15% to 20% nano titanium dioxide (by mass of sodium alginate), and disperse evenly to obtain a composite carrier colloid. S3: The centrifuged wet bacterial mud was resuspended in phosphate buffer to form a bacterial suspension. The bacterial suspension was mixed evenly with the composite carrier colloid. After being mixed evenly, it was added dropwise to calcium chloride solution to obtain a preliminary gel microsphere. S4: Transfer the preliminarily formed gel microspheres into a solution containing a cross-linking agent, and allow them to stand at 2-4℃ for 4-6 hours for cross-linking; S5: Take out the cross-linked gel microspheres, wash them 4-5 times with phosphate buffer, and then perform surface activation treatment on the gel microspheres; S6: Place the activated gel microspheres into a freeze dryer and freeze dry to obtain solid catalyst particles.

[0012] By adopting the above technical solution, this preparation method optimizes the entire process from enzyme source acquisition, carrier construction, molding and cross-linking to post-processing, specifically addressing the core defects of traditional free bacterial catalysts. S1 uses high-density fermentation combined with centrifugation to obtain high-enzyme-activity wet bacterial sludge, removing impurities from the fermentation broth and providing a high-purity enzyme source for immobilization, avoiding interference from impurities in subsequent processes. S2 uses a composite carrier of sodium alginate and nano-titanium dioxide; the former ensures biocompatibility and molding ability, while the latter enhances the carrier's mechanical strength, thermal stability, and surface active sites, overcoming the limitations of single-carrier performance. S3 involves mixing the bacterial suspension and carrier and adding it dropwise to a calcium chloride solution to achieve uniform encapsulation and initial molding of the bacterial cells. S4 uses low-temperature static cross-linking to strengthen the carrier network structure and improve the catalyst's resistance to mechanical shearing. S5 washing removes redundant impurities, and surface activation further enhances the catalyst's stability and hydrophobicity, promoting effective contact between the substrate and enzyme. S6 freeze-drying yields solid particles, not only solving the problem of difficult separation between traditional catalysts and products but also facilitating storage, transportation, and filling of fixed-bed reactors, adapting to continuous production, and significantly improving the stability and economy of acrylamide production.

[0013] Preferably, the nitrile hydratase-producing bacteria in step S1 is Rhodococcus.

[0014] By adopting the above technical solution, Rhodococcus, as a high-yield nitrile hydratase strain, has excellent substrate tolerance and enzyme production stability. It can stably exert catalytic effects in a high-concentration acrylonitrile environment, and its industrial cultivation is mature, providing a reliable enzyme source for the preparation of highly active catalysts.

[0015] Preferably, the fermentation culture in step S1 is a fed-batch fermentation culture.

[0016] By adopting the above technical solution, the shortcomings of traditional single-feed fermentation are addressed. Batch-feed fermentation can dynamically supplement carbon and nitrogen sources according to the nutritional needs of cell growth and enzyme synthesis, avoiding premature cell death due to nutrient depletion in the later stages of fermentation, extending cell growth and enzyme production time, and significantly increasing cell density and enzyme activity in wet sludge. At the same time, it avoids the accumulation of metabolites caused by initial nutrient excess, reducing the inhibition of cell growth and enzyme activity, achieving efficient and stable enzyme source production, laying the foundation for the subsequent preparation of highly active immobilized catalysts, and reducing the enzyme source cost per unit product.

[0017] Preferably, the nano-titanium dioxide in step S2 is modified with a silane coupling agent beforehand.

[0018] By adopting the above technical solution, the dispersibility of nano-titanium dioxide in sodium alginate can be improved, its interfacial bonding force with the carrier can be enhanced, the mechanical strength and structural stability of the composite carrier can be improved, and the carrier aggregation defects can be avoided.

[0019] Preferably, the mixing ratio of the bacterial suspension to the composite carrier colloid in step S3 is 1:3.

[0020] By adopting the above technical solution, this ratio can achieve a balance between sufficient encapsulation of bacteria and catalytic efficiency, ensuring uniform distribution of bacteria within the microspheres. This avoids bacterial exposure due to insufficient carrier and prevents excessive carrier from reducing unit enzyme activity.

[0021] Preferably, the crosslinking agent in step S4 is glutaraldehyde.

[0022] By adopting the above technical solution, glutaraldehyde can efficiently crosslink bacteria and carriers to form a dense network structure, enhance the mechanical strength of microspheres, and the crosslinking process is mild, reducing enzyme activity loss and improving the catalyst's shear resistance.

[0023] Preferably, the calcium chloride solution in step S3 contains 0.3 to 0.5 mol / L of glutaraldehyde.

[0024] By adopting the above technical solution, preliminary cross-linking can be achieved while microspheres are being formed, improving the initial structural stability, avoiding deformation of newly formed microspheres or leakage of bacteria, and laying the foundation for subsequent deep cross-linking.

[0025] Preferably, the surface activation treatment in step S5 involves first immersing the gel microspheres in a 0.8-1.0 wt% solution of 1,4-butanediol diglycidyl ether and reacting at 25-30°C for 1-2 hours, then transferring them to a solution containing 0.5-1.0 wt% cysteine ​​and reacting at 30-35°C for 2-3 hours.

[0026] By employing the above technical solution, a two-step activation process achieves dual optimization: 1,4-butanediol diglycidyl ether enhances the structural stability and anti-swelling ability of the gel microspheres, while simultaneously introducing active sites; cysteine ​​modifies the hydrophobicity of the microsphere surface by modifying the active sites, making it easier for the substrate acrylonitrile to contact the enzyme's active site. The entire process is gentle and does not damage enzyme activity, ultimately improving the catalyst's environmental adaptability and catalytic efficiency.

[0027] Secondly, this application provides a catalyst for acrylamide production, employing the following technical solution: A catalyst for acrylamide production is prepared by the above-described method for preparing acrylamide production catalyst.

[0028] By adopting the above technical solution, the catalyst integrates the advantages of each step: using highly active Rhodococcus bacteria as the enzyme source, through composite carrier encapsulation, glutaraldehyde cross-linking and surface activation, it has high stability and strong operational tolerance, and excellent reusability; the solid particle morphology is easy to separate from the product, and it can be directly packed into a fixed bed, making it suitable for continuous production, and comprehensively solving the core defects of traditional catalysts.

[0029] In summary, this application has the following beneficial effects: The immobilized nitrile hydratase catalyst of this application has formed a comprehensive advantage of high reusability, high stability, easy separation and adaptability to continuous operation by means of synergistic optimization of multiple technologies. Its core performance comes from scientific preparation logic and structural design. Regarding reusability and stability, the catalyst uses high-density fermented Rhodococcus as a high-quality enzyme source, combined with a composite carrier of sodium alginate and nano-titanium dioxide modified with a silane coupling agent. The former ensures the biocompatibility of the encapsulated bacteria, while the latter significantly improves the mechanical strength of the carrier. A 1:3 mixing ratio of bacterial suspension and carrier ensures uniform distribution of bacteria within the carrier. Simultaneously, a stepwise cross-linking process using glutaraldehyde is employed. Initial cross-linking is achieved in the microsphere forming stage using a calcium chloride solution containing glutaraldehyde, followed by deep cross-linking at 2-4℃ for 4-6 hours to construct a dense and stable network structure, significantly reducing the risk of enzyme leakage. The two-step surface activation treatment in step S5 (1,4-butanediol diglycidyl ether enhances the anti-swelling properties of the microspheres, and cysteine ​​regulates surface hydrophobicity) further enhances the catalyst's resistance to mechanical shearing and environmental adaptability, enabling it to withstand reaction temperature fluctuations of 25-30℃ and adapt to high-concentration acrylonitrile substrate environments, maintaining a high enzyme activity of approximately 900 U / g even after 10 reuses. In terms of ease of separation and adaptability to continuous production, the catalyst is in the form of solid particles after freeze-drying. This structure not only allows for rapid separation from the acrylamide product solution after the reaction, avoiding catalyst loss and product contamination, but also allows for direct loading into a fixed-bed reactor, perfectly adapting to industrial continuous production processes. This fundamentally solves the core pain points of traditional free bacterial catalysts, such as poor stability, difficulty in separation, and difficulty in continuous use, thus balancing catalytic performance and industrial production efficiency. Detailed Implementation

[0030] The present application will be further described in detail below with reference to the embodiments.

[0031] The raw materials used in the embodiments and comparative examples of this invention are all commercially available products.

[0032] Example 1 A catalyst for acrylamide production is prepared by the following method: S1: Rhodococcus bacteria cultured at high density were selected as the production strain, and a fed-batch fermentation method was adopted. In the initial stage of fermentation, the culture medium contained a solution of 50 g / L glucose, 10 g / L yeast extract, 3 g / L potassium dihydrogen phosphate, and 1 g / L magnesium sulfate. The fermentation temperature was controlled at 32℃, the pH was maintained at 7.0, and the dissolved oxygen was maintained at 30%–35% saturation. Feeding was performed every 6 hours during fermentation, for a total of two times. The glucose feed solution was added at 2% of the fermentation broth volume, and the urea feed solution was added at 0.5% of the fermentation broth volume. During the stabilization period, the temperature was lowered to 28℃, and the pH was adjusted to 7.4. After fermentation, the bacterial cells were collected by high-speed centrifugation at 8000 rpm for 15 minutes to obtain wet bacterial sludge. The enzyme activity of the wet bacterial sludge was determined by spectrophotometry, ensuring that the enzyme activity was higher than 2000 U / g.

[0033] S2: Weigh a certain amount of nano-titanium dioxide, add an ethanol solution containing 3wt% γ-aminopropyltriethoxysilane, stir and react at 60℃ for 3 hours, centrifuge after the reaction, wash repeatedly with ethanol, and dry at 80℃ to obtain surface-modified nano-titanium dioxide. Dissolve sodium alginate in deionized water to prepare a 5wt% solution, add 15% of the surface-modified nano-titanium dioxide equivalent to the mass of sodium alginate, stir at 40℃ for 1 hour, and ultrasonically disperse for 30 minutes to form a homogeneous and stable composite carrier colloid.

[0034] S3: Wash the centrifuged wet bacterial sludge 3-4 times with physiological saline, and resuspend it in a pH 7.0 phosphate buffer containing 1 wt% trehalose, 2 wt% glycerol, 0.5 wt% proline, 0.3 wt% betaine, and 0.1 wt% ascorbic acid to prepare a homogeneous bacterial suspension. Mix the bacterial suspension with the composite carrier colloid at a volume ratio of 1:3. Using a syringe, slowly add the mixture dropwise at a rate of 1-2 drops per second to a calcium chloride solution containing 0.3 mol / L glutaraldehyde. After the addition is complete, let it stand at room temperature for 1 hour to allow the gel microspheres to initially form.

[0035] S4: The initially formed gel microspheres are transferred to a solution containing 0.1-mol / L glutaraldehyde and allowed to stand at 2°C for 4 hours to crosslink, thereby further hardening the gel microspheres and strengthening their internal structure.

[0036] S5: Remove the cross-linked gel microspheres and wash them four times with pH 7.0 phosphate buffer to remove unfixed cells, excess cross-linking agent, and reaction byproducts. First, immerse the microspheres in a 0.8 wt% solution of 1,4-butanediol diglycidyl ether and react at 25°C for 1 hour. Then, transfer them to a solution containing 0.5 wt% cysteine ​​and react at 30°C for 2 hours to complete the surface activation treatment.

[0037] S6: The activated immobilized catalyst microspheres were placed in a freeze dryer, pre-frozen at -55°C for 3 hours, and then vacuum freeze-dried for 18 hours to obtain dry solid catalyst particles.

[0038] Example 2 A catalyst for acrylamide production is prepared by the following method: S1: Rhodococcus faecalis, cultured at high density, was selected as the production strain, and a fed-batch fermentation method was adopted. In the initial stage of fermentation, the culture medium contained a solution of 60 g / L glucose, 15 g / L yeast extract, 5 g / L potassium dihydrogen phosphate, and 2 g / L magnesium sulfate. The fermentation temperature was controlled at 32℃, the pH was maintained at 7.2, and the dissolved oxygen was maintained at 35% saturation. Feeding was performed every 6 hours during fermentation, for a total of 3 times. Glucose was added at 2% of the fermentation broth volume, and urea at 0.5% of the fermentation broth volume. During the stabilization period, the temperature was lowered to 28℃, and the pH was adjusted to 7.6. After fermentation, the bacterial cells were collected by high-speed centrifugation at 10,000 rpm for 20 minutes to obtain wet bacterial sludge. The enzyme activity of the wet bacterial sludge was determined by spectrophotometry, ensuring that the enzyme activity was higher than 2000 U / g.

[0039] S2: Weigh a certain amount of nano-titanium dioxide, add an ethanol solution containing 5 wt% γ-aminopropyltriethoxysilane, stir and react at 70℃ for 4 hours, centrifuge after the reaction, wash repeatedly with ethanol, and dry at 90℃ to obtain surface-modified nano-titanium dioxide. Dissolve sodium alginate in deionized water to prepare a 6 wt% solution, add 20% of the surface-modified nano-titanium dioxide equivalent to the mass of sodium alginate, stir at 50℃ for 2 hours, and then ultrasonically disperse for 45 minutes to form a homogeneous and stable composite carrier colloid.

[0040] S3: Wash the centrifuged wet bacterial sludge 3-4 times with physiological saline, and resuspend it in a pH 7.0 phosphate buffer containing 1 wt% trehalose, 2 wt% glycerol, 0.5 wt% proline, 0.3 wt% betaine, and 0.1 wt% ascorbic acid to prepare a homogeneous bacterial suspension. Mix the bacterial suspension with the composite carrier colloid at a volume ratio of 1:3. Using a syringe, slowly add the mixture dropwise at a rate of 1-2 drops per second to a calcium chloride solution containing 0.5 mol / L glutaraldehyde. After the addition is complete, allow it to stand at room temperature for 2 hours to allow the gel microspheres to initially form.

[0041] S4: The preliminarily formed gel microspheres are transferred to a solution containing 0.2 mol / L glutaraldehyde and allowed to stand at 4°C for 6 hours to crosslink, thereby further hardening the gel microspheres and strengthening their internal structure.

[0042] S5: Remove the cross-linked gel microspheres and wash them five times with pH 7.0 phosphate buffer to remove unfixed cells, excess cross-linking agent, and reaction byproducts. First, immerse the microspheres in a 1% (w / w) solution of 1,4-butanediol diglycidyl ether and react at 30°C for 2 hours. Then, transfer them to a solution containing 1 wt% cysteine ​​and react at 35°C for 3 hours to complete the surface activation treatment.

[0043] S6: The activated immobilized catalyst microspheres are placed in a freeze dryer, pre-frozen at -60℃ for 4 hours, and then vacuum freeze-dried for 24 hours to obtain dry solid catalyst particles.

[0044] Example 3 A catalyst for acrylamide production is prepared by the following method: S1: High-density fermentation culture was selected as the production strain, and a fed-batch fermentation method was adopted. In the initial stage of fermentation, the culture medium contained a solution of 55 g / L glucose, 12 g / L yeast extract, 4 g / L potassium dihydrogen phosphate, and 1.5 g / L magnesium sulfate. The fermentation temperature was controlled at 32℃, the pH was maintained at 7.1, and the dissolved oxygen was maintained at 32% saturation. Feeding was performed every 6 hours during fermentation, for a total of 2 times. Glucose feed solution was added at 2% of the fermentation broth volume, and urea feed solution was added at 0.5% of the fermentation broth volume. During the stabilization period, the temperature was lowered to 28℃, and the pH was adjusted to 7.5. After fermentation, the bacterial cells were collected by high-speed centrifugation at 9000 rpm for 18 minutes to obtain wet bacterial sludge. The enzyme activity of the wet bacterial sludge was determined by spectrophotometry, ensuring that the enzyme activity was higher than 2000 U / g.

[0045] S2: Weigh a certain amount of nano-titanium dioxide, add it to an ethanol solution containing 4 wt% γ-aminopropyltriethoxysilane, stir and react at 65℃ for 3.5 hours, centrifuge after the reaction, wash repeatedly with ethanol, and dry at 85℃ to obtain surface-modified nano-titanium dioxide. Dissolve sodium alginate in deionized water to prepare a 5.5 wt% solution, add 18% of the surface-modified nano-titanium dioxide (equivalent to 18% of the mass of sodium alginate), stir at 45℃ for 1.5 hours, and then ultrasonically disperse for 40 minutes to form a homogeneous and stable composite carrier colloid.

[0046] S3: The centrifuged and collected wet bacterial sludge was washed three times with physiological saline and resuspended in a pH 7.0 phosphate buffer containing 1 wt% trehalose, 2 wt% glycerol, 0.5 wt% proline, 0.3 wt% betaine, and 0.1 wt% ascorbic acid to prepare a homogeneous bacterial suspension. The bacterial suspension was mixed with the composite carrier colloid at a volume ratio of 1:3. The mixture was then slowly added dropwise at a rate of 1-2 drops per second to a calcium chloride solution containing 0.4 mol / L glutaraldehyde. After the addition was complete, the mixture was allowed to stand at room temperature for 1.5 hours to allow the gel microspheres to initially form.

[0047] S4: The preliminarily formed gel microspheres are transferred to a solution containing 0.15 mol / L glutaraldehyde and allowed to stand at 3°C ​​for 5 hours to crosslink, thereby further hardening the gel microspheres and strengthening their internal structure.

[0048] S5: Remove the cross-linked gel microspheres and wash them five times with pH 7.0 phosphate buffer to remove unfixed cells, excess cross-linking agent, and reaction byproducts. First, immerse the microspheres in a 0.9 wt% solution of 1,4-butanediol diglycidyl ether and react at 28°C for 1.5 hours. Then, transfer them to a solution containing 0.8 wt% cysteine ​​and react at 32°C for 2.5 hours to complete the surface activation treatment.

[0049] S6: The activated immobilized catalyst microspheres were placed in a freeze dryer, pre-frozen at -58°C for 3.5 hours, and then vacuum freeze-dried for 20 hours to obtain dry solid catalyst particles.

[0050] Comparative Example 1 A catalyst for acrylamide production, which differs from Example 2 in that it only includes the wet sludge prepared in step S1.

[0051] Comparative Example 2 A catalyst for acrylamide production differs from that in Example 2 in that the catalyst in this comparative example is prepared by encapsulating the wet bacterial sludge obtained in step S1 in sodium alginate using an encapsulation method.

[0052] Performance testing Test method: The catalysts of Examples 1-3 and Comparative Examples 1-2 were loaded into a fixed-bed reactor. The reaction conditions were controlled as follows: temperature 25℃, pH 7.0, 15wt% acrylonitrile aqueous solution as the catalyst feedstock, and space velocity 1-2 / h through the reactor to catalyze the production of acrylamide. The reaction was repeated 10 times, and the enzyme activity of the catalyst was recorded before the start, after 5 reactions, and after 10 reactions. The test results are shown in Table 1.

[0053] Table 1 Performance Test Results

[0054] As shown in Table 1, the catalysts of Examples 1-3 of this invention maintained an enzyme activity of approximately 900 U / g after 10 uses, significantly higher than the comparative catalysts, indicating good stability and repeatability. In contrast, the catalyst of Comparative Example 1, made directly from wet bacterial sludge, achieved an enzyme activity as high as 1400 U / g before initial use, higher than all catalysts of Examples 1-3. However, the enzyme activity of Comparative Example 1 decreased by more than 80% after one use, demonstrating poor stability and unusable for repeated use. The catalyst of Comparative Example 2, made using sodium alginate-encapsulated wet bacterial sludge, showed a 50% decrease in enzyme activity after one use, which, while better than Comparative Example 1, was still far lower than the catalysts of this invention. Furthermore, the catalysts of this invention are solid particles, making them inherently easy to separate.

[0055] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for preparing a catalyst for acrylamide production, characterized in that, Includes the following steps: S1: Nitrile hydratase producing bacteria that have undergone high-density fermentation culture are selected as the production strain for fermentation culture. After fermentation, the bacterial cells are collected by centrifugation to obtain wet bacterial mud. S2: Dissolve sodium alginate in deionized water to prepare a 5-6 wt% solution, add 15%-20% nano titanium dioxide (equivalent to sodium alginate mass), disperse evenly, and obtain a composite carrier colloid. S3: The centrifuged wet bacterial mud is resuspended in phosphate buffer to prepare a bacterial suspension. The bacterial suspension is mixed evenly with the composite carrier colloid and then added dropwise to calcium chloride solution to obtain preliminarily formed gel microspheres. S4: Transfer the pre-formed gel microspheres to a solution containing a cross-linking agent and allow them to stand at 2-4℃ for 4-6 hours for cross-linking. S5: Take out the cross-linked gel microspheres, wash them 4-5 times with phosphate buffer, and then perform surface activation treatment on the gel microspheres. S6: The activated gel microspheres are placed in a freeze dryer and freeze-dried to obtain solid catalyst particles.

2. The method for preparing a catalyst for acrylamide production according to claim 1, characterized in that: The nitrile hydratase producing bacteria in step S1 is Rhodococcus.

3. The method for preparing a catalyst for acrylamide production according to claim 1, characterized in that: The fermentation culture in step S1 is a fed-batch fermentation culture.

4. The method for preparing a catalyst for acrylamide production according to claim 1, characterized in that: The nano-titanium dioxide in step S2 is modified with a silane coupling agent beforehand.

5. The method for preparing a catalyst for acrylamide production according to claim 1, characterized in that: The bacterial suspension and composite carrier colloid in step S3 are mixed in a ratio of 1:

3.

6. The method for preparing a catalyst for acrylamide production according to claim 1, characterized in that: The crosslinking agent in step S4 is glutaraldehyde.

7. The method for preparing a catalyst for acrylamide production according to claim 6, characterized in that: The calcium chloride solution in step S3 contains 0.3–0.5 mol / L of glutaraldehyde.

8. The method for preparing a catalyst for acrylamide production according to claim 1, characterized in that: The surface activation treatment in step S5 involves first immersing the gel microspheres in a 0.8-1.0 wt% solution of 1,4-butanediol diglycidyl ether at 25-30°C for 1-2 hours, and then transferring them to a solution containing 0.5-1.0 wt% cysteine ​​and reacting them at 30-35°C for 2-3 hours.

9. A catalyst for the production of acrylamide, characterized in that: It is prepared by the method for preparing acrylamide production catalyst according to any one of claims 1 to 8.

10. The application of the catalyst for acrylamide production according to claim 9 in the preparation of acrylamide.

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