A method for promoting the growth of nitrite-oxidizing bacteria

Abstract

This invention discloses a method for promoting the growth of nitrite-oxidizing bacteria, belonging to the field of nitrifying microorganism cultivation technology within the field of environmental microbiology. The method provides an adsorption medium for bacterial growth, accelerating the growth rate of nitrite-oxidizing bacteria. Under conditions where cationic polyacrylamide and closed-cell perlite are used as culture medium additives, the growth rate of nitrite-oxidizing bacteria is significantly faster and the production cycle is shortened compared to the original culture medium conditions. This method is simple to operate and low in cost, theoretically reducing costs and increasing efficiency: on the one hand, the cultivation time is shortened; on the other hand, due to the low density of closed-cell perlite, the bacteria are adsorbed onto its pores and easily dispersed with the flow of the culture medium liquid, averaging the cell density per unit volume in the culture medium, thereby reducing the competitive pressure between bacteria, increasing the bacterial culture density and the amount of bacteria obtained, and significantly reducing production costs compared to previous methods involving large-scale aeration and stirring.

Description

Technical Field

[0001] This invention relates to the field of nitrifying microorganism cultivation technology in the field of environmental microbiology, and particularly to a method for promoting the growth of nitrite-oxidizing bacteria, using cationic polyacrylamide and / or closed-cell perlite as the culture medium carrier components for promoting the growth of nitrite-oxidizing bacteria (NOB). Background Technology

[0002] Currently, the problem of nitrite pollution in water bodies is receiving increasing attention. Many application areas, such as aquaculture, eutrophic lake management, and treatment of industrial wastewater with high nitrite content, urgently need to remove nitrite.

[0003] Nitrite-oxidizing bacteria (NOB) are key functional microorganisms in the biological nitrification process, playing a crucial role in wastewater treatment, aquaculture, and biological denitrification systems by reducing nitrite (NO2) levels. - ) is oxidized to nitrate (NO3) - The core role of NOB is that it uses nitrite as its sole energy source, is strictly aerobic, has a slow growth rate, and a long average generation time. However, because NOB is a chemoautotrophic bacterium, it has physiological characteristics such as using nitrite as its sole energy source, being strictly aerobic, having a slow growth rate, and having a long average generation time. This results in a long industrial production cycle, high aeration energy consumption, and high production costs, which seriously limits its promotion and application in the treatment of nitrite pollution in water bodies.

[0004] Nitrifying bacteria can be obtained through activated sludge enrichment or cultivation. Compared to activated sludge enrichment, cultivation yields cultures with higher purity and concentration, allowing for high-density cultivation of nitrifying bacteria in a shorter time and exhibiting strong specificity for pollutants. However, during cultivation, the average generation time of NOB and its adherent, aggregated growth characteristics limit the concentration of nitrifying bacteria that can be cultivated within a certain timeframe. Therefore, this invention introduces a culture medium carrier component that will enhance the growth rate of the bacteria and the final bacterial concentration of the culture, which is crucial for obtaining high-density, high-treatment-rate bacterial agents under large-scale cultivation conditions.

[0005] Chinese patent application CN104004690A, "A Method for Cultivating Nitrifying Bacteria," proposes using biodegradable fibrous materials such as straw powder, sawdust powder, corn cob powder, and polycaprolactone as culture carriers for nitrifying bacteria, and employing intermittent aeration for cultivation. This method can increase the concentration of nitrifying bacteria and shorten the batch culture time. However, this method is only suitable for cultivating ammonia-oxidizing bacteria and not for cultivating nitrite-oxidizing bacteria.

[0006] Chinese patent CN109234265B, "A Microcarrier for Increasing the Culture Density of Nitrifying Bacteria and its Preparation Method," discloses a microcarrier made from a mixture of calcium carbonate and basic magnesium carbonate prepared using Na₂CO₃ solution, CaCl₂ solution, MgCl₂ solution, and sodium polyacrylate, for increasing the culture density of nitrifying bacteria. However, the preparation process of this mixed microcarrier is complex and unsuitable for large-scale culture of nitrifying bacteria.

[0007] Therefore, a new culture method is needed to improve the growth rate of bacteria and shorten the culture cycle. Summary of the Invention

[0008] In order to overcome the shortcomings and deficiencies of the prior art, the purpose of this invention is to provide a method for promoting the growth of nitrite-oxidizing bacteria.

[0009] To address the problems existing in the cultivation of nitrifying bacteria, a cultivation method is provided that incorporates cationic polyacrylamide (CPAM) and closed-cell expanded perlite (CCEP) as promoters for nitrite-oxidizing bacteria. CPAM carries a positive charge and possesses a long-chain molecular structure, while closed-cell expanded perlite particles are small and have a porous surface. Both can provide abundant attachment sites for bacteria, creating a protective microenvironment. Furthermore, CPAM can stabilize CCEP through bridging, resulting in a more effective promotion of nitrite-oxidizing bacteria. This method is low-cost, accelerates the growth rate of nitrite-oxidizing bacteria, shortens the production cycle, and reduces energy consumption and production costs. It is a rapid and efficient cultivation method for the large-scale co-cultivation of one or more types of nitrite-oxidizing bacteria.

[0010] The objective of this invention is achieved through the following technical solution:

[0011] Application of cationic polyacrylamide and / or closed-cell perlite in promoting the growth of nitrite-oxidizing bacteria and / or increasing the culture density of nitrite-oxidizing bacteria.

[0012] Furthermore, the final concentration of the cationic polyacrylamide is 0.05–0.1 g / L; preferably 0.1 g / L.

[0013] Furthermore, the molecular weight of the cationic polyacrylamide is 8 million to 10 million; preferably 9 million.

[0014] Furthermore, the final concentration of the closed-cell perlite is 0.5–1.5 g / L; preferably 0.5–1.0 g / L; more preferably 0.5 g / L.

[0015] Furthermore, the closed-cell perlite undergoes pretreatment, specifically by crushing it and passing it through a 150-mesh sieve and a 250-mesh sieve in sequence to obtain closed-cell perlite particles between 150 and 250 mesh.

[0016] Furthermore, the nitrite-oxidizing bacteria include nitrifying bacteria of the genus Nitrobacter and / or nitrifying bacteria of the genus Nitrospira.

[0017] Furthermore, the nitrite-oxidizing bacteria include Nitrobacter sp. N1 and / or Nitrospirasp. Z02, etc.

[0018] A method for promoting the growth of nitrite-oxidizing bacteria includes the following steps: adding cationic polyacrylamide and / or closed-cell perlite to a nitrite-oxidizing bacteria culture system to accelerate the growth rate of nitrite-oxidizing bacteria, shorten the production cycle, and increase the culture density of nitrite-oxidizing bacteria.

[0019] In the above method, the final concentration of the cationic polyacrylamide is 0.05–0.1 g / L; preferably 0.1 g / L.

[0020] In the above method, the final concentration of the closed-cell perlite is 0.5–1.5 g / L; preferably 0.5–1.0 g / L; more preferably 0.5 g / L.

[0021] In the above method, the nitrite-oxidizing bacteria include nitrifying bacteria of the genus Nitrobractus and / or nitrifying bacteria of the genus Nitrospira; preferably, the nitrite-oxidizing bacteria include Nitrobractus sp. N1 and / or Nitrospira sp. Z02.

[0022] The above method includes a shaking and mixing step after adding cationic polyacrylamide and closed-cell perlite to the nitrite-oxidizing bacteria culture system.

[0023] Preferably, the oscillation mixing conditions are 30±2℃ and 150~200 rpm for 1~2 h; more preferably, 30℃ and 150 rpm for 1 h.

[0024] A carrier additive for increasing the growth rate of nitrite-oxidizing bacteria includes cationic polyacrylamide and closed-cell perlite.

[0025] Preferably, the final concentration of the cationic polyacrylamide is 0.05–0.1 g / L; more preferably, it is 0.1 g / L.

[0026] Preferably, the final concentration of the closed-cell perlite is 0.5–1.5 g / L; more preferably, it is 0.5–1.0 g / L; and even more preferably, it is 0.5 g / L.

[0027] The present invention has the following advantages and effects compared with the prior art:

[0028] (1) Simple operation and low preparation cost: Only two materials are needed to prepare the culture medium, and according to market prices, the average cost of additive materials per liter of culture medium is only RMB 0.01 to RMB 0.06 / kg.

[0029] (2) The method of this invention can provide an adsorption medium for bacterial growth, accelerating the growth rate of nitrite-oxidizing bacteria: Under the condition of using cationic polyacrylamide and closed-cell perlite as culture medium additives, the growth rate of nitrite-oxidizing bacteria is significantly faster than that under the original culture medium conditions. The time for Nitrobacter sp. N1 nitrifying bacteria to completely consume the same concentration of substrate was shortened from 8 days to 4 days, and the rate increased to more than 200% of the original; the time for Nitrospira sp. Z02 nitrifying bacteria to completely consume the same concentration of substrate was shortened from 12 days to 9 days, and the rate increased to more than 130% of the original. This result can indirectly prove that the growth and reproduction of bacteria are accelerated.

[0030] (3) The method of the present invention can theoretically reduce costs and increase efficiency: on the one hand, the culture time is shortened, and on the other hand, due to the low density of closed-cell perlite, the bacteria are adsorbed on its pores and easily dispersed with the flow of liquid in the culture medium, which averages the cell density per unit volume in the culture medium, thereby reducing the competitive pressure between bacteria, increasing the culture density and the amount of bacteria obtained in the system, and significantly reducing the production cost compared with the previous large-scale aeration and stirring culture method. Attached Figure Description

[0031] Figure 1 The nitrification rate of Nitrobacter sp. N1 is given by the following conditions: CPAM concentrations of 0 g / L-0 g / L (Control), 0 g / L-1 g / L (CCEP), 0.05 g / L-0 g / L (CPAM), and 0.05 g / L-1 g / L (Composite).

[0032] Figure 2 The nitrification rate of Nitrospira sp. Z02 is given by the following conditions: CPAM concentrations of 0 g / L-0 g / L (Control), 0 g / L-1 g / L (CCEP), 0.05 g / L-0 g / L (CPAM), and 0.05 g / L-1 g / L (Composite).

[0033] Figure 3The nitrification rate of Nitrobacter sp. N1 was determined under orthogonal experimental conditions with CPAM concentrations of 0.01 g / L, 0.05 g / L, and 0.1 g / L, and CCEP concentrations of 0.5 g / L, 1.0 g / L, and 1.5 g / L.

[0034] Figure 4 The nitrification rate of Nitrospira sp. Z02 was determined under orthogonal experimental conditions with CPAM concentrations of 0.01 g / L, 0.05 g / L, and 0.1 g / L, and CCEP concentrations of 0.5 g / L, 1.0 g / L, and 1.5 g / L.

[0035] Figure 5 This is a comparison of nitrate production in Nitrobacter sp. N1 at the optimal CPAM and CCEP ratio (0.1 g / L-0.5 g / L) with that in the untreated control group.

[0036] Figure 6 This is a comparison of nitrate production in Nitrospira sp. Z02 at the optimal CPAM and CCEP ratio (0.1 g / L-1.5 g / L) with that in the untreated control group.

[0037] Figure 7 The nitrification rate of Nitrosomonas sp. SCUT-1 is given by the following conditions: CPAM and CCEP concentrations of 0 g / L-0 g / L (Control), 0 g / L-1 g / L (CCEP), 0.05 g / L-0 g / L (CPAM), and 0.05 g / L-1 g / L (Composite).

[0038] Figure 8 The comparison shows the nitrite production of Nitrosomonas sp. SCUT-1 under the conditions of CPAM and CCEP concentrations of 0 g / L-0 g / L (Control), 0 g / L-1 g / L (CCEP), 0.05 g / L-0 g / L (CPAM), and 0.05 g / L-1 g / L (Composite). Detailed Implementation

[0039] The present invention will be further described in detail below with reference to embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto. Test methods in the following embodiments that do not specify specific experimental conditions are generally performed under conventional experimental conditions or according to the manufacturer's recommended experimental conditions. Unless otherwise specified, the materials and reagents used are commercially available.

[0040] The strains used in the examples are as follows:

[0041] Nitrobacter sp. N1 in the literature "Yu, Chenchen & Zheng, Yuyi & Lin, Weitie &Luo, Jianfei. (2025). Nitrifier released extracellular organics: Characterization and their ecological role in synergy with heterotrophs. Biochemical Engineering Journal. 227. 110046. 10.1016 / j.bej.2025.110046."

[0042] Nitrospira sp. Z02 is disclosed in the literature “CN120424837B, A Nitrospira Nitrite-oxidizing bacterium and its application”.

[0043] Nitrosomonas sp. SCUT-1 in the literature "Wu, Jiajie & Zhan, Manjun & Yuan, Lingling & Zhu, Yueyue & Lin, Weitie & Luo, Jianfei. (2024). Sealing solidagar in serum bottles for rapid isolation and long-term preservation ofchemoautotrophic ammonia-oxidizing bacteria. Water Research. 260. 121916.10.1016 / j.watres.2024.121916."

[0044] The materials used in the examples are as follows:

[0045] 1. Preparation of the carrier

[0046] 1.1. Material Preparation:

[0047] Cationic polyacrylamide (CPAM) solution: Weigh 0.05 g of cationic polyacrylamide particles with a molecular weight of approximately 9 million (range 8-10 million), dissolve in 50 mL of deionized water, shake until completely dissolved, and prepare a CPAM stock solution with a concentration of 1 g / L. Store at room temperature away from light for later use.

[0048] Closed-cell perlite: Crush closed-cell perlite and pass it through a 150-mesh sieve and a 250-mesh sieve in sequence to obtain closed-cell perlite particles with a mesh size between 150 and 250.

[0049] Culture medium base solution: Prepare inorganic salt culture medium base solution according to Table 1 and Table 2, and adjust pH to 7.5±0.2.

[0050] Table 1. Culture medium formulation components

[0051]

[0052] *The formula for the trace element mother liquor is shown in Table 2:

[0053] Table 2. Composition of trace element mother liquor

[0054]

[0055] 1.2. Carrier preparation:

[0056] Take 150mL sterile Erlenmeyer flasks and divide them into 4 groups: Control, CCEP, CPAM and Composite (Table 3). Add 50mL of the above inorganic salt culture medium solution.

[0057] Add closed-cell perlite: Add pretreated closed-cell perlite (i.e., closed-cell perlite particles) to the CCEP and Composite group bottles respectively, so that the final concentration in the culture medium is 1 g / L.

[0058] Add CPAM: Add the prepared CPAM stock solution to the CPAM and Composite group bottles respectively, so that the final concentration in the culture medium is 0.05 g / L.

[0059] Mixing to form a carrier: Place the Erlenmeyer flask in a constant-temperature shaker and mix for 1 hour at 30°C and 150 rpm. During this time, CPAM fully expands in the solution and combines with closed-cell perlite particles through electrostatic adsorption, bridging, and other effects, forming a uniformly dispersed suspended composite carrier in the liquid.

[0060] Table 3. Carrier content in each experimental group

[0061]

[0062] Example 1: Cultivation of nitrifying bacteria (Nitrobacter sp. N1) on a composite carrier

[0063] First, culture the nitrifying bacteria (Nitrobacter sp. N1) that are already present in the laboratory.

[0064] Complete culture medium preparation: Add NaNO2 solution as substrate and nitrogen source to the four groups of culture media prepared in 1.2 above. The initial concentration of NaNO2 is 15 mM.

[0065] Inoculation and culture: Nitrobacter sp. N1 bacterial suspension in the logarithmic growth phase was inoculated into the prepared complete culture medium at an inoculation rate of 0.2% (v / v) (i.e., 100 μL of bacterial suspension was inoculated into 50 mL of culture medium).

[0066] After inoculation, the Erlenmeyer flasks were placed in a constant temperature shaker at 30℃ and 150 rpm for shaking culture.

[0067] Growth monitoring: Samples were taken every 24 hours, and nitrite (NO2) was detected and monitored using a UV-Vis spectrophotometer with a colorimetric method. - ) and nitrate (NO3) - The content of substrate and product is monitored to track the consumption and generation of substrate and product, and the growth and metabolic activity of the cells are indirectly reflected by the substrate consumption rate and product generation rate.

[0068] result( Figure 1 As shown in Table 4, compared with the Control group, the nitrification rates of both groups with added CCEP and CPAM were significantly improved, P(CCEP-Control) < 0.001, P(CPAM-Control) < 0.001. Among them, the CPAM group added alone was faster than the CCEP group added alone. The Composite experimental group containing the composite carrier showed the most significant improvement compared with the Control group, and the nitrification rate was not much different from that of the CPAM group added alone. However, after the difference analysis, a significant difference was still found between the two, P(Composite-CPAM) < 0.01.

[0069] Table 4. Analysis of differences between Nitrobacter sp. N1 groups

[0070]

[0071] As can be seen, the addition of the carrier additive can significantly shorten the lag time of Nitrobacter sp. N1 and significantly accelerate the rate of nitrite consumption and nitrate formation.

[0072] Example 2: Cultivation of nitrifying bacteria (Nitrospira sp. Z02) on a composite carrier

[0073] The operation steps in this embodiment are basically the same as those in embodiment 1, except for the following parameters:

[0074] Nitrogen source concentration: The initial concentration of NaNO2 was adjusted to 10 mM to meet the growth requirements of Nitrospira sp. Z02.

[0075] The cultivation and monitoring methods are the same as in Example 1.

[0076] result( Figure 2 Table 5 also shows that, compared with the Control group, the nitrification rates of both groups with added CCEP and CPAM were significantly improved, P(CCEP-Control) < 0.001, P(CPAM-Control) < 0.01. Unlike Nitrospira sp. N1, the Nitrospira sp. Z02 group with CCEP added alone was faster than the group with CPAM added alone. The Composite experimental group containing the composite carrier showed the most significant improvement compared with the Control group, P(Composite-Control) < 0.001. In addition, the Composite experimental group containing the composite carrier also showed a significant difference compared with the experimental group with CCEP added alone, P(Composite-CCEP) < 0.01.

[0077] Table 5. Analysis of differences between Nitrospira sp. Z02 groups

[0078]

[0079] As can be seen, the addition of carrier additives can significantly shorten the lag phase of Nitrospira sp. Z02, and its growth rate and metabolic activity are significantly better than those of the control group.

[0080] Example 3: Optimization Experiment of Nitrobacter sp. N1 Carrier Formulation

[0081] To illustrate the adjustability and range of the composite carrier formulation of this invention, the following optimization orthogonal experiments were conducted:

[0082] The concentrations of CPAM were 0.01 g / L, 0.05 g / L, and 0.1 g / L; the concentrations of CCEP were 0.5 g / L, 1.0 g / L, and 1.5 g / L; Nitrobacter sp. N1 was cultured according to the method in Example 1.

[0083] result( Figure 3The results showed that as the concentration of CPAM increased, the nitrite oxidation rate of each experimental group increased significantly. The three groups under the condition of 0.1 g / L CPAM were significantly better than the other experimental groups. The group with the fastest activity, 0.1 g / L CPAM + 0.5 g / L CCEP, had a nitrification rate of 4.0455 mM / d, which was 209.67% of the untreated control group's 1.9295 mM / d.

[0084] Example 4: Optimization experiment of Nitrospira sp. Z02 carrier formulation

[0085] Nitrospira sp. Z02 was cultured according to the same orthogonal ratio as in Example 3, following the method of Example 2.

[0086] result( Figure 4 This also shows that the three groups under the 0.1 g / L CPAM condition were significantly better than the other experimental groups. However, the group with the fastest Nitrospira sp. Z02 activity was 0.1 g / L CPAM + 1.5 g / L CCEP, with a nitrification rate of 1.061 mM / d, which is 136.03% higher than the untreated control group of 0.78 mM / d.

[0087] Example 5:

[0088] Nitrobacter sp. N1 was cultured using the fastest-active group from Example 3, 0.1 g / L CPAM + 0.5 g / L CCEP, as the optimal carrier group; nitrate (NO3) was determined according to the method in Example 1. - ) content, results as follows Figure 5 As shown, the optimal carrier group significantly shortened the time required to completely consume the same concentration of nitrite, significantly accelerating the growth rate of Nitrobacter sp. N1; the nitrite oxidation rate significantly increased to 209.67%, indicating that the addition of CPAM and CCEP significantly enhanced the activity of Nitrobacter sp. N1.

[0089] Nitrospira sp. Z02 was cultured using the fastest-active group from Example 4, 0.1 g / L CPAM + 1.5 g / L CCEP, as the optimal carrier group; nitrate (NO3) was determined according to the method in Example 1. - ) content, results as follows Figure 6 As shown, the optimal carrier group significantly shortened the time required to completely consume the same concentration of nitrite, significantly accelerating the growth rate of Nitrospira sp. Z02; the nitrite oxidation rate significantly increased to 136.03%, indicating that the addition of CPAM and CCEP significantly enhanced the activity of Nitrospira sp. Z02.

[0090] Nitrification activity and cell count are strongly positively correlated. Based on this, we can conclude that the introduction of carrier additives can not only increase the nitrification rate of cells, but also promote cell proliferation and increase the number of NOB cells obtained at a fixed substrate consumption and time.

[0091] Example 6: Feasibility verification of this vector for Nitrosomonas sp. SCUT-1 nitrite-oxidizing bacteria strain

[0092] The operation steps in this embodiment are basically the same as those in embodiment 1, except for the following parameters:

[0093] Nitrogen source replacement and concentration change: The nitrogen source was replaced with NH4Cl, and the initial concentration was adjusted to 3mM to meet the growth requirements of Nitrosomonas sp. SCUT-1.

[0094] The cultivation and monitoring methods are basically the same as in Example 1, but NO3 is not measured. - Increase the substrate NH4 + During the detection, the pH was controlled and adjusted to around 7.5, and the growth and metabolic activity of the bacteria were indirectly reflected by the substrate consumption rate and the product formation rate.

[0095] result( Figure 7 and Figure 8 The results showed that, compared with the control group, the two groups with added 0.05 g / L CPAM almost lost their nitrification activity, while the experimental group with added CCEP alone had similar activity to the control group. After difference analysis, there was no significant difference between the two groups (p = 0.0733 > 0.05), indicating that the nitrification activity was not promoted.

[0096] In summary, in the Nitrobractoria sp. N1 orthogonal experimental group, the difference in CCEP between 0.5 g / L and 1 g / L under 0.1 g / L CPAM conditions was small, while the 0.5 g / L and 1 g / L groups were faster than the 1.5 g / L group. However, in the Nitrospira sp. Z02 orthogonal experimental group, the difference in CCEP between 0.5 g / L and 1 g / L under 0.1 g / L CPAM conditions was small, but unlike Nitrobractoria sp. N1, the 0.5 g / L and 1 g / L groups were slightly slower than the 1.5 g / L group. Considering cost factors, 0.5 g / L CCEP is less expensive; therefore, 0.1 g / L CPAM + 0.5 g / L CCEP is the better choice when comprehensively cultivating multiple NOB nitrifying bacteria.

[0097] In summary, the recommended formulation range for the composite carrier in this invention is: CCEP: 0.5–1.5 g / L, CPAM: 0.05–0.1 g / L. The optimal formulation is: CCEP: 0.5 g / L, CPAM: 0.1 g / L.

[0098] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. Use of cationic polyacrylamide and closed cell perlite in combination to promote growth of and / or increase culture density of nitrite oxidizing bacteria, characterized in that: Cationic polyacrylamide and closed-cell perlite were added together to the culture medium of nitrite-oxidizing bacteria and mixed by shaking. The final concentration of the cationic polyacrylamide in the nitrite-oxidizing bacteria culture medium is 0.05–0.1 g / L; The final concentration of the closed-cell perlite in the nitrite-oxidizing bacteria culture medium was 0.5–1.5 g / L; The cationic polyacrylamide has a molecular weight of 8 million to 10 million. The closed-cell perlite is pretreated by crushing it and passing it through a 150-mesh sieve and a 250-mesh sieve in sequence to obtain closed-cell perlite particles between 150 and 250 mesh. The nitrite-oxidizing bacteria are Nitrobacter sp. N1 and / or Nitrospira sp. Z02.

2. The application of cationic polyacrylamide in promoting the growth of nitrite-oxidizing bacteria and / or increasing the culture density of nitrite-oxidizing bacteria, characterized in that: Cationic polyacrylamide was added to the culture medium of nitrite-oxidizing bacteria; The final concentration of the cationic polyacrylamide in the nitrite-oxidizing bacteria culture medium is 0.05–0.1 g / L; The cationic polyacrylamide has a molecular weight of 8 million to 10 million. The nitrite-oxidizing bacteria are Nitrobacter sp. N1 and / or Nitrospira sp. Z02.

3. A method for promoting the growth of nitrite-oxidizing bacteria, characterized in that, The steps include: adding cationic polyacrylamide and closed-cell perlite together to the culture medium for nitrite-oxidizing bacteria, shaking and mixing, in order to accelerate the growth rate of nitrite-oxidizing bacteria, shorten the production cycle, and increase the culture density of nitrite-oxidizing bacteria; The final concentration of the cationic polyacrylamide in the nitrite-oxidizing bacteria culture medium is 0.05–0.1 g / L; The final concentration of the closed-cell perlite in the nitrite-oxidizing bacteria culture medium was 0.5–1.5 g / L; The cationic polyacrylamide has a molecular weight of 8 million to 10 million. The closed-cell perlite is pretreated by crushing it and passing it through a 150-mesh sieve and a 250-mesh sieve in sequence to obtain closed-cell perlite particles between 150 and 250 mesh. The nitrite-oxidizing bacteria are Nitrobacter sp. N1 and / or Nitrospira sp. Z02.

4. The method according to claim 3, characterized in that: The conditions for the oscillation mixing are 30±2℃ and 150~200 rpm for 1~2 h.

5. The method according to claim 4, characterized in that: The conditions for the oscillation mixing were 30°C and 150 rpm for 1 hour.

6. A method for promoting the growth of nitrite-oxidizing bacteria, characterized in that, The steps include: adding cationic polyacrylamide to the culture medium for nitrite-oxidizing bacteria to accelerate the growth rate of nitrite-oxidizing bacteria, shorten the production cycle, and increase the culture density of nitrite-oxidizing bacteria; The final concentration of the cationic polyacrylamide in the nitrite-oxidizing bacteria culture medium is 0.05–0.1 g / L; The cationic polyacrylamide has a molecular weight of 8 million to 10 million. The nitrite-oxidizing bacteria are Nitrobacter sp. N1 and / or Nitrospira sp. Z02.

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