Fresh water and saline-alkali water dual-adaptive multifunctional water quality regulation and control strain and application thereof

Abstract

The invention discloses a fresh water and saline-alkali water dual-adaptive multifunctional water quality regulation and control strain and application thereof, and belongs to the technical field of aquaculture. The problems that existing commercially available microbial water quality regulation and control products are narrow in adaptability, single in function, not remarkable in water quality collaborative optimization effect and the like are solved. The sewage treatment agent has the functions of alkali resistance, organic acid production, flocculation and ammonia nitrogen removal. The strain is preserved in the China Center for Type Culture Collection (CCTCC), the preservation number is CCTCC NO: M 20252030, and the strain is (Metabacillus hrfinensis) mfcN25. The invention also discloses a preparation method of the strain. The application method comprises the following steps: preparing a zymophyte solution of the strain, and combining with a carbon source to apply in a common fresh water or saline-alkali water culture pond. The multifunctional water quality regulation and control strain is screened from alkali-resistant bacteria in northeast carbonate type saline-alkali water areas and is preserved. The strain can effectively reduce the ammonia nitrogen concentration of a water body in a saline-alkali aquaculture pond, reduce the pH value of the water body and realize effective regulation and control of water quality in a saline-alkali aquaculture process. The strain provided by the invention is suitable for pH regulation, water purification and ammonia nitrogen removal of common fresh water or saline-alkali water culture water.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of aquaculture, and particularly relates to a freshwater and saline-alkali water dual-adapted multifunctional water quality regulation strain and an application method thereof. BACKGROUND

[0002] A healthy and stable water environment plays a crucial role in the healthy growth and yield improvement of farmed animals. In recent years, with the continuous expansion of saline-alkali fishery, the inherent characteristics of saline-alkali water quality combined with the intensive farming mode have caused a series of complex water environmental problems, which have seriously hindered the sustainable development of saline-alkali water aquaculture.

[0003] Saline-alkali water bodies generally have characteristics such as high pH value (> 9.0) and high alkalinity. The high pH value and high carbonate alkalinity of the water body can cause damage to the gills of fish, interfere with the ion regulation and osmotic pressure balance of animals, destroy the acid-base balance and respiratory function in the body, and inhibit the digestive capacity and food intake of farmed animals, thereby directly leading to physiological dysfunction, decreased immunity, slow growth, and even death of aquatic animals. In addition, the high pH value of saline-alkali aquaculture water bodies can also enhance the toxicity of ammonia nitrogen: ammonia nitrogen exists in water bodies in the form of ionic ammonia (NH4 + -N) and non-ionic ammonia (NH3), of which non-ionic ammonia (NH3) has a toxic effect on farmed animals. According to the chemical equilibrium reaction of NH3·H2O NH4 + +OH - , high pH value will promote the reaction to move towards non-ionic ammonia, resulting in a higher proportion of non-ionic ammonia in ammonia nitrogen of the same concentration, thereby producing higher toxicity.

[0004] In order to cope with these water environmental problems, water quality regulation technology for aquaculture water bodies (including chemical, physical and microbial methods) has become an effective solution. Among these methods, the microbial method has become the most important method for water quality regulation due to its safety, environmental protection, low cost, and simple operation. Through the action of functional microorganisms, water quality regulation effects such as ammonia nitrogen reduction, pH reduction, and alkalinity reduction can be achieved.

[0005] However, the current market microbial water quality regulation products that meet national regulations have some defects, such as narrow adaptability (only suitable for freshwater or low salinity water), single function (lack of simultaneous ammonia reduction, pH adjustment, and flocculation ability), etc. The existing products are difficult to adapt to different acid-base environments; when facing complex water quality problems, it is usually necessary to add different microbial preparations with single function several times to regulate water quality, which not only increases the cost of aquaculture, but also complicates the operation, and the synergistic optimization effect of water quality is not significant. Therefore, for freshwater and saline-alkali water aquaculture environment, developing a wide-adapted multifunctional strain with salt-tolerant, pH-lowering, ammonia-nitrogen-lowering, and flocculation functions has important practical significance for breaking the limitations of water quality regulation application scenarios, achieving synergistic improvement of complex water quality problems, simplifying aquaculture management, reducing costs, and improving water quality regulation efficiency, and meets the development needs of green ecological aquaculture. SUMMARY

[0006] The purpose of the present application is to solve the problems of the existing commercially available microbial water quality regulation products, which are mainly aimed at freshwater aquaculture environment, have single function, and have complex application technology and poor effect for complex water quality problems, and to provide a dual-adapted multifunctional water quality regulation strain for freshwater and saline-alkali water and its application method.

[0007] The dual-adapted multifunctional water quality regulation strain for freshwater and saline-alkali water according to the present application is (Metabacillus hrfriensis) mfcN25, which is preserved in the China Center for Type Culture Collection, with the preservation number CCTCC NO: M 20252030, the preservation time being September 15, 2025, and the preservation address being Wuhan University, Wuhan, China.

[0008] The dual-adapted multifunctional water quality regulation strain for freshwater and saline-alkali water according to the present application is used to prepare a bacterial agent with one or more of alkali tolerance, flocculation, organic acid production, and ammonia nitrogen removal.

[0009] Further, the organic acid production is under the condition of pH 7.0-9.0.

[0010] Further, the bacterial agent is used for water quality improvement of ordinary freshwater or saline-alkali water aquaculture water bodies.

[0011] Further, the water quality improvement is to reduce the ammonia nitrogen and pH of the water body.

[0012] Further, the use process of the bacterial agent is as follows:

[0013] I. Inoculate the strain (Metabacillus hrfriensis) mfcN25 into LB medium, and ferment and culture until the final concentration of bacteria reaches 1×10 9 -10 10CFU / mL, fermentation broth was obtained;

[0014] II. According to the dosage of 300-400 mL / mu, it is splashed into the pond, and it is used with molasses to improve the water quality of freshwater or saline-alkali water aquaculture.

[0015] Further, the inoculation amount of the strain (Metabacillus hrfriensis) mfcN25 in step one is 2%.

[0016] Further, after the fermentation culture for 24 hours in step one, the fermentation broth is further transferred and amplified according to the above-mentioned steps, and the inoculation amount of the transfer and amplification is 5%.

[0017] Further, the culture medium for the fermentation culture in step one is: 10 g of tryptone, 5 g of yeast powder, 10 g of sodium chloride, pH is adjusted to 8.0, and sterile water is added to 1000 mL.

[0018] Further, the fermentation process in step one is: the pH of the fermentation broth is monitored during the fermentation, and the sterile NaOH solution is added every 6 hours to adjust the pH of the fermentation broth to 8.0.

[0019] Further, the splashing in step two is regular splashing every 10-15 days, and the splashing time is in the morning on sunny days; the oxygenation machine is started when splashing; the splashing mode is uniform splashing in the whole pond or splashing on the windward head of the pond.

[0020] The present application collects representative water and soil samples in the carbonate type saline-alkali water environment unique to the northeast region, and successfully isolates strains with alkali tolerance characteristics. In order to evaluate the alkali tolerance ability of these strains, the present application tests the reproductive ability of these strains in alkaline and neutral pH conditions, especially in pH=9.0 and pH=7.0 culture medium. In this process, the pH value change of the culture solution is also monitored synchronously to accurately determine the pH adjustment ability of each strain under different pH conditions.

[0021] In order to further clarify the metabolic characteristics of these functional strains in alkaline environment, the present application cultures the strains in pH=9.0 and pH=7.0 culture medium for 24 hours, and collects the fermented bacterial cells. By using non-targeted metabolomics monitoring analysis technology, the pH adjustment metabolites produced by the strains are clarified. In addition, the present application also evaluates the ammonia nitrogen removal ability of the strains by culturing the strains under pH=9.0 and pH=7.0 conditions and measuring the change of ammonia nitrogen content in the culture solution. At the same time, by observing the flocculation efficiency of the strain culture solution under these two pH conditions, the flocculation ability of the strain is comprehensively evaluated.

[0022] The present application has undergone a series of strict screening and identification work, and finally from a large number of alkali-tolerant strains distributed in carbonate saline-alkali water area in northeast China, a multifunctional water quality regulating strain (Metabacillus hrfriensis) mfcN25 is successfully identified. The strain not only has excellent alkali tolerance, but also can produce organic acid, has high flocculation effect and significant ammonia nitrogen reduction function, and shows stable functional effect under neutral and alkaline pH conditions. The strain has been officially preserved in China Center for Type Culture Collection on September 15, 2025, and obtained the preservation number: CCTCC NO: M20252030.

[0023] The present application further prepares the (Metabacillus hrfriensis) mfcN25 strain by fermentation, and makes high-efficiency fermentation broth. Combined with suitable carbon source, the fermentation broth is applied in actual breeding ponds to improve water quality and breeding environment by biological means, and provides new technical support for the sustainable development of aquaculture industry.

[0024] The strain of the present application can effectively reduce ammonia nitrogen in freshwater and saline-alkali water breeding pond water, reduce water pH, and realize effective regulation of water quality in the breeding process.

[0025] The strain (Metabacillus hrfriensis) mfcN25 in the present application is suitable for water quality purification, ammonia nitrogen removal and pH regulation of freshwater and saline-alkali breeding water. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is the column chart of the strain biomass in the present application;

[0027] Figure 2 is the curve graph of pH change over time in the present application;

[0028] Figure 3 is the graph of strain metabolites in the present application; figure A is a scatter plot of strain metabolomics analysis model evaluation, and figure B is a pie chart of different pH conditions of strain differential metabolites classification;

[0029] Figure 4 is the column chart of ammonia nitrogen removal rate in the present application;

[0030] Figure 5 is the column chart of flocculation rate in the present application;

[0031] Figure 6 is the phylogenetic tree spectrum graph of a strain of freshwater and saline-alkali water double-adaptive multifunctional water quality regulating strain in the present application;

[0032] Figure 7A flow chart for application of a freshwater and saline water dual-type multifunctional water quality regulation strain in saline aquaculture water in the present application;

[0033] Figure 8 A curve graph of pH time change of saline aquaculture water in the present application;

[0034] Figure 9 A curve graph of ammonia nitrogen concentration change of saline aquaculture water in the present application. DETAILED DESCRIPTION

[0035] To make the purpose, technical scheme and advantages of the embodiments of the present application more clear and explicit, the spirit of the present application will be described in detail below, and any person skilled in the art can make changes and modifications to the technology taught by the present application without departing from the spirit and scope of the present application after understanding the embodiments of the present application.

[0036] The schematic embodiments of the present application and their descriptions are used to explain the present application, but not as a limitation of the present application.

[0037] EMBODIMENT

[0038] The freshwater and saline water dual-type multifunctional water quality regulation strain in the present embodiment has been preserved in China Typical Culture Collection Center, the preservation number is CCTCC NO: M 20252030, the preservation time is September 15, 2025, and the preservation address is Wuhan University, Wuhan, China, and it is (Metabacillus hrfriensis) mfcN25.

[0039] The freshwater and saline water dual-type multifunctional water quality regulation strain is evaluated and identified as follows:

[0040] 1. Alkali tolerance evaluation:

[0041] (1) Culture medium

[0042] Activated culture medium: 10 g of tryptone, 5 g of yeast powder, 10 g of sodium chloride, pH 7.0 adjusted by sodium hydroxide, and 1000 mL of sterile water;

[0043] Alkali tolerance evaluation medium: 10 g of tryptone, 5 g of yeast powder, 10 g of sodium chloride, pH 9.0, pH 9.5, pH 10.0, pH 10.5, and pH 11.0 adjusted by sodium hydroxide, and 1000 mL of sterile water.

[0044] (2) Implementation steps

[0045] After overnight culture in activation medium, the strain was inoculated at a 1% inoculum into alkali tolerance evaluation media at pH 9.0, pH 9.5, pH 10.0, pH 10.5, and pH 11.0, respectively. After 24 h of incubation at 37℃ and shaking at 150 rpm / min, the OD was measured using a spectrophotometer. 600 nm Absorbance.

[0046] The results are as follows Figure 1 As shown, in pH 7.0 medium, the OD of strain mfcN25 600 nm The absorbance was 1.283 ± 0.044, and the OD at pH 9.0 was... 600 nm The absorbance was 1.823 ± 0.018. In a culture medium with pH 9.5–11.0, the OD… 600 nm The absorbance values ​​were all <0.3. The results indicate that the strain can reproduce well under both neutral and alkaline conditions, and its upper limit of pH tolerance is pH 9.0.

[0047] 2. Evaluation of pH regulation capability

[0048] (1) Culture medium

[0049] Activation medium: Same as 1;

[0050] pH regulation capacity evaluation medium: 10 g tryptone, 5 g yeast extract, 10 g sodium chloride, add sodium hydroxide to adjust pH to 7.0 or 9.0, add sterile water to make up to 1000 mL.

[0051] (2) Implementation steps

[0052] The strain was activated and cultured overnight in medium. It was then inoculated at a rate of 1% into mediums with pH 7.0 and pH 9.0, respectively, and cultured at 37°C with shaking at 150 rpm / min. The pH value of the culture was measured every 4 hours until the culture was completed after 24 hours.

[0053] The results are as follows Figure 2 As shown, in a culture medium with an initial pH of 7.0, mfcN25 lowered the pH to 5.243 ± 0.045 within 12 h, and then the pH remained stable; in a culture medium with an initial pH of 9.0, mfcN25 culture lowered the pH to 8.047 ± 0.013 within 24 h. These results suggest that the strain may regulate pH by secreting acidic substances.

[0054] 3. Determination of organic acid secretion by the strain

[0055] (1) Implementation steps

[0056] The strain was activated and cultured overnight in medium, then inoculated at a 1% inoculum into media at pH 7.0 and pH 9.0, respectively, and cultured at 37°C with shaking at 150 rpm / min for 24 h. The freshly cultured bacterial suspension was centrifuged at 8,000 rpm at 4°C for 15 min, the supernatant was discarded, and the suspension was washed once with sterile water. The bacterial pellet was then sent to Shanghai Paiseno Biotechnology Co., Ltd., where its metabolites were analyzed using non-targeted metabolomics high-throughput sequencing technology.

[0057] A total of 1128 differentially expressed metabolites were detected using liquid chromatography / mass spectrometry. Multivariate statistical analysis was performed using the OPLS-DA model. The OPLS-DA score plot showed a clear separation between the pH 7.0 and pH 9.0 groups, with each group's samples exhibiting tight aggregation (…). Figure 3 A), Model Evaluation R 2 Y=0.995, Q 2 =0.974, indicating a significant difference between the two groups of metabolites, and demonstrating the reliability of the metabolomics analysis model with good stability, repeatability, and dependability. All identified metabolites were classified and statistically analyzed according to their chemical classification information, with "organic acids and derivatives" accounting for the highest proportion, reaching 28.9%. Figure 3 B). Metabolites showing significant differences were screened using OPLS-DA VIP>1 and P value<0.05, and the differentially metabolites in the "organic acids and derivatives" category are listed in Table 1. The results showed significant differences in various metabolites in the "organic acids and derivatives" category between the pH 9.0 and pH 7.0 experimental combinations. The main differentially metabolites included amino acids, short peptides, and organic acids, with the pH 7.0 combination showing a richer variety of short peptides and organic acids. These results indicate that the mfcN25 strain synthesizes different types of organic acids under pH 7.0 and pH 9.0 conditions to achieve pH regulation.

[0058] Table 1 Differential metabolites of organic acids in mfcN25 strain

[0059]

[0060] Table 1 (Continued) shows the differential organic acid metabolites of mfcN25 strain.

[0061]

[0062] 4. Evaluation of ammonia nitrogen removal capacity

[0063] Activation medium: Same as activation medium in section 1

[0064] Ammonia nitrogen removal detection medium: glucose 5.0 g, sodium chloride 1.0 g, potassium phosphate dibasic 0.5 g, magnesium sulfate heptahydrate 0.25 g, ammonium sulfate added at a required concentration, sodium hydroxide added as required to adjust pH (7.0, 8.0, 9.0), and sterile water added to 1000 mL;

[0065] Inoculate the test strain at an inoculation amount of 1% in fresh medium, and cultivate at 37°C with shaking at 150 rpm to activate overnight. Centrifuge the activated fresh bacterial liquid at 12,000 rpm at 4°C for 10 min, discard the supernatant, wash once with sterile water, and resuspend in an equal amount of sterile water. Inoculate the prepared bacterial suspension into the ammonia nitrogen removal detection medium at an inoculation amount of 1%, and cultivate at 37°C with shaking at 150 rpm for 24 h. Centrifuge the culture liquid at 12,000 rpm at 4°C for 10 min, and measure the ammonia nitrogen concentration of the supernatant. Calculate the ammonia nitrogen degradation rate according to the following formula:

[0066] Ammonia nitrogen degradation rate = 1 - ammonia nitrogen residual concentration / ammonia nitrogen initial concentration x 100%.

[0067] The results are shown in Table 1. Figure 4 As shown in Table 1, the ammonia nitrogen degradation rate of strain mfcN25 was 64.56±0.56% at an initial pH of 7.0, the ammonia nitrogen removal rate was 56.13±0.83% at an initial pH of 8.0, and the ammonia nitrogen removal rate was 58.33±1.57% at an initial pH of 9.0. The results show that the strain has a relatively stable ammonia nitrogen removal rate under neutral and alkaline conditions.

[0068] 5. Evaluation of flocculation ability

[0069] (1) Medium and buffer

[0070] Activated medium: same as the activated medium in 1.

[0071] Kaolin suspension: 0.2 g of kaolin, 500 μl of 1% CaCl2, and 50 mL of 0.1 mol / l Tris-HCl were mixed to prepare kaolin suspension at different pH (pH 7.0, pH 8.0, pH 9.0), and the pH value was rechecked to ensure that the pH was unchanged.

[0072] (2) Implementation steps

[0073] Determine the flocculation effect of the culture liquid using kaolin suspension: take 1 mL of the activated bacterial liquid and add it to the kaolin suspension at the corresponding pH, and stir it with a vortex mixer at 120 rpm / min for 1 min, then at 60 rpm / min for 1 min, and let it stand for 5 min. Take the liquid 1 cm below the surface of the kaolin suspension, and measure the OD 550 nmAbsorbance. Add 1 mL of sterile water to the kaolin suspension and repeat the above steps to measure the OD. 550 nm Absorbance was used as a blank control. All measurements were performed in triplicate. The flocculation rate was calculated using the following formula:

[0074] Flocculation rate = (OD) 550 nm Sterile water - OD 550 nm Bacterial solution / OD 550 nm 100% sterile water.

[0075] The results are as follows Figure 5 As shown, the flocculation rate of strain mfcN25 was 64.33±0.71% in kaolin suspension at pH 7.0, 68.67±0.57% in kaolin suspension at pH 8.0, and 70.44±0.46% in kaolin suspension at pH 9.0. The results indicate that the strain is effective in flocculation under neutral to alkaline pH conditions, and the flocculation activity exhibits a significant pH dependence.

[0076] 6. Strain screening and identification:

[0077] The overnight activated pure culture bacterial suspension was sent to the Beijing BGI Research Institute for bacterial identification, and phenotypic characteristics such as colony morphology, color, and microscopic morphology were recorded.

[0078] Morphological characteristics of the strain: rod-shaped cells with spores; morphological characteristics of the colony: pale yellow, round colonies with raised edges and regular margins.

[0079] Physicochemical properties of the strain: aerobic bacteria, Gram-positive, grows well at 37 ℃, and has an alkali tolerance limit of pH 9.0 in LB medium.

[0080] Strain identification:

[0081] (1) The 16S rRNA gene of the strain was amplified by polymerase chain reaction (PCR). The 16S sequence of the target strain was amplified using the universal primers 27F (5'-AGAGTTTGATCCTGGCTCAG-3') and 1492R (5'-GGTTACCTTGTTACGACTT-3'). The PCR products were sequenced by the Beijing BGI Research Institute (see SEQ ID No: 3). The sequences were compared with those available in the NCBI database using the BLAST program.

[0082] (2) PCR reaction system: 1 μL template bacterial culture, 12.5 μL Taq enzyme mixture, 1 μL primer 27F, 1 μL primer 1492R, add sterile deionized water to 25 μL;

[0083] PCR amplification conditions: 95℃ pre-denaturation 1 min, 95℃ denaturation 30 s, 55℃ annealing 30 s, 72℃ extension 90 s, cycle 25 times, 72℃ extension 10 min.

[0084] After amplifying the 16S sequence of the target strain, sequencing analysis is performed for molecular identification; finally, based on the molecular biology means, the species level taxonomic information of the target strain is judged by comparing with the NCBI database.

[0085] The identification results show (see Figure 6 ): the 16S rRNA sequence GenBank registration number is PX205061, and the similarity with Metabacillus hrfriensis CT-WN-B3 sequence reaches 100%, and the closest genetic relationship; named as strain (Metabacillus hrfriensis) mfcN25.

[0086] Example 2

[0087] The application method of a strain of freshwater and saline-alkaline water cultivation double-adaptive multifunctional water quality regulation strain in this embodiment is as follows:

[0088] I. The strain (Metabacillus hrfriensis) mfcN25 is inoculated into the fermentation medium according to the inoculation amount of 2%, and is fermented at 37℃ with 150 rpm / min shaking. After 24 h, the fermentation broth is subjected to secondary transfer amplification (the inoculation amount of the transfer amplification is 5%), and the fermentation (the fermentation process: the pH of the fermentation broth is detected every 6 h, and the sterile sodium hydroxide solution is added to adjust the pH to 8.0) is carried out until the final concentration of bacteria reaches 1×10 9 -10 10 CFU / mL, and the fermentation bacterial solution is obtained.

[0089] The fermentation medium is 10 g of tryptone, 5 g of yeast powder, 10 g of sodium chloride, pH 8.0 adjusted by sodium hydroxide, and 1000 ml of sterile water.

[0090] II. When the cultivation process of the saline-alkaline water cultivation pond is carried out to the middle-late stage (such as the middle and late of June for northern river crab cultivation), the fermentation bacterial solution is regularly splashed into the pond at a dosage of 300 ml / acre every 14 days, and molasses is added at the same time, that is, the use of the freshwater and saline-alkaline water cultivation double-adaptive multifunctional water quality regulation strain is completed.

[0091] The splashing time into the pond is in the morning on sunny days; the splashing is carried out with the oxygenation machine turned on; the splashing mode is uniform splashing in the whole pond or splashing in the upper wind head of the pond.

[0092] Among them, the molasses addition amount A is kg; according to the formula A = H × S × (30 × C TAN-NCalculate using -19) / 1000, where H is the pond depth in meters (m) and S is the pond area in square meters (m²). 2 C TAN-N The initial total ammonia nitrogen concentration in the pond is expressed in mg / L.

[0093] The effectiveness of a dual-adaptive, multifunctional water quality regulating strain for aquaculture in both freshwater and saline-alkali water in this embodiment:

[0094] The fermentation solution obtained in step one above was used in saline-alkali water crab farming ponds in Zhaoyuan County, Daqing City, Heilongjiang Province. During the farming process, from mid to late June, ammonia nitrogen gradually accumulated in the water, and its concentration increased significantly. Figure 6 The fermentation broth of (Metabacillus hrfriensis) mfcN25 was used regularly starting on June 22nd, following the procedure described in Specific Implementation Method 2.

[0095] Meanwhile, a saline-alkali water crab farming pond with the same geographical location, similar size, and the same stocking density was selected as a control. Throughout the farming process, the experimental group only started using the (Metabacillus hrfriensis) mfcN25 fermented bacterial solution after June 22nd, while the control group used conventional commercially available animal health products as needed to improve the farming water quality from the start of farming on May 20th until August 1st, and then switched to using the (Metabacillus hrfriensis) mfcN25 fermented bacterial solution as needed after August 1st. Regular sampling was conducted from the mid-stage of farming (June 22nd) to monitor and compare the water quality indicators of the two groups of ponds (see...). Figure 7 ).

[0096] The results show (see) Figure 8 From June 22nd to August 1st, only the experimental group was treated with the fermentation solution of *Metabacillus hrfriensis* mfcN25. During this period, the ammonia nitrogen concentration in the experimental pond was significantly lower than that in the control group (p<0.05), and the pH of the experimental pond was significantly lower than that in the control group (p<0.05). From August 1st to August 20th, both the control and experimental groups were treated with the fermentation solution of *Metabacillus hrfriensis* mfcN25. During this period, the ammonia nitrogen concentration and pH of the control group decreased rapidly, showing no significant difference from those of the experimental group. The results indicate that the *Metabacillus hrfriensis* mfcN25 strain can effectively reduce the ammonia nitrogen concentration and pH of saline-alkali aquaculture ponds, achieving effective water quality control during saline-alkali aquaculture.

Claims

1. A dual-adaptive multifunctional water quality regulating bacterial strain for fresh water and saline-alkaline water, characterized in that, The strain is (Metabacillus hrfriensis) mfcN25, which is preserved in China Center for Type Culture Collection, the preservation number is CCTCC NO: M 20252030, the preservation time is September 15, 2025, and the preservation address is Wuhan University, Wuhan, China.

2. The application of the dual-adapted multifunctional water quality regulating bacterial strain for freshwater and saline-alkaline water according to claim 1, characterized in that, The strain is used for preparing a microbial agent capable of resisting alkali, flocculating, producing organic acid and removing ammonia nitrogen.

3. Use according to claim 2, characterized in that, The organic acid is produced under the condition of pH 7.0-9.

0.

4. Use according to claim 2, characterized in that, The microbial agent is used for improving the water quality of ordinary freshwater or saline-alkaline water aquaculture water bodies.

5. Use according to claim 4, characterized in that, The use process of the microbial agent is as follows: I. The strain (Metabacillus hrfriensis) mfcN25 is inoculated into LB medium, and fermented to a final concentration of 1 x 10 9 -10 10 CFU / mL, to obtain a fermentation bacterial solution; II. Sprinkle into the pond according to the dosage of 300-400 mL / acre, and use with molasses to complete the improvement of the water quality of freshwater or saline-alkaline water aquaculture water bodies.

6. Use according to claim 5, characterized in that, The inoculation amount of the strain (Metabacillus hrfriensis) mfcN25 in step one is 2%.

7. Use according to claim 5, characterized in that, After the fermentation culture for 24 h in step one, the fermentation broth is transferred and amplified according to the above steps again, and the inoculation amount of the transfer and amplification is 5%.

8. Use according to claim 5, characterized in that, The culture medium for the fermentation culture in step one is as follows: 10 g of tryptone, 5 g of yeast powder and 10 g of sodium chloride are adjusted to pH 8.0, and then sterilized water is added to 1000 mL.

9. Use according to claim 5, characterized in that, The fermentation process in step one is as follows: the pH of the fermentation broth is monitored during the fermentation, and the sterile NaOH solution is added every 6 h to adjust the pH of the fermentation broth to 8.

0.

10. Use according to claim 5, characterized in that, In step two, the sprinkling is regularly performed every 10-15 days, the sprinkling time is in the morning on sunny days, the oxygenation machine is started when sprinkling, and the sprinkling mode is full-pool uniform sprinkling or pond upwind sprinkling.

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