Cryogenic bacterium SD-C-1-7 and application thereof in rainbow trout culture

Abstract

The invention discloses a cryobacterium SD-C-1-7 and application thereof in rainbow trout culture, and belongs to the technical field of aquaculture water quality purification. The strain is classified and named as Pseudomonas sp., when the strain is in a low-temperature environment of 8-18 DEG C, the removal rate of ammonia nitrogen in a rainbow trout culture water body is larger than or equal to 87%, the removal rate of nitrite nitrogen is larger than or equal to 91%, the removal rate of total phosphorus is larger than or equal to 52%, and the preservation number is CCTCC NO: M20251642. The method has the core advantages that the low-temperature adaptability is high, and the problem of low low-temperature denitrification efficiency of traditional nitrifying bacteria is solved; the purification function is comprehensive, ammonia nitrogen, nitrite nitrogen and nitrate nitrogen can be synchronously removed, and total phosphorus can be synergistically reduced; the purification efficiency is stable, in a 60-day rainbow trout breeding test, ammonia nitrogen is stabilized to be 0.4 mg / L or below, nitrite nitrogen is lower than 0.2 mg / L, and the average removal rate of total nitrogen and the average removal rate of total phosphorus reach 29.86% and 39.45% respectively. Meanwhile, the invention provides a water quality purification fungicide containing the strain and a rainbow trout circulating water culture water quality purification method, the fungicide preparation process is mature, application is convenient, rainbow trout culture benefits are remarkably improved, and the requirements of green sustainable development are met.

Description

Technical Field

[0001] This invention relates to the field of aquaculture water purification technology, specifically to a low-temperature bacterium SD-C-1-7 and its application in rainbow trout farming, particularly suitable for the removal of water pollutants and the maintenance of stable water quality in rainbow trout recirculating aquaculture systems under low-temperature conditions. Background Technology

[0002] Rainbow trout (Oncorhynchus mykiss), a cold-water fish with high economic value, has an optimal growth temperature of 12-18℃. Recirculating aquaculture systems (RAS) have become the core model for efficient and intensive rainbow trout farming due to their ability to provide a stable water temperature and quality environment. However, during rainbow trout farming, fish excrement and uneaten feed continuously decompose, producing large amounts of ammonia nitrogen (…). ), nitrite nitrogen ( Toxic pollutants such as toxic pollutants can accumulate and lead to decreased immunity, stunted growth, and even death in rainbow trout, severely restricting aquaculture efficiency.

[0003] Traditional recirculating aquaculture systems (RAS) rely on the synergistic action of nitrifying and denitrifying bacteria for nitrogen removal. However, nitrifying bacteria (especially ammonia-oxidizing bacteria) are mostly autotrophic. In the low-temperature environment (<15℃) suitable for rainbow trout, their growth rate slows significantly and their metabolic activity decreases drastically, resulting in low nitrogen removal efficiency and an easy exceedance of toxic nitrogen compounds. To maintain water quality, the industry often needs to add heating devices to raise the water temperature, extend the hydraulic retention time, or frequently change the water. This not only increases energy consumption and operating costs but also increases the load on wastewater treatment, contradicting the trend of green and sustainable development in aquaculture. Therefore, developing a highly efficient and stable water purification microbial resource and related application technologies that are suitable for low-temperature environments has become a key requirement for solving the water quality problems in rainbow trout recirculating aquaculture. Summary of the Invention

[0004] To address the problems of low denitrification efficiency, difficulty in stabilizing water quality, and high farming costs associated with traditional nitrifying bacteria in existing technologies, this invention provides a low-temperature bacterium SD-C-1-7, along with a water purification agent containing this strain and its application method in rainbow trout farming, thereby achieving efficient purification and stable maintenance of rainbow trout farming water in low-temperature environments.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A low-temperature bacterium, SD-C-1-7, is classified and named *Pseudomonas sp.*, and is Gram-negative. Under low-temperature conditions of 8-18℃, this strain achieves extraction rates of ≥87% for ammonia nitrogen, ≥91% for nitrite nitrogen, and ≥52% for total phosphorus in rainbow trout aquaculture water. The accession number is CCTCC NO: M20251593, the accession date is July 21, 2025, and the accession location is the China Center for Type Culture Collection.

[0006] The preferred bacterial agent for water purification has the active ingredient being the low-temperature bacterium SD-C-1-7.

[0007] Preferably, the microbial agent is prepared by activation with a seed culture medium and high-density fermentation in a fermenter; the seed culture medium formula is: 4-6g glucose, 0.4-0.6g 0.4-0.6g 0.1-0.3g, 1-3mL of trace salt solution, 1-3mL of 1% yeast powder solution, 1-3mL of 1% peptone solution, 950-1050mL of distilled water, pH 7.0-7.2; wherein, the concentration of yeast powder solution is 45-55g / L and the concentration of peptone solution is 100g / L.

[0008] This invention also provides the application of the low-temperature bacterium SD-C-1-7 in the purification of aquatic aquaculture water.

[0009] Preferably, the aquaculture is rainbow trout farming, and the farming water temperature is 8-18℃.

[0010] Preferably, it is used to remove ammonia nitrogen from rainbow trout aquaculture water. ), nitrite nitrogen ( ), nitrate nitrogen ( ), total nitrogen (TN) and total phosphorus (TP).

[0011] Preferably, the low-temperature bacteria SD-C-1-7 is used by attaching a biofilm to a biological filter or by directly adding it to the aquaculture water.

[0012] The present invention also provides a method for purifying water quality in rainbow trout recirculating aquaculture, comprising the following steps: 1) inoculating the low-temperature bacteria SD-C-1-7 described in claim 1 into a seed culture medium and activating it at 14-17℃ and 150-170r / min for 48h to obtain a seed liquid; 2) Inoculate the seed culture solution into the seed culture medium of the fermenter at a volume fraction of 1%, and ferment at high density for 48 hours to obtain the inoculum; 3) Add the bacterial agent to the rainbow trout recirculating aquaculture system and maintain the water temperature at 8-18℃.

[0013] Preferably, in step 3), the amount of bacterial agent added is 0.15-0.25% (volume fraction) of the total volume of the aquaculture water, and it is added once every 7 days.

[0014] Preferably, the method achieves a maximum removal rate of ≥87% for ammonia nitrogen, ≥91% for nitrite nitrogen, and ≥52% for total phosphorus; and can keep the ammonia nitrogen concentration in the aquaculture water below 0.4 mg / L and the nitrite nitrogen concentration always below 0.2 mg / L.

[0015] The present invention provides the application of a low-temperature bacterium SD-C-1-7 in rainbow trout farming, which, compared with the prior art: The strains are clearly identified and easy to screen. The colony morphology of the low-temperature bacterium SD-C-1-7 has been clarified. It can be directly observed and screened through LB medium culture. The strains can be preliminarily identified without complex molecular identification, which reduces the difficulty of identification in the process of strain isolation and application and improves the efficiency of industrial application.

[0016] Strong adaptability to low temperatures and low energy consumption: This strain can metabolize efficiently within the range of 8-18℃ without the need for additional heating to raise the water temperature, which can reduce the energy consumption of rainbow trout recirculating aquaculture systems by more than 30%, and completely solve the core problem of low denitrification efficiency of traditional nitrifying bacteria at low temperatures.

[0017] Comprehensive purification function and stable water quality: Simultaneously removes three types of nitrogenous pollutants, namely ammonia nitrogen, nitrite nitrogen and nitrate nitrogen, and synergistically reduces total phosphorus content, avoiding water quality fluctuations caused by incomplete removal of a single pollutant; water quality indicators remained stable during the 60-day aquaculture trial, effectively curbing eutrophication and reducing stress response in rainbow trout.

[0018] High aquaculture efficiency and low cost: By stabilizing water quality, the survival rate of rainbow trout can be increased by more than 15%, the average body weight growth rate can be increased by more than 60%, and the aquaculture losses caused by water quality deterioration can be reduced; at the same time, the frequency of water change can be reduced (from 10% of the water change per day to less than 3%), saving water resources and wastewater treatment costs, and significantly improving the economic benefits of aquaculture.

[0019] Convenient to use and easy to promote: The preparation process of the microbial agent is mature and the addition method is flexible (biofilm attachment in biological filters or direct addition). It can be directly adapted to existing rainbow trout recirculating aquaculture systems without large-scale equipment modification. The strains can be initially identified by colony morphology. The operation is simple and suitable for promotion and application in rainbow trout farming scenarios of different scales (family farms and large-scale farms).

[0020] Environmentally friendly and highly safe: Water purification relies on the natural metabolism of microorganisms, leaving no chemical residues. Acute toxicity tests have verified that the bacterial agent's 96-hour median lethal concentration (LD50) for rainbow trout is... With a volume fraction >10%, it is highly safe and will not cause secondary environmental pollution, which is in line with the industry trend of green and sustainable development of aquaculture. Attached Figure Description

[0021] Figure 1 Morphological diagram of strain SD-C-1-7; Figure 2 This is a schematic diagram of the phylogenetic tree of strain SD-C-1-7; Figure 3 For NH4 + The denitrification effect diagram when -N is a single carbon source; Figure 4 For NO2 - The denitrification effect diagram when -N is a single carbon source; Figure 5 For NO3 - The denitrification effect diagram when -N is a single carbon source; Figure 6 The figure shows the denitrification performance of SD-C-1-7 at different temperatures; Figure 7 The degradation effect of strain SD-C-1-7 on aquaculture wastewater Figure 1 ; Figure 8 The degradation effect of strain SD-C-1-7 on aquaculture wastewater (Part 2); Figure 9 Diagram of a low-temperature recirculating aquaculture system for snakehead fish; Figure 10 The application effect of SD microbial agent in low-temperature culture of snakehead fish Figure 1 (a: No bacterial agent added; b: SD group with bacterial agent) Figure 11 The application effect of SD microbial agent in low-temperature culture of snakehead fish Figure 2 (a: No bacterial agent added; b: SD group with bacterial agent) Figure 12 The graph shows the water temperature changes of systems a and b during the experiment. Figure 13 Degradation of NH4 by the microbial agent SD in cultured rainbow trout + -N and NO2 - The effect of -N; Figure 14 Degradation of NO3 by the microbial agent SD in farmed rainbow trout - Renderings of -N, TN, and TP; Figure 15 This is a graph showing the water temperature during the experiment. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0023] A low-temperature bacterium, SD-C-1-7, classified as *Pseudomonas sp.*, exhibits regular, round colonies on LB medium, 2-4 mm in diameter, plump, moist, with smooth edges, and Gram-negative staining. This strain, under low-temperature conditions of 8-18℃, achieves extraction rates of ≥87% for ammonia nitrogen, ≥91% for nitrite nitrogen, and ≥52% for total phosphorus in rainbow trout aquaculture water. Its accession number is CCTCC NO: M20251593, the accession date is July 21, 2025, and the accession location is the China Center for Type Culture Collection. Specific implementation examples: Culture medium: LB medium: 10g peptone; 5g yeast extract; 10g NaCl; pH 7.0-7.2; 1000mL distilled water.

[0025] Nitrification medium: 5g sodium acetate, 0.0943g (NH4)2SO4 (20mg / L); 0.5g KH2PO4; 0.5g Na2HPO4; 0.4g MgSO4•7H2O; 2ml trace salt solution; 1000ml distilled water; pH 7.0-7.2, solid medium with 2% agar added.

[0026] Denitrification medium: Sodium acetate 5g; KNO3 0.36g (50mg / L); Na2HPO4 0.5g, KH2PO4 0.5g; MgSO4•7H2O 0.4g; trace salt solution 2ml; distilled water 1000ml; pH 7.0-7.2, solid medium with 2% agar.

[0027] Trace salt solution: 50g ethylenediaminetetraacetic acid (EDTA), 2.2g ZnSO4, 5.5g CaCl2, 1.57g CuSO4•5H2O, 5.06g MnCl2•4H2O, 5g FeSO4•7H2O, 1.61g CoCl2•6H2O, 1000mL distilled water, pH 7.0-7.2.

[0028] Seed culture medium: 5g glucose, 0.5g K₂HPO₄, 0.5g KH₂PO₄, 0.2g MgSO₄; 2mL trace salt solution, 1% yeast extract solution, 1% peptone solution, 1000mL distilled water, pH 7.0-7.2. Yeast extract solution concentration: 50g / L; peptone solution concentration: 100g / L.

[0029] Solid culture medium with 2% agar; Instruments: Clean bench, low-temperature biochemical incubator, UV-Vis spectrophotometer, vertical high-pressure steam sterilizer, constant temperature shaker (4-65℃), water quality rapid tester, etc.

[0030] Example 1: Screening and purification of heterotrophic simultaneous nitrification-aerobic denitrification strains 1. Isolation and Purification: Water samples and sediment were inoculated into enrichment medium (nitrification medium) and cultured for 10 days at 15℃ and 160 rpm in a low-temperature shaker to obtain enriched bacterial solutions. The enriched bacterial solutions were serially diluted 10⁴-10⁸ times, and 100 μL of each dilution was spread onto LB agar plates and incubated at 15℃. When single colonies appeared on the plates, different single colonies were picked and streaked onto LB agar plates. This streaking process was repeated at least three times to purify the strain.

[0031] 2. Secondary Screening: The initially screened strains were activated in LB medium for 48 hours. The activated bacterial suspension was centrifuged at 6000 rpm for 5 minutes, the supernatant was discarded, and distilled water was added for washing. The initial inoculum size of the nitrification medium was adjusted to OD600 = 0.2, and the culture was carried out at 15℃ and 160 rpm with shaking. The ammonia nitrogen concentration in the solution was measured every 12 hours. The strain with the highest ammonia nitrogen removal rate was selected as the experimental strain. A total of 13 strains were isolated. Among them, Pseudomonas sp. SD-C-1-7 (63.66%) had the highest ammonia nitrogen removal rate under the conditions of 15℃, initial NH4+-N concentration of 20 mg / L, and C / N = 10.

[0032] Example 2 Identification of the strain 1. Colony morphology: Pseudomonas sp. SD-C-1-7 grows well on LB medium, such as... Figure 1 As shown, the colonies are regularly round, 2-4 mm in diameter, plump, moist, with smooth edges, and Gram-negative.

[0033] 2. Molecular biological identification of the strain: Single colonies were selected for colony PCR using primers 27F (5'-agagtttgatcctggctag-3') and 1495R (5'-CTACGGCTACCTTGTTACGA-3'). The products were purified and sequenced. Sequences obtained by BLAST search in GenBank were compared to identify 16S rDNA sequences with high similarity. A phylogenetic tree was constructed using MEGA to find the strain with the closest homology.

[0034] 3. The 16S rDNA sequence of strain SD-C-1-7 was determined as follows: 4. The results were compared with the 16S rDNA gene sequence of the type strain in the NCBI database for homology, identifying the cryogenically resistant and efficient strain as *Pseudomonas* sp., named *Pseudomonas* sp. SD-C-1-7, with accession number CCTCCNO: M20251593, accession date July 21, 2025, and accession location China Center for Type Culture Collection. The phylogenetic tree of the strain is as follows: Figure 2 As shown.

[0035] Example 3: Effects of different nitrogen sources on the denitrification performance of strain SD-C-1-7 Strain strain SD-C-1-7 was inoculated into LB medium and activated for 48 h. The activated bacterial suspension was centrifuged at 6000 r / min for 5 min, the supernatant was discarded, and the bacteria were washed with distilled water. Nitrification and denitrification media were prepared using (NH4)2SO4, NaNO2, and KNO3 as the sole nitrogen sources, respectively. The initial inoculum size of the nitrification and denitrification media was adjusted to OD200. 600 =0.2, and cultured with shaking at 15℃ and 160r / min, with the contents of ammonia nitrogen, nitrate nitrogen, and nitrite nitrogen in the solution measured every 12h. Nitrate nitrogen and nitrite nitrogen were measured using a UV spectrophotometer, and corresponding standard curves were prepared. The contents of nitrate nitrogen and nitrite nitrogen were calculated based on the standard curves, and the ammonia nitrogen content was measured using a water quality rapid analyzer.

[0036] The results are as follows Figure 3 As shown, strain SD-C-1-7 exhibits good nitrogen removal performance and possesses simultaneous nitrification and denitrification capabilities. When ammonia nitrogen is the sole nitrogen source, ammonia nitrogen levels over 48 and 72 hours are... The removal rates reached 95.38% and 99.39%, with a small amount remaining. , The accumulation; in the When nitrogen is the sole source, 48 and 72 hours The removal rates reached 95.34% and 99.07%, with a small amount... The accumulation; in the When nitrogen is the sole source, within 48 and 72 hours The removal rates reached 64.36% and 97.18%, and there were no... , The accumulation of.

[0037] Note: This example describes the strain performance under ideal conditions in a pure culture medium. In actual rainbow trout farming water bodies, which contain complex substrates such as uneaten feed and excrement, the maximum removal rates of ammonia nitrogen, nitrite nitrogen, and total phosphorus by the strain are ≥87%, ≥91%, and ≥52% as described in the claims.

[0038] Example 4: Denitrification performance of strain SD-C-1-7 at different temperatures Strain strain SD-C-1-7 was inoculated into LB medium and activated for 48 h. The activated bacterial suspension was centrifuged at 6000 r / min for 5 min, the supernatant was discarded, and distilled water was added for washing. The initial inoculum size of the nitrification medium was adjusted to OD. 600 =0.2, and cultured with shaking at 10, 15, 20, and 30℃ and 160 r / min, respectively, with the concentration of the solution measured every 12 h. , , The content was determined using a UV spectrophotometer. , And create the corresponding standard curve, and calculate based on the standard curve. , The content was determined using a rapid water quality analyzer. content.

[0039] according to Figure 6 It can be seen that strain SD-C-1-7 exhibits high activity at temperatures of 10, 15, and 20℃. The removal rates were 93.33%, 98.14%, and 91.20% on average, with the highest removal rates observed at 30℃. However, the denitrification effect of the strain was inhibited at 30℃, with the highest average removal rate being 60.17%. These results indicate that this strain is a cold-resistant bacterium and exhibits good performance in the low-temperature environment (8-18℃) suitable for rainbow trout farming. The removal effect is good, and it retains a certain level of activity even at 20℃.

[0040] Example 5: Degradation effect of bacteria on pollutants in aquaculture wastewater Strain SD-C-1-7 was inoculated into LB medium and activated for 48 h. The activated bacterial suspension was centrifuged at 6000 r / min for 5 min, the supernatant was discarded, and the bacteria were washed with distilled water to bring the OD600 of the bacterial suspension to 1.0. 100 mL portions of aquaculture wastewater collected from the wastewater treatment pond were added, with strain SD-C-1-7 added at 0.2% (volume fraction). Degradation was carried out in a low-temperature shaker at 15℃ and 160 r / min. Samples were taken every 12 h, and the aquaculture wastewater was analyzed. , , The content of TN and TP.

[0041] The results showed that after treatment with microbial agents, the amount of bacteria in the aquaculture effluent decreased. and Almost completely removed The concentration also decreased significantly, and the contents of total nitrogen (TN) and total phosphorus (TP) also decreased significantly. From Figure 7 and Figure 8 It can be seen that within 48 hours, , , The removal rates of nitrogen, nitrogen (TN), and phosphorus (TP) were 88.95%, 61.19%, 64.93%, 26.64%, and 34.38%, respectively. After 72 hours of treatment, the removal rates of each indicator further improved, reaching 94.09%, 84.17%, 74.16%, 34.11%, and 40.29%, respectively. This demonstrates that this strain plays a dominant role in the nitrogen removal process and significantly improves phosphorus removal, thereby achieving an overall improvement in the quality of aquaculture effluent.

[0042] Example 6: Application of bacteria in snakehead fish farming in a laboratory small recirculating aquaculture system 1. Preparation of microbial agents Strain strain SD-C-1-7 was inoculated into seed culture medium and activated for 48 h in a low-temperature shaker at 15℃ and 160 r / min to obtain seed liquid. The seed liquid was then inoculated into seed culture medium in a fermenter at a volume fraction of 1% for high-density fermentation for 48 h to obtain fermentation broth (inoculum SD).

[0043] 2. Application of microbial agent SD in snakehead fish farming (under low temperature conditions) The microbial agent operation in this experiment was carried out according to the following procedure: After the fermentation broth was expanded in a pre-fermentation tank, it was added at a volume fraction of 0.2% of the total volume of the aquaculture water. During the 20-day experimental period (experimental equipment see...),... Figure 9 For the first three days, no bacterial agent was added; starting from the fourth day (August 16th), the first addition was given, and a procedure was established to add it every seven days. It is worth noting that, as... Figure 10 and Figure 11 The data shown on the day of addition represents the water quality condition before addition.

[0044] like Figure 10 and Figure 11 As shown, the comparison was made under low temperature conditions ( Figure 12 Water quality changes during the experiment (water temperature) in two snakehead fish farming systems (System A: no bacterial agent added; System B: with SD bacterial agent added). Initial phase (August 14–16) in both systems. , , The average concentrations of TN and TP were 0.47, 0.21, 2.651, 3.688, and 0.325 mg / L, respectively. In subsequent experiments, the indicators in system a (without bacterial agent) showed a gradual upward trend. The concentration range is 0.475–0.6648 mg / L. The concentration range was 0.221–0.3014 mg / L; while system b (microbial agent SD) showed a significant purification effect 2 days after the first addition of the microbial agent (August 18th), compared with system a, , , TN and TP decreased by 22.42%, 53.18%, 7.43%, 10.06%, and 8.50%, respectively. Although the effect of the bacterial agent subsequently weakened, by replenishing the agent every 7 days, the system continued to maintain good water purification capabilities. , Nitrogenous substances were kept at low levels. Throughout the experiment, the bacterial agent SD was effective against... , , The highest degradation rates of TN and TP reached 43.9%, 88.80%, 75.39%, 38.19%, and 55.76%, respectively. The results indicate that the bacterial agent SD has a significant water quality improvement capability in low-temperature snakehead aquaculture water, especially with outstanding denitrification performance, which helps alleviate environmental stress and reduce mortality in farmed animals.

[0045] Example 7: Application of bacteria in rainbow trout farming in recirculating aquaculture systems 1. Preparation of microbial agents Strain strain SD-C-1-7 was inoculated into seed culture medium and activated for 48 h in a low-temperature shaker at 15℃ and 160 r / min to obtain seed liquid. The seed liquid was then inoculated into seed culture medium in a fermenter at a volume fraction of 1% for high-density fermentation for 48 h to obtain fermentation broth (inoculum SD).

[0046] 2. Application of microbial agent SD in rainbow trout farming The microbial agent operation in this experiment was carried out according to the following procedure: After the fermentation broth was expanded in a pre-fermentation tank, it was added at a volume fraction of 0.2% of the total aquaculture water volume. During the 60-day experimental period, the first addition began on July 29th, and a procedure of replenishing every 7 days was established. It is worth noting that the data on the day of addition represents the water quality status before addition. Given the strong acute toxicity of ammonia nitrogen and nitrite, these were measured daily to closely monitor their dynamic changes. For indicators characterizing the long-term nutrient load of the system, such as nitrate, total nitrogen, and total phosphorus, measurements were set to be taken every 7 days. The sampling time point was determined based on previous experimental data, i.e., water samples were collected and measured 96 hours after each addition of the microbial agent to assess the continuous effect of the microbial agent on water quality within an addition cycle. For ease of description, the experimental system with added microbial agent SD will be referred to as the SD group, and the control system without added microbial agent will be referred to as the CK group.

[0047] ammonia nitrogen ( ) and nitrite ( As the most biotoxic form of nitrogen in aquaculture water, its concentration changes directly affect aquaculture safety. Throughout the experimental period, the SD group showed significantly better control of both nitrogen species than the CK group. Figure 13 ). CK group The concentration remained at a consistently high level (up to 1.0 mg / L) and fluctuated significantly. The concentration peaked significantly between August 17 and 27, indicating a high potential toxicity risk and reflecting insufficient self-purification capacity of the water body. In contrast, the SD group... The concentration remained stable below 0.4 mg / L. The concentration remained consistently below 0.2 mg / L, and the curve remained stable. The results indicate that the bacterial agent SD-C-1-7 can effectively remove... And efficiently transfer This inhibits its accumulation. Regarding degradation efficiency, the SD group showed better performance than the [previous group]. and The highest removal rates were 87.15% and 91.67%, respectively, and the average removal rates were 55.37% and 66.13%, respectively. SD bacterial agent can stably and efficiently degrade [the pollutants] in water. and To prevent the accumulation of toxic substances.

[0048] nitrates ( Total nitrogen (TN) and total phosphorus (TP) are key indicators for evaluating eutrophication of water bodies. SD bacterial agents also demonstrate good removal capabilities for these indicators (see reference). Figure 13 and Figure 14 ). CK group The concentration continued to rise, leading to high TN concentrations (exceeding 40 mg / L at its highest), reflecting the continuous accumulation of nitrogen in the system without intervention. In contrast, the SD group... The concentration remained stable at 11.52–15.37 mg / L, and the TN concentration remained stable at 29.59–35.75 mg / L, with average removal rates of 20.97% and 29.86% respectively, and a maximum removal rate of 37.35%. This indicates that the SD agent not only removes harmful substances but also... change Furthermore, nitrogen can be further removed through denitrification and other pathways, achieving effective reduction of total nitrogen (TN). Regarding phosphorus removal, the TP concentration in the SD group (0.41–0.70 mg / L) was significantly lower than that in the CK group (0.84–0.91 mg / L), with a maximum removal rate of 52.33% and an average removal rate of 39.45%. This indicates that the microbial agent SD may possess polyphosphate accumulation or phosphorus reduction functions, enabling synergistic phosphorus removal while simultaneously removing nitrogen.

[0049] In summary, compared with the control group (CK), the experimental group treated with SD bacterial agent showed better results in all monitored water quality indicators (…). , , All three (TN, TP) showed significant purification effects. SD bacterial agent not only rapidly degraded highly toxic ammonia, but also... , Furthermore, it effectively reduced the concentration of pollutants in the water. The microbial agent effectively controlled eutrophication by regulating TN and TP levels. Results showed that this agent is suitable for rainbow trout recirculating aquaculture systems and can effectively maintain the long-term stability and safety of the water body.

[0050] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A low-temperature bacterium, SD-C-1-7, characterized in that, The strain was classified and named Pseudomonas ( ). Pseudomonas The strain (sp.) was Gram-negative; under low temperature conditions of 8-18℃, the extraction rates of ammonia nitrogen, nitrite nitrogen, and total phosphorus in rainbow trout aquaculture water were ≥87%, ≥91%, and ≥52%, respectively. The accession number was CCTCC NO: M20251642, the accession date was July 21, 2025, and the accession location was China Center for Type Culture Collection.

2. A bacterial agent for water purification, characterized in that, The active ingredient is the low-temperature bacteria SD-C-1-7 as described in claim 1.

3. The microbial agent according to claim 2, characterized in that, The microbial agent is prepared by activation with a seed culture medium and high-density fermentation in a fermenter; the seed culture medium formula is: 4-6g glucose, ... 0.4-0.6g 0.4-0.6g 0.1-0.3g, 1-3mL of trace salt solution, 1-3mL of 1% yeast powder solution, 1-3mL of 1% peptone solution, 950-1050mL of distilled water, pH 7.0-7.2; wherein, the concentration of yeast powder solution is 45-55g / L and the concentration of peptone solution is 100g / L.

4. The application of the low-temperature bacteria SD-C-1-7 as described in claim 1 in the purification of aquatic aquaculture water.

5. The application according to claim 4, characterized in that, The aquaculture is rainbow trout farming, with a farming water temperature of 8-18℃.

6. The application according to claim 5, characterized in that, Used to remove ammonia nitrogen from rainbow trout farming water ( ), nitrite nitrogen ( ), nitrate nitrogen ( ), total nitrogen (TN) and total phosphorus (TP).

7. The application according to claim 5, characterized in that, The low-temperature bacteria SD-C-1-7 is used by attaching a biofilm to a biological filter or by directly adding it to the aquaculture water.

8. A method for purifying water quality in rainbow trout recirculating aquaculture systems, characterized in that, Includes the following steps: 1) The low-temperature bacteria SD-C-1-7 described in claim 1 is inoculated into seed culture medium and activated at 14-17℃ and 150-170 r / min for 48 h to obtain seed liquid; 2) Inoculate the seed culture solution into the seed culture medium of the fermenter at a volume fraction of 1%, and ferment at high density for 48 hours to obtain the inoculum; 3) Add the bacterial agent to the rainbow trout recirculating aquaculture system and maintain the water temperature at 8-18℃.

9. The water purification method according to claim 8, characterized in that, In step 3), the amount of bacterial agent added is 0.15-0.25% (volume fraction) of the total volume of the aquaculture water, and it is added once every 7 days.

10. The water purification method according to claim 8 or 9, characterized in that, The method achieves a maximum removal rate of ≥87% for ammonia nitrogen, ≥91% for nitrite nitrogen, and ≥52% for total phosphorus; and can keep the ammonia nitrogen concentration in the aquaculture water below 0.4 mg / L and the nitrite nitrogen concentration always below 0.2 mg / L.

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