Bacillus subtilis and application thereof in aquaculture

Abstract

The invention provides a strain of bacillus subtilis (a strain of bacillus Guangxi Z1 bacillus) and an application of the bacillus subtilis in aquaculture. Through screening and optimization, the strain has good environmental adaptability, remarkable disease resistance and excellent water quality improvement effect, and can effectively solve the common problems of water quality pollution, disease prevention and control and the like in aquaculture. Specifically, the bacillus Guangxi Z1 can significantly reduce the concentration of harmful substances such as ammonia nitrogen, nitrite, total phosphorus and the like in a culture water body, improve the dissolved oxygen level and improve the water quality environment; meanwhile, growth of various aquatic pathogenic bacteria such as vibrio, green algae and fungi can be inhibited, the disease incidence rate of cultured organisms is reduced, and the immunity and survival rate of the cultured organisms are improved. The strain disclosed by the invention is widely applied to aquaculture and has relatively high ecological safety and economic benefits, and a green, environment-friendly, efficient and stable solution is provided for sustainable development of modern aquaculture industry.

Description

Technical Field

[0001] The present invention relates to the technical fields of aquaculture and microbiology, and particularly to a Bacillus subtilis strain and its application in aquaculture. Background Art

[0002] With the rapid development of the global aquaculture industry, problems such as water pollution and the prevention and control of diseases in cultured organisms have gradually emerged, posing a severe challenge to the sustainable development of aquaculture. Common environmental problems in the aquaculture process include water eutrophication, ammonia nitrogen pollution, the spread of pathogenic microorganisms, etc. These problems not only affect the economic benefits of aquaculture but may also lead to the imbalance of the ecosystem. Therefore, it is urgent to adopt effective means for water quality improvement and disease prevention and control to improve the efficiency and sustainability of aquaculture.

[0003] Bacillus subtilis, as a probiotic with strong environmental adaptability and disease resistance, is widely used in the fields of agriculture and aquaculture. By secreting various antibacterial substances, degrading organic wastes, and improving water quality, it can effectively improve the water quality of aquaculture and the health of cultured organisms. However, the existing Bacillus subtilis strains still face some deficiencies in the application of aquaculture, such as poor adaptability to harsh environments, limited inhibitory effects on certain pathogenic bacteria, and stability problems during the actual use of preparations, which limit their wide application in aquaculture.

[0004] Therefore, developing a new type of Bacillus subtilis strain that can stably grow and play a stronger role in water quality improvement and disease prevention and control in the harsh aquaculture environment has become an urgent problem to be solved. Through screening and optimization, the present invention has obtained a Bacillus subtilis strain with stronger environmental adaptability and disease resistance, providing an innovative application solution for aquaculture, which can significantly improve the production efficiency and sustainability of aquaculture and meet the needs of modern aquaculture for efficient, green, and environmentally friendly technologies. Summary of the Invention

[0005] The purpose of the present invention is to provide a new type of Bacillus subtilis strain and its application method in aquaculture to effectively improve water quality, promote the growth and development of cultured organisms, enhance their immunity, reduce the incidence of diseases, and thus improve the overall efficiency of aquaculture. The strain described in the present invention is different from the known Bacillus subtilis strains in the prior art, and has more excellent tolerance, disease resistance, and water quality improvement effects, with significant novelty and creativity.

[0006] Based on the above purpose, the present invention provides a Bacillus subtilis strain and its application in aquaculture.

[0007] A Bacillus subtilis strain (Bacillus yuejinran Z1, preservation number CGMCC NO. 33331; has been preserved in the China General Microbiological Culture Collection Center (CGMCC); taxonomic name: Bacillus subtilis; preservation date: January 8, 2025; viability of the strain: alive), the strain has high resistance to high temperature, high salt, and low pH environments, can produce a variety of antibacterial substances, significantly inhibit common pathogenic bacteria in the aquaculture environment, promote the growth of cultured organisms, and improve water quality.

[0008] Furthermore, the Bacillus yuejinran Z1 strain was identified as belonging to the genus Bacillus subtilis by 16S rRNA gene sequencing.

[0009] Furthermore, the preparation contains the above-mentioned Bacillus yuejinran Z1 strain and is a freeze-dried powder preparation or a liquid preparation.

[0010] Furthermore, the content of the Bacillus yuejinran Z1 strain in the preparation is at least 10^8 viable units per gram of the preparation.

[0011] Furthermore, an application method in aquaculture includes the following steps: a. Prepare a bacterial agent according to the above-mentioned preparation; b. Uniformly put the bacterial agent into the aquaculture pond at a dose of 5 grams to 10 grams per ton of water body; c. Put it once or multiple times a week for 6 to 12 weeks.

[0012] Furthermore, the aquaculture species cultured in the pond are selected from prawns, tilapia, sea bass, black carp, or a polyculture system of shrimps and shellfish.

[0013] Furthermore, the Bacillus yuejinran Z1 strain reduces the concentrations of ammonia nitrogen, nitrite, total nitrogen, total phosphorus, and chemical oxygen demand by degrading organic waste.

[0014] Furthermore, the Bacillus yuejinran Z1 strain is applied to the aquaculture environment in the form of a freeze-dried powder preparation or a liquid preparation to maintain water quality stability and promote the healthy growth of cultured organisms.

[0015] Advantages of the present invention:

[0016] 1. High-efficient water quality improvement ability: The Bacillus yuejinran Z1 strain can effectively degrade organic waste in the water body, significantly reduce the concentrations of ammonia nitrogen, nitrite, total nitrogen, total phosphorus, and chemical oxygen demand, improve the water quality environment, and promote the ecological balance of the water body.

[0017] 2. Significant effect in promoting the growth of farmed organisms: By secreting growth factors and enzymes, the Yuejinran Z1 Bacillus strain can significantly promote the growth and development of farmed organisms, increase their final body weight and average daily weight gain, and improve aquaculture output and economic benefits.

[0018] 3. Enhanced immunity and disease resistance: After applying the Yuejinran Z1 Bacillus strain, the immune indicators of farmed organisms (such as white blood cell count, lymphocyte ratio, antioxidant enzyme activity and immunoglobulin level) were significantly improved, which enhanced their disease resistance, reduced the incidence of diseases and reduced farming losses.

[0019] 4. Excellent tolerance and adaptability: Yuejinran Z1 Bacillus strain has the characteristics of high resistance to high temperature, high salt and low pH. It can survive and function stably in a variety of complex aquaculture environments, has strong adaptability and a wide range of applications.

[0020] 5. Significant environmental protection and economic benefits: The present invention reduces the pollution risk of the breeding environment by reducing the use of chemical agents, which meets the requirements of sustainable development. At the same time, by improving breeding efficiency, it reduces breeding costs, has good economic benefits and broad market application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only for the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 This is a schematic diagram of the effects of different strains of the present invention on growth in aquaculture;

[0023] Figure 2 It is a comparative schematic diagram of the disease resistance of the strains of the present invention. DETAILED DESCRIPTION

[0024] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. At the same time, it is explained here that in order to make the embodiments more detailed, the following embodiments are the best and preferred embodiments, and those skilled in the art may also adopt other alternatives to implement some known technologies; and the accompanying drawings are only for more specific description of the embodiments, and are not intended to specifically limit the present invention.

[0025] It should be noted that in the specification, references to "one embodiment", "an embodiment", "exemplary embodiments", "some embodiments", etc. indicate that the described embodiments may include specific features, structures, or characteristics, but not every embodiment necessarily includes such specific features, structures, or characteristics. Additionally, when describing a specific feature, structure, or characteristic in connection with an embodiment, implementing such feature, structure, or characteristic in connection with other embodiments (whether explicitly described or not) should be within the knowledge of those skilled in the relevant art.

[0026] Generally, terms can be understood, at least in part, from their use in context. For example, depending at least in part on the context, the term "one or more" as used herein can be used to describe any feature, structure, or characteristic in a singular sense, or can be used to describe a combination of features, structures, or characteristics in a plural sense. Additionally, the term "based on" can be understood as not necessarily intended to convey a set of exclusive factors, but rather, depending at least in part on the context, can alternatively allow for the existence of other factors that may not be explicitly described.

[0027] The following describes in detail a Bacillus subtilis strain (Bacillus subtilis Yue Jinran Z1) and its application method in aquaculture in combination with the embodiments of the present invention. Through the detailed description of the specific implementation manner, it aims to fully demonstrate the technical characteristics and superior performance of the present invention, facilitating the understanding and application by those skilled in the relevant technical field.

[0028] 1. Screening and Identification of Strains

[0029] 1.1 Strain Source

[0030] Water samples were collected from different aquaculture environments, including shrimp culture ponds, tilapia culture ponds, bass culture ponds, black carp culture ponds, and shrimp and shellfish polyculture systems. Using aseptic techniques, the samples were immediately separated in the laboratory after sampling.

[0031] 1.2 Strain Isolation

[0032] Using a selective medium (Bacillus subtilis selective medium) for cultivation, multiple single colonies were isolated. By observing the colony morphology under a microscope, strains with morphological characteristics conforming to Bacillus subtilis were screened out.

[0033] 1.3 Molecular Biology Identification

[0034] The genomic DNA of each isolated strain was extracted and 16S rRNA gene sequencing was performed. The sequencing results were compared with the 16S rRNA sequences in the existing database to confirm the species of the strains.

[0035] 1.4 Screening of Excellent Strains

[0036] A series of growth experiments, disease resistance tests, and harmful bacteria inhibition experiments were conducted to screen the isolated Bacillus subtilis strains. Finally, a strain with high tolerance, significant disease resistance, and good water quality improvement effect was selected and named Bacillus subtilis Yuejinran Z1.

[0037] 2. Cultivation and Preparation of Bacillus subtilis Yuejinran Z1

[0038] 2.1 Preparation of Culture Medium

[0039] A liquid culture medium containing peptone, yeast extract, glucose, phosphate buffer, etc. was used, and the pH was adjusted to 7.0. After sterilization, it was cooled to an appropriate temperature.

[0040] 2.2 Inoculation and Cultivation

[0041] The Bacillus subtilis Yuejinran Z1 strain was inoculated into the pre-prepared liquid culture medium and cultured at a constant temperature of 37°C with sufficient aeration for 24 - 48 hours until the bacteria reached the logarithmic growth phase.

[0042] 2.3 Fermentation Culture

[0043] The fermentation culture of Bacillus subtilis Yuejinran Z1 was carried out in a large fermenter, and parameters such as temperature, pH, and dissolved oxygen were controlled to maximize the bacterial cell yield and activity. After fermentation, the bacterial cells were collected by centrifugation, filtration, and other methods.

[0044] 2.4 Preparation of Preparation

[0045] The collected Bacillus subtilis Yuejinran Z1 bacterial cells were freeze-dried to obtain freeze-dried powder preparations, or liquid preparations were prepared by mixing other excipients in proportion. Both the freeze-dried powder preparations and the liquid preparations have good stability and are convenient for storage and transportation.

[0046] 3. Application Methods in Aquaculture

[0047] 3.1 Determination of Application Dosage

[0048] According to different aquaculture scales and aquaculture species, the usage dosage of the Bacillus subtilis Yuejinran Z1 preparation was determined. The specific dosages are as follows:

[0049] For shrimp aquaculture: 5 grams of the freeze-dried powder of Bacillus subtilis Yuejinran Z1 was added per ton of water body once a week for 6 weeks.

[0050] For tilapia aquaculture: 6 grams of the liquid preparation of Bacillus subtilis Yuejinran Z1 was added per ton of water body twice a week for 7 weeks.

[0051] For sea bass aquaculture: 5 grams of the freeze-dried powder of Bacillus subtilis Yuejinran Z1 was added per ton of water body once a week for 8 weeks.

[0052] Black carp farming: Add 7 grams of Yuejinran Z1 Bacillus liquid preparation per ton of water body, once every two weeks for 10 weeks.

[0053] Mixed culture system of shrimp and shellfish: Add 10 grams of Yuejinran Z1 Bacillus mixed preparation (freeze-dried powder and liquid preparation) per ton of water body, twice a week for 12 weeks.

[0054] 3.2 Application method

[0055] According to the specific farming species, select an appropriate application method:

[0056] For penaeid shrimp and sea bass: Dissolve the freeze-dried powder in an appropriate amount of water and evenly add it to the farming pond.

[0057] For tilapia and black carp: Directly add the liquid preparation to the farming pond according to the specified dose.

[0058] Mixed culture system of shrimp and shellfish: After dissolving the mixed preparation in proportion, evenly distribute and add it to the farming pond.

[0059] 3.3 Application frequency and cycle

[0060] Strictly apply according to the dosage and application frequency of each farming species to ensure that Yuejinran Z1 Bacillus maintains a stable flora level in the farming environment and achieves the best effect.

[0061] 4. Detailed operation and results of the examples

[0062] The following combines Example 1 and Example 2 to describe in detail the application process and experimental results of Yuejinran Z1 Bacillus in penaeid shrimp and tilapia farming.

[0063] Example 1: Application of Yuejinran Z1 Bacillus in penaeid shrimp farming

[0064] 4.1 Experimental design

[0065] Set up a control group and an experimental group in the penaeid shrimp farming pond, with three replicate ponds in each group. The experimental period is 6 weeks, and water quality indicators, penaeid shrimp growth parameters, and disease occurrence are monitored.

[0066] 4.2 Application method

[0067] Strain preparation: Use Yuejinran Z1 Bacillus agent in the form of freeze-dried powder.

[0068] Dosage: Add 5 grams of Yuejinran Z1 Bacillus preparation per ton of water body.

[0069] Application frequency: Once a week for 6 weeks.

[0070] 4.3 Experimental results

[0071] Table 1-1: Changes in Water Quality Indicators

[0072]

[0073]

[0074] Table 1-2: Growth Parameters of Penaeus vannamei

[0075] Growth parameter Control group Experimental group Growth rate (%) Initial weight (g) 20 20 - Final weight (g) 80 100 25 Average daily weight gain (g) 1.0 1.25 25 Survival rate (%) 85 92 -7

[0076] Table 1-3: Disease Incidence

[0077] Disease type Incidence rate of control group (%) Incidence rate of experimental group (%) Standard number Bacterial disease 20 5 SC / T3016 - 2004 Fungal disease 12 3 SC / T3015 - 2002 Parasitic disease 10 2 -

[0078] 4.4 Experimental Analysis

[0079] The experimental group showed significant advantages in water quality improvement, Penaeus vannamei growth, and disease prevention and control. The concentrations of ammonia nitrogen, nitrite, total phosphorus, and chemical oxygen demand (COD) decreased significantly, and the dissolved oxygen and pH value were optimized. The growth rate and survival rate of Penaeus vannamei increased significantly, and the disease incidence decreased significantly, indicating that the application of Bacillus sp. YJRZ1 in Penaeus vannamei farming had good effects.

[0080] Example 2: Application of Bacillus sp. YJRZ1 in Tilapia Farming

[0081] 4.5 Experimental Design

[0082] A control group and an experimental group were set up in the tilapia farming pond, and each group had four replicated ponds. The experimental period was 7 weeks, and water quality indicators, tilapia growth parameters, and immune indicators were monitored.

[0083] 4.6 Application Method

[0084] Strain preparation: Use the Bacillus sp. YJRZ1 bacterial agent in the form of a liquid preparation. Dosage: 6 grams of Bacillus sp. YJRZ1 preparation was added per ton of water body. Application frequency: Twice a week for 7 weeks.

[0085] 4.7 Experimental Results

[0086] Table 2-1: Changes in Water Quality Indicators

[0087]

[0088] Table 2-2: Growth Parameters of Tilapia

[0089] Growth parameter Control group Experimental group Growth rate (%) Initial weight (g) 30 30 - Final weight (g) 120 150 25 Average daily weight gain (g) 1.5 1.9 26.7 Survival rate (%) 88 95 -7

[0090] Table 2-3: Immune Indicators

[0091]

[0092]

[0093] 4.8 Experimental Analysis

[0094] The experimental group showed outstanding performance in water quality control, growth and immunity improvement of tilapia. The concentrations of total nitrogen, total phosphorus, chemical oxygen demand (COD) and nitrate decreased significantly, and the dissolved oxygen and pH value were improved. The growth rate and survival rate of tilapia increased significantly, and the immune indexes (white blood cell count, lymphocyte ratio, antioxidant enzyme activity, immunoglobulin level) were significantly enhanced, indicating that the application of Bacillus subtilis Yuejinran Z1 in tilapia farming can effectively improve the farming effect and fish health level.

[0095] In addition to Example 1 and Example 2, the present invention also includes the following examples, which demonstrate the wide application of Bacillus subtilis Yuejinran Z1 strain in different aquaculture environments:

[0096] Example 3: Application of Bacillus subtilis Yuejinran Z1 in bass farming

[0097] 1. Experimental design

[0098] A control group and an experimental group were set up in the bass farming pond, and each group had three replicated ponds. The experimental period was 8 weeks, and water quality indexes, bass growth parameters and disease occurrence were monitored.

[0099] 2. Application method

[0100] Strain preparation: Use the Bacillus subtilis Yuejinran Z1 bacterial agent in the form of freeze-dried powder.

[0101] Dosage: Put 5 grams of Bacillus subtilis Yuejinran Z1 preparation per ton of water body.

[0102] Application frequency: Once a week for 8 weeks.

[0103] 3. Experimental results

[0104] Table 3-1: Changes in water quality indexes

[0105]

[0106]

[0107] Table 3-2: Bass growth parameters

[0108] Growth parameter Control group Experimental group Growth rate (%) Initial weight (g) 50 50 - Final weight (g) 150 180 20 Average daily weight gain (g) 2.0 2.5 25 Survival rate (%) 90 95 -5

[0109] Table 3-3: Disease incidence

[0110] Disease type Incidence rate of control group (%) Incidence rate of experimental group (%) Standard number Bacterial disease 15 5 The same as above Fungal disease 10 3 The same as above Parasitic disease 8 2 -

[0111] Experimental analysis

[0112] The experimental group showed significant advantages in water quality improvement, bass growth, and disease prevention and control. The concentrations of ammonia nitrogen and nitrite decreased significantly, and the dissolved oxygen and pH value were optimized. The growth rate and survival rate of bass increased significantly, and the disease incidence decreased significantly, indicating that the application of Bacillus mojavensis YJRZ1 in bass farming had good effects.

[0113] Example 4: Application of Bacillus mojavensis YJRZ1 in Grass Carp Farming

[0114] 1. Experimental Design

[0115] A control group and an experimental group were set up in the grass carp farming pond, with three replicate ponds for each. The experimental period was 10 weeks, and water quality indicators, grass carp growth parameters, and immune indicators were monitored.

[0116] 2. Application Method

[0117] Strain Preparation: Use the Bacillus mojavensis YJRZ1 bacterial agent in liquid preparation form.

[0118] Dosage: Put 7 grams of Bacillus mojavensis YJRZ1 preparation per ton of water body.

[0119] Application Frequency: Once every two weeks for 10 weeks.

[0120] 3. Experimental Results

[0121] Table 4-1: Changes in Water Quality Indicators

[0122]

[0123] Table 4-2: Grass Carp Growth Parameters

[0124] Growth parameter Control group Experimental group Growth rate (%) Initial weight (g) 100 100 - Final weight (g) 300 380 26.7 Average daily weight gain (g) 3.0 3.8 26.7 Survival rate (%) 85 95 -7

[0125] Table 4-3: Immune Indicators

[0126]

[0127]

[0128] Experimental Analysis

[0129] The experimental group performed outstandingly in water quality control, grass carp growth, and immunity improvement. The concentrations of total nitrogen and total phosphorus decreased significantly, and the dissolved oxygen and pH value were improved. The growth rate and survival rate of grass carp increased significantly, and the immune indicators (white blood cell count, lymphocyte ratio, antioxidant enzyme activity) were significantly enhanced, indicating that the application of Bacillus mojavensis YJRZ1 in grass carp farming could effectively improve the farming effect and the health level of fish.

[0130] Example 5: Application of Bacillus mojavensis YJRZ1 in the Polyculture System of Shrimp and Shellfish

[0131] 1. Experimental Design

[0132] In the polyculture system of shrimp and shellfish, a control group (without adding Bacillus cereus Z1 of Yuejinran) and an experimental group (adding Bacillus cereus Z1 of Yuejinran) were set up, and each group had two replicate ponds. The experimental period was 12 weeks, and water quality indicators, shrimp growth parameters and shellfish filtration rates were monitored.

[0133] 2. Application Method

[0134] Strain Preparation: Use a mixture of freeze-dried powder and liquid preparation.

[0135] Dosage: 10 grams of Bacillus cereus Z1 preparation of Yuejinran was added per ton of water body.

[0136] Application Frequency: Twice a week for 12 weeks.

[0137] 3. Experimental Results

[0138] Table 5-1: Changes in Water Quality Indicators

[0139]

[0140]

[0141] Table 5-2: Shrimp Growth Parameters

[0142] Growth parameter Control group Experimental group Growth rate (%) Initial body length (cm) 5.0 5.0 - Final body length (cm) 12 15 25 Initial weight (g) 10 10 - Final weight (g) 50 65 30 Survival rate (%) 88 94 -6

[0143] Shellfish Filtration Rate

[0144]

[0145] Experimental Analysis

[0146] The experimental group showed significant water quality improvement effects in the polyculture system. The concentrations of COD, ammonia nitrogen and nitrate decreased significantly, and the pH value was optimized. The growth rate and survival rate of shrimp increased significantly, and the filtration amount and filtration efficiency of shellfish were significantly enhanced, indicating that the application of Bacillus cereus Z1 of Yuejinran in the polyculture system of shrimp and shellfish can effectively improve the aquaculture efficiency and water quality management level.

[0147] Through the experimental design and result analysis of the above embodiments, the Bacillus cereus Z1 strain of Yuejinran showed excellent water quality improvement ability, growth promotion effect of aquaculture organisms and immunity enhancement ability in different aquaculture environments. Especially in the application of tilapia and black carp farming, the Bacillus cereus Z1 strain of Yuejinran not only significantly improved the water quality conditions, but also effectively promoted the growth and development of fish and the improvement of immunity, reduced the disease incidence rate, and further improved the aquaculture efficiency.

[0148] The Bacillus cereus strain YJZ1 of the present invention exhibits superior performance compared to known strains in the prior art through optimized culture conditions and application methods, solves the problems of water quality control and maintenance of the health of aquaculture organisms in existing aquaculture, and has significant technical advantages and broad market application prospects.

[0149] The standards adopted in the above embodiments ensure the standardization of the experimental process and the reliability of the data, providing a solid foundation for the effectiveness of the present invention. Through the experimental data analysis of Example 1 and Example 2, it can be seen that the application effect of the Bacillus cereus strain YJZ1 in different aquaculture environments is significant. The specific manifestations are as follows:

[0150] Water quality improvement effect

[0151] The Bacillus cereus YJZ1 can significantly reduce the concentrations of harmful substances such as ammonia nitrogen, nitrite, total nitrogen, total phosphorus, chemical oxygen demand (COD), and nitrate in various aquaculture systems, increase dissolved oxygen, optimize the pH value, and improve the quality of the aquaculture environment.

[0152] Promotion of the growth of aquaculture organisms

[0153] The Bacillus cereus YJZ1 significantly promotes the growth and development of aquaculture organisms, increases the final body weight and average daily weight gain of shrimp and tilapia, and the growth rates reach 25% and 26.7% respectively.

[0154] Disease prevention and control and immune enhancement

[0155] The disease incidence rate of the aquaculture organisms in the experimental group is significantly reduced. At the same time, the immune indexes (white blood cell count, lymphocyte ratio, antioxidant enzyme activity, immunoglobulin level) are greatly improved, enhancing the disease resistance of the aquaculture organisms.

[0156] Experimental cycle and economic benefits

[0157] The experimental cycles of Example 1 and Example 2 are 6 weeks and 7 weeks respectively. The experimental results are shown in a relatively short time, meeting the requirements of actual aquaculture production. By reducing the concentration of harmful substances in the water quality and the disease incidence rate, the application of the Bacillus cereus YJZ1 can significantly improve the aquaculture yield and quality, reduce the aquaculture cost, and has good economic benefits.

[0158] Based on the experimental data analysis of the foregoing embodiments, Example 2: The application of the Bacillus cereus YJZ1 in tilapia aquaculture is recommended as the best embodiment, and the specific reasons are as follows:

[0159] Outstanding water quality improvement effect: The Bacillus cereus YJZ1 can effectively reduce the concentrations of total nitrogen, total phosphorus, chemical oxygen demand (COD), and nitrate in tilapia aquaculture, improve the water quality conditions, and provide a healthier growth environment for tilapia.

[0160] Significantly promotes the growth of cultured organisms: Both the growth rate and survival rate of tilapia are significantly increased. The final weight has increased by 25%, and the average daily weight gain has been increased to 1.9 g, demonstrating the high efficiency of Yuejinran Z1 Bacillus in promoting the growth of tilapia.

[0161] Significantly enhances immunity: The immune indexes (white blood cell count, lymphocyte ratio, antioxidant enzyme activity, immunoglobulin level) of tilapia in the experimental group have been greatly improved, significantly enhancing the disease resistance of tilapia and reducing the disease incidence rate.

[0162] Reasonable experimental period: The 7-week experimental period ensures the effect while meeting the time requirements of actual aquaculture production, enabling the application effect of Yuejinran Z1 Bacillus to be reflected in a relatively short time, and having high practicality and popularization value.

[0163] This invention covers any substitutions, modifications, equivalent methods, and solutions made within the essence and scope of this invention. To enable the public to have a thorough understanding of this invention, specific details are described in detail in the following preferred embodiments of this invention. However, those skilled in the art can fully understand this invention without the description of these details. Additionally, well-known methods, processes, procedures, components, etc. are not described in detail to avoid unnecessary confusion to the essence of this invention.

[0164] The above are only the preferred embodiments of this invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of this invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of this invention.

Claims

1. A Bacillus subtilis strain, characterized in that, The strain is Bacillus sp. Yuejinran Z1 with the preservation number of CGMCC NO. 33331, which has been preserved in the China General Microbiological Culture Collection Center (CGMCC). The strain has high resistance to high temperature, high salt and low pH environment, can produce a variety of antibacterial substances, significantly inhibit common pathogenic bacteria in the aquaculture environment, promote the growth of cultured organisms and improve water quality.

2. The strain according to claim 1, wherein The Bacillus sp. Yuejinran Z1 strain is identified as the genus Bacillus subtilis by 16S rRNA gene sequencing.

3. A probiotic preparation for aquaculture, characterized in that, The preparation contains the Bacillus sp. Yuejinran Z1 strain described in claim 1 and is in the form of freeze-dried powder or liquid preparation.

4. The preparation according to claim 3, characterized in that, The content of the Bacillus sp. Yuejinran Z1 strain in the preparation is at least 10^8 viable cell units per gram of the preparation.

5. An application method in aquaculture, characterized in that, It includes the following steps: a. Prepare the bacterial agent according to the preparation described in claim 3; b. Uniformly put the bacterial agent into the aquaculture pond at a dose of 5 g to 10 g per ton of water body; c. Put it once or more a week for 6 to 12 weeks.

6. The method according to claim 5, wherein The aquatic species cultured in the aquaculture pond are selected from prawns, tilapia, sea bass, black carp or a polyculture system of shrimps and shellfish.

7. A method for improving the water quality of the aquaculture environment, characterized in that, Using the Bacillus sp. Yuejinran Z1 strain described in claim 1, the concentration of ammonia nitrogen, nitrite, total nitrogen, total phosphorus and chemical oxygen demand is reduced by degrading organic waste.

8. The method according to any one of claims 5 to 7, characterized in that The Bacillus sp. Yuejinran Z1 strain is applied to the aquaculture environment in the form of freeze-dried powder or liquid preparation to maintain the stability of water quality and promote the healthy growth of cultured organisms.

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