Rose half-photosynthetic bacteria, strain fermentation liquor and application thereof

Abstract

This invention belongs to the field of microbial technology, specifically relating to a rose-colored hemiphotosynthetic bacterium, its fermentation broth, and its applications. This invention discloses a rose-colored hemiphotosynthetic bacterium, deposited at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCC No. 30684. The rose-colored hemiphotosynthetic bacterium can dissolve algae through direct contact, exhibiting highly efficient algicidal activity against *Microcystis aeruginosa*. This invention also discloses a fermentation broth prepared based on the rose-colored hemiphotosynthetic bacterium. The rose-colored hemiphotosynthetic bacterium and its fermentation broth can be used as a microbial algicidal agent, showing promising application prospects in the control of cyanobacterial blooms.

Description

Technical Field

[0001] This invention belongs to the field of microbial technology, specifically relating to a rose-colored semi-photosynthetic bacterium, its fermentation broth, and its applications. Background Technology

[0002] While traditional physical and chemical algae control methods are effective to some extent, they are prone to causing secondary pollution and hindering the sustainable restoration of ecosystems. In contrast, biological control technologies have attracted widespread attention due to their advantages such as environmental friendliness, lower cost, and minimal disturbance to aquatic ecosystems. Among these, using algicidal bacteria to control cyanobacterial blooms is considered a promising biological algae control method. Therefore, screening out safe and efficient algicidal bacterial strains is of great significance for the prevention and control of cyanobacterial blooms and the restoration of aquatic ecological environments. Summary of the Invention

[0003] To address the aforementioned problems, this invention provides a rose-colored hemiphotosynthetic bacterium, its fermentation broth, and its applications. The rose-colored hemiphotosynthetic bacterium can dissolve algae through direct contact, exhibiting highly efficient algicidal activity against Microcystis aeruginosa. The rose-colored hemiphotosynthetic bacterium and its fermentation broth can serve as a microbial algicidal agent, showing promising application prospects in the control of cyanobacterial blooms.

[0004] To achieve the above objectives, the specific technical solution of the present invention is as follows: The first aspect of this invention provides a rose-colored hemiphotosynthetic bacterium ( Roseateles sp. The rose-colored hemiphotosynthetic bacterium is deposited at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCC No. 30684.

[0005] A second aspect of the present invention provides a fermentation broth, which is obtained by the following preparation method: The rose-colored hemisynthetic bacteria described above were inoculated into a liquid culture medium and activated at 25℃~30℃ for 16h~22h to obtain a rose-colored hemisynthetic bacteria culture. Based on the total volume of the liquid culture medium, the rose-colored semi-photosynthetic bacteria solution was transferred to the liquid culture medium at an inoculum rate of 0.8% to 1.2%, and fermented at 25℃ to 30℃ for 16 to 22 hours to obtain the fermentation broth.

[0006] Furthermore, the viable count of rose-colored hemiphotosynthetic bacteria per milliliter of the fermentation broth is 8.6 × 10⁻⁶. 8 CFU ~ 1.2 × 10 9 CFU.

[0007] Furthermore, the liquid culture medium is R2A medium.

[0008] Furthermore, each liter of the R2A medium contains 1.25 g of beef extract, 2.75 g of tryptone, 1.25 g of yeast extract, 0.5 g of acid-hydrolyzed casein, 0.5 g of yeast extract, 0.5 g of soluble starch, 0.3 g of dipotassium hydrogen phosphate, 0.1 g of magnesium sulfate, 0.3 g of sodium pyruvate, 0.25 g of peptone, and 0.25 g of glucose.

[0009] Furthermore, the activation culture was carried out at a temperature of 28°C for 20 hours.

[0010] Furthermore, the fermentation culture was carried out at a temperature of 28°C for 20 hours.

[0011] Furthermore, the transfer volume of the rose-colored semi-photosynthetic bacteria culture is 1% of the total volume of the liquid culture medium.

[0012] A third aspect of the present invention provides the application of the aforementioned rose-colored semi-photosynthetic bacteria or fermentation broth in the preparation of microbial algaecides.

[0013] Furthermore, the microbial algaecide is used to inhibit the growth of algae or kill algae; the algae are Microcystis aeruginosa, Chlamydomonas reinhardtii, Anabaena, Synechococcus, Scenedesmus obliquus, or Chlorella vulgaris.

[0014] Furthermore, the microbial algaecide inhibits or kills algae by suppressing their photosynthesis.

[0015] The fourth aspect of the present invention provides the application of the above-described rose-colored semi-photosynthetic bacteria or fermentation broth in the prevention and control of cyanobacterial blooms.

[0016] Furthermore, the rose-colored semi-photosynthetic bacteria or fermentation broth is introduced into an aquatic environment containing cyanobacteria for a treatment time of ≥8 days.

[0017] Furthermore, the cyanobacterium is Microcystis aeruginosa.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a rose-colored hemiphotosynthetic bacterium, its fermentation broth, and its applications. The rose-colored hemiphotosynthetic bacterium is deposited at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCC No. 30684 and is classified as *Rose-colored hemiphotosynthetic bacterium*. Roseateles sp. The rose-colored hemiphotosynthetic bacteria can dissolve algae through direct contact, exhibiting highly efficient algicidal activity against Microcystis aeruginosa, with a dissolution rate exceeding 90% within 8 days of treatment. This invention also discloses a fermentation broth prepared from the rose-colored hemiphotosynthetic bacteria. The rose-colored hemiphotosynthetic bacteria and its fermentation broth provided by this invention can be used as a microbial algaecide for the control of cyanobacterial blooms.

[0019] Of the algicidal bacteria reported so far, approximately 70% exert their algicidal effects indirectly, while strains relying on direct cell-to-cell contact are relatively few. During indirect algicidal processes, bacteria typically release algicides such as antibiotics, squalene, and extracellular enzymes into the aquatic environment. These compounds may adversely affect non-target aquatic organisms and even cause secondary pollution. In contrast, bacteria that dissolve algae through direct contact do not require the secretion of large amounts of such soluble substances, thus exhibiting greater advantages in terms of environmental friendliness and ecological safety, and better meeting the needs of sustainable algal bloom management.

[0020] Instructions for the Preservation of Biological Materials JY-HY1, referred to in this invention as *Rose-colored Hemiphotosynthetic Bacterium JY-HY1*, is classified and named as: *Rose-colored Hemiphotosynthetic Bacterium*. Roseateles sp. Its Latin name is: Roseateles sp. It was deposited on May 17, 2024, at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCC No. 30684. The address of the depository is Institute of Microbiology, Chinese Academy of Sciences, No. 3, No. 1 Beichen West Road, Chaoyang District, Beijing. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 The colony morphology of the rose-colored hemiphotosynthetic bacterium strain JY-HY1.

[0023] Figure 2 Scanning electron microscope image of the rose-colored hemiphotosynthetic bacterium JY-HY1, scale bar: 10 μm.

[0024] Figure 3 Phylogenetic tree of the rose-colored hemiphotosynthetic bacterium JY-HY1.

[0025] Figure 4 This is a statistical chart showing the algicidal effect of different concentrations of JY-HY1 strain fermentation broth on Microcystis aeruginosa.

[0026] Figure 5 A statistical chart showing the algicidal effect of different component solutions on Microcystis aeruginosa.

[0027] Figure 6 Scanning electron microscope image of Microcystis aeruginosa treated with the rose-colored hemiphotosynthetic bacterium JY-HY1. Figure 6 A in the figure represents the control group. Figure 6 B in the text represents the 5% treatment group. Figure 6 C in the figure represents the 10% treatment group. Scale bar: 5μm.

[0028] Figure 7 The results show the effects of the rose-colored hemiphotosynthetic bacterium JY-HY1 on the photosynthetic system of Microcystis aeruginosa. Figure 7 In the figure, A represents the change in chlorophyll a content of Microcystis aeruginosa. Figure 7 In this context, B represents the change in the chlorophyll fluorescence parameter Fv / Fm. Figure 7 C in the figure represents the change in light utilization efficiency of Microcystis aeruginosa. Figure 7 D in the figure represents the trend of the maximum electronic transport rate.

[0029] Figure 8 The effect of the rose-colored hemiphotosynthetic bacterium JY-HY1 on the photosynthetic pigments of Microcystis aeruginosa. Figure 8 In the figure, A represents the change in allophycocyanin content. Figure 8 In the figure, B represents the change in phycocyanin content. Figure 8 C in the figure represents the change in phycoerythrin content. Figure 8 D in the figure represents the change in carotenoid content.

[0030] Figure 9 Statistical analysis of the algicidal results of the rose-colored hemiphotosynthetic bacterium JY-HY1 on different freshwater algae. Figure 9 In the figure, A represents the statistical results of algicidal activity of Chlamydomonas reinhardtii by the rose-colored hemiphotosynthetic bacterium JY-HY1. Figure 9 In the figure, B represents the statistical results of algicidal activity of the rose-colored hemiphotosynthetic bacterium JY-HY1 against Anabaena. Figure 9 In the figure, C represents the statistical results of algicidal activity of Synechococcus by the rose-colored hemiphotosynthetic bacterium JY-HY1 against Synechococcus. Figure 9 In the figure, D represents the statistical results of algicidal activity of Chlorella by the rose-colored hemiphotosynthetic bacterium JY-HY1. Figure 9 E in the figure represents the statistical results of algicidal activity of the rose-colored hemiphotosynthetic bacterium JY-HY1 against Scenedesmus obliquus. Detailed Implementation

[0031] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise specified, the experimental methods described in the embodiments of the present invention are conventional methods, and the materials and reagents used in the following embodiments are commercially available unless otherwise specified.

[0032] The *Microcystis aeruginosa*, *Chlorella vulgaris*, *Scenedesmus obliquus*, *Synechococcus*, *Anabaena*, and *Chlamydomonas reinhardtii* used in this invention were all purchased from Shanghai Guangyu Biotechnology Co., Ltd.

[0033] The R2A medium formula is as follows: 1.25g beef extract powder, 2.75g tryptone, 1.25g yeast extract, 0.5g acid-hydrolyzed casein, 0.5g yeast extract powder, 0.5g soluble starch, 0.3g dipotassium hydrogen phosphate, 0.1g magnesium sulfate, 0.3g sodium pyruvate, 0.25g peptone, 0.25g glucose, and diluted with water to 1L.

[0034] This invention provides a rose-colored hemiphotosynthetic bacterium, its fermentation broth, and its applications. This rose-colored hemiphotosynthetic bacterium is deposited at the China General Microbiological Culture Collection Center (CGMCC), with accession number CGMCC No. 30684. This rose-colored hemiphotosynthetic bacterium can dissolve algae through direct contact and exhibits highly efficient algicidal activity against *Microcystis aeruginosa*. This invention also discloses a fermentation broth prepared based on the rose-colored hemiphotosynthetic bacterium. The rose-colored hemiphotosynthetic bacterium and its fermentation broth can be used as a microbial algicidal agent, showing promising application prospects in the control of cyanobacterial blooms.

[0035] Example 1: Isolation and identification of the rose-colored hemiphotosynthetic bacterium strain JY-HY1 This invention isolated and screened a candidate strain with algicidal activity from environmental samples in Liushi Town, Yueqing City, Wenzhou City, Zhejiang Province, and named this candidate strain JY-HY1. The taxonomic position of strain JY-HY1 was determined through morphological, physiological and biochemical characteristics, and 16S rDNA sequence analysis.

[0036] First, the morphology of strain JY-HY1 was observed using plate culture and scanning electron microscopy, and the results are as follows: Figure 1 and Figure 2 As shown, the colonies of JY-HY1 are round, pale yellow-green, slightly raised, with relatively smooth edges, and the bacteria are rod-shaped without flagella.

[0037] As shown in Table 1, the physiological and biochemical test results of JY-HY1 were negative in the Gram staining test. JY-HY1 could not use glucose, mannitol, sucrose, fructose, maltose, or lactose as the sole carbon source for bacterial growth, and could not produce amylase, oxidase, or catalase. The results of the methyl red test and VP test on JY-HY1 were negative.

[0038] Table 1. Results of physiological and biochemical tests on strain JY-HY1

[0039] Note: "+" represents positive, and "-" represents negative.

[0040] Genomic DNA was extracted from strain JY-HY1 and amplified by PCR using universal primers 27F and 1492R. The obtained 16S rRNA gene sequence was sequenced by Sangon Biotech Co., Ltd. After sequencing, the sequence was compared with the BLAST database. A phylogenetic tree was constructed using MEGA 7.0 software and the Neighbor-joining method. The phylogenetic tree is shown below. Figure 3 .

[0041] like Figure 3 The results showed that when the strain's sequence was submitted to NCBI's GenBank, the strain with the highest homology was *Hemiphotosynthetic bacterium*. Therefore, strain JY-HY1 was identified as *Hemiphotosynthetic bacterium*.

[0042] Example 2: Preparation of fermentation broth The rose-colored hemiphotosynthetic bacterium JY-HY1 strain from Example 1 was inoculated into R2A medium and activated at 180 rpm and 28°C for 20 hours. The resulting bacterial culture was then transferred to fresh R2A medium at an inoculation rate of 1 v / v% and fermented at 180 rpm and 28°C for 20 hours to obtain a fermentation broth. The viable count of the rose-colored hemiphotosynthetic bacterium JY-HY1 strain in this fermentation broth was 8.6 × 10⁻⁶. 8 CFU / mL.

[0043] Example 3: Algal lysing effect of different concentrations of fermentation broth on Microcystis aeruginosa The fermentation broth prepared in Example 2 was added to *Microcystis aeruginosa* algal solution in the exponential growth phase at 5%, 10%, 15%, and 20% of the total volume, respectively, for co-cultivation, i.e., 5%, 10%, 15%, and 20% treatment groups. *Microcystis aeruginosa* algal solution in the exponential growth phase without added fermentation broth served as the control group (CK). Both the experimental and control groups were replicated in triplicate. The number of algal cells was counted daily under a microscope using a hemocytometer, and the algal lysis rate was further calculated.

[0044] like Figure 4 As shown, the number of algal cells in the 15% and 20% treatment groups approached zero around the seventh day, while the algal dissolution rate in the 10% treatment group reached 94% on the eighth day.

[0045] Example 4: Study on the algicidal mechanism of the rose-colored hemiphotosynthetic bacterium JY-HY1 Preparation of sterile supernatant: The fermentation broth prepared in Example 2 was centrifuged at 8000 rpm for 3 minutes and filtered through a 0.22 μm filter membrane. The resulting filtrate was sterile supernatant.

[0046] Preparation of sterile aqueous cell resuspension: The fermentation broth prepared in Example 2 was centrifuged at 8000 rpm for 3 minutes, the supernatant was removed, and the cells were resuspended in sterile water of the same volume as the cells to obtain sterile aqueous cell resuspension.

[0047] Preparation of R2A cell resuspension: The fermentation broth prepared in Example 2 was centrifuged at 8000 rpm for 3 minutes, the supernatant was removed, and the cells were resuspended in an equal volume of R2A culture medium to obtain R2A cell resuspension.

[0048] Equal volumes of sterile supernatant, sterile aqueous cell resuspension, R2A cell resuspension, and fermentation broth were added to Microcystis aeruginosa in its exponential growth phase, respectively, with a sample containing an equal volume of R2A medium used as a control group. The number of algal cells was counted daily under a microscope using a hemocytometer.

[0049] The results are as follows Figure 5 As shown, the fermentation broth and R2A cell resuspension had a significant inhibitory effect on Microcystis aeruginosa, while the sterile aqueous cell resuspension had no algal inhibitory effect, indicating that strain JY-HY1 kills algal cells through direct contact.

[0050] Example 5: Observation of the algicidal process of Microcystis aeruginosa by JY-HY1 under scanning electron microscopy The fermentation broth prepared in Example 2 was added to *Microcystis aeruginosa* algal solutions in the exponential growth phase at 5% / v% and 10% / v% of the total volume, respectively, for co-culturing for 4 days (5% treatment group and 10% treatment group). *Microcystis aeruginosa* algal solutions in the exponential growth phase without added fermentation broth served as a control group. Morphological changes in *Microcystis aeruginosa* were observed using scanning electron microscopy.

[0051] The results are as follows Figure 6 As shown, normal Microcystis aeruginosa cells are relatively plump and round. After 4 days of treatment with fermentation broth, algal cells in the 5% treatment group showed a small amount of shrinkage, while algal cells in the 10% treatment group showed a large amount of shrinkage and began to break down. Smooth and flat algal cells could hardly be found in the microscope field of view.

[0052] Example 6: Effects of the rose-colored hemiphotosynthetic bacterium JY-HY1 on the photosynthetic system of Microcystis aeruginosa The fermentation broth prepared in Example 2 was added to *Microcystis aeruginosa* algal solution in the logarithmic growth phase at 5% v / v% and 10% v / v%, respectively, to form the 5% JY-HY1 treatment group and the 10% JY-HY1 treatment group. The total volume after mixing was fixed at 20 mL, with *Microcystis aeruginosa* algal solution in the logarithmic growth phase without added fermentation broth serving as the control group. Three replicates were set up for each group, and changes in chlorophyll fluorescence parameters were measured using a modulated fluorescence spectrometer. Samples were taken every other day to measure changes in fluorescence parameters such as chlorophyll a content, Fv / Fm, light utilization efficiency, and maximum electron transport rate.

[0053] Depend on Figure 7 It was found that the photosynthetic activity, light utilization efficiency, and maximum electron transport rate of *Microcystis aeruginosa* in the 10% JY-HY1 treatment group gradually decreased over time. This indicates that JY-HY1 caused serious damage to the photosynthetic system of *Microcystis aeruginosa*. Chlorophyll a content continued to decline very slowly even on the eighth day.

[0054] Example 7: Effects of JY-HY1 on photosynthetic pigments of Microcystis aeruginosa The fermentation broth prepared in Example 2 was added to *Microcystis aeruginosa* algal solution in the logarithmic growth phase at 5 v / v% and 10 v / v% of the total volume for co-culture, i.e., the 5% JY-HY1 treatment group and the 10% JY-HY1 treatment group. *Microcystis aeruginosa* algal solution in the logarithmic growth phase without added fermentation broth served as the control group. 10 mL of co-culture broth was collected every other day. The co-culture broth was centrifuged at 10,000 rpm for 10 min at 4 °C. The collected algal cells were placed in a 10 mL centrifuge tube, and 8 mL of 95 v / v% ethanol solution was added. Extraction was carried out at 4 °C in the dark for 24 h, with the sample inverted and shaken three times during the extraction. After extraction, the sample was centrifuged at 8,000 rpm for 5 min at 4 °C. The supernatant was collected, and the absorbance was measured spectrophotometrically at 665 nm, 649 nm, and 470 nm. The carotenoid content was calculated using the following formula, in mg / L.

[0055] Chlorophyll a concentration = ; Carotenoid concentration ; In the above formula, A 665 The absorbance value at 665 nm, A 649 The absorbance value at 649 nm, A 470 The absorbance value is at 470 nm.

[0056] Then, take 10 mL of the co-culture sample and centrifuge at 4℃ and 10000 rpm for 10 min. Resuspend the centrifuged precipitate in 5 mL of 0.05 mol / L phosphate buffered saline, freeze at -80℃, thaw at room temperature, and repeat the freeze-thaw cycle three times to lyse the algal cells. Finally, centrifuge the lysed algal cells at 4℃ and 12000 rpm for 10 min, collect the supernatant, and measure the absorbance at 565 nm, 620 nm, and 650 nm. Calculate the phycobilin content using the following formula, with the unit of phycobilin being mg / L.

[0057] Phycocyanin concentration ; Allophycocyanin concentration ; Phycoerythrin concentration ; In the above formula, A 620 The absorbance value at 620 nm, A 650 The absorbance value at 650 nm, A 565 The absorbance value is at 565 nm.

[0058] Statistical results are as follows Figure 8 As shown, with prolonged culture time, the carotenoid concentration in the 10% JY-HY1 treatment group gradually decreased, while the concentration in the control group steadily increased. This indicates that strain JY-HY1 disrupts the functional metabolism and photosynthesis of algae, preventing them from effectively capturing energy, affecting carotenoid synthesis, and causing a downward trend in carotenoid concentration over time. Phycobilins include phycocyanin, allophycocyanin, and phycoerythrin. Phycobilins, along with chlorophyll, give cyanobacteria their characteristic blue-green color. The results indicate that JY-HY1 affects the ability of *Microcystis aeruginosa* to produce phycobilins, reduces its light-harvesting and light-transmitting efficiency, thereby decreasing the content of pigment molecules and inhibiting its photosynthesis.

[0059] Example 8: Study on the algicidal specificity of the rose-colored hemiphotosynthetic bacterium JY-HY1 Five freshwater algae from different genera were used in the experiment: *Chlorella vulgaris*, *Scenedesmus obliquus*, *Synechococcus*, *Anabaena*, and *Chlamydomonas reinhardtii*. Except for *Chlamydomonas reinhardtii*, which was cultured in Se medium, the other four algae were cultured in BG11 medium. All algae were cultured under a light intensity of 2500 Lx and a 12h / 12h light / dark cycle.

[0060] Experimental group: Based on the total volume of algal solution, the fermentation broth prepared in Example 2 was inoculated into five algal solutions cultured to the logarithmic growth phase and in the same state at a volume ratio of 10 v / v%.

[0061] Control group: R2A medium was added to five algal cultures that had reached the logarithmic growth phase and were in the same condition, based on the total volume of the algal culture.

[0062] Samples were taken on the fourth and eighth days, and the number of algal cells was counted under a microscope using a hemocytometer.

[0063] Figure 9 A in the text represents Chlamydomonas reinhardtii. Figure 9 B in the text represents Anabaena, Figure 9 C in the text represents Synechococcus, Figure 9 D in the text represents Chlorella vulgaris. Figure 9 E in the text refers to Scenedesmus obliqueis, which is composed of... Figure 9 It can be seen that JY-HY1 has a slight inhibitory effect on Chlamydomonas reinhardtii, Anabaena, Synechococcus, Scenedesmus obliquus and Chlorella vulgaris, indicating that JY-HY1 has a very strong specificity for Microcystis aeruginosa.

[0064] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of the invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this invention.

[0065] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A rose-colored semi-photosynthetic fungus ( Roseateles sp. ), characterized in that, The rose-colored hemiphotosynthetic bacterium is deposited at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCC No. 30684.

2. A fermentation broth, characterized in that, The fermentation broth is obtained by the following preparation method: The rose-colored hemiphotosynthetic bacteria described in claim 1 were inoculated into R2A medium and activated and cultured at 25℃~30℃ for 16h~22h to obtain rose-colored hemiphotosynthetic bacteria culture. Based on the total volume of R2A medium, the rose-colored semi-photosynthetic bacteria culture was transferred to R2A medium at an inoculum of 0.8% to 1.2%, and fermented at 25°C to 30°C for 16 to 22 hours to obtain the fermentation broth.

3. The fermentation broth according to claim 2, characterized in that, The viable count of rose-colored hemiphotosynthetic bacteria per milliliter of the fermentation broth was 8.6 × 10⁻⁶. 8 CFU ~ 1.2 × 10 9 CFU.

4. The application of the fermentation broth according to claim 2 in the preparation of a microbial algaecide, characterized in that, The microbial algaecide is used to inhibit the growth of algae or kill algae; the algae are Microcystis aeruginosa, Chlamydomonas reinhardtii, Anabaena, Synechococcus, Scenedesmus obliqueis, or Chlorella vulgaris.

5. The application of the fermentation broth according to claim 2 in the prevention and control of cyanobacterial blooms, characterized in that, The cyanobacterium is Microcystis aeruginosa.

6. The application according to claim 5, characterized in that, The fermentation broth was introduced into an aquatic environment containing Microcystis aeruginosa for ≥8 days.

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