A yeast microorganism, its preparation method and use

Abstract

The application relates to the technical field of microorganisms, and discloses a yeast microorganism and a preparation method and application thereof. The yeast microorganism comprises inactivated yeast, arginine, chitosan, trace elements and an emulsified coating layer. The emulsified coating layer coats the yeast which is surface-modified by arginine and chitosan and adsorbs trace elements. The emulsified coating layer comprises cholesterols and phospholipids. After the surface of the yeast microorganism is treated by chitosan and arginine, the surface potential of the yeast microorganism is positive, the yeast microorganism can effectively adsorb trace elements and is coated by phospholipid cholesterols, the average density of the yeast microorganism is less than that of untreated yeast microorganisms, the suspension property of the yeast microorganism in water can be obviously improved, the yeast microorganism can be more effectively ingested by Daphnia, water deterioration can be reduced, and the existing plight that Daphnia breeding highly depends on microalgae as bait can be improved, thereby providing a basis for factoryized Daphnia breeding.

Description

Technical Field

[0001] This application relates to the field of microbial technology, and in particular to a yeast microorganism, its preparation method, and its application. Background Technology

[0002] Cladocera are an important group of zooplankton, belonging to the order Cladocera in the class Crustacea of ​​the phylum Arthropoda. They have laterally compressed bodies and often move short distances by hopping in the water, hence the name "water flea" or simply "Daphnia". Cladocera play a vital role in the ecosystem, especially in the food chain as primary consumers and a source of live food for fish and shrimp larvae. They also have a significant advantage in assisting domesticated fish larvae in consuming formulated feeds.

[0003] Current cladoceran farming primarily relies on outdoor ponds. In outdoor pond farming, fermented chicken manure and oilseed cakes are used as the main feed, supplemented by naturally growing microalgae in the water. This method has low production costs but suffers from problems such as unstable quality and supply, contamination by various protozoa, and a high incidence of pathogens. A small number of indoor cladoceran farming methods use concentrated algae (such as concentrated Chlorella and Microcystis) as feed. While the quality is more stable, this method suffers from high overall production costs and unstable supply of concentrated algae.

[0004] Common yeasts include brewer's yeast and baker's yeast. These yeasts contain a complete range of essential amino acids in sufficient quantities and appropriate proportions, with total protein accounting for 40%-55% of their dry weight, making them excellent protein sources. Brewer's yeast has a larger production volume; the beer industry alone produces approximately 35,000 to 57,000 tons of brewer's yeast (equivalent to dry yeast) annually, ensuring ample supply. Yeast particles are generally 3-8 micrometers (µm) in diameter, a size suitable for most cladocerans. However, because yeast itself lacks the cholesterol, phospholipids, and trace elements such as iron, copper, zinc, manganese, and cobalt necessary for cladoceran growth, and because the yeast cell wall is difficult for cladocerans to digest, using yeast as feed for cladocerans often results in nutrient deficiencies, slow growth, and even death. Therefore, yeast must be processed before using it as feed for cladocerans. Summary of the Invention

[0005] Therefore, the purpose of this application is to provide a yeast microorganism and its preparation method, so that the yeast microorganism has good suspension properties and comprehensive nutrition, which is conducive to being consumed by cladocerans.

[0006] Another objective of this application is to provide bait prepared based on the aforementioned yeast microorganisms and its related applications in bait preparation.

[0007] In order to solve the above-mentioned technical problems / achieve the above-mentioned objectives, or at least partially solve the above-mentioned technical problems / achieve the above-mentioned objectives, as a first aspect of this application, a yeast microorganism is provided, comprising inactivated yeast, arginine, chitosan, trace elements and an emulsion coating layer, wherein the emulsion coating layer coats yeast with surface modified with arginine and chitosan and volume-adsorbed trace elements, and the emulsion coating layer comprises cholesterol and phospholipids.

[0008] Optionally, the trace elements include one or more of iron, copper, zinc, manganese, and cobalt.

[0009] Optionally, the yeast includes baker's yeast cells or brewer's yeast.

[0010] Optionally, the chitosan has a degree of deacetylation ≥95 and a molecular weight of 50,000-60,000.

[0011] As a second aspect of this application, a method for preparing yeast microorganisms as described in this application is provided, comprising: Inactivate the yeast; The inactivated yeast was thoroughly mixed with a solution composed of chitosan and arginine. By controlling the amount of chitosan and arginine solution added, the mixed solution was made free of flocculation and precipitation, thus obtaining yeast treated with chitosan and arginine. The treated yeast is thoroughly mixed with the trace element solution to obtain yeast that adsorbs trace elements. The yeast that adsorbs trace elements is thoroughly mixed with an emulsion containing cholesterol and phospholipids to form an emulsion coating layer, thereby obtaining the yeast microorganism.

[0012] Optionally, the solution composed of chitosan and arginine uses glacial acetic acid as a solvent, and the solution pH is 4.0-4.5.

[0013] Optionally, the trace element solution includes iron glycinate, iron citrate, zinc glycinate, copper glycinate, manganese glycinate, and cobalt chloride.

[0014] Optionally, the mass ratio of cholesterol to phospholipids in the emulsion is 1:(10-20).

[0015] Optionally, the yeast is dry yeast, which needs to be rehydrated before inactivation.

[0016] As a third aspect of this application, the application of the yeast microorganism described in this application in the preparation of bait is provided.

[0017] As a fourth aspect of this application, a bait is provided, comprising the yeast microorganism described in this application.

[0018] This application uses arginine to treat the surface of yeast microorganisms, making their surface potential positively charged. This allows for the effective adsorption of trace elements and the coating of phospholipids and cholesterol, resulting in an average density lower than that of untreated yeast microorganisms. This significantly improves their suspension in water, making them more readily consumed and utilized by cladocerans, reducing water pollution, and alleviating the current predicament of cladoceran aquaculture being highly dependent on microalgae as feed. This provides a foundation for the industrialized aquaculture of cladocerans. Attached Figure Description

[0019] Figure 1 The diagram shown is a schematic representation of the structure of the yeast microorganism of this application; Figure 2 The image shows an example of determining the volume ratio of chitosan and arginine solutions; Figure 3 The example shown illustrates how to determine the maximum volume ratio of an emulsion. Detailed Implementation

[0020] This application discloses a yeast microorganism, its preparation method, and its application. Those skilled in the art can refer to this document and appropriately modify the process parameters to achieve the desired result. It is particularly important to note that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this application. The products, processes, and applications described in this application have been described through preferred embodiments. Those skilled in the art can obviously modify or appropriately change and combine the methods described herein without departing from the content, spirit, and scope of this application to implement and apply the technology of this application. Obviously, the described embodiments are only some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without creative effort are within the scope of protection of this application.

[0021] It should be noted that, in this document, relational terms such as "first" and "second," "step 1" and "step 2," and "(1)" and "(2)" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. Moreover, the embodiments and features described in this application can be combined with each other without conflict.

[0022] Among the feeds for cladocerans, untreated yeast feed refers to the dry powder or wet cells of brewer's yeast or baker's yeast. These yeasts contain a complete range of essential amino acids in sufficient quantities and appropriate proportions, and the total protein accounts for 40%-55% of the dry weight, making them an excellent protein source. However, when yeast is used as the sole feed for cladocerans, the lack of cholesterol, phospholipids, and trace elements such as iron, copper, zinc, manganese, and cobalt often leads to nutritional deficiencies, slow growth, and even death in cladocerans.

[0023] Cholesterol, phospholipids, and trace elements cannot be directly fed to cladocerans; they must be fed through a carrier. Yeast itself is an excellent carrier, but because cholesterol, phospholipids, and the yeast surface zeta potential are all negative, simple mixing cannot enable the yeast to absorb these nutrients, or the absorption effect is poor.

[0024] To address these deficiencies in the prior art, in the first aspect of this application, a yeast microorganism is provided, comprising inactivated yeast, chitosan, arginine, trace elements, and an emulsion coating layer, wherein the emulsion coating layer coats the surface modified with arginine, chitosan, and yeast that adsorbs trace elements, and the emulsion coating layer comprises cholesterol and phospholipids.

[0025] In the yeast microorganisms provided in this application, chitosan and arginine assist in altering the surface potential of the yeast, enabling it to adsorb trace elements and be coated by phospholipid and cholesterol emulsions. A schematic diagram of the structure is shown below. Figure 1 Arginine treatment induces a positive surface potential in yeast, facilitating the subsequent adsorption of trace elements and the binding of particles with negative surface potentials, such as phospholipids and cholesterol. Compared to using arginine alone to alter the yeast surface potential, the combined treatment with chitosan and arginine can better improve the suspension of yeast microorganisms, maintain a high level of suspension over a long period, and improve the feeding effect on cladocerans.

[0026] In some embodiments of this application, the trace elements may be added according to the nutritional needs of cladocerans, including but not limited to one or more of iron, copper, zinc, manganese, and cobalt. More specifically, these trace elements are added by adding their salts, which may be organic or inorganic salts, such as iron glycinate, iron citrate, zinc glycinate, copper glycinate, manganese glycinate, cobalt chloride, etc.

[0027] In some embodiments of this application, the mass ratio of cholesterol to phospholipid in the emulsion is 1:10-20, for example 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19, 1:20 or any value between the two.

[0028] In some embodiments of this application, the yeast includes baker's yeast cells or brewer's yeast.

[0029] In some embodiments of this application, the chitosan has a degree of deacetylation ≥95 and a molecular weight of 50,000-60,000. Chitosan within this range is more effective at maintaining suspension compared to chitosan with other degrees of deacetylation and molecular weights.

[0030] In a second aspect of this application, a method for preparing yeast microorganisms as described in this application is provided, comprising: Inactivate the yeast; The inactivated yeast was thoroughly mixed with a solution composed of chitosan and arginine. By controlling the amount of chitosan and arginine added, the mixed solution was made free of flocculation and precipitation, thus obtaining yeast treated with arginine. The arginine-treated yeast was thoroughly mixed with the trace element solution to obtain yeast that adsorbs trace elements. The yeast that adsorbs trace elements is thoroughly mixed with an emulsion containing cholesterol and phospholipids to form an emulsion coating layer, thereby obtaining the yeast microorganism.

[0031] In some embodiments of this application, yeast is inactivated by pasteurization, which can kill yeast microorganisms while preserving the maximum amount of nutrients in the yeast itself. Inactivation ensures that the prepared yeast microorganisms are readily digestible and usable by cladocerans, and avoids the continuous use of added nutrients by live yeast for reproduction, which would lead to nutrient loss and the generation of large amounts of metabolic waste detrimental to cladoceran growth. In other embodiments of this application, the pasteurization temperature is 62-63°C, and inactivation can be assisted by continuous stirring at 60-80 rpm for 15 minutes. After inactivation, detection can be performed by adding methylene blue solution; all inactivated yeast cells should be stained blue by the methylene blue solution.

[0032] In some embodiments of this application, the yeast is dry yeast. Dry yeast cells have a dense surface, making it difficult to effectively adsorb subsequent nutrients and difficult for cladocerans to digest. Therefore, dry yeast needs to be rehydrated before inactivation; fresh (wet) yeast does not require rehydration. In other embodiments of this application, the rehydration is usually performed by adding a sodium chloride solution, for example, adding approximately 10 times the volume of the dry yeast in a 0.9% sodium chloride solution. Stirring may be performed if necessary.

[0033] In some embodiments of this application, the solution composed of chitosan and arginine uses glacial acetic acid as a solvent, such as a 1-2% glacial acetic acid solution. In specific preparation, to ensure complete dissolution, chitosan can be first added to the glacial acetic acid solution and completely dissolved, and then arginine can be added until completely dissolved. The final pH value of the solution is 4.0-4.5. If the pH value is too high, the amount of arginine used can be reduced. In other embodiments of this application, the percentage content of chitosan is 0.2-0.4%, and the percentage content of arginine is 0.2-0.8%. The percentage content of both can be selected from any point within their respective ranges, such as 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, etc.

[0034] In some embodiments of this application, the inactivated yeast cells are centrifuged to obtain a precipitate, and then a solution composed of chitosan and arginine is added for treatment. The volume of the solution is 1-10 times the volume of the precipitate, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 times, or any value between the two. The state of the mixed solution containing the yeast cells is observed by controlling the volume multiple of the chitosan and arginine solution. When the mixed solution is uniform, without flocculation or precipitation, the volume of the chitosan and arginine solution is increased by another 1-2 times, which is the final chitosan and arginine solution usage multiple. At this time, the surface potential of the treated yeast cells is positive.

[0035] In some embodiments of this application, the trace element solution includes one or more solutions of iron glycinate, iron citrate, zinc glycinate, copper glycinate, manganese glycinate, and cobalt chloride; in other embodiments of this application, each 500 mL of trace element solution includes 200-500 mg of iron glycinate or iron citrate, 80-150 mg of zinc glycinate, 10-20 mg of copper glycinate, 20-40 mg of manganese glycinate, and 1-5 mg of cobalt chloride; preferably, it is prepared with distilled water or sterile water.

[0036] In some embodiments of this application, 200-800 mL of trace element stock solution is added per kilogram of yeast (on dry weight).

[0037] In some embodiments of this application, the volume ratio of the emulsion to the yeast to the emulsion is 1000:(1~10), for example, 1000:1, 1000:2, 1000:3, 1000:4, 1000:5, 1000:6, 1000:7, 1000:8, 1000:9, 1000:10 or any value between the two, wherein the yeast is measured by dry weight. By controlling the volume ratio of the emulsion, the state of the mixed solution containing the yeast is observed. When the mixed solution is uniform, without flocculation or precipitation, the ratio is reduced by 1-2, which is the maximum emulsion usage ratio. For example, when the volume ratio of the emulsion to the yeast is 1000:6, the mixed solution is uniform, without flocculation or precipitation, then the maximum emulsion usage ratio is 1000:4 or 1000:5.

[0038] In some embodiments of this application, the mass ratio of cholesterol to phospholipid in the emulsion is 1:10-20, for example 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19, 1:20 or any value between the two.

[0039] In other embodiments of this application, a co-solvent and / or heating may be added to promote cholesterol dissolution. For example, 60-100% anhydrous ethanol (by weight of phospholipid) may be added to cholesterol as a co-solvent, and the mixture may be heated to 60-65°C and stirred at 200 rpm for 5 minutes to fully dissolve the cholesterol in the anhydrous ethanol. After the cholesterol is dissolved, it is then thoroughly mixed with phospholipids and water to prepare an emulsion.

[0040] In a third aspect of this application, the yeast microorganisms treated in this application can maintain a suspension rate of over 95% for an extended period, resulting in better feeding performance and higher cladoceran yields. Based on this, this application provides the application of the yeast microorganisms described herein in feed preparation, particularly in the preparation of cladoceran feed.

[0041] In a fourth aspect of this application, a bait is provided, comprising the yeast microorganisms described in this application; in addition, substances that meet the requirements of other nutrients needed by cladocerans and / or the usage and storage conditions of the yeast microorganisms may be added.

[0042] In the comparative experiments provided in this application, unless otherwise specified, all experimental conditions and materials remain consistent to ensure comparability. Furthermore, all materials used in this application are commercially available.

[0043] The following provides a further description of a yeast microorganism, its preparation method, and its application provided in this application.

[0044] Example 1: Rehydration of dry yeast: Take 100g of dry bread yeast, add 10 times the yeast weight of 0.9% sodium chloride solution, and stir at 32℃ and 160rpm for 30min.

[0045] Pasteurization inactivation: After rehydration, the yeast is heated to a constant temperature of 63°C and stirred continuously at 80 rpm for 15 minutes.

[0046] Chitosan (degree of deacetylation ≥ 95%, molecular weight 50,000-60,000) and arginine were analytical grade reagents. Prepare 1L of 1% glacial acetic acid solution using sterilized tap water, add 2g of chitosan and stir until completely dissolved, then add 2g of arginine and stir until completely dissolved. The final pH of the solution was 4.1.

[0047] The pasteurized yeast was centrifuged at 3000 rpm for 3 min, and the supernatant was discarded while the precipitate was retained.

[0048] Take 1 mL of centrifuged yeast and place it in a 12-well plate. Add chitosan and arginine solutions at volumes of 1, 2, 3, ... 10, 11, and 12 times the yeast volume, respectively. Mix well, let stand for 2 minutes, and then observe. Figure 2 As shown, a 3-fold increase in the concentration of chitosan and arginine solution indicates uniformity, no flocculation, and no precipitation. Therefore, a 4-fold increase in the final concentration of chitosan and arginine solution is determined. Four times the concentration of chitosan and arginine solution is added to the centrifuged yeast to resuspend the yeast in a single-cell state.

[0049] Preparation of trace element stock solution: Dissolve 450 mg of iron glycine or iron citrate, 120 mg of zinc glycine, 18 mg of copper glycine, 32 mg of manganese glycine, and 2 mg of cobalt chloride in 500 mL of distilled water and mix well. Add 500 mL of trace element stock solution per kilogram of dry yeast (based on yeast dry weight).

[0050] Add trace element stock solution to yeast treated with chitosan and arginine, and stir at 60 rpm for 5 minutes at room temperature to allow the trace elements to be fully adsorbed into the yeast cells.

[0051] The cholesterol was an analytical grade pharmaceutical product, and the phospholipids were feed-grade soybean phospholipid oil. The cholesterol:phospholipid ratio was 1:16 by mass. 100% anhydrous ethanol (by weight of the phospholipids) was added to the cholesterol as a co-solvent, and the mixture was stirred at 200 rpm for 5 minutes at room temperature to ensure complete dissolution of the cholesterol in the anhydrous ethanol. The phospholipids were then added to the prepared cholesterol solution, and the mixture was stirred at 200 rpm for 5 minutes until no large white cholesterol particles were visible to the naked eye. Distilled water, one volume larger than the mixture, was slowly added to the homogenized cholesterol-phospholipid mixture, and an emulsion was prepared using ultrasound with a probe.

[0052] After preparing the emulsion, take 2 mL of yeast solution and place it in each well of a 12-well plate. Add yeast to the emulsion at volume ratios of 1000:1, 1000:2, 1000:3...1000:8, 1000:9, and 1000:10, respectively. Mix well and let stand for 2 minutes before observing. Figure 3 As shown, the highest ratio of uniformity, no flocculation, and no sedimentation is 1000:4, and the emulsion usage ratio is determined to be 1000:3.

[0053] Add phospholipid cholesterol emulsion to yeast liquid at a ratio of 1000:3, stir at 60 rpm for 5 minutes at room temperature to ensure that the phospholipid cholesterol emulsion fully coats the yeast cells.

[0054] Example 2: Take 100g of fresh brewing yeast and skip the rehydration step.

[0055] Pasteurization inactivation: Heat the yeast to 63°C and keep stirring at 80 rpm for 15 minutes.

[0056] Chitosan (degree of deacetylation ≥ 95%, molecular weight 50,000-60,000) and arginine were analytical grade reagents. Using sterilized tap water, prepare 1L of 1% glacial acetic acid solution, add 2.5g of chitosan and stir until completely dissolved, then add 4g of arginine and stir until completely dissolved. The final pH of the solution is 4.3.

[0057] The pasteurized yeast was centrifuged at 3000 rpm for 3 min, and the supernatant was discarded while the precipitate was retained.

[0058] Take 1 mL of centrifuged yeast and place it in a 12-well plate. Add chitosan and arginine solutions at volumes of 1, 2, 3, ... 10, 11, and 12 times the yeast volume, respectively. Mix well and let stand for 2 minutes. Observe the mixture. The 3-fold volume indicates uniformity, no flocculation, and no precipitation. Determine the final chitosan and arginine solution volume to be 4 times. Add 4 times the volume of chitosan and arginine solution to the centrifuged yeast to resuspend the yeast in a single-cell state.

[0059] Preparation of trace element stock solution: Dissolve 400 mg of iron glycine or iron citrate, 140 mg of zinc glycine, 20 mg of copper glycine, 30 mg of manganese glycine, and 1 mg of cobalt chloride in 500 mL of distilled water and mix well. Add 500 mL of trace element stock solution per kilogram of dry yeast (based on yeast dry weight).

[0060] Add trace element stock solution to yeast treated with chitosan and arginine, and stir at 60 rpm for 5 minutes at room temperature to allow the trace elements to be fully adsorbed into the yeast cells.

[0061] The cholesterol was an analytical grade pharmaceutical product, and the phospholipids were feed-grade soybean phospholipid oil. The cholesterol:phospholipid ratio was 1:12 by mass. 100% anhydrous ethanol (by weight of the phospholipids) was added to the cholesterol as a co-solvent, and the mixture was heated in a water bath to 40°C and stirred at 200 rpm for 5 minutes to ensure the cholesterol was fully dissolved in the anhydrous ethanol. The phospholipids were then added to the prepared cholesterol solution, and the mixture was heated in a water bath to 40°C and stirred at 200 rpm for 5 minutes until no large white cholesterol particles were visible to the naked eye. Distilled water, once the volume of the mixture, was slowly added to the homogenized cholesterol-phospholipid mixture, and an emulsion was prepared using ultrasound with a probe.

[0062] After the emulsion was prepared, 2 mL of yeast solution was placed in each 12-well plate. The yeast solution was added to the emulsion at volume ratios of 1000:1, 1000:2, 1000:3...1000:8, 1000:9, and 1000:10. The two were stirred and mixed thoroughly. After standing for 2 minutes, the mixture was observed. The highest ratio that was uniform, without flocculation or precipitation was 1000:5. Therefore, the emulsion usage ratio was determined to be 1000:4.

[0063] Add the target amount of phospholipid cholesterol emulsion to the yeast liquid and stir at 60 rpm for 5 minutes at room temperature to ensure that the phospholipid cholesterol emulsion fully coats the yeast cells.

[0064] Comparative Example 1: The comparative example was untreated fresh yeast. Fresh yeast preparation: Take 100g of dry bread yeast, add 10 times the yeast weight of 0.9% sodium chloride solution, and use a vortex mixer to stir at 32℃ and 160rpm for 30min. Then centrifuge at 3000rpm for 3min, discard the supernatant and retain the precipitate.

[0065] Comparative Example 2: This comparative example only shows yeast treated by pasteurization; the specific treatment method is the same as in Example 1. Comparative Example 3: This comparative example only shows yeast treated with chitosan and arginine solution, without trace element adsorption and emulsion coating. The specific treatment method is the same as in Example 1. Comparative Example 4: This comparative example uses yeast without added trace elements; the other treatment methods are the same as in Example 1. Comparative Example 5: This comparative example only involves arginine solution treatment (without adding chitosan); the other treatment methods are the same as in Example 1. Comparative Example 6: In this comparative example, the degree of deacetylation of chitosan is ≥80 and the molecular weight is 200kDa. The other treatment methods are the same as in Example 1. Experimental example: 1. Suspension property: Using a spectrophotometer, absorbance was measured at OD600 and a path length of 10 mm. Each group of yeast was diluted to an isoabsorbance, and the initial absorbance was measured. After waiting 10 minutes or storing at 4°C for 7 days, the suspension property was tested, and the final absorbance was measured. Suspension property = [1 - (initial absorbance - final absorbance) / initial absorbance] × 100% 2. Method for measuring the wet weight of cladocerans: Cut a suitable size 100-mesh sieve silk, soak it in tap water for 10 minutes to fully moisten it, gently shake it dry until no water drips down but a water film remains in the mesh, place it on an electronic scale to weigh the sieve silk, pour the cladocerans into the sieve silk, shake it slightly dry until no water drips down, and weigh the wet weight of the insects on the electronic scale.

[0066] 3. Experimental Methods: In a constant temperature chamber at 26℃ with a light intensity of 1000-3000 Lux, 3L of tap water was added to a 4.5L plastic container and aerated for 30 minutes. The initial inoculum was calculated by wet weight. After aeration, 1g of *Daphnia magna* (cladocerans suborder - Daphniaceae family) was inoculated into each group. A small amount of air was introduced to maintain dissolved oxygen above 5mg / L throughout the experiment. The cell density of yeast in each group was determined using a hemocytometer, and the cells were diluted with sterile tap water to an isodense concentration of 6×10⁻⁶. 9 cells / mL; feeding was conducted at 9:00 and 21:00 daily. On the first day, each group was fed 1 mL of diluted yeast solution, and on the second day, 1.5 mL was fed each time, and so on. Water was changed at 15:00 daily, with a water change volume of 100%. A feeding trial was conducted for 7 days. After 7 days, the final yield (based on wet weight) was measured at full harvest.

[0067] Table 1

[0068] As can be clearly seen from the results in Table 1, the suspension of yeast microorganisms treated in this application is greater than 95%, and even after being left for 7 days, it can still maintain a suspension of more than 90%. At the same time, the final yield after feeding naked daphnia is close to 3g. In the comparative examples, Comparative Examples 1-3 used fresh yeast, pasteurized yeast, and yeast treated only with chitosan and arginine solution, respectively. The results showed that their suspension was significantly lower than that of the proposed method, and the feeding effect was also poor. Compared with Comparative Example 4, the proposed method in this application did not mainly add trace elements. In terms of suspension, it was basically the same as the proposed method in this application, but the effect after feeding cladocerans was not good, with a yield of 2.33g and the insects turned white. Comparative Example 5, treated with only arginine, showed that although the initial suspension was above 90%, after 7 days of storage, the suspension dropped significantly to about 68%, indicating that using arginine alone cannot maintain a high suspension for a long time. Comparative Example 6 used chitosan with different parameters than those in this application. The results showed that the initial and long-term suspension properties were poor, indicating that the degree of deacetylation and molecular weight of chitosan have a significant impact on the surface potential of yeast modified with arginine.

[0069] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A yeast microorganism, characterized in that, It includes inactivated yeast, arginine, chitosan, trace elements, and an emulsion coating layer. The emulsion coating layer is coated with arginine, chitosan, and yeast that adsorbs trace elements. The emulsion coating layer includes cholesterol and phospholipids.

2. The yeast microorganism according to claim 1, characterized in that, The trace elements include one or more of iron, copper, zinc, manganese, and cobalt.

3. The yeast microorganism according to claim 1, characterized in that, The yeast includes baker's yeast cells or brewer's yeast.

4. The yeast microorganism according to claim 1, characterized in that, The degree of deacetylation of the chitosan is ≥95, and the molecular weight is 50,000-60,000.

5. A method for preparing yeast microorganisms as described in claim 1, characterized in that, include: Inactivate the yeast; The inactivated yeast was thoroughly mixed with a solution composed of chitosan and arginine. By controlling the amount of chitosan and arginine solution added, the mixed solution was made free of flocculation and precipitation, thus obtaining yeast treated with chitosan and arginine. The treated yeast is thoroughly mixed with the trace element solution to obtain yeast that adsorbs trace elements. The yeast that adsorbs trace elements is thoroughly mixed with an emulsion containing cholesterol and phospholipids to form an emulsion coating layer, thereby obtaining the yeast microorganism.

6. The preparation method according to claim 5, characterized in that, The solution composed of chitosan and arginine uses glacial acetic acid as a solvent, and the solution pH is 4.0-4.

5.

7. The preparation method according to claim 5, characterized in that, The trace element solution includes iron glycine, iron citrate, zinc glycine, copper glycine, manganese glycine, and cobalt chloride.

8. The preparation method according to claim 5, characterized in that, The mass ratio of cholesterol to phospholipids in the emulsion is 1:(10-20).

9. The use of the yeast microorganism according to any one of claims 1-4 in the preparation of feed.

10. A type of bait, characterized in that, Includes the yeast microorganism described in any one of claims 1-4.

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