Preparation method of microalgae bait

Abstract

The invention provides a preparation method of microalgae bait, the microalgae bait is prepared through microalgae culture, magnetic separation, microencapsulation wrapping, drying and other methods, during culture, a specific culture solution is added, culture conditions are adjusted, algae liquid cells are separated by adopting a nano magnetic dispersant, effective components in the microalgae cells are ensured, mixed cell sap is screened out, and the microalgae bait is prepared. The components in the core material are wrapped through microencapsulation wrapping, the components of the wall material are used for isolating the external environment, good oxidation resistance and water resistance are achieved, notches and pores of the bait are reduced after wrapping, the performance is stable, the storage life is long, the swelling and collapsing time in water is prolonged, collapsing of nutritional ingredients in the core material is delayed, and the bait has the advantages of being good in stability and good in stability. The loss rate is low, the acid value change rate is within 2.20%, the peroxide value change rate is within 1.41%, the water resistance time reaches 8.5 h, the loss rate is within 4.85%, the sinking rate reaches 98%, the bait is easy to sink into the water bottom and beneficial to being ingested by aquatic animals, and the utilization rate of the bait is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of aquatic feed production, and in particular to a method for preparing microalgae bait. Background Art

[0002] With the rapid development of aquaculture, market demand for fish continues to rise. Therefore, finding raw materials that can improve the survival rate and resilience of aquatic animals is crucial to increasing aquatic production. Microalgae are a type of phytoplankton that is rich in nutrients and widely distributed. Currently, beneficial microalgae used in aquaculture include Chlorella, Spirulina, Chlamydomonas, Chlorella, and Oocystis. Microalgae are rich in nutrients such as protein, fat, sugar, and minerals. They also contain various active substances such as astaxanthin, lutein, polysaccharides, antioxidants, and pigments. They are a new type of bio-bait. Produced by microalgae through photosynthesis, they offer excellent nutritional value and can be used as bait for aquatic animals such as fish and shellfish. The development prospects of microalgae bio-bait are promising. First, because microalgae bio-bait is produced from microalgae, its production cost is low, effectively reducing aquaculture costs. Second, microalgae bio-bait is rich in protein, fat, carbohydrates, vitamins, and minerals, making it an excellent feed for aquatic animals and improving their growth rate and disease resistance.

[0003] Therefore, microalgae are widely used in aquatic feeds, and their effectiveness has been well-established. Adding microalgae to aquatic feeds can effectively prevent disease, reduce the use of medications during the breeding process, and avoid the harmful effects of drug residues in aquatic products on human health. This has a significant impact on promoting the economic and social benefits of my country's aquaculture industry. With the increasing demand for aquatic products, the application prospects of microalgae-based biofeeds will continue to expand. Furthermore, with the continuous advancement of science and technology, the production technology of microalgae-based biofeeds will continue to improve, resulting in lower production costs and higher quality.

[0004] However, various nutrients in current microalgae baits are often affected by various factors and oxidized, resulting in a decrease in their nutritional value. To meet the needs of modern intensive aquaculture, microalgae baits are often supplemented with ingredients such as oil, fish meal, and fat-soluble vitamins to provide a more comprehensive and balanced nutritional profile. These substances are the most susceptible to oxidation in feeds, and especially in summer, high temperatures and high humidity accelerate oxidation. Energy substances (such as oil) in the feed become oxidatively rancid, leading to a decrease in energy levels and a reduction in the conversion rate of the microalgae bait. The oxidative loss of oil in microalgae baits also affects the transport, absorption, and utilization of fat-soluble vitamins and pigments in the body. Oxidative denaturation of proteins (such as fish meal) in microalgae baits can reduce the nutritional level of the feed. Furthermore, as aquatic feeds, microalgae baits are prone to dissolving, swelling, and collapsing in water, which is not only detrimental to aquatic animal ingestion but also causes water pollution. Summary of the Invention

[0005] In view of this, the present invention proposes a method for preparing microalgae bait to solve the above problems.

[0006] The technical solution of the present invention is achieved as follows: A method for preparing microalgae bait comprises the following steps:

[0007] S1. Cultivation of microalgae: Cultivate microalgae in culture medium, control the temperature at 20-30°C, and the light intensity at 80-150 μmol / (m 2 s), the light / dark time ratio is 5-7:3, and the culture is carried out for 24-48 hours. The mixed gas is introduced into the culture solution at a gas flow rate of 0.05-0.5 L / min until the microalgae cells grow to the logarithmic growth phase and the concentration is 1-5×10 10 cells / mL of microalgae liquid;

[0008] S2. Magnetic separation: Add a nano-magnetic dispersant to the microalgae solution obtained above at a volume ratio of 0.3-0.5:80, control the pH to 6-7, magnetically stir at room temperature for 20-60 minutes, then allow to stand at 30-50°C for 15-20 hours, filter, and collect the precipitate for later use;

[0009] S3, microencapsulation: The precipitate obtained in S2 is used as the core material, and a stabilizer and vegetable oil are added, and the mixture is sheared and emulsified at a rate of 2000-4000 rpm for 10-16 min to obtain a core material oil phase liquid, wherein the mass volume ratio of the core material, the stabilizer and the vegetable oil is (5-10):(0.3-0.9):8 g / mL, and the vegetable oil is preferably peanut oil, sunflower oil or soybean oil. Microencapsulated liposomes are used as the wall material, and water 1.5-3 times the mass of the wall material is added and mixed to form a wall material mixed solution. The core material oil phase liquid is added to the wall material mixed solution and homogenized at a homogenization pressure of 10-30 MPa and a homogenization time of 2-5 min to obtain an emulsion;

[0010] S4. Drying: The emulsion is spray-dried to obtain a powder, which is then polymerized and granulated to obtain a final product powder with a particle size distribution of 40-60 meshes to obtain a microalgae bait.

[0011] Furthermore, the percentage content of microalgae in S1 includes 10-15% of Scenedesmus obliquus, 8-12% of Platymonas subcordiformis, 5-10% of Chaetoceros muelleri, 3-11% of Phaeodactylum triangularis, 10-15% of Isochrysis galbana, 10-15% of Haematococcus pluvialis, 20-35% of Chlorella pyrenoidosa, and 15-20% of Pavlova, and the total density is 1.2-5.8×10 5 cells / mL.

[0012] Furthermore, the culture medium in S1 includes the following raw materials in parts by weight: 2-6 parts of dipotassium hydrogen phosphate, 0.4-0.8 parts of citric acid, 5-10 parts of zinc chloride, 1-3 parts of disodium edetate, 3-6 parts of sodium carbonate, 18-22 parts of sodium metasilicate, and 20-30 parts of seawater.

[0013] Furthermore, the C:N:Si ratio in the seawater is (10-15):(7-10):(0.5-1.5), and the pH value is 7.8-9.0.

[0014] Furthermore, the mixed gas in S1 is carbon dioxide and nitrogen in a volume ratio of 3-5:1.

[0015] Furthermore, the nanomagnetic dispersant in S2 is a mixed solution of superparamagnetic ferroferric oxide nanoparticle powder, triethanolamine and water with a volume-to-mass ratio g / mL of (20-40):(6-12):50.

[0016] Furthermore, the magnetic field intensity of the magnetic stirring in S2 is 300-500 GS, and the rotation speed is 60-150 rpm.

[0017] Furthermore, the stabilizer in S3 is one or a combination of vitamin E, polyethylene glycol laurate, sodium deoxycholate, whey protein, and polyglycerol fatty acid ester.

[0018] Furthermore, the microencapsulated liposomes in S3 are chitosan, calcium alginate, magnesium stearate, sodium tripolyphosphate, whey protein and beeswax in a mass ratio of (1-3): (4-7): (8-12): (3-5): (0.8-2.5): 10.

[0019] Furthermore, the volume ratio of the core material oil phase liquid and the wall material mixed solution in S3 is 15-20:80-90.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention prepares microalgae bait by cultivating microalgae, magnetic separation, microencapsulation, drying and other methods. First, the microalgae are placed in a culture solution for cultivation, and the temperature, light and aeration are controlled to cultivate microalgae with photosynthetic autotrophic ability, which can stimulate the growth of microalgae and significantly increase the biomass and biomass content of algae cells. Nano-magnetic dispersants are used to separate the algae liquid to separate algae cells with high effective ingredients, reduce damaged microalgae cell vacuoles in the algae liquid, and improve the nutritional content of the bait. The core material oil phase liquid is prepared. The microencapsulated solution is mixed with the wall material to isolate the core material from the outside world, thereby controlling the release, retaining the activity and integrity of the microalgae cells, and protecting the effective ingredients of the microalgae from oxidation and disintegration in water; it has excellent antioxidant and water resistance, with an acid value change rate within 2.20%, a peroxide value change rate within 1.41%, a water resistance time of 8.5 hours, a loss rate within 4.85%, a sinking rate of 98%, and is easy to sink to the bottom of the water, which is conducive to being eaten by aquatic animals and improving the utilization rate of bait. DETAILED DESCRIPTION

[0022] In order to better understand the technical content of the present invention, specific examples are provided below to further illustrate the present invention.

[0023] Unless otherwise specified, the experimental methods used in the examples of the present invention are all conventional methods.

[0024] Unless otherwise specified, the materials, reagents, etc. used in the examples of the present invention can be obtained from commercial sources.

[0025] Example 1

[0026] A method for preparing microalgae bait comprises the following steps:

[0027] S1. Cultivation of microalgae: Cultivate microalgae in culture medium, control the temperature at 20°C, and the light intensity at 80 μmol / (m 2 s), the light / dark time ratio was 5:3, and the culture was carried out for 24 h. The mixed gas was introduced into the culture solution at a gas flow rate of 0.05 L / min until the microalgae cells grew to the logarithmic growth phase and the concentration was 1×10 10 cells / mL of microalgae liquid;

[0028] The percentage of microalgae included 10% of Scenedesmus obliquus, 12% of Platymonas subcordiformis, 6% of Chaetoceros muelleri, 11% of Phaeodactylum triangularis, 11% of Isochrysis galbana, 10% of Haematococcus pluvialis, 20% of Chlorella pyrenoidosa, and 20% of Pavlova, with a total density of 1.2×10 5 cells / mL;

[0029] The culture medium includes the following raw materials in parts by weight: 2 parts dipotassium hydrogen phosphate, 0.4 parts citric acid, 5 parts zinc chloride, 1 part disodium edetate, 3 parts sodium carbonate, 18 parts sodium metasilicate, and 20 parts seawater, wherein the C:N:Si ratio in the seawater is 10:7:0.5 and the pH value is 7.8;

[0030] S2. Magnetic separation: Add nano-magnetic dispersant to the microalgae solution obtained above, control the pH to 6, set the magnetic field strength to 300 GS at room temperature, stir magnetically at 60 rpm for 20 min, then let stand at 30°C for 15 h, filter, and collect the precipitate for later use;

[0031] The nanomagnetic dispersant is a mixed solution of superparamagnetic ferroferric oxide nanoparticle powder, triethanolamine and water in a volume-to-mass ratio of 20:6:50 g / mL;

[0032] S3, microencapsulation: the precipitate obtained in S2 was used as the core material, and a stabilizer and vegetable oil were added and sheared and emulsified at a rate of 2000 rpm for 10 min to obtain a core material oil phase liquid, the mass volume ratio of the core material, stabilizer and vegetable oil g / mL was 5:0.3:8, the stabilizer was whey protein, microencapsulated liposomes were used as the wall material, 1.5 times the mass of the wall material was added and mixed with water to form a wall material mixed solution, the core material oil phase liquid was added to the wall material mixed solution and homogenized, the volume ratio of the core material oil phase liquid and the wall material mixed solution was 15:80, the homogenization pressure was 10 MPa, and the homogenization time was 2 min to obtain an emulsion;

[0033] The microencapsulated liposomes are chitosan, calcium alginate, magnesium stearate, sodium tripolyphosphate, whey protein, and beeswax in a mass ratio of 1:4:8:3:0.8:10;

[0034] S4. Drying: The emulsion is spray-dried to obtain a powder, which is then polymerized and granulated to obtain a final product powder with a particle size distribution of 40-60 meshes to obtain a microalgae bait.

[0035] Example 2

[0036] A method for preparing microalgae bait comprises the following steps:

[0037] S1. Cultivation of microalgae: Cultivate microalgae in culture medium at a temperature of 30°C and a light intensity of 150 μmol / (m 2 s), the light / dark time ratio was 7:3, and the culture was carried out for 48 h. The mixed gas was introduced into the culture solution at a gas flow rate of 0.5 L / min until the microalgae cells grew to the logarithmic growth phase and the concentration was 5×10 10 cells / mL of microalgae liquid;

[0038] The percentage of microalgae included 12% of Scenedesmus obliquus, 10% of Platymonas subcordiformis, 10% of Chaetoceros muelleri, 8% of Phaeodactylum triangularis, 15% of Isochrysis galbana, 10% of Haematococcus pluvialis, 20% of Chlorella pyrenoidosa, and 15% of Pavlova, with a total density of 5.8×10 5 cells / mL;

[0039] The culture medium includes the following raw materials in parts by weight: 6 parts of dipotassium hydrogen phosphate, 0.8 parts of citric acid, 10 parts of zinc chloride, 3 parts of disodium edetate, 6 parts of sodium carbonate, 22 parts of sodium metasilicate, and 30 parts of seawater, wherein the C:N:Si ratio in the seawater is 15:10:1.5 and the pH value is 9.0;

[0040] S2. Magnetic separation: Add nano-magnetic dispersant to the microalgae solution obtained above, control the pH to 7, set the magnetic field strength to 500 GS at room temperature, stir magnetically at 150 rpm for 60 min, then stand at 50°C for 20 h, filter, and collect the precipitate for later use;

[0041] The nanomagnetic dispersant is a mixed solution of superparamagnetic ferroferric oxide nanoparticle powder, triethanolamine and water in a volume-to-mass ratio of 40:12:50 g / mL;

[0042] S3, microencapsulation: The precipitate obtained in S2 was used as the core material, and a stabilizer and vegetable oil were added, and the mixture was sheared and emulsified at a rate of 4000 rpm for 16 minutes to obtain a core material oil phase liquid, wherein the mass volume ratio of the core material, stabilizer, and vegetable oil was 10:0.9:8 g / mL, and the stabilizer was vitamin E. Microencapsulated liposomes were used as the wall material, and water 3 times the mass of the wall material was added and mixed to form a wall material mixed solution. The core material oil phase liquid was added to the wall material mixed solution and homogenized, wherein the volume ratio of the core material oil phase liquid and the wall material mixed solution was 20:90, the homogenization pressure was 30 MPa, and the homogenization time was 5 minutes to obtain an emulsion;

[0043] The microencapsulated liposomes are chitosan, calcium alginate, magnesium stearate, sodium tripolyphosphate, whey protein, and beeswax in a mass ratio of 3:7:12:5:2.5:10;

[0044] S4. Drying: The emulsion is spray-dried to obtain a powder, which is then polymerized and granulated to obtain a final product powder with a particle size distribution of 40-60 meshes to obtain a microalgae bait.

[0045] Example 3

[0046] A method for preparing microalgae bait comprises the following steps:

[0047] S1. Cultivation of microalgae: Cultivate microalgae in culture medium at a temperature of 25°C and a light intensity of 100 μmol / (m 2s), the light / dark time ratio was 6:3, and the culture was carried out for 36 h. The mixed gas was introduced into the culture solution at a gas flow rate of 0.35 L / min until the microalgae cells grew to the logarithmic growth phase and the concentration was 3×10 10 cells / mL of microalgae liquid;

[0048] The percentage of microalgae included 13% of Scenedesmus obliquus, 10% of Platymonas subcordiformis, 8% of Chaetoceros muelleri, 5% of Phaeodactylum triangularis, 15% of Isochrysis galbana, 12% of Haematococcus pluvialis, 20% of Chlorella pyrenoidosa, and 17% of Pavlova, with a total density of 3.8×10 5 cells / mL;

[0049] The culture medium includes the following raw materials in parts by weight: 4 parts of dipotassium hydrogen phosphate, 0.6 parts of citric acid, 7 parts of zinc chloride, 2 parts of disodium edetate, 4 parts of sodium carbonate, 20 parts of sodium metasilicate, and 25 parts of seawater, wherein the C:N:Si ratio in the seawater is 12:9:1 and the pH value is 8.0;

[0050] S2. Magnetic separation: Add nano-magnetic dispersant to the microalgae solution obtained above, control the pH to 6, set the magnetic field strength to 400 GS at room temperature, stir magnetically at 100 rpm for 40 minutes, and then stand at 40°C for 18 hours. Filter and collect the precipitate for later use.

[0051] The nanomagnetic dispersant is a mixed solution of superparamagnetic ferroferric oxide nanoparticle powder, triethanolamine and water in a volume-to-mass ratio of 30:8:50 g / mL;

[0052] S3, microencapsulation: The precipitate obtained in S2 was used as the core material, and a stabilizer and vegetable oil were added, and the mixture was sheared and emulsified at a rate of 3000 rpm for 14 minutes to obtain a core material oil phase liquid, wherein the mass volume ratio of the core material, stabilizer, and vegetable oil was 7:0.6:8 g / mL. Microencapsulated liposomes were used as the wall material, and water 2.5 times the mass of the wall material was added and mixed to form a wall material mixed solution. The core material oil phase liquid was added to the wall material mixed solution and homogenized, wherein the volume ratio of the core material oil phase liquid to the wall material mixed solution was 17:85. The homogenization pressure was 20 MPa, and the homogenization time was 4 minutes to obtain an emulsion;

[0053] The stabilizer is lauric acid macrogol glyceride and whey protein in a mass ratio of 1:2;

[0054] The microencapsulated liposomes are chitosan, calcium alginate, magnesium stearate, sodium tripolyphosphate, whey protein, and beeswax in a mass ratio of 2:5:10:4:1.7:10;

[0055] S4. Drying: The emulsion is spray-dried to obtain a powder, which is then polymerized and granulated to obtain a final product powder with a particle size distribution of 40-60 meshes to obtain a microalgae bait.

[0056] Example 4

[0057] The difference between this embodiment and embodiment 3 is that the culture medium in S1 includes the following raw materials in parts by weight: 1 part of dipotassium hydrogen phosphate, 0.1 part of citric acid, 2 parts of zinc chloride, 7 parts of disodium edetate, 9 parts of sodium carbonate, 30 parts of sodium metasilicate, and 10 parts of seawater.

[0058] Example 5

[0059] The difference between this embodiment and embodiment 3 is that the nanomagnetic dispersant in S2 is a mixed solution of superparamagnetic ferroferric oxide nanoparticle powder, triethanolamine and water in a volume-to-mass ratio of g / mL of 15:20:50.

[0060] Example 6

[0061] The difference between this embodiment and embodiment 3 is that the microencapsulated liposomes in S3 are chitosan, calcium alginate, magnesium stearate, sodium tripolyphosphate, whey protein and beeswax in a mass ratio of 1:1:2:8:0.5:7.

[0062] 1. Antioxidant performance test

[0063] 1. Sample preparation: Weigh 100 g each of the microalgae baits prepared in Examples 1-6 and commercially available microalgae bait (Spree brand). The present example groups were divided into 6 experimental groups, and the commercially available microalgae bait served as a control group, for a total of 7 groups.

[0064] 2. Oxygen Exposure Test: Microalgae bait samples from the experimental and control groups were placed in a quantitative device and aerated with oxygen at 5 L / min. The temperature was set at 20 ± 3°C and the relative humidity was 50% to simulate storage conditions. The baits were stored for 30 days. The acid value and peroxide value were measured before and after the test, and their change rates were calculated.

[0065] Acid value change rate = (A1-A0) / A1*100%; A0 is the acid value content of the bait before the test, and A1 is the acid value content of the bait after the test;

[0066] Peroxide value change rate = (P1-P0) / P1*100%; P0 is the peroxide value content of the bait before the test, and P1 is the peroxide value content of the bait after the test;

[0067] 3. Result analysis table 1:

[0068]

[0069]

[0070] 2. Water resistance test

[0071] 1. Prepare samples: same as above;

[0072] 2. Water immersion test: The bait samples of the experimental group and the control group were immersed in simulated seawater at a temperature of 23±2℃;

[0073] 3. Evaluate bait properties: Based on the soaking time, take out bait samples for property evaluation, and test the bait's water resistance time, loss rate, and sinking speed;

[0074] Water resistance time: Fill a 500ml beaker with seawater and add 30 microalgae bait pellets to each beaker. Observe the disintegration of the pellets. When half of the pellets in the beaker have disintegrated, record the soaking time of the pellets in the beaker. This will be used as the water resistance time of the pellets.

[0075] Loss rate: For baits with water resistance time greater than 5 hours, water resistance is expressed as loss rate, which is determined by rapid turbidity method. A certain mass of granular samples are weighed separately in a six-tube disintegrator and disintegrated in 1000mL deionized water at 25°C for 30 minutes. After the disintegration is completed, 100mL of disintegration liquid is transferred to a turbidity tube, oscillated with a vortex oscillator for 2 minutes, and quickly placed in a turbidity meter. Using turbidity-free water as a reference, the instrument zero point is adjusted and the turbidity value is measured, recorded as B1. Then accurately weigh the same mass of crushed material as the disintegrator, immerse it in 1000mL deionized water, keep a constant temperature in a water bath at 25°C for 20 minutes, stir the soaking liquid evenly, take 100mL of the solution and oscillate to measure its turbidity, recorded as B2. The loss rate of the product (%) = B1 / B2×100;

[0076] Sinking speed: Take a glass beaker with a length of 50 cm and a diameter of 5 cm, fill it with water to a depth of 40 cm, randomly take 50 particles from the sample, and put them into the glass beaker. The number of particles that sink to the bottom of the water is recorded as n.

[0077] Sinking rate (%) = n / 50 × 100;

[0078] 4. Result Analysis Table 2:

[0079]

[0080]

[0081] As shown in Tables 1 and 2, the microalgae bait of the present invention has better antioxidant properties, stable performance, and a longer storage period than the control group. Moreover, after microencapsulation, the bait has fewer cuts and pores, ensuring the surface integrity of the bait and avoiding surface cracks. As a result, the relative amount of dissolved substances in the bait is smaller, and the bait has better water resistance. After encapsulation, the time for swelling and collapse in water is prolonged, delaying the collapse of nutrients in the core material, resulting in a lower loss rate of less than 5%. The surface is intact and smooth and is easily wetted by water. After being put into water, it easily sinks to the bottom of the water, which is conducive to ingestion by aquatic animals and improves the utilization rate of the bait.

[0082] Through the above test comparison, the effect of Example 3 is the best, and the following comparative examples are set for Example 3:

[0083] Comparative Example 1

[0084] The difference between this comparative example and Example 3 is that step S2 magnetic separation is not performed, and the specific steps are as follows:

[0085] S1. Cultivation of microalgae: Cultivate microalgae in culture medium at a temperature of 25°C and a light intensity of 100 μmol / (m 2 s), the light / dark time ratio was 6:3, and the culture was carried out for 36 h. The mixed gas was introduced into the culture solution at a gas flow rate of 0.35 L / min until the microalgae cells grew to the logarithmic growth phase and the concentration was 3×10 10 cells / mL of microalgae liquid;

[0086] The percentage of microalgae included 13% of Scenedesmus obliquus, 10% of Platymonas subcordiformis, 8% of Chaetoceros muelleri, 5% of Phaeodactylum triangularis, 15% of Isochrysis galbana, 12% of Haematococcus pluvialis, 20% of Chlorella pyrenoidosa, and 17% of Pavlova, with a total density of 3.8×10 5 cells / mL;

[0087] The culture medium includes the following raw materials in parts by weight: 4 parts of dipotassium hydrogen phosphate, 0.6 parts of citric acid, 7 parts of zinc chloride, 2 parts of disodium edetate, 4 parts of sodium carbonate, 20 parts of sodium metasilicate, and 25 parts of seawater, wherein the C:N:Si ratio in the seawater is 12:9:1 and the pH value is 8.0;

[0088] S2. Separation: The microalgae solution obtained above was controlled at pH 6, stirred at 100 rpm at room temperature for 40 min, and then allowed to stand at 40°C for 18 h. The precipitate was filtered and collected for later use.

[0089] S3, microencapsulation: The precipitate obtained in S2 was used as the core material, and a stabilizer and vegetable oil were added, and the mixture was sheared and emulsified at a rate of 3000 rpm for 14 minutes to obtain a core material oil phase liquid, wherein the mass volume ratio of the core material, stabilizer, and vegetable oil was 7:0.6:8 g / mL. Microencapsulated liposomes were used as the wall material, and water 2.5 times the mass of the wall material was added and mixed to form a wall material mixed solution. The core material oil phase liquid was added to the wall material mixed solution and homogenized, wherein the volume ratio of the core material oil phase liquid to the wall material mixed solution was 17:85. The homogenization pressure was 20 MPa, and the homogenization time was 4 minutes to obtain an emulsion;

[0090] The stabilizer is lauric acid macrogol glyceride and whey protein in a mass ratio of 1:2;

[0091] The microencapsulated liposomes are chitosan, calcium alginate, magnesium stearate, sodium tripolyphosphate, whey protein, and beeswax in a mass ratio of 2:5:10:4:1.7:10;

[0092] S4. Drying: The emulsion is spray-dried to obtain a powder, which is then polymerized and granulated to obtain a final product powder with a particle size distribution of 40-60 meshes to obtain a microalgae bait.

[0093] Comparative Example 2

[0094] The difference between this comparative example and Example 3 is that no stabilizer is added to the core material in the microencapsulation package in step S3. Step S3 specifically comprises the following steps: using the precipitate obtained in S2 as the core material, adding vegetable oil, and shearing and emulsifying at a rate of 3000 rpm for 14 minutes to obtain a core material oil phase liquid, wherein the mass volume ratio of the core material and the vegetable oil is 7:8 g / mL; microencapsulated liposomes are used as the wall material, and water 2.5 times the mass of the wall material is added to mix to form a wall material mixed solution; the core material oil phase liquid is added to the wall material mixed solution and homogenized; the volume ratio of the core material oil phase liquid and the wall material mixed solution is 17:85, the homogenization pressure is 20 MPa, and the homogenization time is 4 minutes to obtain an emulsion; the microencapsulated liposomes are chitosan, calcium alginate, magnesium stearate, sodium tripolyphosphate, whey protein and beeswax in a mass ratio of 2:5:10:4:1.7:10.

[0095] Comparative Example 3

[0096] The difference between this comparative example and Example 3 is that the microalgae precipitate is not microencapsulated, and specifically includes the following steps:

[0097] S1. Cultivation of microalgae: Cultivate microalgae in culture medium at a temperature of 25°C and a light intensity of 100 μmol / (m 2 s), the light / dark time ratio was 6:3, and the culture was carried out for 36 h. The mixed gas was introduced into the culture solution at a gas flow rate of 0.35 L / min until the microalgae cells grew to the logarithmic growth phase and the concentration was 3×10 10cells / mL of microalgae liquid;

[0098] The percentage of microalgae included 13% of Scenedesmus obliquus, 10% of Platymonas subcordiformis, 8% of Chaetoceros muelleri, 5% of Phaeodactylum triangularis, 15% of Isochrysis galbana, 12% of Haematococcus pluvialis, 20% of Chlorella pyrenoidosa, and 17% of Pavlova, with a total density of 3.8×10 5 cells / mL;

[0099] The culture medium includes the following raw materials in parts by weight: 4 parts of dipotassium hydrogen phosphate, 0.6 parts of citric acid, 7 parts of zinc chloride, 2 parts of disodium edetate, 4 parts of sodium carbonate, 20 parts of sodium metasilicate, and 25 parts of seawater, wherein the C:N:Si ratio in the seawater is 12:9:1 and the pH value is 8.0;

[0100] S2. Magnetic separation: Add nano-magnetic dispersant to the microalgae solution obtained above, control the pH to 6, set the magnetic field strength to 400 GS at room temperature, stir magnetically at 100 rpm for 40 minutes, and then stand at 40°C for 18 hours. Filter and collect the precipitate for later use.

[0101] The nanomagnetic dispersant is a mixed solution of superparamagnetic ferroferric oxide nanoparticle powder, triethanolamine and water in a volume-to-mass ratio of 30:8:50 g / mL;

[0102] S3. Drying: The precipitate is spray-dried to obtain a powder, which is then polymerized and granulated to obtain a final product powder with a particle size distribution of 40-60 meshes to obtain a microalgae bait.

[0103] According to the above test method, the antioxidant performance and water resistance were measured, and the comparison results are shown in the following table;

[0104] Table 3:

[0105]

[0106] Table 4:

[0107]

[0108]

[0109] By setting up comparative test results and analyzing them, compared with Comparative Example 1, Example 3 uses magnetic separation and adds a specific nano-magnetic dispersant to separate the microalgae liquid, which can not only efficiently separate and select the effective nutrients in the microalgae liquid, but also stabilize the effective nutrients to prevent dissolution; compared with Comparative Example 2, adding a stabilizer to the core material makes the bait have better water resistance after being put into water, so that the nutrients in the core material are slowly released in the form of diffusion after being ingested by aquatic animals, thereby slowly exerting their effects; compared with Comparative Example 3, the microalgae precipitate is microencapsulated, which can encapsulate the effective nutrients in the core material and form a core material oil phase liquid that is not easily water-soluble, increases water resistance, and reduces the loss rate. The wall material mixed solution forms an outer wall, isolating the core material from the outside world, thereby controlling the release, protecting and stabilizing the core material, protecting the effective ingredients of the microalgae from oxidation and disintegration in water, and providing energy for the life activities of aquatic animals.

[0110] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing microalgae bait, characterized in that: The following steps are involved: S1. Cultivation of microalgae: Cultivate microalgae in culture medium, control the temperature at 20-30°C, and the light intensity at 80-150 μmol / (m 2 s), the light / dark time ratio is 5-7:3, and the culture is carried out for 24-48 hours. The mixed gas is introduced into the culture solution at a gas flow rate of 0.05-0.5 L / min until the microalgae cells grow to the logarithmic growth phase and the concentration is 1-5×10 10 cells / mL of microalgae liquid; S2. Magnetic separation: Add a nano-magnetic dispersant to the microalgae solution obtained above at a volume ratio of 0.3-0.5:80, control the pH to 6-7, magnetically stir at room temperature for 20-60 minutes, then allow to stand at 30-50°C for 15-20 hours, filter, and collect the precipitate for later use; S3, microencapsulation: The precipitate obtained in S2 is used as the core material, and a stabilizer and vegetable oil are added, and the mixture is sheared and emulsified at a rate of 2000-4000 rpm for 10-16 min to obtain a core material oil phase liquid, wherein the mass volume ratio of the core material, the stabilizer, and the vegetable oil is (5-10):(0.3-0.9):8 g / mL. Microencapsulated liposomes are used as the wall material, and water 1.5-3 times the mass of the wall material is added and mixed to form a wall material mixed solution. The core material oil phase liquid is added to the wall material mixed solution and homogenized at a homogenization pressure of 10-30 MPa and a homogenization time of 2-5 min to obtain an emulsion; S4. Drying: The emulsion is spray-dried to obtain a powder, which is then polymerized and granulated to obtain a final product powder with a particle size distribution of 40-60 meshes to obtain a microalgae bait.

2. The method for preparing a microalgae bait according to claim 1, wherein: The percentage of microalgae in S1 includes 10-15% of Scenedesmus obliquus, 8-12% of Platymonas subcordiformis, 5-10% of Chaetoceros muelleri, 3-11% of Phaeodactylum triangularis, 10-15% of Isochrysis galbana, 10-15% of Haematococcus pluvialis, 20-35% of Chlorella pyrenoidosa, and 15-20% of Pavlova, and the total density is 1.2-5.8×10 5 cells / mL.

3. The method for preparing a microalgae bait according to claim 1, wherein: The culture medium in S1 includes the following raw materials in parts by weight: 2-6 parts of dipotassium hydrogen phosphate, 0.4-0.8 parts of citric acid, 5-10 parts of zinc chloride, 1-3 parts of disodium edetate, 3-6 parts of sodium carbonate, 18-22 parts of sodium metasilicate, and 20-30 parts of seawater.

4. The method for preparing a microalgae bait according to claim 3, wherein: The C:N:Si ratio in the seawater is (10-15):(7-10):(0.5-1.5), and the pH value is 7.8-9.

0.

5. The method for preparing a microalgae bait according to claim 1, wherein: The mixed gas in S1 is carbon dioxide and nitrogen in a volume ratio of 3-5:

1.

6. The method for preparing a microalgae bait according to claim 1, wherein: The nanomagnetic dispersant in S2 is a mixed solution of superparamagnetic ferroferric oxide nanoparticle powder, triethanolamine and water with a volume-to-mass ratio of g / mL of (20-40):(6-12):

50.

7. The method for preparing a microalgae bait according to claim 1, wherein: The magnetic field intensity of the magnetic stirring in S2 is 300-500 GS, and the rotation speed is 60-150 rpm.

8. The method for preparing a microalgae bait according to claim 1, wherein: The stabilizer in S3 is one or a combination of vitamin E, polyethylene glycol laurate, sodium deoxycholate, whey protein, and polyglycerol fatty acid ester.

9. The method for preparing a microalgae bait according to claim 1, wherein: The microencapsulated liposomes in S3 are chitosan, calcium alginate, magnesium stearate, sodium tripolyphosphate, whey protein and beeswax in a mass ratio of (1-3):(4-7):(8-12):(3-5):(0.8-2.5):

10.

10. The method for preparing a microalgae bait according to claim 1, wherein: The volume ratio of the core material oil phase liquid and the wall material mixed solution in S3 is 15-20:80-90.

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