Unicellular diatom cultured in seawater culture medium, processing method thereof, and processed product

Abstract

The present invention discloses a unicellular diatom cultured in a seawater culture medium, a processing method thereof, and a processed product thereof. The seawater culture medium includes a nitrogen source, a phosphorus source, a silicon source, trace elements, and vitamins. The processing method includes the following steps: using the seawater culture medium to culture the unicellular diatom and prepare fresh algae mud; using an adhesive to suspend the fresh algae mud and further granulate to obtain diatom particles; the adhesive includes one or more of polyvinyl alcohol, hydroxypropyl methylcellulose, gum arabic, starch, and silica sol; and processing the diatom particles by a roasting method to obtain a processed product, which is a diatom shell. The method provided by the present application is simple, efficient, and environmentally friendly. The yield rate of the processed product reaches 15-30%. The product has good integrity, high cleanliness, a wide range of applications, and can be produced and processed in large quantities at the kilogram level. Providing a stable source of new materials will contribute to the development of diatoms in various fields.

Description

Technical Field

[0001] The present invention relates to the technical field of unicellular diatom cultivation and processing, and in particular to a unicellular diatom cultivated based on a seawater culture medium, a processing method and a processed product thereof, and particularly to C12N1 / 12 (unicellular algae; and culture medium thereof) in the international patent classification number. Background Art

[0002] Diatoms are a type of photosynthetic, autotrophic, single-celled eukaryotic algae that are numerous, numerous, and widely distributed. Diatoms are found in nearly all water bodies, including rivers, lakes, seas, and wetlands. The ocean is their primary habitat. Diatoms absorb large amounts of carbon dioxide through photosynthesis and produce approximately 20% of the world's oxygen. Research has shown that diatoms produce more oxygen than tropical rainforests. Diatoms are crucial primary producers on Earth, accounting for 20% of global primary productivity and making significant contributions to the Earth's carbon and silicon cycles.

[0003] Diatoms are unique microalgae with numerous potential applications. Rich in oils, proteins, pigments, vitamins, and minerals, their processing potential includes: use in the food and pharmaceutical industries (nutritional supplements for humans and animals: vitamins, proteins, fatty acids, polysaccharides, etc.); extraction of chemical products such as cosmetics and fine chemicals; use as an energy source to generate biogas and fuel; use in the bait and feed industry (bait for aquatic animals such as fish, shrimp, and crustaceans, as well as poultry feed); use in agriculture as soil conditioners and fertilizers, and as nanomaterials in the electronics field. However, the vast majority of diatom applications are derived from living, single-celled diatoms, necessitating the expansion of algal species for processing and production needs.

[0004] Currently, processing of single-celled diatoms primarily involves removing organic matter from the diatoms' bodies or surfaces, as well as inorganic matter from the culture medium. The diatom cell wall, known as the diatom frustule, is a durable shell formed by absorbing silicates from the environment and depositing them through a biomineralization process. It is primarily composed of amorphous hydrated silicon dioxide (SiO2·xH2O). Further processing of single-celled diatoms yields diatom frustules, which can be applied in various applications, both large and small.

[0005] However, existing single-cell diatom processing methods are all at the experimental stage and cannot be processed on a large scale. For example, the patent document with publication number CN112978738A discloses pickling by high concentrations of hydrochloric acid, nitric acid and sulfuric acid to remove organic matter and pigments on the surface of diatom shells. However, concentrated hydrochloric acid, concentrated nitric acid and concentrated sulfuric acid are highly dangerous chemicals that hinder experimental safety and easily cause environmental pollution. The patent document with publication number CN114229856A discloses first using dilute acid washing and then using hydrogen peroxide to remove organic matter, and finally adding alcohol or acetone to remove pigments, thereby realizing the processing of single-cell diatoms. However, if hydrogen peroxide is not heated, the removal effect of organic matter is not ideal. If it is heated, a large amount of foam will overflow, resulting in a large amount of material loss. However, the operation process is relatively cumbersome, the purity of the diatom shells is not high, and they adhere to each other; multiple centrifugation and calcination cause the shells to break and the number of silanol groups to decrease, affecting downstream applications.

[0006] Therefore, the key to unicellular diatom processing is how to expand the culture of unicellular diatoms and use the expanded living unicellular diatoms to obtain processed products in a simple, convenient and high-harvest manner while retaining the complete morphology of the siliceous shell. Summary of the Invention

[0007] The purpose of the present invention is to cultivate unicellular diatoms and process the cultured living unicellular diatoms in a simple, convenient and high-harvest manner while retaining the complete morphology of the diatom shells, in order to solve the technical problem:

[0008] A first aspect of the present invention provides a seawater culture medium for culturing unicellular diatoms. The seawater culture medium is formulated as follows: sterilizing A1 mother liquor, A2 mother liquor, B mother liquor, C mother liquor, D mother liquor, and E mother liquor and mixing them with sterile, impurity-free seawater at a ratio of 1:1000 to obtain the seawater culture medium.

[0009] Furthermore, the A1 mother liquor includes a nitrogen source, which is NaNO3; the A2 mother liquor includes a phosphorus source, which is Na2SiO3·9H2O; the B mother liquor includes a silicon source, which is Na2SiO3·9H2O; the C mother liquor includes a first trace element, which is FeCl3·6H2O and Na2EDTA; the D mother liquor includes a second trace element, which is CuSO4·5H2O, ZnSO4·7H2O, CoCl2·6H2O, MnCl2·4H2O and Na2MoO4·2H2O; the E mother liquor includes vitamins and biotin H, and the vitamins are vitamin B1 and vitamin B12.

[0010] Furthermore, the A1 mother liquor was prepared by weighing 75 g of NaNO₃ and dissolving it in 800 mL of deionized water. Stirring until completely dissolved, the dissolved solution was transferred to a volumetric flask and diluted to 1 L with deionized water, resulting in a NaNO₃ concentration of 75 g / L, to obtain the A1 mother liquor.

[0011] Furthermore, the A2 mother liquor was prepared by weighing 5 g of NaH2PO4·2H2O, dissolving it in 800 mL of deionized water, and stirring until completely dissolved. The dissolved solution was transferred to a volumetric flask and diluted to 1 L with deionized water, resulting in an A2 mother liquor with a concentration of 5 g / L.

[0012] Furthermore, mother liquor B was prepared by weighing 30 g of Na₂SiO₃・9H₂O and dissolving it in 800 mL of deionized water. Stirring until completely dissolved, the dissolved solution was transferred to a volumetric flask and diluted to 1 L with deionized water to obtain mother liquor B. The Na₂SiO₃・9H₂O concentration in this solution was 30 g / L.

[0013] Furthermore, the mother solution C was prepared by weighing 3.15 g of FeCl₃·6H₂O and dissolving it in 800 mL of deionized water. Then, 4.36 g of Na₂EDTA was added and stirred until completely dissolved. The dissolved solution was transferred to a volumetric flask and diluted to 1 L with deionized water to obtain the mother solution C.

[0014] To prepare mother liquor D, weigh 9.8 g CuSO₄·5H₂O, 22 g ZnSO₄·7H₂O, 10 g CoCl₂·6H₂O, 180 g MnCl₂·4H₂O, and 6.3 g Na₂MoO₄·2H₂O, respectively, and dissolve them in 800 mL of deionized water. Stir until completely dissolved. Transfer the dissolved solution to a volumetric flask, dilute to 1 L with deionized water, and add 1 mL of this solution to mother liquor C to obtain mother liquor D.

[0015] Furthermore, the preparation method of E mother solution is as follows: weigh 0.1 g of vitamin B1, dissolve it in 800 mL of deionized water, and stir until completely dissolved. Transfer the dissolved solution to a volumetric flask and dilute to 1 L with deionized water to obtain vitamin 1 mother solution. Weigh 0.5 g of vitamin B12 and 0.5 g of biotin H respectively, dissolve them in 80 mL of deionized water, and stir until completely dissolved. Transfer the dissolved solution to a volumetric flask and dilute to 100 mL with deionized water to obtain vitamin 2 mother solution. Take 100 μL of vitamin 2 mother solution and dissolve it in vitamin 1 mother solution to obtain E mother solution.

[0016] Furthermore, all mother solutions except the vitamin mother solution were sterilized using a vertical automatic pressure steam sterilizer at 121°C for 30 min, and after cooling, they were refrigerated and stored at 4°C.

[0017] Furthermore, the vitamin stock solution needs to be sterilized by filtration using a sterile 0.22 μm filter membrane in an ultra-clean workbench and then refrigerated and stored at 4°C in the dark.

[0018] Another aspect of the present invention provides a method for processing unicellular diatoms, comprising the following steps:

[0019] Step A: Cultivating and propagating single-cell diatoms using the above-mentioned seawater culture medium and preparing fresh algae mud;

[0020] Step B: suspending the fresh algae mud with an adhesive, and granulating the suspended fresh algae mud to obtain diatom particles; the adhesive includes one or more of polyvinyl alcohol, hydroxypropyl methylcellulose, gum arabic, starch, and silica sol; preferably, granulating the suspended fresh algae mud with a granulator;

[0021] Step C: roasting the diatom particles by a roasting method to obtain a processed product.

[0022] Furthermore, step A specifically comprises: mixing an algal liquid of a unicellular diatom in a logarithmic growth phase with a seawater culture medium in a ratio of 3:7 to expand and culture the unicellular diatom until the end of the logarithmic growth phase, then settling, washing and centrifuging at least once, discarding the supernatant to obtain a precipitate, which is fresh algal mud;

[0023] Further, unicellular diatoms include Central Bacillales or Pennate Bacillales; Central Bacillales include Cyclostriales, Rhizoschiales and Box-shaped Bacillales; Pennate Bacillales include Naviculales, Curculigoles, Diploschiales, Phaeoschiales, Aconomorphales and Brachyschiales; Cyclostriales includes Cyclostriaceae; Box-shaped Bacillales includes Ceratocystaceae; Naviculales includes Naviculaceae; Phaeoschiales includes Phaeoschiaceae.

[0024] On the other hand, step B includes: step B-1: suspending fresh algae mud with an adhesive to obtain a fresh algae mud suspension; step B-2: granulating the fresh algae mud suspension with a spray granulation dryer to obtain diatom particles.

[0025] Furthermore, in step B-1, the ratio of algal mud to adhesive is (1:1)~(1:5); the viscosity of the adhesive is 50~500 mPa·s; in step B-2, the inlet air temperature of the spray granulation dryer is 180~260°C, the outlet air temperature is 80~150°C, the atomization volume is 5~200 μm, the feed rate is 500~2000 mL / h, and the drying time is 0.8~2.0 s.

[0026] Furthermore, the concentration of the polyvinyl alcohol solution is 0.1-5.0%, the concentration of hydroxypropyl methylcellulose is 0.5-5.0%, the concentration of gum arabic or starch is 1.0-5.0%, and the concentration of the silica sol is 10.0-40.0%.

[0027] On the other hand, step B includes: step B-1: drying fresh algae mud to obtain diatom powder; step B-2: placing the diatom powder on a wheel granulator, spraying an adhesive on the diatom powder for granulation, and obtaining diatom granules after drying.

[0028] Preferably, the drying treatment is oven drying or natural air drying; the oven drying condition is 50-90° C. for 20-40 hours.

[0029] Furthermore, step B-2 is specifically as follows: placing diatom powder on the granulation disk of the wheel granulator, turning on the wheel granulator, rotating the granulation disk, spraying the adhesive onto the surface of the diatom powder, and mixing the diatom powder and the adhesive to form diatom particles; the flow rate of the adhesive on the wheel granulator is 0.5~5.0 mL / min; and the particle size of the diatom particles is 0.5~1.0 mm.

[0030] Preferably, the drying temperature is 80-90° C. and the drying time is 20-28 h.

[0031] Furthermore, the viscosity of the adhesive is 50-500 mPa·s.

[0032] Furthermore, the concentration of the polyvinyl alcohol solution is 0.1-5.0%, the concentration of hydroxypropyl methylcellulose is 0.5-5.0%, the concentration of gum arabic or starch is 1.0-5.0%, and the concentration of the silica sol is 10.0-40.0%.

[0033] Furthermore, step C specifically comprises: placing the diatom particles in air, oxygen or nitrogen and roasting them to obtain a processed product, wherein the processed product is a diatom shell, and the diatom shell includes a complete diatom shell without impurities.

[0034] Furthermore, the calcining container is a crucible or a ceramic fiberboard; the crucible or ceramic fiberboard is placed in a high-temperature calcining device such as a muffle furnace, a tubular furnace, a cyclone dynamic calcining drying system or a microwave high-temperature calcining furnace for calcination to obtain a processed product.

[0035] Furthermore, the calcination temperature is 400-600°C; and the calcination heating rate is 2-5°C / min.

[0036] Furthermore, the yield of the processed product is 15% or more, and the complete diatom shells without impurities account for 65% or more of the processed product.

[0037] Furthermore, step B does not include acid heat treatment.

[0038] Another aspect of the present invention provides a processed product obtained by the above-mentioned processing method of unicellular diatoms, wherein the processed product includes diatom frustules.

[0039] Compared with the prior art, the present application provides a unicellular diatom cultured in seawater culture medium, a processing method thereof, and a processed product thereof, which have the following beneficial effects:

[0040] (1) The pure and pollution-free culture and propagation of unicellular diatoms can be achieved through seawater culture medium. The seawater culture medium is easy to prepare, the culture process is simple, efficient and environmentally friendly.

[0041] (2) The processing method of the present application is used to process the unicellular diatoms in the logarithmic growth phase after the above-mentioned propagation. The processed products have a high harvest rate, high safety, no residue and pollution, and the processing method has a wide range of applicability. It is applicable to diatoms of different genera and species, which is a further development and utilization of marine resources.

[0042] (3) The processing method provided in this application can realize the processing of kilogram-level large-scale single-cell diatoms, providing a reasonable solution for industrial large-scale production. The obtained processed products contain diatom shells, which can provide a stable source in different fields and contribute to the development of single-cell diatoms in various fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The above content and the following specific embodiments of the present invention will be better understood when read in conjunction with the accompanying drawings. It should be noted that the accompanying drawings are only examples of the technical solutions claimed.

[0044] Figure 1 This is a scanning electron microscope image of the fresh algal mud in Example 1 (scale bar: 50 μm);

[0045] Figure 2 This is a scanning electron microscope image of the diatom frustule in Example 1 (scale bar: 30 μm);

[0046] Figure 3 for Figure 2 Scanning electron microscopy image of a single diatom frustule (scale bar: 5 μm);

[0047] Figure 4 The Fourier infrared spectrum of the diatom shell in Example 1 (the horizontal axis is the wavelength, the unit is (cm -1 ));

[0048] Figure 5 This is a scanning electron microscope image of the fresh algal mud in Example 2 (scale bar: 50 μm);

[0049] Figure 6This is a scanning electron microscope image of the diatom frustule in Example 2 (scale bar: 50 μm);

[0050] Figure 7 for Figure 6 Scanning electron microscopy image of a single diatom frustule (scale bar 10 μm);

[0051] Figure 8 The Fourier infrared spectrum of the diatom shell in Example 2 (the horizontal axis is the wavelength, the unit is (cm -1 ));

[0052] Figure 9 This is a scanning electron microscope image of the damaged diatom shell in Comparative Example 1 (scale bar: 40 μm). DETAILED DESCRIPTION

[0053] The detailed features and advantages of the present invention are described in detail below in the specific embodiments, and the content is sufficient to enable any person skilled in the art to understand the technical content of the present invention and implement it accordingly. Based on the description, claims and drawings disclosed in this specification, those skilled in the art can easily understand the relevant purposes and advantages of the present invention.

[0054] It should be noted that in this specification, similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0055] To make the objectives, technical solutions, and advantages of the present invention more apparent, embodiments of the present invention will be described in further detail below with reference to the accompanying drawings. The experimental methods described in the examples of the present invention are conventional methods unless otherwise specified. The materials, reagents, etc. used in the following examples are all commercially available unless otherwise specified.

[0056] All other terms used herein that are not specifically defined in this patent are intended to have the general meanings understood by ordinary technicians in the field to which they belong, and in particular, ordinary technicians in the field can directly and unambiguously determine the meaning of how to implement the technical solution of this patent after reading the claims, description and drawings of this patent.

[0057] It should be understood that in the present invention, the term "complete diatom shell" refers to the acquisition of diatom shells by the method provided by the present invention, and the projection area of ​​the front view of the obtained single diatom shell accounts for 85% or more of the projection area of ​​the front view of the single diatom shell before extraction, that is, the obtained single diatom shell is considered to be a "complete diatom shell", also known as "complete diatom shell without impurities"; "damaged diatom shell" refers to the acquisition of diatom shells by the method provided by the present invention, and the projection area of ​​the front view of the obtained single diatom shell accounts for less than 85% of the projection area of ​​the front view of the single diatom shell before extraction, excluding 85%, that is, the obtained single diatom shell is considered to be a "damaged diatom shell", also known as an "incomplete diatom shell". The term "algal mud" refers to fresh algal mud, that is, the material obtained by sedimentation, filtration or washing and centrifugation of living diatoms, which retains a relatively original state and structure. Living diatoms are easy to obtain and renewable, and are essentially different from "diatomaceous earth" or "siliceous rock"; "Diatomaceous earth" or "siliceous rock" is a sedimentary rock formed by long-term sedimentation, compaction and geological action of diatom remains. It is mainly composed of diatom shells, but has undergone a complex diagenetic process. In this process, the diatom shells may have been partially mineralized, compacted or mixed with other minerals, resulting in the diatom shell structure in the diatom earth being not as complete and clear as fresh diatom shells, and diatomaceous earth usually needs to be mined, purified and processed before it can be used to prepare diatom shell-related products. It is not easy to obtain and is not renewable.

[0058] Example 1

[0059] S1. Cultivation and propagation of unicellular diatoms. The specific steps are as follows:

[0060] (1) Prepare seawater culture medium stock solution:

[0061] Prepare A1 mother solution (nitrogen source): Weigh 75 g of NaNO₃ and dissolve it in 800 mL of deionized water. Stir until completely dissolved. Transfer the dissolved solution to a volumetric flask and dilute to 1 L with deionized water, so that the NaNO₃ concentration is 75 g / L. This is A1 mother solution.

[0062] Prepare A2 stock solution (phosphorus source): Weigh 5 g of NaH2PO4·2H2O and dissolve it in 800 mL of deionized water. Stir until completely dissolved. Transfer the dissolved solution to a volumetric flask and dilute to 1 L with deionized water to obtain an A2 stock solution with a concentration of 5 g / L.

[0063] Prepare mother solution B (silicon source): Weigh 30 g of Na₂SiO₃・9H₂O and dissolve it in 800 mL of deionized water. Stir until completely dissolved. Transfer the dissolved solution to a volumetric flask and dilute to 1 L with deionized water to obtain mother solution B. The Na₂SiO₃・9H₂O concentration in this solution is 30 g / L.

[0064] Prepare mother solution C (trace 1): Weigh 3.15 g of FeCl₃・6H₂O and dissolve it in 800 mL of deionized water. Then, weigh 4.36 g of Na₂EDTA and stir until completely dissolved. Transfer the dissolved solution to a volumetric flask and dilute to 1 L with deionized water to obtain mother solution C.

[0065] Prepare mother solution D (trace 2): Weigh 9.8 g CuSO₄·5H₂O, 22 g ZnSO₄·7H₂O, 10 g CoCl₂·6H₂O, 180 g MnCl₂·4H₂O, and 6.3 g Na₂MoO₄·2H₂O, respectively, and dissolve them in 800 mL of deionized water. Stir until completely dissolved. Transfer the dissolved solution to a volumetric flask and dilute to 1 L with deionized water. Add 1 mL of this solution to mother solution C to obtain mother solution D.

[0066] Prepare Vitamin E mother solution: Weigh 0.1 g of vitamin B1 and dissolve it in 800 mL of deionized water. Stir until completely dissolved. Transfer the dissolved solution to a volumetric flask and dilute to 1 L with deionized water to obtain Vitamin 1 mother solution. Weigh 0.5 g of vitamin B12 and 0.5 g of biotin H, respectively, and dissolve them in 80 mL of deionized water. Stir until completely dissolved. Transfer the dissolved solution to a volumetric flask and dilute to 100 mL with deionized water to obtain Vitamin 2 mother solution. Dissolve 100 μL of Vitamin 2 mother solution in Vitamin 1 mother solution to obtain Vitamin E mother solution.

[0067] The prepared stock solutions, except for the vitamin stock solution, were sterilized (121°C, 30 min) using a vertical automatic pressure steam sterilizer (YXQ-LS-S2 model) (Shanghai Boxun Industrial Medical Equipment Factory). After cooling, they were refrigerated at 4°C. The vitamin stock solution was sterilized by filtration using a sterile 0.22 μm filter in a laminar flow hood and then refrigerated at 4°C in the dark. (All reagents used were purchased from Sinopharm Group and were of analytical grade.)

[0068] (2) Seawater filtration and sterilization: Sterilize 800-mesh gauze at high temperature at 121°C for 15 minutes. Filter the required seawater through the sterilized 800-mesh gauze to remove impurities and then boil it for 10 minutes to sterilize it. The cooled seawater after sterilization is filtered through 800-mesh gauze again and set aside to obtain sterile and impurity-free seawater.

[0069] In other specific embodiments, 600-1000 mesh gauze can also be used for sterilization and filtration.

[0070] (3) Preparation of seawater culture medium: The sterile, impurity-free seawater and the above-mentioned 6 seawater culture medium mother solutions were mixed evenly at a ratio of 1000:1 to obtain seawater culture medium.

[0071] For example, take 1 mL of A1 mother liquor, 1 mL of A2 mother liquor, 1 mL of B mother liquor, 1 mL of D mother liquor, and 1 mL of E mother liquor, respectively, and add them to 1000 mL of deionized water to prepare seawater culture medium.

[0072] (4) Single-cell diatom culture: Take the algae solution of Cyclotella cryptocarpa in the logarithmic growth cycle ( Cyclotella cryptica (Original: [The text then abruptly shifts topics.]) [The text then abruptly shifts topics.] [The text then abruptly shifts topics.] [The text then abruptly shifts topics.] [The text then abruptly shifts topics.] [The text then abruptly shifts topics.] [The text then abruptly shifts topics.] [The text then abruptly shifts topics.] [The text then abruptly shifts topics.] [The text then abruptly shifts topics.] [The text then abruptly shifts topics.] [The text then abruptly shifts topics.] [The text then abruptly shifts topics.] [The text then abruptly shifts topics.] The ...

[0073] (5) After inoculation, 3 mL of Cyclotella cryptica algae liquid was collected at a fixed time every day, counted under an optical microscope (Olympus, CX31), and its growth status was recorded. It was found that Cyclotella cryptica had reached the logarithmic growth phase, and half of the Cyclotella cryptica algae liquid was further harvested. The remaining Cyclotella cryptica algae liquid was regularly subcultured and examined under a microscope to observe whether there was any contamination.

[0074] S2. Processing of unicellular diatoms. The specific steps are as follows:

[0075] 1. Preparation of fresh algae mud

[0076] (1) Let the algae solution stand: Take 20 L of Cyclotella cryptica at the end of the logarithmic growth phase (also known as the early stage of the plateau phase) in S1 above, place it in a beaker, and let it stand at room temperature for 14 h. Remove most of the supernatant, and divide the remaining algae solution containing a small amount of supernatant and precipitate into 1000 mL centrifuge bottles. Centrifuge at 6000 rpm for 10 min, discard the supernatant, and obtain the first precipitate.

[0077] In other specific embodiments, Cyclotella cryptica at the end of its logarithmic growth phase can be settled at room temperature for at least 10 hours. The rotational speed is adjusted to 4000-8000 rpm, and the corresponding centrifugation time is 5-20 minutes. The higher the rotational speed, the shorter the centrifugation time. The supernatant is discarded to obtain a first precipitate. Alternatively, an appropriate volume of Cyclotella cryptica can be used, such as 1-5 L, 5-10 L, or 10-20 L, depending on the specific experimental requirements.

[0078] (2) Pure water washing: Add 3 times the volume of pure water to the first precipitate for suspension, that is, the volume ratio of the first precipitate to pure water is 1:3, to obtain the first suspension; the first suspension is divided into 100 mL centrifuge tubes, centrifuged at 7200 rpm for 10 min, and the supernatant is discarded to obtain the second precipitate.

[0079] (3) Repeat step (2) in the above S2, wash with pure water again, and obtain a third precipitate after centrifugation, which is fresh algae mud.

[0080] In other embodiments, other volume multiples of pure water can be added, for example, 1-2 times. Alternatively, the speed can be adjusted to 4,000-10,000 rpm, corresponding to a centrifugation time of 5-20 minutes. Higher speeds result in shorter centrifugation times. If the suspension remains turbid after two washes with pure water, increase the number of washes.

[0081] (4) The fresh algae mud was placed under a scanning electron microscope for observation. The results were as follows: Figure 1 As shown, it can be seen that the untreated fresh algae mud is aggregated together, and there is more organic matter and impurities on the fresh algae mud.

[0082] 2. Adhesive suspended algae mud, the specific steps are as follows:

[0083] (1) Preparation of polyvinyl alcohol solution: Add 1900 mL of distilled water to a 5000 mL heat-resistant beaker and heat the beaker on a hot plate until the distilled water reaches 80°C. Weigh 100 g of polyvinyl alcohol (PVA, purchased from Sigma, catalog number J00968) powder and slowly add it to the heated distilled water. Stir until completely dissolved. Allow to cool to room temperature before use to obtain 2 L of a 5.0% polyvinyl alcohol solution. The viscosity of the 5.0% polyvinyl alcohol solution was tested according to the national standard GB / T173-93 and the viscosity of the 5.0% polyvinyl alcohol solution was 392 mPa·s.

[0084] In other specific embodiments, other organic molecules with a certain viscosity that can be fully calcined without producing excess impurities can be prepared according to the above-mentioned method for preparing the polyvinyl alcohol solution, and the viscosity of the adhesive can be set within the range of 50-500 mPa·s. For example, a polyvinyl alcohol solution (PVA solution) with a concentration of 0.1-5.0%, hydroxypropyl methylcellulose (HPMC) with a concentration of 0.5-5.0%, gum arabic or starch paste with a concentration of 1.0-5.0%, or silica sol with a concentration of 10.0-40.0% can be prepared.

[0085] (2) Take 50 g of the fresh algae mud obtained in step 1 of S2, add 100 mL of a 5.0% polyvinyl alcohol solution cooled to room temperature, and stir thoroughly so that the fresh algae mud is completely suspended in the 5.0% polyvinyl alcohol solution to obtain a fresh algae mud suspension.

[0086] In other specific embodiments, the fresh algae mud can be mixed with a 5.0% polyvinyl alcohol solution in a ratio of W / V = (1:1) to (1:5), that is, the fresh algae mud can be completely dispersed in the polyvinyl alcohol solution.

[0087] 3. Granulation processing of diatom particles, the specific steps are as follows:

[0088] (1) The fresh algae mud suspension obtained in the above step is granulated using a spray granulation dryer (purchased from Shanghai Bilang Instrument Manufacturing Co., Ltd., model BILON-9000Y). The spray granulation dryer mainly uses pressure to disperse the liquid or suspension into small droplets, and then contacts with hot air flow to make the water or other volatile components on the surface of the small droplets evaporate rapidly, and finally form dry particles.

[0089] The operation process of the spray granulation dryer is as follows: start the fan and heater, adjust the atomizer, and start the spray drying process. The inlet temperature of the spray granulation dryer is set to 220℃, the outlet temperature is 100℃, the atomization volume is 100 μm, and the feed rate is 800 mL / h, that is, the rate at which the algae mud suspension enters the spray granulation dryer is 800 mL / h; the drying time is set to 1.5 s; turn on the peristaltic pump and send the material into the spray granulation dryer atomizer for atomization. After drying, the powder is collected by cyclone separation to obtain diatom particles.

[0090] In other specific embodiments, the operating parameters of the spray granulation dryer can be changed, that is, the inlet air temperature of the spray granulation dryer is set to 180~260°C, and the outlet air temperature is set to 80~150°C to avoid the particles from breaking due to over-drying; the atomization volume is set to 5~200 μm; the feed rate is set to 500~2000 mL / h; and the drying time is set to 0.8~2.0 s, so that the granules required by the experiment can be obtained.

[0091] 4. The roasting method is used to process diatom shells. The specific steps are as follows:

[0092] 1000 g of the diatom particles obtained in the above steps were placed in a crucible (corundum crucible, purchased from Henan Andy High Temperature Products Co., Ltd.), and the crucible was placed in a muffle furnace (purchased from Tianjin Zhonghuan Electric Furnace Co., Ltd., model SK-G06123K-R). The temperature was raised to 500°C at a heating rate of 3°C / min and calcined for 240 min to obtain a white solid powder, which was the processed product. The processed product was the diatom shell.

[0093] In other specific embodiments, 1000-5000 g of the diatom particles obtained by the above process can be selected and placed in a ceramic fiber board, and the ceramic fiber board is placed in a high-temperature calcination equipment such as a muffle furnace, a tubular furnace (purchased from Tianjin Zhonghuan Electric Furnace Co., Ltd., model SK-G08123K-610), a cyclonic dynamic calcination drying system, or a microwave high-temperature calcination furnace for calcination to obtain complete and clean diatom shells. Among them, the calcination temperature can be selected from 400 to 600 ° C, the heating rate is 2 to 5 ° C / min, and the product collected after calcination is the processed product, which can also obtain complete and clean diatom shells.

[0094] S3. Detection of diatom frustules. The specific steps are as follows:

[0095] (1) An appropriate amount of the diatom frustules obtained by the above process was adhered to a conductive adhesive, sprayed with gold, and placed under a scanning electron microscope (JEOL, JSM-6010LA) to observe the morphology and structure of the diatom frustules and preliminarily evaluate the feasibility of this scheme. The main components and group composition of the diatom frustules were analyzed using a Fourier transform infrared spectrometer (Nicolet, 5700).

[0096] Scanning electron microscopy results Figure 2 As shown, it can be seen that compared with fresh algae mud, the diatom shells processed by the method provided in this embodiment are more dispersed as a whole, and the organic matter on the diatom shells has also been removed.

[0097] Further magnification of the diatom shells revealed the following results: Figure 3 As shown, the diatom frustules obtained by the processing method provided in this embodiment contain complete diatom frustules, that is, the projected area of ​​the front view of a single diatom frustule accounts for 85% or more of the projected area of ​​the front view of a single diatom frustule before extraction, the structure of the diatom frustule is complete, all organic matter is removed, the shell of the diatom frustule is transparent, the pores are clear, and the hierarchical porous structure of different scales can be seen.

[0098] (2) Take an appropriate amount of the diatom shells obtained by the above processing and place them on a Fourier transform infrared spectrometer for broad spectrum analysis. The results are as follows: Figure 4 As shown in the figure, the diatom shells of Cyclotella exhibit the characteristic peaks of silicon oxide (Si-O-Si, Si-OH), specifically, at 3424 cm -1 A peak representing Si-OH stretching appeared at 1092 cm -1 、466 cm -1 The Si-O-Si stretching peaks appeared at all locations, and there were no other organic peaks, which indicated that pure SiO2 material was prepared, that is, complete diatom shells without impurities were obtained by the processing method of this embodiment.

[0099] S4. Diatom frustule harvest rate statistics. The specific reference steps are as follows:

[0100] The harvest rate of diatom frustules was calculated according to the following formula:

[0101] ;

[0102] Wherein, W0 is the weight of diatom particles before treatment; W a is the weight of diatom frustules after treatment.

[0103] Statistics show that the final diatom frustule harvest rate was 15%. Further statistics on the harvest rate of intact and impurity-free diatom frustules showed that intact and impurity-free diatom frustules accounted for 65% of the total harvested diatom frustules, indicating that the harvest rate of intact and impurity-free diatom frustules was relatively high.

[0104] Example 2

[0105] S1. Cultivation and propagation of unicellular diatoms. The specific steps are as follows:

[0106] (1) According to the method of step S1 in Example 1, the radiata sclerotium ( Coscinodiscus radiatus Radiata algae (FACHB-2550, belonging to the family Cynocephalae, purchased from the Freshwater Algae Seed Bank of the Chinese Academy of Sciences) were cultured for expansion. Results revealed that Cynocephala radiata had reached its logarithmic growth phase. Half of the Cynocephala radiata algae solution was harvested, and the remaining solution was regularly subcultured and examined microscopically for contamination.

[0107] S2. Processing of unicellular diatoms. The specific steps are as follows:

[0108] 1. Preparation of fresh algae mud

[0109] (1) Standing algae solution: 8-10 L of S. radiata at the end of the logarithmic growth phase (also known as the early stage of the plateau phase) in Example S1 was placed in a beaker and allowed to settle at room temperature for 16 h. Most of the supernatant was removed, and the remaining algae solution containing a small amount of supernatant and precipitate was divided into 100 mL centrifuge tubes. The tubes were centrifuged at 8400 rpm for 10 min, and the supernatant was discarded to obtain the first precipitate.

[0110] (2) Pure water washing: According to the volume of the first precipitate, add 1 to 3 times the volume of pure water for suspension, that is, the volume ratio of the first precipitate to pure water is (1:1)~3, to obtain the first suspension; the first suspension is divided into 100 mL centrifuge tubes, centrifuged at 8400 rpm for 10 min, and the supernatant is discarded to obtain the second precipitate.

[0111] (3) Repeat step (2) of this embodiment, wash with pure water again, and obtain a third precipitate after centrifugation.

[0112] In other embodiments, other volume multiples of pure water can be added, for example, 1-2 times. Alternatively, the speed can be adjusted to 4,000-10,000 rpm, corresponding to a centrifugation time of 5-20 minutes. Higher speeds result in shorter centrifugation times. If the suspension remains turbid after two washes with pure water, increase the number of washes.

[0113] (4) The third precipitate was placed under a 100-mesh sieve (purchased from Beijing Biolab Technology Co., Ltd., product number QN3040) and sieved to obtain fresh algae mud.

[0114] In other specific embodiments, a 40-200 mesh sieve can be used for sieving to obtain fresh algae mud with different degrees of fineness.

[0115] (5) The fresh algae mud was placed under a scanning electron microscope for observation. The results were as follows: Figure 5 As shown, it can be seen that the untreated fresh algae mud is aggregated together, and there is more organic matter and impurities on the fresh algae mud.

[0116] 2. Adhesive suspended algae mud, the specific steps are as follows:

[0117] The preparation method of the polyvinyl alcohol solution was the same as step S2 of Example 1. The viscosity of the 5.0% polyvinyl alcohol solution was tested according to the national standard GB / T173-93, and the viscosity of the 5.0% polyvinyl alcohol solution was 392 mPa·s.

[0118] In other specific embodiments, other organic molecules with a certain viscosity that can be fully calcined without producing excess impurities can be prepared according to the above-mentioned method for preparing the polyvinyl alcohol solution, and the viscosity of the adhesive can be set within the range of 50-500 mPa·s. For example, a polyvinyl alcohol solution (PVA solution) with a concentration of 0.1-5.0%, hydroxypropyl methylcellulose (HPMC) with a concentration of 0.5-5.0%, gum arabic or starch paste with a concentration of 1.0-5.0%, or silica sol with a concentration of 10.0-40.0% can be prepared.

[0119] 3. Granulation processing of diatom particles, the specific steps are as follows:

[0120] (1) The fresh algae mud obtained in this example is dried. The drying process is oven drying. The fresh algae mud is spread flatly in an oven, the oven temperature is set to 80°C, and the drying time is set to 28 hours. After drying, the powder is collected to obtain diatom powder.

[0121] In other specific embodiments, the temperature and time of oven drying can be changed. For example, the drying temperature is set between 50 and 90°C, and the drying time is correspondingly increased to 40 hours or reduced to 24 hours. In another specific embodiment, the drying process can also be selected as natural air drying, that is, fresh algae mud is spread on a receiving tray and placed in a cool, ventilated and dry place for natural air drying to obtain diatom powder. A finer mesh gauze or other material can also be covered above the receiving tray to prevent the loss of the diatom powder after drying.

[0122] (2) Clean the granulation disk on the wheel granulator (purchased from Zhengzhou Hongda Mining Equipment Co., Ltd., model ZL-SP) and wipe it with alcohol to remove residue. Set the initial speed to 10 rpm and the tilt angle to 30°. Connect the peristaltic pump and set the adhesive flow rate to 5.0 mL / min. Then take 300 g of dry diatom powder and spread it evenly on the bottom of the granulation disk. Then start the granulation disk rotation and turn on the peristaltic pump. When the particle diameter reaches 0.1 mm, increase the speed and reduce the spray rate. Stop spraying the adhesive when the particle size reaches 1.0 mm. Keep the granulation disk rotating for 30 minutes to obtain diatom particles.

[0123] In other specific embodiments, different weights of dried diatom frustule powder can be used, for example, 100 to 1000 g. The initial speed of the disc granulator is set to 10 to 40 rpm, the tilt angle is 30 to 60 degrees, and the adhesive flow rate is set to 0.5 to 5.0 mL / min. When the particle diameter reaches 0.1 to 0.5 mm, the speed is increased and the spray rate is reduced. When the particle size reaches 0.5 to 1.0 mm, the adhesive spraying is stopped and the disc rotation is maintained for 5 to 30 minutes to obtain the granular shape required for the experiment.

[0124] (3) Drying the diatom granules obtained by the above granulation. The drying process is oven drying. Fresh algae mud is spread flatly in an oven, and the oven temperature is set to 80°C and the drying time is set to 28 hours. After drying, the powder is collected to obtain diatom powder. In addition, the diatom granules are turned every 4 hours to ensure uniform drying, thereby obtaining dry diatom granules.

[0125] 4. The roasting method is used to process diatom shells. The specific steps are as follows:

[0126] 3000 g of the dried diatom particles obtained in this example were placed in a crucible, and the crucible was placed in a muffle furnace for calcination. The temperature was raised to 600°C at a heating rate of 4°C / min and calcined for 120 min to obtain a white solid powder, which was the processed product. The processed product was the diatom shell.

[0127] In other specific embodiments, 1000~5000 g of diatom particles obtained by processing in this embodiment can be selected and placed in a ceramic fiber board, and the ceramic fiber board is placed in a high-temperature calcination equipment such as a muffle furnace, a tubular furnace, a cyclone dynamic calcination drying system or a microwave high-temperature calcination furnace for roasting to obtain a complete and clean diatom shell. Among them, the roasting temperature can be selected from 400~600℃, the heating rate is 2~5℃ / min, and the product is collected after roasting, and a complete and clean diatom shell can also be obtained. The roasting temperature is 400~600℃, the heating rate is 2~5℃ / min, and the product collected after roasting is the processed product, that is, a complete and clean diatom shell.

[0128] S3. Detection of diatom frustules. The specific steps are as follows:

[0129] (1) Take an appropriate amount of the diatom frustules obtained by the above processing and stick them on the conductive glue. Spray gold on them and place them under a scanning electron microscope to observe the morphology and structure of the diatom frustules to preliminarily evaluate the feasibility of this scheme. The main components and group composition of the diatom frustules are analyzed using a Fourier transform infrared spectrometer.

[0130] Scanning electron microscopy results Figure 6 As shown, it can be seen that compared with fresh algae mud, the diatom shells processed by the method provided in this embodiment are more dispersed as a whole, and the organic matter on the diatom shells has also been removed.

[0131] Further magnification of the diatom shells revealed the following results: Figure 7 As shown, the diatom frustules obtained by the processing method provided in this embodiment contain complete diatom frustules, that is, the projected area of ​​the front view of a single diatom frustule accounts for 85% or more of the projected area of ​​the front view of a single diatom frustule before extraction, the structure of the diatom frustule is complete, all organic matter is removed, the shell of the diatom frustule is transparent, the pores are clear, and the hierarchical porous structure of different scales can be seen.

[0132] (2) Take an appropriate amount of diatom shells obtained in this example and place them on a Fourier transform infrared spectrometer for broad spectrum analysis. The results are as follows: Figure 8 As shown in the figure, the diatom shell of Cynomorium sclerite shows the characteristic peaks of silicon oxide (Si-O-Si, Si-OH), specifically, at 3440 cm -1 A peak representing Si-OH stretching appeared at 1094 cm -1 、466 cm -1 Si-O-Si stretching peaks appeared everywhere, and there were no other organic peaks, so it was regarded as pure SiO2 material.

[0133] S4. Diatom frustule harvest rate statistics. The specific reference steps are as follows:

[0134] The harvest rate of diatom frustules was calculated according to the following formula:

[0135] ;

[0136] Wherein, W0 is the weight of diatom powder before treatment; W a is the weight of diatom frustules after treatment.

[0137] Statistics show that the final diatom frustule harvest rate was 30%. Further statistics on the harvest rate of intact and impurity-free diatom frustules showed that intact and impurity-free diatom frustules accounted for 65% of the total harvested diatom frustules, indicating that the harvest rate of intact and impurity-free diatom frustules was higher.

[0138] Comparative Example 1

[0139] Compared with Example 1, the difference is that in Comparative Example 1, the acid-heat method is used to process the Cyclotella, and the processed product obtained is diatom frustules.

[0140] Specifically, the specific reference steps for the acid-heat method of processing Cyclotella are as follows:

[0141] (1) When the Cyclotella cryptica reached the early plateau phase (this is exactly the same as the state of Cyclotella cryptica in Example 1), half of the Cyclotella cryptica algae liquid in the columnar photobioreactor was removed and allowed to settle for 24 hours before removing the supernatant. The concentrated algae liquid at the bottom was further concentrated to a slurry using a centrifuge at 6000 rpm. The slurry was removed and dried in an oven for 48 hours, then gently pressed into dry algae powder.

[0142] (2) Preparation of urea-potassium hydroxide solution: Dissolve urea and potassium hydroxide in deionized water, where the mass ratio of urea, potassium hydroxide, and deionized water is 8:16:76. For example, to prepare 1 L of urea-potassium hydroxide solution, weigh 80 g of urea and 160 g of potassium hydroxide, dissolve them in pure water, and you will get 1 L of urea-potassium hydroxide solution.

[0143] (3) 50 g of the algae powder prepared in the comparative example was added to 150 mL of a urea-potassium hydroxide solution and stirred until the algae powder was evenly dispersed and suspended in the urea-potassium hydroxide solution. The sample was then frozen at -30°C. After 6 h, the sample was removed and thawed in an oven. The freeze-thaw process was repeated once. After centrifugation to remove the alkali solution, the precipitate was washed several times with deionized water and collected to obtain preliminarily treated biomineralized silicon.

[0144] (4) At low temperature, slowly add 30% hydrogen peroxide solution into sulfuric acid with a volume ratio of hydrogen peroxide to sulfuric acid of 3:7 to obtain a hydrogen peroxide and sulfuric acid mixture (referred to as piranha solution). Cool it naturally and set aside.

[0145] (5) Acid-heat treatment: Take 100 mL of cooled piranha liquid and slowly add the biomineralized silicon prepared in the comparative example while stirring. The biomineralized silicon and piranha liquid are mixed in a ratio of 1:2 to obtain a reaction solution. The reaction solution is then heated in a water bath at 80°C for 1 h. After the reaction solution is cooled, it is allowed to precipitate at room temperature. The supernatant acid solution is removed and then diluted with deionized water. After repeated dilution and precipitation processes, sodium hydroxide solution is added to adjust the pH value to neutral. After centrifugal washing, the precipitate is dried to obtain the purified Cyclotella biomineralized silicon, which is the Cyclotella diatom shell.

[0146] The harvest rate of diatom frustules was calculated according to the following formula:

[0147] ;

[0148] Wherein, W0 is the weight of dry algae powder; W a is the weight of diatom frustules after treatment.

[0149] Statistics show that the final harvested diatom frustule yield was 8%, which was significantly lower than the diatom frustule yield in Example 1. The diatom frustule yield of the complete and impurity-free diatom frustules harvested in the comparative example was further statistically analyzed, and the results showed that the complete and impurity-free diatom frustules in the comparative example accounted for less than 50% of the total diatom frustules harvested in the comparative example, that is, the harvest rate of the complete and impurity-free diatom frustules was low.

[0150] like Figure 9 As shown, the proportion of damaged diatom frustules in the diatom frustules obtained in Comparative Example 1 is higher than that of intact diatom frustules. Although the shell of the diatom frustule is transparent and the holes are clear, it is damaged, that is, the projection area of ​​the front view of a single diatom frustule is less than 85% of the projection area of ​​the front view of a single diatom frustule before extraction, and does not include 85%.

[0151] Complete diatom shells have good porosity, multi-layer mesoporous structure, large specific surface area, high adsorption, mechanical stability, heat resistance and other excellent properties, collectively referred to as spatial performance; they can be used as ideal templates for preparing nanomaterials, polymer composites, such as nanoparticles, nanofilms, photonic crystals, microlens arrays and biosensors. Through surface modification, complete diatom shells can also be widely used in drug delivery, catalytic reactions, aerospace, lightweight automobiles and other fields, thereby achieving specific functions. Although incomplete diatom shells can also be used after being damaged, the incomplete diatom shells after being damaged will reduce their stability and spatial performance. The more incomplete diatom shells are, the worse the porosity is, the multi-layer mesoporous structure is destroyed, and the worse the spatial performance is.

[0152] Comparative Example 2

[0153] Compared with Example 1, the difference is that Comparative Example 2 only uses a roasting method without using an adhesive treatment. Because the algae mud is accumulated and adhered together over a large area, the organic matter and impurities cannot be removed by the roasting method, resulting in the small ring algae diatom shells obtained by Comparative Example 2 being unable to be used in subsequent applications.

[0154] Therefore, under conventional circumstances, it is impossible to obtain complete and impurity-free diatom shells only by roasting.

[0155] In addition, according to the processing method described in the above embodiment, other unicellular diatoms can be cultured and propagated using seawater culture medium, and further processed to obtain diatom shells, so that the diatom shell harvest rate is more than 15%, and the complete diatom shells without impurities account for 65% or more of the total harvested diatom shells. Among them, other unicellular diatoms are central diatoms or pinnate diatoms; central diatoms include Cyclostriales, Rhizoschiales and Boxes; Pinnate diatoms include Navicales, Curvilineares, Diploschiales, Phaeophyales, Aconicales and Brachyschiales. Cyclostriales includes Cyclostriales; Boxes include Ceratophyceae; Navicales includes Navicaceae; Phaeophyales includes Phaeophyceae. Specifically, the Coscinodiscus family includes Coscinodiscus radiatus; the Chaetoceros family includes Chaetoceros muelleri; the Navicula family includes Navicula elegans; and the Phaeodactylum family includes Phaeodactylumtricornutum Bohlin.

[0156] It can be concluded that the present application provides a unicellular diatom cultured based on seawater culture medium and its processing method and processed product, which realizes pure and pollution-free culture and propagation of unicellular diatoms through seawater culture medium. The seawater culture medium is easy to configure, the culture process is simple, and it is efficient and environmentally friendly. The processing method of the present application using an adhesive combined with granulation and roasting method is used to process the unicellular diatoms in the logarithmic growth phase after the above-mentioned propagation. The harvest rate of the processed product is 15-30%, and the complete diatom shells without impurities account for 65% or more of the total amount of harvested diatom shells, so that the structure of the processed product is complete, the pores are clear, and there is no organic matter residue on the surface. The purity is high, and the original complete multi-layer mesoporous structure and spatial performance of the diatom shell are greatly retained. It has high safety, no residue and pollution, and the processing method has a wide range of applications. It is applicable to diatoms of different genera and species, which is a further development and utilization of marine resources. At the same time, the processing method provided in this application can realize the processing of kilogram-level large-scale single-cell diatoms, providing a reasonable solution for industrial large-scale production, and the processed products obtained are diatom shells, which can provide a stable source in different fields and contribute to the development of single-cell diatoms in various fields.

[0157] The terms and expressions used herein are for descriptive purposes only, and the present invention should not be limited to these terms and expressions. The use of these terms and expressions is not intended to exclude any equivalent features illustrated and described (or portions thereof), and it should be recognized that various modifications are also within the scope of the claims. Other modifications, variations, and substitutions are possible. Accordingly, the claims are intended to cover all such equivalents.

[0158] Similarly, it should be pointed out that although the present invention has been described with reference to the current specific embodiments, ordinary technicians in this technical field should realize that the above embodiments are only used to illustrate the present invention, and various equivalent changes or substitutions can be made without departing from the spirit of the present invention. Therefore, as long as the changes and modifications to the above embodiments are within the scope of the essential spirit of the present invention, they will fall within the scope of the claims of the present invention.

Claims

1. A method for processing unicellular diatoms, characterized in that: The following steps are involved: Step A: Cultivating single-cell diatoms using seawater culture medium and preparing fresh algae mud; the seawater culture medium is formulated by sterilizing mother liquor A1, mother liquor A2, mother liquor B, mother liquor C, mother liquor D, and mother liquor E and mixing them with sterile, impurity-free seawater at a ratio of 1:1000 to obtain the seawater culture medium; The A1 mother liquor includes a nitrogen source, and the nitrogen source is NaNO3; The A2 mother liquor includes a phosphorus source, which is NaH2PO4·2H2O; The B mother solution includes a silicon source, and the silicon source is Na2SiO3·9H2O; The C mother solution includes a first trace element, wherein the first trace element is FeCl3·6H2O and Na2EDTA; The D mother solution includes a second trace element, wherein the second trace element is CuSO4·5H2O, ZnSO4·7H2O, CoCl2·6H2O, MnCl2·4H2O and Na2MoO4·2H2O; The E mother solution includes vitamins, which are vitamin B1, vitamin B12 and biotin H; Step B: suspending the fresh algae mud with an adhesive, and granulating the suspended fresh algae mud to obtain diatom particles; The fresh algae mud and the adhesive are mixed in a ratio of W / V = (1:1) to (1:5); the adhesive is a polyvinyl alcohol solution with a concentration of 0.1 to 5.0%, and the viscosity of the adhesive is 50 to 500 mPa·s; Step C: Processing the diatom particles by a roasting method to obtain a processed product; the roasting temperature is 400-600° C., and the roasting heating rate is 2-5° C. / min.

2. The method for processing unicellular diatoms according to claim 1, characterized in that: The step A specifically comprises: mixing the algal liquid of the unicellular diatom in the logarithmic growth phase with the seawater culture medium in a ratio of 3:7, and expanding and culturing the unicellular diatom until the end of the logarithmic growth phase; then sedimenting, washing and centrifuging at least once, and discarding the supernatant to obtain a precipitate, which is the fresh algal mud; The unicellular diatoms include the Central Bacillariophyceae; the Central Bacillariophyceae include the Cynocephales; the Cynocephales include the Cynocephalaceae.

3. The method for processing unicellular diatoms according to claim 1, characterized in that: The step B comprises: Step B-1: suspending the fresh algae mud with the adhesive to obtain a fresh algae mud suspension; Step B-2: Granulating the fresh algae mud suspension using a spray granulation dryer to obtain the diatom particles.

4. The method for processing unicellular diatoms according to claim 3, characterized in that: The inlet air temperature of the spray granulation dryer in step B-2 is 180-260°C, the outlet air temperature is 80-150°C, the atomization volume is 5-200 μm, the feed rate is 500-2000 mL / h, and the drying time is 0.8-2.0 s.

5. The method for processing unicellular diatoms according to claim 1, characterized in that: The step B comprises: Step B-1: drying the fresh algae mud to obtain diatom powder; Step B-2: placing the diatom powder on a wheel granulator, spraying the adhesive onto the diatom powder for granulation, and obtaining the diatom granules after drying.

6. The method for processing unicellular diatoms according to claim 5, characterized in that: The step B-2 specifically comprises: placing the diatom powder on the granulation disk of the wheel granulator, turning on the wheel granulator, rotating the granulation disk, spraying the adhesive onto the surface of the diatom powder, and mixing the diatom powder and the adhesive to form the diatom granules; the flow rate of the adhesive in the wheel granulator is 0.5-5.0 mL / min; and the particle size of the diatom granules is 0.5-1.0 mm; The drying process is performed at a temperature of 50-90° C. and for a time of 20-40 h.

7. The method for processing unicellular diatoms according to claim 1, characterized in that: The step C specifically comprises: placing the diatom particles in air, oxygen or nitrogen and performing the roasting to obtain the processed product, wherein the processed product is diatom frustules, and the yield of the processed product is 15% or more; The calcining container is a crucible or a ceramic fiberboard; the crucible or the ceramic fiberboard is placed in a muffle furnace, a tubular furnace, a cyclone dynamic calcining drying system or a microwave high-temperature calcining furnace for calcination.

8. The method for processing unicellular diatoms according to any one of claims 1 to 7, characterized in that: The step B does not include acid heat treatment.

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