CN113730949A - Preparation method of microalgae extract - Google Patents

Abstract

The invention relates to the technical field of microalgae bioengineering, and discloses a preparation method of a microalgae extract. The method comprises the following steps: carrying out first contact on microalgae and an organic phase extractant under a pressurized condition, carrying out solid-liquid separation to obtain an organic phase and a solid phase, and removing the organic phase extractant from the organic phase to obtain a microalgae oil soluble substance; wherein the organic phase extractant contains hydrocarbon solvent and ether solvent; the hydrocarbon solvent is one or more selected from C3-6 alkane, C2-4 alkene and C1-4 halogenated hydrocarbon; the ether solvent is C2-C4 ether. The preparation method of the microalgae extract has the advantages of simple and stable operation, easy quality control, high separation efficiency, low cost and no waste liquid discharge and environmental pollution, and all the extracting agents can be recycled in the separation process.

Description

Preparation method of microalgae extract

Technical Field

The invention relates to the technical field of microalgae bioengineering, in particular to a preparation method of a microalgae extract.

Background

The microalgae is a unicellular organism with wide distribution, high growth speed and simple structure. When the microalgae grows, a large amount of carbon dioxide can be fixed, and the method has great significance for reducing the emission of the carbon dioxide in the atmosphere. Through the own specific metabolic process, microalgae can generate various valuable compounds with unique structures, including microalgae oil-soluble substances, water-soluble substances and the like, wherein the microalgae oil-soluble substances can be used as basic raw materials of biodiesel, and the microalgae water-soluble substances mainly comprise active ingredients such as microalgae proteins and microalgae polysaccharides and the like, so that the microalgae is a promising economic crop. Various components in the microalgae are fully utilized, so that the economic value of the microalgae can be improved, the cost of reducing carbon dioxide emission by the microalgae can be effectively reduced, and a foundation is laid for large-scale application of microalgae cultivation. Therefore, efficient access to microalgae constituents is a critical issue. At present, methods such as wall breaking, solvent extraction, water washing, oil-water separation, salting out, alcohol precipitation and the like are mostly adopted to realize the separation of oil, protein and polysaccharide in microalgae.

CN101352249A discloses a production method for fully utilizing oil-containing microalgae. Wherein, the microalgae is subjected to high-pressure homogenization wall breaking, then fatty acid methyl ester is extracted, and centrifugal separation is carried out after extraction. After the solid phase is washed for three times, the water washing liquid and the extract liquid are mixed for oil-water separation. Obtaining the microalgae oil of the oil phase, and obtaining the microalgae protein and the microalgae polysaccharide by sequentially carrying out ammonium sulfate and ethanol precipitation on the water phase.

CN104560357A discloses a method for simultaneously extracting microalgae oil and microalgae polysaccharide, which mainly comprises obtaining pretreated microalgae by enzymatic degradation and secondary treatment at 80-120 ℃ and 0.05-0.25MPa, then extracting with diethyl ether or chloroform, and simultaneously obtaining microalgae polysaccharide and microalgae oil by ethanol precipitation of extract liquor.

CN101429467A discloses a method for simultaneously extracting oil and protein from microalgae, which is to break the wall and dissolve out the oil and protein by steam. Demulsifying and separating oil and water to obtain an oil phase and a water phase. The oil phase is used for obtaining oil, and the water phase is concentrated and subjected to pH acid adjustment to obtain protein.

It can be seen from the above documents that the first oil-water mixture obtained by the above method is subjected to emulsion breaking and oil-water separation to obtain oil-dissolved substance and water-dissolved substance. However, the method has the disadvantages of multiple operation steps, high cost, low demulsification efficiency and difficult separation of oil phase and water phase, and finally influences the purity and efficiency of microalgae component extraction.

Disclosure of Invention

The invention aims to overcome the technical problems that the extraction of microalgae water-soluble substances is difficult to directly carry out after the extraction of the microalgae oil-soluble substances in the prior art, and the operations such as demulsification, oil-water separation and the like are usually needed, and provides a preparation method of a microalgae extract.

In order to achieve the above object, the present invention provides a method for preparing a microalgae extract, comprising: carrying out first contact on microalgae and an organic phase extractant under a pressurized condition, carrying out solid-liquid separation to obtain an organic phase and a solid phase, and removing the organic phase extractant from the organic phase to obtain a microalgae oil soluble substance; the organic phase extracting agent contains hydrocarbon solvent and ether solvent, wherein the hydrocarbon solvent is one or more selected from C3-6 alkane, C2-4 alkene and C1-4 halogenated hydrocarbon, and the ether solvent is C2-C4 ether.

Preferably, the hydrocarbon solvent is propane, butane, ethylene, propylene, CH₃CH₂F and CH₃One or more of Cl, more preferably propane and/or butane.

Preferably, the ether solvent is dimethyl ether and/or methyl ethyl ether, more preferably dimethyl ether.

Preferably, in the organic phase extractant, the molar ratio of the hydrocarbon solvent to the ether solvent is 1: 0.05 to 20, more preferably 1: 0.1-10.

Preferably, the weight ratio of the organic phase extractant to the microalgae is 1-100: 1, more preferably 5 to 80: 1.

preferably, the pressure of the first contact is from 0.1 to 1MPa, preferably from 0.3 to 0.8MPa, more preferably from 0.4 to 0.8 MPa.

Preferably, the time of the first contact is 5 to 120 minutes.

Preferably, the first contacting is performed 1 to 8 times.

Preferably, the removal of the organic phase extractant from the organic phase is carried out using a reduced pressure process.

More preferably, the reduced pressure is between-0.1 and-0.01 MPa, preferably between-0.05 and-0.01 MPa.

Preferably, the method further comprises carrying out second contact on the solid phase and the aqueous phase extractant, and separating to obtain the microalgae water-soluble substance.

More preferably, the aqueous phase extractant is water or an aqueous solution of a base, preferably the base is sodium hydroxide and/or potassium hydroxide.

Preferably, the weight ratio of the aqueous phase extractant to the microalgae is 1-100: 1.

preferably, the time of the second contact is 0.5 to 10 hours.

Preferably, the temperature of the second contact is 10-90 ℃.

Preferably, the second contacting is performed in 1-5 separate times, each for 10-30 minutes.

Preferably, the first contacting and the second contacting are each performed using a separation vessel, preferably a stainless steel separation vessel. More preferably, the separation tank has a stirring member.

Preferably, the microalgae is one or more selected from chlorella, microspherococcus sp, oil-ball algae, monoraphidium, haematococcus pluvialis and scenedesmus, preferably monoraphidium and/or haematococcus pluvialis.

More preferably, the microalgae are subjected to wall breaking prior to first contacting with the organic phase extractant; more preferably, the wall breaking is performed by mechanical milling, high pressure homogenization, enzymatic degradation or ultrasound, preferably mechanical milling.

Preferably, the water content of the microalgae is between 0 and 30 wt%, more preferably between 0 and 20 wt%.

The inventor of the invention finds that the extraction rate and the extraction efficiency of the microalgae oil-soluble matter can be improved by using the organic phase extracting agent containing the hydrocarbon solvent and the ether solvent, the extraction of the microalgae water-soluble matter can be continuously carried out without operations such as demulsification and the like, and the extraction rate and the extraction efficiency of the microalgae water-soluble matter are good.

Through the technical scheme, the preparation method can realize continuous and sequential extraction and efficient separation of the microalgae oil-soluble substances and the microalgae water-soluble substances to the maximum extent. In the whole process, the extraction of the microalgae oil-soluble substances and the extraction of the microalgae water-soluble substances are separately carried out, so that the problem of oil-water separation is solved. Stable operation, easy quality control, high extraction efficiency, low cost and no waste liquid discharge and environmental pollution, and all the extractants can be recycled in the extraction process. The water soluble substance obtained by separation can be separated into microalgae protein and microalgae polysaccharide by conventional salting out, alcohol precipitation and other methods.

Detailed Description

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

The preparation method of the microalgae extract comprises the following steps: carrying out first contact on microalgae and an organic phase extractant under a pressurized condition, carrying out solid-liquid separation to obtain an organic phase and a solid phase, and removing the organic phase extractant from the organic phase to obtain a microalgae oil soluble substance; wherein the organic phase extractant contains hydrocarbon solvent and ether solvent; the hydrocarbon solvent is one or more selected from C3-6 alkane, C2-4 alkene and C1-4 halogenated hydrocarbon; the ether solvent is C2-C4 ether.

According to the present invention, in order to facilitate the removal of the organic phase extractant from the organic phase, the organic extractant is preferably a low boiling point organic solvent, more preferably an organic solvent which is gaseous at normal temperature and normal pressure or at a temperature close to room temperature (e.g., 0 to 50 ℃) and which is liquefiable under pressure. The pressure for the pressurization may be, for example, 2MPa or less, preferably 1MPa or less, and more preferably 0.1 to 1 MPa.

According to the invention, the hydrocarbon solvent can be one or more of alkane, alkene and halogenated hydrocarbon, preferably one or more of alkane selected from C3-6, alkene selected from C2-4 and halogenated hydrocarbon selected from C1-4. Specifically, the alkane of C3-6 can be n-propane, isopropane, n-butane, isobutane, n-pentane, isopentane, neopentane, cyclopentane, n-hexane, isohexane, neohexane, 1, 2-dimethylbutane, cyclohexane, etc.; the C2-4 olefin can be ethylene, propylene, 1-butene, 2-methylpropene, cyclopropene, cyclobutene, etc.; the C1-4 halogenated hydrocarbon can be C1-4 alkane substituted by chlorine or fluorine (the alkane can include methane, ethane, n-propane, isopropane, n-butane, isobutane, etc.), such as CH₃Cl、CH₂Cl₂、CH₃CH₂Cl、CH₃CH₂F, and the like. Among them, preferred are propane, butane, ethylene, propylene and CH₃CH₂F and CH₃One or more of Cl, more preferably propane and/or butane.

According to the present invention, the ether solvent may be C2-C4 ether, such as dimethyl ether, diethyl ether, methyl ethyl ether, methyl propyl ether, etc., wherein dimethyl ether and/or methyl ethyl ether are preferred, and dimethyl ether is more preferred.

According to a preferred embodiment of the present invention, in order to achieve better microalgae oil-soluble product preparation effect, the organic phase extractant has a molar ratio of the hydrocarbon solvent to the ether solvent of 1: 0.05 to 20, preferably 1: 0.05 to 15, more preferably 1: 0.1 to 10, more preferably 1: 1-5. By using the hydrocarbon solvent and the ether solvent in the molar ratio in a matching manner, the extraction rate and the extraction efficiency of the microalgae oil-soluble matter of the obtained organic phase extractant can be further improved.

According to the invention, in order to obtain better preparation effect of the microalgae oil-soluble substance, the weight ratio of the organic phase extractant to the microalgae can be 1-100: 1, preferably 5 to 80: 1, e.g. 5: 1. 10: 1: 20: 1. 30: 1. 40: 1. 50: 1. 60: 1. 70: 1 or 80: 1.

in the present invention, the first contacting is to extract the oil-soluble substances in the microalgae by using an organic phase extractant, and the specific conditions are not particularly limited, and the extraction of the oil-soluble substances in the microalgae can be completed. According to the components and the proportion of the selected organic phase extractant, the condition for leading the organic phase extractant to be liquid is required to be selected for the first contact. In order to ensure the preparation effect of the microalgae oil-soluble substance, the pressure of the first contact can be 0.1-1MPa, preferably 0.3-0.8MPa, and more preferably 0.4-0.8 MPa. Also, the time of the first contact is preferably 5 to 120 minutes, more preferably 5 to 60 minutes. In addition, in order to further improve the extraction effect of the microalgae oil-soluble matter, the first contacting is preferably performed 1 or more times, for example, may be performed 1 to 8 times, for example, 1 to 3 times.

After the first contact by the above method, a solid-liquid separation method can be used to separate an organic phase and a solid phase (i.e., microalgae residue left after extraction of oil-soluble substances). Wherein, the organic phase obtained by separation is used for separating microalgae oil-soluble substances, and the solid phase can be used for further extracting microalgae water-soluble substances. The specific mode of solid-liquid separation may be one or more selected from the group consisting of filtration separation, centrifugal separation and gravity settling, and filtration separation is preferred. Among them, the filter used in the filtration separation is preferably 100-500 mesh, more preferably 200-450 mesh. The removal of the organic phase extractant from the organic phase is preferably carried out by a method of reducing the pressure, preferably from-0.1 to 0MPa, more preferably from-0.1 to-0.01 MPa, and still more preferably from-0.05 to-0.01 MPa, and the pressure reduction may be carried out, for example, in a buffer tank. Since the organic phase extractant is gaseous under the reduced pressure, the microalgae oil-soluble can be directly obtained by removing the organic phase from the organic phase.

In addition, the organic phase extractant removed from the organic phase may be reused for the first contact. Specifically, the organic phase extractant may be liquefied after being compressed by a compressor, and the liquefied organic phase extractant may be directly reused in the first contacting process.

By using the method for extracting the microalgae oil-soluble substance, the microalgae oil-soluble substance with higher purity can be directly obtained, and the obtained solid phase is more suitable for extracting the microalgae water-soluble substance. That is, the method of the invention can realize continuous extraction and high-efficiency separation of microalgae oil-soluble substances and microalgae water-soluble substances to the maximum extent. Preferably, the solid phase may be subjected to standing at atmospheric pressure or reduced pressure to remove a small amount of the organic phase extractant remaining therein, and the reduced pressure condition may be the same as the reduced pressure condition described above for removing the organic phase extractant from the organic phase.

In order to extract the microalgae hydrosoluble substance, the method also comprises a second contact of the solid phase and the aqueous phase extractant, and the microalgae hydrosoluble substance is obtained by separation. The extraction of the microalgae aqueous solution can be carried out by any conventional preparation method of microalgae aqueous solution, and the used aqueous phase extractant is not particularly limited as long as the aqueous phase extractant can be used for separating microalgae aqueous solution such as saccharide and protein in microalgae according to needs. Preferably, the aqueous phase extractant is water or an aqueous solution of a base, wherein preferably the base is sodium hydroxide and/or potassium hydroxide, more preferably the aqueous solution of a base is used before water.

According to the present invention, the amount of the aqueous phase extractant to be used may be appropriately selected depending on the need of extraction. In order to achieve a good separation effect of microalgae water-soluble substances, the weight ratio of the aqueous phase extractant to the microalgae is preferably 1-100: 1, more preferably 5 to 20: 1.

in the present invention, the second contacting is to leach the water-soluble microalgae with the aqueous phase extractant, and the conditions are not particularly limited, and the separation of the water-soluble microalgae can be completed. In order to achieve better microalgae water-soluble substance preparation effect, the second contact time is preferably 0.5-10 hours, and preferably 1-5 hours. Preferably the temperature of the second contacting is from 10 to 90 deg.C, more preferably from 25 to 80 deg.C, more preferably from 25 to 60 deg.C. After the second contact, the microalgae aqueous solution can be separated by any one or more of filtration separation, centrifugal separation and gravity settling, wherein filtration separation is preferred, and pressure suction filtration separation is most preferred, and the filter used is preferably 100-500 meshes, and preferably 200-450 meshes. Furthermore, the second contact may also be carried out in a plurality of times (e.g. 1 to 8 times, preferably 1 to 5 times), each time ranging from 10 minutes to 5 hours, for example from 10 to 50 minutes. When the second contact is performed for a plurality of times, the microalgae aqueous solutions separated after the second contact for a plurality of times can be combined to be used as the microalgae aqueous solution finally extracted. According to a preferred embodiment of the invention, after the second contact with water or an aqueous alkali solution, the second contact is carried out with water for more than 3 times for 10 to 30 minutes each.

In the present invention, both the first contact and the second contact are preferably leaching, and may be performed using any reactor, and in order to facilitate separation of the products after the contact, the first contact and the second contact are preferably performed using separate vessels, and more preferably, using a separate vessel made of stainless steel. In order to achieve better separation effect, the separation kettle is preferably provided with a stirring component, and the stirring component can be in an anchor type, a frame type or a spiral belt type, and is preferably in an anchor type.

In the present invention, the microalgae is oil-soluble microalgae, and for example, may be one or more selected from chlorella, parachloropsis, oleococcus, chrysomyodytes, haematococcus pluvialis and scenedesmus, wherein preferably chrysomyia pluvialis and/or haematococcus pluvialis. The water content of the microalgae used for the first contact is preferably 0 to 30% by weight, more preferably 0 to 20% by weight, further preferably 10 to 20% by weight, more preferably 15 to 18% by weight.

According to a preferred embodiment of the present invention, the microalgae are subjected to a pre-treatment before they are subjected to the first contact with the organic phase extractant. The pretreatment may include one or more of drying treatment, wall breaking treatment, molding treatment, and the like. The drying treatment may be carried out under any conditions as long as the oil-soluble and water-soluble substances are not destroyed, and for example, the drying may be carried out at 20 to 50 deg.C (preferably 30 to 40 deg.C) to achieve the desired water content. The method of the wall-breaking treatment is not particularly limited, and any conventional method for breaking the wall of the microalgae can be used, for example, mechanical grinding, high-pressure homogenization, enzymatic degradation or ultrasound can be used, and among them, mechanical grinding is preferred. In addition, in the present invention, the microalgae may be in a powdery form,or may be formed into a sheet or a pellet, preferably a sheet. Specifically, microalgae (preferably wall-broken microalgae) can be added into water, stirred, tabletted, and sliced into tablet with size of 0.1-10cm². The weight ratio of the water to the microalgae is preferably 0.01-0.3: 1.

the present invention will be described in detail below by way of examples. In the present invention, "%" means "% by weight" and the pressures are gauge pressures unless otherwise specified.

In the following examples, the monochoria algae of examples 1-4 and 7-14 and comparative examples 1 and 2 were treated as follows: collecting air-dried Mono-needled algae 300g (water content of 8 wt%), mechanically pulverizing, adding water 30g, mixing, tabletting, and slicing into slices with length of 10 mm, width of 5 mm, and thickness of 0.5 mm (water content of 18 wt%).

The monochoria algae of example 7 was treated as follows: 350g of air-dried single needle algae (water content of 8 wt%) is mechanically pulverized, 30g of water is added, and the mixture is uniformly mixed, and then is tabletted and sliced into slices (water content of 16.6 wt%) with the length of 10 mm, the width of 5 mm and the thickness of 0.5 mm.

Scenedesmus of example 8 was treated as follows: collecting dry Scenedesmus 210g (water content of 10 wt%), mechanically pulverizing, adding 12g water, mixing, tabletting, and slicing into slices (water content of 15.7 wt%) with length of 10 mm, width of 5 mm and thickness of 0.5 mm.

Examples 1 to 14 and comparative examples 1 to 2

The microalgae shown in table 1 were placed in a 10L, non-agitated, stainless steel extraction kettle. After vacuum pumping, 3L of organic phase extractant shown in Table 1 was added, extraction was performed for 3 times under the microalgae oil-soluble extraction conditions shown in Table 1, the extraction time for each time is shown in Table 1, and the extract obtained by filtration (400 mesh) after each extraction was completed was placed in a stainless steel oil-soluble separation vessel having a volume of 10L. And (3) decompressing the stainless steel oil-soluble substance separation kettle to-0.01 MPa to gasify the organic phase extractant, thereby recovering the organic phase extractant to obtain the microalgae oil-soluble substance.

And (3) removing residual oil soluble substances in the organic phase extractant after the organic phase extractant passes through a buffer tank to obtain a pure organic phase extractant. The pure organic phase extractant is liquefied after being compressed by a compressor, and the liquefied organic phase extractant returns to an organic phase extractant storage tank for reuse. And after extraction is finished, decompressing the stainless steel extraction kettle to-0.01 MPa, and recovering the residual organic phase extractant in the microalgae residue to obtain dry microalgae residue without the organic phase extractant after oil-soluble extraction.

After extraction of the microalgae oil-soluble matter, 3000g of water phase extracting agent shown in table 1 is added into an extraction kettle, and the microalgae water-soluble matter is extracted under the microalgae water-soluble matter extraction conditions shown in table 1. After leaching, the solution is separated by suction filtration (400 mesh), and the leaching solution enters a water solution tank. Soaking microalgae residue for 3 times, adding 1000g of water each time, soaking for 30 min, filtering, and separating. After immersion cleaning, the immersion cleaning liquid enters a water-soluble material tank.

The yields and extraction rates of the microalgae oil-soluble substances and microalgae water-soluble substances in the above examples and comparative examples were calculated according to the following methods, and the results are shown in table 2.

The oil-soluble physical content of the microalgae is calculated by taking the weight M0 of a methanol/chloroform mixed solvent (the molar ratio is 2: 1) extracted for 10 hours in a Soxhlet extractor as a reference, and the extraction rate C is calculated according to a formula (1):

wherein M is the weight of the organic phase extractant. The theoretical content of oil-soluble substances in the monoraphidium algae used in the following examples and comparative examples was 27% by weight and the theoretical content of oil-soluble substances in scenedesmus was 22.2% by weight, as determined by measurement.

The extraction yield S of the microalgae oil-soluble matter is calculated according to a formula (2):

wherein M is the weight of the organic phase extractant, M₀Is the initial weight of the microalgae.

The extraction yield Q of the microalgae water-soluble substance is calculated according to a formula (3):

wherein m is the weight of the microalgae remained after water-soluble substances are extracted, m is₀Is the initial weight of the microalgae.

TABLE 1

TABLE 2

As can be seen from the results in tables 1 and 2, the technical solutions of the present invention adopted in examples 1 to 14 of the present invention can achieve higher extraction yield, extraction rate and microalgae water soluble extract yield of microalgae oil soluble. It can be seen from comparing examples 1 to 14 with comparative examples 1 to 2 that the method for preparing a microalgae extract according to the present invention can simultaneously obtain higher yields of microalgae oil-soluble substances and microalgae water-soluble substances by using a complex organic phase extractant composed of a hydrocarbon solvent and an ether solvent.

In examples 1 and 9 to 14, the oil-soluble microalgae were extracted from the same treated single-needle algae by using organic phase extractants in different ratios. As can be seen from the results of extraction of the microalgae oil-soluble substance in table 2, the molar ratio of the hydrocarbon solvent to the ether solvent was set to 1: 0.05 to 15, preferably 1: 0.1 to 10, more preferably 1: 1-5, can achieve higher extraction yield and extraction rate of microalgae oil-soluble matters.

In examples 1 to 6, the aqueous phase extractants with different ratios were used to extract the aqueous microalgae extract from the oil-soluble monoraphidium. As can be seen from the results of extraction of aqueous microalgae solutions in Table 2, higher yield of aqueous microalgae solutions can be achieved by using 3-8% aqueous alkali and extracting at 40-80 deg.C (preferably 60-80 deg.C).

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.

Claims (10)

1. A method for preparing a microalgae extract, comprising: carrying out first contact on microalgae and an organic phase extractant under a pressurized condition, carrying out solid-liquid separation to obtain an organic phase and a solid phase, and removing the organic phase extractant from the organic phase to obtain a microalgae oil soluble substance;

wherein the organic phase extractant contains hydrocarbon solvent and ether solvent;

the hydrocarbon solvent is one or more selected from C3-6 alkane, C2-4 alkene and C1-4 halogenated hydrocarbon; the ether solvent is C2-C4 ether.

2. The process of claim 1, wherein the hydrocarbon solvent is propane, butane, ethylene, propylene, CH₃CH₂F and CH₃One or more of Cl, more preferably propane and/or butane;

preferably, the ether solvent is dimethyl ether and/or methyl ethyl ether, more preferably dimethyl ether.

3. The process according to claim 1, wherein the organic phase extractant has a molar ratio of the hydrocarbon solvent to the ether solvent of 1: 0.05 to 20, more preferably 1: 0.1-10.

4. The method of claim 1, wherein the weight ratio of the organic phase extractant to the microalgae is from 1 to 100: 1, more preferably 5 to 80: 1.

5. the process according to any one of claims 1 to 4, wherein the pressure of the first contact is from 0.1 to 1MPa, preferably from 0.3 to 0.8MPa, more preferably from 0.4 to 0.8 MPa;

preferably, the time of the first contact is 5 to 120 minutes;

preferably, the first contacting is performed 1 to 8 times.

6. The process of any one of claims 1-5, wherein removing the organic phase extractant from the organic phase is performed using a reduced pressure process;

preferably, the reduced pressure is between-0.1 and-0.01 MPa, preferably between-0.05 and-0.01 MPa.

7. The method of any one of claims 1 to 6, further comprising a second contacting of the solid phase with an aqueous phase extractant and separation to obtain an aqueous microalgae extract;

preferably, the aqueous phase extractant is water or an aqueous solution of a base, preferably the base is sodium hydroxide and/or potassium hydroxide;

preferably, the weight ratio of the aqueous phase extractant to the microalgae is 1-100: 1;

preferably, the time of the second contact is 0.5 to 10 hours;

preferably, the temperature of the second contact is 10-90 ℃;

preferably, the second contacting is performed in 1-5 separate times, each for 10-30 minutes.

8. The method of claim 7, wherein the first and second contacting are each performed using a separation vessel, preferably a stainless steel separation vessel;

preferably, the separation tank has a stirring member.

9. The method according to any one of claims 1 to 8, wherein the microalgae is one or more selected from chlorella, microspherococcus sp, oil globule algae, chrysomyia sp, haematococcus pluvialis and scenedesmus, preferably chrysomyia sp and/or haematococcus pluvialis;

preferably, the microalgae are subjected to wall breaking prior to the first contacting with the organic phase extractant; more preferably, the wall breaking is performed by mechanical milling, high pressure homogenization, enzymatic degradation or ultrasound, preferably mechanical milling.

10. The method according to any one of claims 1 to 9, wherein the microalgae has a water content of 0-30 wt.%, preferably 0-20 wt.%.