CN113322186B - Method for rapidly harvesting microalgae by using ionic liquid - Google Patents

Abstract

The invention provides a method for rapidly harvesting microalgae by using an ionic liquid, which comprises the following steps: culturing microalgae with BG-11 liquid culture medium; after the microalgae is cultured to a stable period, adding 2-pyrrolidone tetrafluoroborate ionic liquid to promote the flocculation of the microalgae cells; the concentration of the ionic liquid is respectively 20mg/L, 50mg/L or 100mg/L; and (5) measuring the OD value of the algae liquid and calculating the flocculation efficiency. The invention has the advantages of less environmental pollution, reusable culture medium, energy conservation, environmental protection, lower harvesting cost and large-scale application.

Description

Method for rapidly harvesting microalgae by using ionic liquid

Technical Field

The invention belongs to the technical field of microalgae flocculation, and particularly relates to a method for rapidly harvesting microalgae by using an ionic liquid.

Background

Microalgae can synthesize various important products, such as polyunsaturated fatty acids, astaxanthin and other products with high added value, can be used for producing renewable clean energy sources such as biodiesel, and can also be used as feed and bait for livestock and aquaculture. The microalgae has high photosynthetic efficiency, fast cell proliferation and short production period, can grow in a severe environment, does not occupy agricultural land and does not compete with people for grain.

Whether the algal cells themselves are obtained as baits and nourishments, or the extraction of high-value products in microalgae cells, the algal cells must be separated from the culture medium, so that the algal cells must be obtained by harvesting techniques. But microalgae have low density, specific gravity close to that of the culture medium and cells with the same kind of charge, so that harvesting is difficult, energy consumption and cost are high, and the promotion of microalgae cell flocculation is the most common harvesting method.

The conventional microalgae cell flocculation method is to add polyvalent metal cations as flocculant, but has strong toxicity to microalgae cells, and can cause secondary pollution to water, so that the water after microalgae harvesting cannot be reused. The method for flocculating and harvesting the microalgae cells is a problem which needs to be solved urgently at present.

Disclosure of Invention

The invention aims to provide a method for rapidly harvesting microalgae by using an ionic liquid, so as to solve the technical problems.

The invention provides a method for rapidly harvesting microalgae by using an ionic liquid, which is characterized by comprising the following steps:

1) Culturing microalgae with BG-11 liquid culture medium with inoculum size of 4X10 ⁶ The cell/L is inoculated into a conical flask filled with 300mL of culture solution/500 mL, and shake cultivation is carried out at 25 ℃ with illumination intensity of 3500lux and 150 rpm;

2) Placing the microalgae on a shelf after the microalgae are cultured to a stable period, and preparing flocculation;

3) Pouring the cultured algae liquid into a 1L beaker, and adding 2-pyrrolidone tetrafluoroborate ionic liquid, wherein the concentration of the ionic liquid is 20mg/L, 50mg/L or 100mg/L respectively;

4) After the algae liquid in the beaker was mixed uniformly, the absorbance at a wavelength of 750nm was measured.

5) Flocculation efficiency was calculated by:

flocculation efficiency = 100× (a-B)/a

Wherein A is the absorbance of the microalgae liquid without adding ionic liquid; and B is the absorbance of the microalgae liquid after the ionic liquid is added.

Compared with the prior art, the invention has the beneficial effects that:

microalgae are collected by adopting 2-pyrrolidone tetrafluoroborate ionic liquid, and the flocculation efficiency is the same as FeCl ₃ ，Al ₂ (SO ₄ ) ₃ The common multivalent metal cation flocculant is not up and down, and the technical requirement is met. Compared with the method for harvesting microalgae by using the polyvalent metal cation flocculant, the method has the advantages of environmental friendliness, no secondary pollution of water, reusable culture medium, energy conservation and environmental friendliness, capability of reducing the culture cost of microalgae, and potential and value for large-scale popularization and application.

Drawings

FIG. 1 shows the flocculation efficiency of microalgae cells under different addition concentrations of the 2-pyrrolidone tetrafluoroborate ionic liquid of the present invention;

FIG. 2 is a graph showing flocculation efficiency of multivalent metal cation flocculants on microalgae cells;

FIG. 3 shows the case of the 2-pyrrolidone tetrafluoroborate ionic liquid of the present invention, in which microalgae are collected by adding the culture medium, and the microalgae are cultured repeatedly.

Detailed Description

The present invention will be described in detail below with reference to the embodiments shown in the drawings, but it should be understood that the embodiments are not limited to the invention, and functional, method, or structural equivalents and alternatives according to the embodiments are within the scope of protection of the present invention by those skilled in the art.

The embodiment provides a method for rapidly harvesting microalgae by using an ionic liquid, which comprises the following steps:

1) Culturing microalgae with BG-11 liquid culture medium with inoculum size of 4X10 ⁶ The cell/L is inoculated into a conical flask filled with 300mL of culture solution/500 mL, and shake cultivation is carried out at 25 ℃ with illumination intensity of 3500lux and 150 rpm;

2) Placing the microalgae on a shelf after the microalgae are cultured to a stable period, and preparing flocculation;

3) Pouring the cultured algae liquid into a 1L beaker, and adding 2-pyrrolidone tetrafluoroborate ionic liquid, wherein the concentration of the ionic liquid is 20mg/L, 50mg/L or 100mg/L respectively;

4) After the algae liquid in the beaker was mixed uniformly, the absorbance at a wavelength of 750nm was measured.

5) Flocculation efficiency was calculated by:

flocculation efficiency = 100× (a-B)/a

Wherein A is the absorbance of the microalgae liquid without adding ionic liquid; and B is the absorbance of the microalgae liquid after the ionic liquid is added.

In the embodiment, the 2-pyrrolidone tetrafluoroborate is a synthetic ionic liquid, which can flocculate microalgae and realize the harvesting of the microalgae. As shown in figure 1, ionic liquids with different concentrations are added into the algae liquid, and flocculation results show that the flocculation effect of the ionic liquid with the concentration of 20mg/L on microalgae is more prominent than that of the ionic liquid with other concentrations, and the flocculation efficiency can reach more than 80 percent, so that the method can be used for microalgae harvesting.

As shown in FIG. 2, the conventional multivalent metal cation flocculants have different flocculation effects on microalgae, generally like FeCl ₃ ，Al ₂ (SO ₄ ) ₃ These flocculants have a good effect on the flocculation of microalgae and their flocculation advantages can be obtained by frequent review in the literature. When FeCl ₃ When the adding amount of the microalgae reaches 1100mg/L, the flocculation efficiency of the microalgae reaches a higher level, which is 83.45%, and the flocculation effect is also better; when Al is added ₂ (SO ₄ ) ₃ When the concentration reaches 900mg/L, the flocculation effect of the microalgae is also good, and the flocculation efficiency reaches 82.19%; znSO at a concentration of 250. Mu. Mol/L ₄ And CuSO ₄ The flocculation efficiency of the microalgae is 53% and 75% respectively; ca (OH) ₂ Has an effect on flocculation of microalgae, and has about 50% of algae liquid flocculation efficiency when the concentration is more than or equal to 500 mg/L. Of course, the corresponding disadvantages also appear, although the flocculation effect is good, the damage to the algae cells is larger, the integrity of the algae cells is not easy to maintain, the extraction rate of other high-added-value products is reduced, the pollution hazard to the environment is larger, the cost is higher, and the culture solution can not be recycled, which is one of the reasons that the metal ion flocculant can not be used on a large scale.

As shown in FIG. 3, the culture solution obtained by adding ionic liquids with different concentrations to collect microalgae can be continuously used for culturing microalgae, and the cell concentration of microalgae can reach 8×10 ⁷ Above cell/mL, compared with the control, the ionic liquid has no obvious drop, which indicates that the use of the ionic liquid can not have obvious influence on the water body, and the culture solution after microalgae harvesting can continue to cultivate the microalgae for use.

The 2-pyrrolidone tetrafluoroborate is a novel ionic liquid, is environment-friendly, does not have pollution to the environment, is stable in performance, is nonflammable, has high melting point and boiling point, has good thermal stability, high heat capacity and low vapor pressure, and can be safely used and conveniently stored.

Compared with other multivalent metal cation flocculants, the ionic liquid flocculant has the advantages of less addition (only about 1/50 of the addition of the metal cation flocculants), environmental friendliness and less pollution, and the culture solution can be reused, so that the microalgae culture cost is reduced, and large-scale application can be considered.

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims (1)

1. The method for rapidly harvesting the microalgae by using the ionic liquid is characterized by comprising the following steps of:

1) Culturing microalgae with BG-11 liquid culture medium with inoculum size of 4X10 ⁶ The cell/L is inoculated into a conical flask filled with 300mL of culture solution/500 mL, and shake cultivation is carried out at 25 ℃ with illumination intensity of 3500lux and 150 rpm;

2) Placing the microalgae on a shelf after the microalgae are cultured to a stable period, and preparing flocculation;

3) Pouring the cultured algae liquid into a 1L beaker, and adding 2-pyrrolidone tetrafluoroborate ionic liquid, wherein the concentration of the ionic liquid is 20mg/L, 50mg/L or 100mg/L respectively;

4) After the algae liquid in the beaker was mixed uniformly, the absorbance at a wavelength of 750nm was measured.

5) Flocculation efficiency was calculated by:

flocculation efficiency = 100× (a-B)/a

Wherein A is the absorbance of the microalgae liquid without adding ionic liquid; and B is the absorbance of the microalgae liquid after the ionic liquid is added.

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