CN115029248A - Method for improving microalgae lipid yield by utilizing recycled wastewater - Google Patents

Abstract

The invention belongs to the technical field of bioengineering, and discloses a method for improving microalgae lipid yield by using recycled wastewater, which adopts a two-stage culture mode, carries out algae species mixotrophic culture in the first stage to enable algae cells to grow rapidly in a short period, then collects the wastewater after microalgae culture, mixes BG-11 after simple filtration to form a mixed culture medium, and combines a photobioreactor to culture microalgae by using the mixed culture medium. The method combines a mixotrophic-photoautotrophic two-stage culture mode, and in the photoautotrophic culture stage, when the concentration of the recycled wastewater is 40%, the lipid content and lipid yield of the microalgae are respectively improved by 14.95% and 14.00% compared with those of a single BG-11 group; the culture method can obviously improve the lipid content and the lipid yield of the microalgae, realizes the rapid synthesis of the lipid in the algae cells, simultaneously reduces the use of fresh water and the culture cost of the microalgae, and provides a new research direction for the culture of the microalgae by using waste water and the treatment of the recycling cost.

Description

A kind of method for improving microalgae lipid production by using recycled wastewater

technical field

The invention belongs to the technical field of bioengineering, and in particular relates to a method for improving the lipid yield of microalgae by utilizing recycled wastewater.

Background technique

At present, with the exploitation of fossil fuels, the energy crisis and environmental pollution have brought serious problems to human society, and it is very urgent to develop new sustainable resources to meet the growing demand in the future. As an emerging raw material, microalgae have the following advantages over biomass from traditional commercial crops: 1) no competition for cultivated land; 2) high photosynthetic efficiency and relatively short growth period; 3) broad adaptability to harsh conditions. Therefore, third-generation biofuels based on microalgal lipids have attracted much attention. Although microalgae can accumulate a large amount of lipids, high cost and low yield have always been the main factors limiting their industrialization. How to reduce the cost of microalgae culture and improve the lipid content and yield of microalgae is an urgent problem to be solved in recent years. The two-stage culture model is a strategy for microalgae to rapidly accumulate biomass and lipids.

In order to further reduce the cost of microalgae cultivation, the use of wastewater to cultivate microalgae can absorb and utilize organic substances such as nitrogen and phosphorus in wastewater, and can also replace traditional culture media. A large amount of wastewater will be generated during the cultivation of microalgae, and it will also cause environmental pollution. However, there are few reports on the use of wastewater produced by the cultivation of microalgae to re-cultivate microalgae. On the other hand, when using pure wastewater to cultivate microalgae, due to some toxic substances in wastewater, the growth rate of microalgae is often slow, which reduces the biomass yield of microalgae, thereby affecting the overall oil production. Therefore, a certain ratio of nutrients can improve the overall biomass and lipid yield of microalgae. This strategy may help to increase the lipid production of microalgae, reduce the cost of microalgae cultivation, reduce the use of fresh water, and also contribute to the improvement of wastewater. Reuse provides new technical ideas.

Through the above analysis, the existing problems and defects in the prior art are: the cost of the existing microalgae is high and the yield is low; a large amount of waste water will be generated during the microalgae cultivation process, and the waste water generated by the microalgae culture is used to re-cultivate the microalgae. Less; lipid yields of microalgae cultured with pure wastewater are low due to the slower growth rate of microalgae caused by toxic substances in wastewater.

SUMMARY OF THE INVENTION

Aiming at the problems existing in the prior art, the present invention provides a method for improving the lipid yield of microalgae by utilizing recycled wastewater.

The present invention is achieved in this way, a method for improving the lipid yield of microalgae by utilizing the reused wastewater, and the method for improving the lipid yield of microalgae by utilizing the reused wastewater comprises:

The two-stage culture mode is adopted. In the first stage, the algae and species are cultivated to make the algal cells grow rapidly in a short period of time. Then, the wastewater after the microalgae culture is collected. After simple filtration, BG-11 is mixed to form a mixed medium. Bioreactors that use mixed media to grow microalgae.

Further, the method for improving the lipid yield of microalgae by recycling wastewater also includes:

The cellulosic algae are cultivated with glucose as the carbon source, and the microalgae grow to the late logarithmic growth phase. After the algal cells settle, the supernatant is poured out, and the remaining algal cells are collected as the seed liquid. The supernatant is obtained after suction filtration. Algae-cultivation wastewater; the algae-cultivation wastewater ratio BG-11 is used as the mixed medium, the microalgae are resuspended in the column photobioreactor with the mixed medium of different ratios, and 10% CO ₂ and air mixed gas are continuously introduced , and cultivated under a certain temperature and light intensity environment, to detect and analyze the biomass, lipid content and yield of microalgae.

Further, the method for improving the lipid yield of microalgae by using the reused wastewater comprises the following steps:

The first step is to collect the reused waste water;

In step 2, the microalgae is cultivated by using the recycled waste water ratio BG-11;

In step 3, the lipids in the algal cells in the culture solution obtained in step 2 are extracted with an organic solvent.

Further, the collection of reused wastewater in the step 1 includes:

The BG-11 medium with glucose as the carbon source was cultured in a 500mL Erlenmeyer flask, and the microalgae were grown to the late logarithmic growth phase. The algal cells are used as the seed solution, and the collected supernatant is filtered to obtain reused wastewater.

Further, the microalgae is the cellulosic alga Ankistrodesmus sp.EHY.

Further, the utilization and reuse of wastewater in the second step to cultivate microalgae with the ratio of BG-11 includes:

The reused wastewater was mixed with fresh BG-11 as a mixed medium, and the seed solution of the first stage was resuspended into a 1L column-type photobioreactor to ensure that the microalgae inoculation amount was 0.9g/L; % CO ₂ and air mixed gas, and placed in a certain temperature and light intensity environment to cultivate to obtain the final culture solution.

Further, the concentration of reused wastewater in the mixed medium is 30-60%.

Further, the temperature is 25°C, and the light intensity is 7000-8000 lux.

Further, the lipids in the algal cells in the nutrient solution obtained in the step 2 by using an organic solvent to extract the steps 3 include:

Centrifuge the final culture solution obtained in step 2 at 5000 r/min for 5 min, collect the algal cells in a centrifuge tube, freeze at -80 °C overnight, freeze-dried for 24 h in a freeze dryer, and weigh; weigh 0.2 g of dry algal powder, add Quartz sand is ground and mixed, and organic solvent is added to repeat the extraction until the algal body turns white, and the organic phase is collected by centrifugation to obtain the total lipid, and the lipid content of the microalgae algal powder is measured by gravimetric method.

Further, the organic solvent is a chloroform-methanol solution, wherein the volume ratio of chloroform and methanol in the chloroform-methanol solution is 2:1; the mass of the quartz sand is twice the mass of the dry algal powder.

In combination with the above-mentioned technical solutions and the technical problems solved, please analyze the advantages and positive effects of the technical solutions to be protected by the present invention from the following aspects:

First, in view of the technical problems existing in the above-mentioned prior art and the difficulty of solving the problems, closely combine the technical solutions to be protected of the present invention and the results and data in the research and development process, etc., and analyze in detail and profoundly how to solve the technical solutions of the present invention. Technical problems, some creative technical effects brought about by solving problems. The specific description is as follows:

The invention combines the facultative-photoautotrophic two-stage cultivation mode, and in the photoautotrophic cultivation stage, 40% of the reused wastewater can significantly improve the lipid content and lipid yield of the microalgae. The rapid synthesis of lipids in algal cells reduces the use of fresh water and the cost of microalgae cultivation, and provides a new research direction for the use of wastewater to cultivate microalgae and the treatment of recycling costs. The invention significantly improves the lipid content of microalgae, when the concentration of recycled wastewater is 40%, the lipid content and lipid yield of microalgae are 52.01% (cell dry weight) and 250.72 mg L ^-1 d ^-1 respectively, 14.95% and 14.00% higher than the BG-11 group alone, respectively.

Second, considering the technical solution as a whole or from the product point of view, the technical effects and advantages of the technical solution to be protected by the present invention are specifically described as follows:

The invention has simple procedures, easy operation and environmental protection, can significantly improve the lipid content and yield of microalgae, reduce the production cost of microalgae, and at the same time provides a new idea for the reuse of algae-cultivating wastewater. Reduce pollution caused by algae culture wastewater; reduce the cost of microalgae cultivation, absorb and reuse organic matter in wastewater, reduce the use of fresh water, and improve the economic feasibility of microalgae cultivation; obtain high value-added metabolites for the production of biodiesel .

Third, as an auxiliary evidence of inventive step for the claims of the present invention, it is also reflected in the following important aspects:

The expected income and commercial value after the transformation of the technical solution of the present invention are as follows: a new technical approach is provided for the reuse of wastewater in the industrialization of microalgae, the cultivation cost of microalgae is reduced, and the use of fresh water is reduced.

Description of drawings

In order to illustrate the technical solutions of the embodiments of the present invention more clearly, the following will briefly introduce the accompanying drawings that need to be used in the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained from these drawings without creative effort.

Fig. 1 is the method flow chart that utilizes reused waste water to improve microalgae lipid output provided by the embodiment of the present invention;

2A is a graph showing the effect of different concentrations of reused medium on microalgal biomass provided in the embodiment of the present invention;

Fig. 2B is a schematic diagram showing the effect of different concentrations of reused medium on oil content and high-quality yield provided by the embodiment of the present invention.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

Aiming at the problems existing in the prior art, the present invention provides a method for improving the lipid yield of microalgae by utilizing recycled wastewater. The present invention is described in detail below with reference to the accompanying drawings.

1. Explain the embodiment. In order for those skilled in the art to fully understand how the present invention is specifically implemented, this part is an explanatory embodiment to expand the description of the technical solutions of the claims.

As shown in Figure 1, the method for improving the lipid yield of microalgae by utilizing recycled wastewater provided by the embodiment of the present invention comprises the following steps:

S101, collecting reused wastewater;

S102, cultivating microalgae by using recycled wastewater with a ratio of BG-11;

S103, using an organic solvent to extract the lipids in the algal cells in the culture solution obtained in S102.

As a preferred embodiment, the method for improving the lipid yield of microalgae by utilizing recycled wastewater provided in the embodiment of the present invention specifically includes the following steps:

(1) Collection of reused wastewater: the BG-11 medium with glucose as the carbon source was cultured in a 500mL Erlenmeyer flask, and the microalgae were grown to the late logarithmic growth phase and settled for two days. The supernatant was poured off, the remaining algal cells were mixed as seed solution, and the collected supernatant was reused after suction filtration; wherein, the microalgae was Ankistrodesmus sp.EHY.

(2) Microalgae cultivation with recycled wastewater ratio BG-11: The recycled wastewater is formulated with fresh BG-11 as a mixed medium, and the concentration of recycled wastewater in the mixed medium is 30-60%; the first stage of resuspension The seed solution was placed in a 1L column photobioreactor to ensure that the microalgae inoculation amount was about 0.9g/L, 10% _CO2 and air mixed gas was continuously introduced, and the temperature was 25°C and the light intensity was Cultivated at 7000-8000 lux to obtain the final culture medium.

(3) Use an organic solvent to extract the lipids in the algal cells in the culture solution obtained in step (2): the final culture solution obtained in step b was centrifuged at 5000 r/min for 5 min, and the algal cells were collected in a centrifuge tube at -80°C Freeze overnight, freeze-dried for 24 hours in a freeze dryer, weighed, then weighed 0.2 g of dry algal powder, added quartz sand, ground and mixed, then added organic solvent and repeated extraction until the algal body turned white, and the organic phase was collected by centrifugation. Lipid, the lipid content of microalgae algal powder was measured by gravimetric method; the organic solvent was chloroform-methanol solution, and the volume ratio of chloroform and methanol in the chloroform-methanol solution was 2:1; the mass of quartz sand was the mass of dry algal powder 2 times.

2. Application examples. In order to prove the creativity and technical value of the technical solution of the present invention, this part is an application example of the technical solution in the claims on specific products or related technologies.

Example 1:

When the concentration of the reused wastewater provided by the embodiment of the present invention is 30%, the specific steps of detecting and analyzing the biomass and lipid content of microalgae are as follows:

(1) Collection of reused wastewater: the BG-11 medium with glucose as the carbon source was cultured in a 500mL Erlenmeyer flask, and the microalgae were grown to the late logarithmic growth phase and settled for two days. Pour out the supernatant, mix the remaining algal cells as seed solution, and the collected supernatant is reused wastewater after suction filtration;

(2) 30% recycled wastewater to cultivate microalgae: use 30% recycled wastewater to mix fresh BG-11 as a mixed medium, and resuspend the first-stage seed solution into a 1L column photobioreactor , ensure that the microalgae inoculum amount is about 0.9g/L, continuously feed 10% _CO2 and air mixed gas, and place it at a temperature of 25 °C and a light intensity of 7000-8000 lux to cultivate to obtain the final culture solution.

Utilize the organic solvent to extract the lipid in the algal cell in the culture solution obtained in the step (2): use the organic solvent to extract the oil in the algal cell in the step (2): wherein the organic solvent is a chloroform-methanol solution, and the chloroform and chloroform in the chloroform-methanol solution are The volume ratio of methanol was 2:1; the final culture solution obtained in step (2) was centrifuged at 5000 r/min for 5 min, the algal cells were collected in a centrifuge tube, frozen at -80°C overnight, and then weighed after being lyophilized by a freeze dryer for 24 hours. Then weigh 0.2g of dry algal powder, add 0.4g of quartz sand and grind and mix, then add an organic solvent and repeat the extraction until the algal body turns white, and the organic phase is collected by centrifugation to obtain total lipids, and the microalgae are measured by gravimetric method. Lipid content of algal flour. The biomass was 4.44g L ^-1 , slightly higher than the control group, but there was no significant difference; the oil content was 49.28%, and the oil yield was 243.38mg L ^-1 d ^-1 (see Figure 2A to Figure 2B ) , increased by 8.93% and 10.66%, respectively, compared with the BG-11 group alone.

Example 2:

When the concentration of the reused wastewater provided in the embodiment of the present invention is 40%, the specific steps of detecting and analyzing the biomass and lipid content of microalgae are as follows:

(1) Collection of reused wastewater: the BG-11 medium with glucose as the carbon source was cultured in a 500mL Erlenmeyer flask, and the microalgae were grown to the late logarithmic growth phase and settled for two days. Pour off the supernatant, mix the remaining algal cells as seed liquid, and the collected supernatant is reused wastewater after suction filtration;

(2) 40% recycled wastewater to cultivate microalgae: use 40% recycled wastewater to mix fresh BG-11 as a mixed medium, and resuspend the first-stage seed solution into a 1L column photobioreactor , ensure that the microalgae inoculum amount is about 0.9g/L, continuously feed 10% _CO2 and air mixed gas, and place it at a temperature of 25 °C and a light intensity of 7000-8000 lux to cultivate to obtain the final culture solution.

Utilize the organic solvent to extract the lipid in the algal cell in the culture solution obtained in the step (2): use the organic solvent to extract the oil in the algal cell in the step (2): wherein the organic solvent is a chloroform-methanol solution, and the chloroform and chloroform in the chloroform-methanol solution are The volume ratio of methanol was 2:1; the final culture solution obtained in step (2) was centrifuged at 5000 r/min for 5 min, the algal cells were collected in a centrifuge tube, frozen at -80°C overnight, and then weighed after being lyophilized by a freeze dryer for 24 hours. Then weigh 0.2g of dry algal powder, add 0.4g of quartz sand and grind and mix, then add an organic solvent and repeat the extraction until the algal body turns white, and the organic phase is collected by centrifugation to obtain total lipids, and the microalgae are measured by gravimetric method. Lipid content of algal flour. Its biomass was 4.33 g L ^-1 , which had no significant difference with the control group; the oil content was 52.01%, and the oil yield was 250.72 mg L ^-1 d ^-1 (see Figure 2A to Figure 2B ), which were higher than those of BG-1 alone. Group 11 improved by 14.95% and 14.00%.

Example 3:

When the concentration of the reused wastewater provided in the embodiment of the present invention is 50%, the specific steps of detecting and analyzing the biomass and lipid content of microalgae are as follows:

(1) Collection of reused wastewater: the BG-11 medium with glucose as the carbon source was cultured in a 500mL Erlenmeyer flask, and the microalgae were grown to the late logarithmic growth phase and settled for two days. Pour off the supernatant, mix the remaining algal cells as seed liquid, and the collected supernatant is reused wastewater after suction filtration;

(2) 50% recycled wastewater to cultivate microalgae: use 50% recycled wastewater to mix fresh BG-11 as a mixed medium, and resuspend the first-stage seed solution into a 1L column photobioreactor , ensure that the microalgae inoculum amount is about 0.9g/L, continuously feed 10% _CO2 and air mixed gas, and place it at a temperature of 25 °C and a light intensity of 7000-8000 lux to cultivate to obtain the final culture solution.

Utilize the organic solvent to extract the lipid in the algal cell in the culture solution obtained in the step (2): use the organic solvent to extract the oil in the algal cell in the step (2): wherein the organic solvent is a chloroform-methanol solution, and the chloroform and chloroform in the chloroform-methanol solution are The volume ratio of methanol was 2:1; the final culture solution obtained in step (2) was centrifuged at 5000 r/min for 5 min, the algal cells were collected in a centrifuge tube, frozen at -80°C overnight, and then weighed after being lyophilized by a freeze dryer for 24 hours. Then weigh 0.2g of dry algal powder, add 0.4g of quartz sand and grind and mix, then add an organic solvent and repeat the extraction until the algal body turns white, and the organic phase is collected by centrifugation to obtain total lipids, and the microalgae are measured by gravimetric method. Lipid content of algal flour. The biomass was 3.69g L ^-1 , which was only 84.67% of the control group; the oil content was 50.64%, an increase of 11.94% compared with the control group, but its oil yield was only 197.70mg L ^{- 1} due to its growth inhibition. d ^-1 (see Figures 2A to 2B).

Example 4:

When the concentration of the reused wastewater provided in the embodiment of the present invention is 50%, the specific steps of detecting and analyzing the biomass and lipid content of microalgae are as follows:

(1) Collection of reused wastewater: the BG-11 medium with glucose as the carbon source was cultured in a 500mL Erlenmeyer flask, and the microalgae were grown to the late logarithmic growth phase and settled for two days. Pour off the supernatant, mix the remaining algal cells as seed liquid, and the collected supernatant is reused wastewater after suction filtration;

(2) 60% recycled wastewater to cultivate microalgae: use 60% recycled wastewater to mix fresh BG-11 as a mixed medium, and resuspend the first-stage seed solution into a 1L column photobioreactor , ensure that the microalgae inoculum amount is about 0.9g/L, continuously feed 10% _CO2 and air mixed gas, and place it at a temperature of 25 °C and a light intensity of 7000-8000 lux to cultivate to obtain the final culture solution.

Utilize the organic solvent to extract the lipid in the algal cell in the culture solution obtained in the step (2): use the organic solvent to extract the oil in the algal cell in the step (2): wherein the organic solvent is a chloroform-methanol solution, and the chloroform and chloroform in the chloroform-methanol solution are The volume ratio of methanol was 2:1; the final culture solution obtained in step (2) was centrifuged at 5000 r/min for 5 min, the algal cells were collected in a centrifuge tube, frozen at -80°C overnight, and then weighed after being lyophilized by a freeze dryer for 24 hours. Then weigh 0.2g of dry algal powder, add 0.4g of quartz sand and grind and mix, then add an organic solvent and repeat the extraction until the algal body turns white, and the organic phase is collected by centrifugation to obtain total lipids, and the microalgae are measured by gravimetric method. Lipid content of algal flour. The biomass was 3.04g L ^-1 , which only reached 69.56% of the control group; the oil content was 48.64%, an increase of 11.94% compared with the control group, its growth was significantly inhibited, and its oil yield was only 143.24 mg L ^-1 d ^-1 , significantly lower than the control group (see Figure 2A-2B).

3. Evidence of the relevant effects of the embodiment. The embodiments of the present invention have achieved some positive effects in the process of research and development or use, and indeed have great advantages compared with the prior art.

Comparative ratio:

The comparative example of the present invention provides detection and analysis of microalgae biomass and lipid content under separate BG-11 culture conditions, and the specific steps are as follows:

(1) The BG-11 medium with glucose as the carbon source was cultured in a 500mL Erlenmeyer flask, and the microalgae were grown to the late stage of the logarithmic growth phase. Mix the remaining algal cells as seed solution;

(2) Use BG-11 to cultivate microalgae: Use fresh BG-11 to resuspend the seed solution of the first stage into a 1L column type photobioreactor to ensure that the microalgae inoculation amount is about 0.9g/L, and the continuous flow of A mixture of 10% CO ₂ and air was introduced, and cultured at a temperature of 25° C. and a light intensity of 7000-8000 lux to obtain the final culture solution.

Utilize the organic solvent to extract the lipid in the algal cell in the culture solution obtained in the step (2): use the organic solvent to extract the oil in the algal cell in the step (2): wherein the organic solvent is a chloroform-methanol solution, and the chloroform and chloroform in the chloroform-methanol solution are The volume ratio of methanol was 2:1; the final culture solution obtained in step (2) was centrifuged at 5000 r/min for 5 min, the algal cells were collected in a centrifuge tube, frozen at -80°C overnight, and then weighed after being lyophilized by a freeze dryer for 24 hours. Then weigh 0.2g of dry algal powder, add 0.4g of quartz sand and grind and mix, then add an organic solvent and repeat the extraction until the algal body turns white, and the organic phase is collected by centrifugation to obtain total lipids, and the microalgae are measured by gravimetric method. Lipid content of algal flour. The biomass was 4.37 g L ^-1 , the oil content was 45.24%, and the oil yield was 219.93 mg L ^-1 d ^-1 (see Figures 2A and 2B).

The invention combines the facultative-photoautotrophic two-stage cultivation mode, and in the photoautotrophic cultivation stage, 40% of the reused wastewater can significantly improve the lipid content and lipid yield of the microalgae. The rapid synthesis of lipids in algal cells reduces the use of fresh water and the cost of microalgae cultivation, and provides a new research direction for the use of wastewater to cultivate microalgae and the treatment of recycling costs.

The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited to this. Any person skilled in the art is within the technical scope disclosed by the present invention, and all within the spirit and principle of the present invention Any modifications, equivalent replacements and improvements made within the scope of the present invention should be included within the protection scope of the present invention.

Claims (10)

1. a method of utilizing recycled waste water to improve microalgae lipid output, is characterized in that, the described method utilizing reused waste water to improve microalgae lipid output comprises: The two-stage culture mode is adopted. In the first stage, the algae and species are cultivated to make the algal cells grow rapidly in a short period of time. Then, the wastewater after the microalgae culture is collected. After simple filtration, BG-11 is mixed to form a mixed medium. Bioreactors that use mixed media to grow microalgae. 2. as claimed in claim 1, it is characterized in that, the method for improving microalgae lipid output of utilizing reused wastewater also comprises: The cellulosic algae are cultivated with glucose as the carbon source, and the microalgae grow to the late logarithmic growth phase. After the algal cells settle, the supernatant is poured out, and the remaining algal cells are collected as the seed liquid. The supernatant is obtained after suction filtration. Algae-cultivation wastewater; the algae-cultivation wastewater ratio BG-11 is used as the mixed medium, the microalgae are resuspended in the column photobioreactor with the mixed medium of different ratios, and 10% CO ₂ and air mixed gas are continuously introduced , and cultivated under a certain temperature and light intensity environment, to detect and analyze the biomass, lipid content and yield of microalgae. 3. the method that utilizes reused wastewater to improve microalgae lipid output as claimed in claim 1, is characterized in that, described utilizing reused wastewater to improve the method for microalgae lipid output comprises the following steps: The first step is to collect the reused waste water; In step 2, the microalgae is cultivated by using the recycled waste water ratio BG-11; In step 3, the lipids in the algal cells in the culture solution obtained in step 2 are extracted with an organic solvent. 4. the method that utilizes reused wastewater to improve microalgae lipid output as claimed in claim 3, is characterized in that, the collection of the reused wastewater in described step 1 comprises: The BG-11 medium with glucose as the carbon source was cultured in a 500mL Erlenmeyer flask, and the microalgae were grown to the late logarithmic growth phase. The algal cells are used as the seed solution, and the collected supernatant is filtered to obtain reused wastewater. 5. The method for improving microalgae lipid yield by utilizing recycled wastewater as claimed in claim 4, wherein the microalgae is the cellulosic alga Ankistrodesmus sp.EHY. 6. as claimed in claim 3, it is characterized in that the utilization of reused wastewater to improve the method for microalgae lipid output, the utilization of reused wastewater ratio BG-11 in the described step 2 cultivates microalgae and comprises: The reused wastewater is mixed with fresh BG-11 as a mixed medium, and the seed solution of the first stage is resuspended into a 1L column photobioreactor to ensure that the microalgae inoculum is 0.9g/L, and 10 % CO ₂ and air mixed gas, and placed in a certain temperature and light intensity environment to cultivate to obtain the final culture solution. 7 . The method for improving microalgal lipid production by utilizing recycled wastewater according to claim 6 , wherein the concentration of recycled wastewater in the mixed medium is 30-60%. 8 . 8 . The method for improving microalgae lipid yield by utilizing recycled wastewater according to claim 6 , wherein the temperature is 25° C., and the light intensity is 7000-8000 lux. 9 . 9. as claimed in claim 3, it is characterized in that, the lipid in the algal cell in the nutrient solution that utilizes organic solvent extraction step 2 to obtain in the described step 3 comprises: Centrifuge the final culture solution obtained in step 2 at 5000 r/min for 5 min, collect the algal cells in a centrifuge tube, freeze at -80 °C overnight, freeze-dried for 24 h in a freeze dryer, and weigh; weigh 0.2 g of dry algal powder, add Quartz sand is ground and mixed, and organic solvent is added to repeat the extraction until the algal body turns white, and the organic phase is collected by centrifugation to obtain the total lipid, and the lipid content of the microalgae algal powder is measured by gravimetric method. 10. as claimed in claim 9, it is characterized in that, described organic solvent is chloroform-methanol solution, wherein the volume ratio of chloroform and methanol is 2 in chloroform-methanol solution: 1; the quality of the quartz sand is twice that of the dry algal powder.

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