Method for enhancing carbon fixation of microalgae by seaweed-based carbon quantum dots in cooperation with plant hormones

Abstract

The present application relates to a kind of seaweed-based carbon quantum dots synergistic plant hormone enhances the method for microalgae carbon fixation, belong to biological carbon fixation technical field.The method with chlorella as carbon fixation carrier, culture in vertical tube type photobioreactor, and add indole-3-acetic acid (IAA) and seaweed-based carbon quantum dots (U-CQDs) in initial stage, optimize culture condition (25~30 ℃, 3000 Lux illumination, 15% CO2 supply).Seaweed-based carbon quantum dots (U-CQDs) are prepared by hydrothermal method with enteromorpha prolifera as raw material, with excellent light conversion characteristics.The present application significantly improves the light energy utilization efficiency of microalgae, CO2 fixation rate and biomass accumulation by the synergistic effect of U-CQDs and IAA, while reducing the energy consumption of culture.The method is simple in operation, low in cost, suitable for efficient capture and resource utilization of industrial flue gas CO2.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of biological carbon fixation, more particularly to a method for enhancing microalgae carbon fixation by seaweed-based carbon quantum dots in cooperation with plant hormones, which is particularly suitable for efficient capture and resource utilization of CO2 in industrial flue gas. BACKGROUND

[0002] The emission of high-concentration CO2 in industrial flue gas aggravates the greenhouse effect, and microalgae carbon fixation technology has become a research hotspot due to its high photosynthetic capacity. However, high-concentration CO2 and light attenuation limit the carbon fixation efficiency of microalgae. Exogenous plant hormones play a key role in the regulation of microalgae cell cycle and carbon fixation metabolism through the regulation of photosynthetic electron transport chain activity, enhancement of antioxidant defense system and alleviation of environmental stress. Carbon-based fluorescent materials (CQDs) are a kind of nanoparticles, which have attracted widespread attention due to their photochemical stability, low cytotoxicity and environmental friendliness. This kind of nanomaterial with a particle size of less than 10 nm has unique photoluminescence properties, which can convert invisible light such as ultraviolet light into visible light. The addition of CQDs in the algal liquid can increase the light absorption band of microalgae and improve the growth rate and photosynthetic activity of microalgae.

[0003] Although plant hormones have the effect of regulating the internal metabolism of microalgae cells, their ability to enhance light energy capture is relatively weak, and it is difficult to regulate the growth cycle of microalgae under industrial flue gas conditions alone. On the other hand, CQDs increase the light absorption band of microalgae, but the action dimension is limited to the optimization of the light physical process. If the carbon fixation capacity of microalgae is to be further improved, simultaneous light energy conversion and carbon flow metabolism regulation are required. Therefore, the present application aims to propose a method for improving the carbon fixation performance of microalgae by combining carbon quantum dots with plant hormones, promoting lipid accumulation in microalgae and reducing cell damage by plant hormones, and increasing the light energy utilization rate of microalgae by using carbon quantum dots as an internal light source to optimize the light physical process and improve the light energy capture efficiency, thereby enhancing the photosynthetic carbon fixation efficiency of microalgae. SUMMARY

[0004] In view of the problems of light attenuation in the photobioreactor and unstable microalgae culture environment caused by high-concentration CO2, the present application provides a method for preparing seaweed-based carbon quantum dots (U-CQDs) and enhancing the carbon fixation performance of microalgae in cooperation with plant hormones (IAA), which improves the CO2 fixation rate and biomass energy yield through the dual mechanisms of light conversion effect and metabolic regulation.

[0005] The present application provides a method for enhancing microalgae carbon fixation by seaweed-based carbon quantum dots in cooperation with plant hormones, comprising:

[0006] S1: Taking Chlorella as a carbon fixation carrier, and culturing in a vertical tubular photobioreactor using BG-11 medium;

[0007] S2: adding plant hormone indole-3-acetic acid (IAA) and seaweed-based carbon quantum dots (U-CQDs) in the initial stage of culture, and the culture conditions are as follows: temperature 25-30℃, light intensity 3000Lux, light and dark cycle 12h light / 12h dark, and gas supply 15% CO2 mixed gas, flow rate 0.18L·min - ¹, the biomass is cultured to the stable growth phase;

[0008] S3: preparing U-CQDs, specifically including: mixing Enteromorpha prolifera powder and deionized water at a weight-volume ratio of 1:10, and placing in a high-pressure hydrothermal kettle in a nitrogen atmosphere to react, separating the aqueous phase product after cooling, and obtaining U-CQDs powder through hydrothermal synthesis, filtration, dialysis and freeze-drying.

[0009] In this scheme, the vertical tubular photobioreactor is a multi-tube design, with a single tube working volume of 500mL and a total capacity of 0.6Lx12.

[0010] In this scheme, the concentration of IAA in the culture solution in step S2 is 1-5mg·L - ¹, the concentration of U-CQDs is 1-10mg·L - ¹.

[0011] In this scheme, the Chlorella vulgaris is ChlorellavulgarisFACHB-2723.

[0012] In this scheme, the preparation process of U-CQDs in step S3 is: mixing Enteromorpha prolifera powder and deionized water at a ratio of 1:10, placing in a stainless steel high-pressure hydrothermal kettle, filling with nitrogen, and performing hydrothermal reaction in a nitrogen atmosphere, nitrogen pressure 4MPa, reaction temperature 300℃, and holding for 1h;

[0013] After the stainless steel high-pressure hydrothermal kettle is cooled, the aqueous and oil phase products after hydrothermal reaction are collected by vacuum filtration, and the aqueous phase product is separated by a separatory funnel, then the aqueous phase product is transferred to a hydrothermal synthesis kettle and reacted in a 180℃ oven for 8h; after the hydrothermal synthesis kettle is cooled to room temperature, the obtained product is filtered through a 0.22μm microporous membrane, and then dialyzed for 24-36h using a dialysis bag with a molecular weight cutoff of 1000Da, and finally freeze-dried to obtain U-CQDs powder.

[0014] In this scheme, the U-CQDs are spherical particles with a diameter of 2-5nm, the main peak of ultraviolet absorption is located at 230nm, the fluorescence emission peak is located at 580nm, and the surface is rich in amino, hydroxyl and carboxyl functional groups.

[0015] In the scheme, the U-CQDs are used in cooperation with IAA to improve the Chlorella biomass accumulation amount, light energy utilization efficiency and CO2 fixation rate.

[0016] Another aspect of the present application provides a use of U-CQDs prepared according to the above method in cooperation with IAA in microalgae carbon fixation.

[0017] The present application solves the defects in the background art, and has the following beneficial effects:

[0018] The present application breaks through the limitation of single regulation, realizes the improvement of microalgae carbon fixation performance, and the use of plant hormones or carbon quantum dots alone in the prior art can only limitedly improve the microalgae carbon fixation efficiency. Through the synergistic effect of the two, the microalgae biomass accumulation amount, CO2 fixation rate and light energy utilization rate are significantly higher than the effect of single regulation means; the U-CQDs prepared by the present application realizes waste resourceization, compared with carbon quantum dots using graphene, blue fruit, etc. as raw materials, the U-CQDs prepared by the present application using Enteromorpha prolifera hydrothermal waste liquid as carbon source not only realizes the reduction of raw material cost, but also avoids the pollution of toxic solvents in traditional synthesis process. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The present application is a U-CQDs in cooperation with IAA under the regulation of the Chlorella biomass accumulation amount.

[0020] Figure 2 The present application is a U-CQDs in cooperation with IAA under the regulation of the Chlorella biomass accumulation amount.

[0021] Figure 3 The present application is a U-CQDs in cooperation with IAA under the regulation of the Chlorella biomass accumulation amount.

[0022] Figure 4 The present application is a U-CQDs in cooperation with IAA under the regulation of the Chlorella biomass accumulation amount. DETAILED DESCRIPTION

[0023] In order to more clearly understand the above purpose, features and advantages of the present application, the present application will be further described in detail below in combination with the drawings and specific embodiments. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0024] In the following description, a lot of specific details are set forth in order to facilitate a thorough understanding of the present application, however, the present application can also be implemented in other ways different from those described herein, therefore, the protection scope of the present application is not limited by the specific embodiments disclosed below.

[0025] The experimental methods in the following examples are all conventional methods unless otherwise specified; the instruments and equipment used in the following examples are all conventional laboratory instruments and equipment unless otherwise specified; the experimental materials used in the following examples are all purchased from conventional biochemical reagent stores unless otherwise specified. The chlorella used in the present application is Chlorella vulgaris FACHB-2723) purchased from the Freshwater Algae Culture Collection of Wuhan Institute of Hydrobiology, Chinese Academy of Sciences, and the plant hormone indole-3-acetic acid (IAA) is purchased from National Medicine Reagent Co., Ltd. and is of high purity.

[0026] Example 1

[0027] A method for enhancing microalgae carbon fixation by seaweed-based carbon quantum dots in cooperation with plant hormones, specifically comprising:

[0028] Preparation of algal liquid: Chlorella was expanded in BG11 medium and cultured in a constant temperature incubator at light intensity of 3000 lux and 25°C to logarithmic growth phase as algal seed liquid for subsequent experiments.

[0029] Microalgae culture: Chlorella was taken as a carbon fixation carrier and cultured in a vertical tube photobioreactor with BG-11 medium, 1 ppm of plant hormone indole-3-acetic acid (IAA) and 5 mg·L - of seaweed-based carbon quantum dots (U-CQDs) were added in the initial stage (2-3 days) of culture; the culture conditions were controlled as follows: temperature: 25-30°C, light intensity: 3000 Lux, light and dark cycle: 12 h light / 12 h dark; the gas supply was 5% CO2 mixed gas with a flow rate of 0.18 L·min - ; the culture was carried out until the chlorella entered the stable growth phase (the culture period was about 12-14 days). The optical density was measured daily, the growth trend of chlorella was judged by testing the dry weight, and the cell dry weight was measured at the end of the experiment.

[0030] Preparation of U-CQDs: 1 g of Enteromorpha prolifera powder was mixed with 10 mL of deionized water, placed in a 25 mL stainless steel high-pressure hydrothermal kettle, filled with nitrogen gas to 4 MPa pressure, and heated to 300°C under nitrogen atmosphere for 1 h. After the stainless steel high-pressure hydrothermal kettle was cooled, the water phase and oil phase products after hydrothermal reaction were collected by vacuum filtration, and the water phase product was separated by a separatory funnel. The water phase product was transferred to a 25 mL hydrothermal synthesis kettle, and reacted in a 180°C oven for 8 h. After the hydrothermal synthesis kettle was cooled to room temperature, the obtained product was filtered through a 0.22 μm microporous membrane to remove the aggregated larger particle mixture, and then dialyzed for 24-36 h using a dialysis bag with a molecular weight cutoff of 1000 Da, and finally freeze-dried to obtain U-CQDs powder.

[0031] Figure 1The blank control group and the addition of 1 ppm IAA and 5 mg·L - The U-CQDs of 1 of the chlorella biomass accumulation amount comparison chart. The experimental results show that under the condition of 1 ppm IAA of exogenous plant hormone, the addition of 5 mg·L - The U-CQDs of 1 promote the accumulation of chlorella biomass: the biomass of chlorella accumulates rapidly from the 6th to the 10th day, and the biomass of chlorella accumulates to 1.62 mg·L - The U-CQDs of 1. Figure 2 The blank control group and the addition of 1 ppm IAA of chlorella biomass accumulation amount comparison chart. The experimental results show that under the condition of only adding 1 ppm IAA, the final biomass accumulation of chlorella is improved by 5.92% compared with the blank control group (1.42 mg·L - The U-CQDs of 1. Figure 1 Comparing

[0032] Example 2

[0033] A method for enhancing microalgae carbon sequestration by seaweed-based carbon quantum dots and plant hormones, specifically:

[0034] Preparation of algal liquid: Chlorella was expanded in BG11 medium and cultured in a constant temperature incubator at light intensity 3000 lux and 25℃ to logarithmic growth phase as algal seed liquid for subsequent experiments.

[0035] Microalgae culture: Chlorella was taken as a carbon sequestration carrier and cultured in a vertical tube type photobioreactor with BG-11 medium. 5 ppm of plant hormone indole-3-acetic acid (IAA) and 5 mg·L - The U-CQDs of 1 were added in the initial stage (2-3 days) of culture. The culture conditions were controlled as follows: temperature: 25-30℃, light intensity 3000 Lux, light and dark cycle 12h light / 12h dark; gas supply: 15% CO2 mixed gas, flow rate 0.18 L·min - The U-CQDs of 1; culture to the stable growth phase of chlorella (culture period about 12-14 days). After the experiment, the chlorophyll and carotenoid content of chlorella, chlorella biomass energy, CO2 utilization rate and light energy utilization efficiency were measured.

[0036] Preparation of U-CQDs: Using Enteromorpha striata as the starting material, 1 g of Enteromorpha striata powder was mixed with 10 mL of deionized water. The mixture was placed in a 25 mL stainless steel autoclave, filled with nitrogen to a pressure of 4 MPa, and heated to 300°C under a nitrogen atmosphere for 1 hour. After the autoclave cooled, the aqueous and oily phases of the hydrothermal reaction were collected by vacuum filtration, and the aqueous phase was separated using a separatory funnel. The aqueous phase was transferred to a 25 mL hydrothermal synthesis reactor and reacted in an oven at 180°C for 8 hours. After the autoclave cooled to room temperature, the resulting product was filtered through a 0.22 μm microporous membrane to remove larger aggregated particles. After filtration, the product was dialyzed using a 1000 Da molecular weight cutoff dialysis bag for 24–36 hours. Finally, the product was freeze-dried using a freeze dryer to obtain U-CQD powder.

[0037] like Figure 3 As shown, when 5 ppm IAA was added, the U-CQDs dosage was 5 mg·L - Under the synergistic effect of IAA and U-CQDs, the total chlorophyll accumulation of Chlorella reached 17.51 ​​mg·L - Chlorophyll accumulation in Chlorella increased by 15.61% compared to the control group, while the addition of 5 ppm IAA reduced carotenoid accumulation. This suggests that U-CQDs and IAA synergistically enhance the efficiency of the antioxidant system, reduce reactive oxygen species (ROS), and mitigate the accumulation of carotenoids as stress-sensitive antioxidants in Chlorella.

[0038] like Figure 4 As shown, at 5 ppm IAA, the U-CQDs dosage was 5 mg·L - Under the conditions of ¹, the biomass energy of Chlorella vulgaris was significantly improved, increasing by 19.51% compared to the control group. Higher biomass energy can improve the production efficiency of biofuels and promote the development of high-value-added products. 5mg·L - The synergistic effect of U-CQDs and 5ppm IAA increased the CO2 utilization efficiency of Chlorella by approximately 17.84%, further strengthening the carbon sequestration capacity of Chlorella. Light energy utilization is an important indicator for evaluating the photosynthetic performance of Chlorella during growth. In the control group, the light energy utilization rate of Chlorella was 13.09%. When 5ppm IAA and 5mg·L were added, the light energy utilization rate of Chlorella was 13.09%. - When treated with U-CQDs, Chlorella achieved 15.65% light energy utilization, a 19.56% increase compared to the control group. This improved light energy utilization can shorten the microalgae cultivation cycle and reduce light energy consumption, making it feasible for large-scale microalgae biofuel production.

[0039] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions recorded in the above embodiments can be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for enhancing microalgae carbon fixation by using seaweed-based carbon quantum dots in collaboration with plant hormones, characterized in that: The following steps are involved: S1: Chlorella vulgaris was used as a carbon fixation carrier and cultured in a vertical tubular photobioreactor using BG-11 medium. The vertical tubular photobioreactor was a multi-tube design with a single tube working volume of 500 mL and a total capacity of 0.6 L × 12; S2: In the initial stage of culture, plant hormone indole-3-acetic acid (IAA) and algae-based carbon quantum dots (U-CQDs) were added. The culture conditions were: temperature 25-30°C, light intensity 3000 Lux, light-dark cycle 12 h light / 12 h dark, gas supply 15% Mixed gas, flow rate 0.18L·min -1 , culture until the biomass enters the growth stable phase; S3: Preparation of seaweed-based carbon quantum dots U-CQDs, specifically including: mixing Enteromorpha striata powder and deionized water in a ratio of 1:10, placing the mixture in a high-pressure hydrothermal autoclave under a nitrogen atmosphere for reaction, separating the aqueous phase product after cooling, and obtaining seaweed-based carbon quantum dots U-CQDs powder through hydrothermal synthesis, filtration, dialysis and freeze-drying.

2. The method of enhancing microalgae carbon fixation by using seaweed-based carbon quantum dots in collaboration with plant hormones according to claim 1, characterized in that: The concentration of the plant hormone indole-3-acetic acid (IAA) in the culture medium in step S2 is 1-5 mg·L -1 The concentration of seaweed-based carbon quantum dots U-CQDs is 1-10 mg·L -1 .

3. The method of enhancing microalgae carbon fixation by using seaweed-based carbon quantum dots in collaboration with plant hormones according to claim 1, characterized in that: The chlorella is Chlorella vulgaris FACHB-2723.

4. The method of enhancing microalgae carbon fixation by using seaweed-based carbon quantum dots in collaboration with plant hormones according to claim 1, characterized in that: The preparation process of seaweed-based carbon quantum dots U-CQDs in step S3 is as follows: Enteromorpha fasciata powder and deionized water are mixed in a weight-to-volume ratio of 1:10, placed in a stainless steel high-pressure hydrothermal autoclave, filled with nitrogen, and subjected to hydrothermal reaction in a nitrogen atmosphere at a nitrogen pressure of 4 MPa and a reaction temperature of 300°C for 1 h; After the stainless steel high-pressure hydrothermal autoclave was cooled, the aqueous phase and oil phase products after the hydrothermal reaction were collected by vacuum filtration, and then the aqueous phase product was separated by a separatory funnel, and the aqueous phase product was transferred to a hydrothermal synthesis autoclave and reacted in an oven at 180°C for 8 hours; after the hydrothermal synthesis autoclave was cooled to room temperature, the obtained product was filtered through a 0.22 μm microporous membrane, and after filtration, it was dialyzed with a dialysis bag with a molecular weight cutoff of 1000 Da for 24 to 36 hours, and finally freeze-dried using a freeze dryer to obtain seaweed-based carbon quantum dots U-CQDs powder.

5. The method of enhancing microalgae carbon fixation by using seaweed-based carbon quantum dots in collaboration with plant hormones according to claim 1, characterized in that: The seaweed-based carbon quantum dots U-CQDs are spherical particles with a diameter of 2-5 nm, a main ultraviolet absorption peak at 230 nm, a fluorescence emission peak at 580 nm, and a surface rich in amino, hydroxyl and carboxyl functional groups.

6. The method of enhancing microalgae carbon fixation by using seaweed-based carbon quantum dots in collaboration with plant hormones according to claim 1, characterized in that: The seaweed-based carbon quantum dots U-CQDs and the plant hormone indole-3-acetic acid IAA are used to enhance the biomass accumulation of Chlorella vulgaris, the light energy utilization efficiency, Fixed rate.

7. An application of seaweed-based carbon quantum dots (U-CQDs) prepared according to the method according to any one of claims 1 to 6 in synergistically combining the plant hormone indole-3-acetic acid (IAA) in carbon fixation in microalgae.

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