A carbon fixation scenedesmus, a culture method, a carbon fixation method and a carbon fixation device

Abstract

The application provides a carbon-fixing Scenedesmus and a culture method, a carbon-fixing method and a carbon-fixing device, and belongs to the technical field of biological carbon fixation.The application provides Scenedesmus XS1, and the preservation number is CGMCC NO.46955.The Scenedesmus XS1 has excellent adaptability and tolerance to 15% CO2, can break through the limitation that part of Scenedesmus is inhibited under high CO2 concentration, and widens the industrial application scene; and the carbon-fixing rate of the Scenedesmus XS1 is significantly higher than that of ordinary freshwater algae species. Therefore, by means of chemical and microbial coupling, a biological reactor for fixing CO2 in flue gas can be constructed and assembled into a carbon-fixing device, CO2 in the flue gas can be converted into chemicals and biomass, and the biomass accumulation amount and CO2 fixation efficiency of the Scenedesmus are improved.

Description

Technical Field

[0001] This invention belongs to the field of biological carbon fixation technology, specifically relating to a carbon-fixing algae, its cultivation method, carbon fixation method, and carbon fixation device. Background Technology

[0002] With the increasing severity of global climate change, the reduction and resource utilization of CO2 emissions from industrial waste gases have become pressing environmental and energy challenges. Biological carbon sequestration technology, due to its environmental friendliness and high sustainability, is considered one of the most promising pathways for CO2 emission reduction. Freshwater microalgae, as highly efficient carbon-sequestering organisms, possess advantages such as short growth cycles and rapid biomass accumulation, resulting in high-value-added products. Among them, *Scenedesmus* genus, due to its wide distribution and strong adaptability, has become a key algal species in carbon sequestration research.

[0003] However, existing technologies for carbon fixation and oil production by *Scenedesmus* still face several technical bottlenecks: First, the algal species have limited adaptability to CO2 concentrations, with most existing *Scenedesmus* species only able to grow in low-concentration CO2 environments, making it difficult to adapt to the actual working conditions of industrial waste gas (usually containing 5%-20% CO2); second, the optimization of cultivation conditions lacks specificity, especially the control of the nitrogen-phosphorus ratio has not received sufficient attention, resulting in a difficulty in simultaneously achieving biomass accumulation and oil synthesis efficiency, thus restricting the synergistic improvement of carbon fixation and oil production performance; third, the process design is imperfect, and a systematic multi-index monitoring and control system under high-concentration CO2 has not been established, leading to poor process stability and difficulties in large-scale application. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a carbon-fixing algae, a cultivation method, a carbon fixation method, and a carbon fixation device. The algae exhibits good tolerance and adaptability to 15% high concentration CO2, and the carbon fixation efficiency is significantly improved.

[0005] This invention provides a carbon-fixing algae (Scenedesmus) Scenedesmus obliquus XS1, the Scenedesmus XS1 has been biologically preserved, with the preservation number CGMCC NO.46955.

[0006] The present invention also provides a method for culturing the above-mentioned Scenedesmus XS1, comprising the following steps: inoculating the Scenedesmus XS1 onto a culture medium for culturing, wherein the mass ratio of N to P in the culture medium is 16~64:1.

[0007] In one specific embodiment of the present invention, the basic culture medium of the culture medium includes BG-11 culture medium, and the pH value of the culture medium is maintained at 7.5~8.5.

[0008] In one specific embodiment of the present invention, the mass ratio of N to P in the culture medium is 32~64:1.

[0009] In one specific embodiment of the present invention, the inoculum amount of Scenedesmus XS1 is 5-25%.

[0010] The present invention also provides the application of the above-mentioned Scenedesmus XS1 or the Scenedesmus XS1 cultured using the above-mentioned culture method in the fixation of CO2 in flue gas.

[0011] In one specific embodiment of the present invention, the volume concentration of CO2 in the flue gas CO2 does not exceed 30%.

[0012] The present invention also provides a bioreactor for fixing CO2 in flue gas, comprising the above-mentioned Scenedesmus XS1 or Scenedesmus XS1 cultured using the above-mentioned culture method.

[0013] In one specific embodiment of the present invention, light is supplied to the bioreactor at an intensity of 12,000 to 15,000 Lux, and the light-dark time is 12h / 12h.

[0014] The present invention also provides a carbon fixation device comprising the bioreactor.

[0015] Beneficial effects: This invention isolates and purifies a dominant Scenedesmups strain from a freshwater environment. The strain is identified as a genus Scenedesmups by 18S rRNA sequence and has a 99.59% similarity to FJ608099.1Scenedesmupssp. in the NCBI database. Therefore, it is named ScenedesmupsXS1.

[0016] Since the CO2 concentration for industrial waste gas emission reduction is generally around 15%, this invention studied the performance of *Scenedesmus xS1* at a 15% CO2 concentration. *Scenedesmus xS1* exhibited excellent adaptability and tolerance, overcoming the limitations of some *Scenedesmus* species whose growth is inhibited at high CO2 concentrations, thus broadening its industrial application scenarios. Furthermore, the carbon fixation rate of *Scenedesmus xS1* was significantly higher than that of common freshwater algae. Therefore, a bioreactor for fixing CO2 in flue gas can be constructed and assembled into a carbon fixation device using a chemical-microbial coupling method. This can convert CO2 in flue gas into chemicals and biomass, increasing the biomass accumulation and CO2 fixation efficiency of *Scenedesmus xS1*.

[0017] Biological Preservation Information Scenedesmus ( Scenedesmus obliquus XS1 was deposited on January 29, 2026, at the China General Microbiological Culture Collection Center (CGMCC), located at No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences, with accession number CGMCC NO.46955. Attached Figure Description

[0018] Figure 1This is a comparison of the effects of using antibiotic culture medium before and after treatment. In the figure, a: the effect of culture without antibiotics; b: the effect of culture with antibiotics. Figure 2 The images show a comparison of the effects of microalgae purification before and after purification under a 40x microscope. In the images, a: the state of the algal solution under a 40x microscope before purification; b: the state of the algal solution under a 40x microscope after purification. Figure 3 An evolutionary clade tree based on 18S rRNA; Figure 4 The graph shows the trend of algal solution concentration changes under different initial nitrogen-phosphorus ratios. Figure 5 Statistical graph of algal effusion accumulation (21 days) under different initial nitrogen-phosphorus ratios; Figure 6 For R z Response surface plot and contour plot of F(A, B); Figure 7 For R z Response surface plot and contour plot of F(A,C); Figure 8 For R z Response surface plot and contour plot of F(B, C); Figure 9 The graph shows the changes in algal solution concentration under different gas components (15 days). Figure 10 A statistical chart showing the accumulation of algal solution under different gas compositions; Figure 11 This shows the trend of CO2 concentration changes; Figure 12 A graph showing the pH changes of the algal solution inside the reactor; Figure 13 The concentration changes of algal solution in the photobioreactor (57 days); Figure 14 The concentrations of each component in the reactor change over time after nitrogen and phosphorus are replenished; Figure 15 This is a graph showing the daily changes in algal solution concentration and CO2 fixation. Detailed Implementation

[0019] This invention provides a carbon-fixing algae (Scenedesmus) Scenedesmus obliquus XS1, the Scenedesmus XS1 has been biologically preserved, with the preservation number CGMCC NO.46955.

[0020] The *Scenedesmus* XS1 described in this invention is a dominant *Scenedesmus* species isolated and purified from a freshwater environment. It was identified as belonging to the genus *Scenedesmus* by its 18S rRNA sequence and corresponds to FJ608099.1 in the NCBI database. Scenedesmups spThe similarity reaches 99.59%. The Scenedesmus XS1 described in this invention has adaptability and tolerance to high concentrations of CO2, and can convert high concentrations of CO2 in extended periods into chemicals and biomass, exhibiting a significant carbon fixation effect.

[0021] The present invention also provides a method for culturing the above-mentioned Scenedesmus XS1, comprising the following steps: inoculating the Scenedesmus XS1 onto a culture medium for culturing, wherein the mass ratio of N to P in the culture medium is 16~64:1.

[0022] The basal culture medium of the culture medium described in this invention includes BG-11 medium, and the nitrogen-to-phosphorus ratio (N / P) is adjusted by regulating the ratio of NaNO3 to K2HPO4. The N / P ratio is 16~64:1, such as 16:1, 17:1, 18:1, 19:1, 20:1, 21:1, 22:1, 23:1, 24:1, 25:1, 26:1, 27:1, 28:1, 29:1, 30:1, 31:1, 32:1, 33:1, 34:1, 35:1, 36:1, 37:1, 38:1, etc. 1. 39:1, 40:1, 41:1, 42:1, 43:1, 44:1, 45:1, 46:1, 47:1, 48:1, 49:1, 50:1, 51:1, 52:1, 53:1, 54:1, 55:1, 56:1, 57:1, 58:1, 59:1, 60:1, 61:1, 62:1, 63:1, or 64:1, and any ratio between two values ​​in decimal or fractional form; and examples have shown that the carbon fixation effect is best when N / P is 42.4:1.

[0023] Each L of the BG-11 culture medium of this invention contains 999 ml of component A and 1 ml of component B. Component A consists of: 1.5 g / L sodium nitrate, 0.04 g / L dipotassium hydrogen phosphate, 0.075 g / L magnesium sulfate heptahydrate, 0.036 g / L calcium chloride dihydrate, 0.02 g / L sodium carbonate, and 0.006 g / L sodium citrate. Component B consists of: 2.86 g / L boric acid, 1.81 g / L manganese chloride tetrahydrate, 0.222 g / L zinc sulfate, 0.39 g / L sodium molybdate, and 0.079 g / L copper sulfate pentahydrate.

[0024] In this invention, the Scenedesmus XS1 is inoculated onto the culture medium at an inoculation amount of 5-25%, such as 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, or 25%, as well as any percentage between two values ​​in decimal or fractional form. Examples have shown that the carbon fixation effect is best when the initial inoculation amount is 9.65%.

[0025] During the cultivation process, this invention requires the supplementation of nitrogen and phosphorus (N and P) to maintain the N / P ratio. Nitrogen and phosphorus are key factors limiting long-term operation. This invention necessitates dynamic monitoring and real-time supplementation of nitrogen and phosphorus, for example, supplementation is performed on the 20th day of cultivation in the embodiment, which is a necessary measure to maintain stable system operation. This invention also requires maintaining a stable pH value in the culture medium during the cultivation process, ideally between 7.5 and 8.5, such as 7.5, 7.6, 7.7, 7.8, 7.9, 8.0, 8.1, 8.2, 8.3, 8.4, or 8.5, as well as any pH value between two values ​​expressed as a decimal or fractional. For example, in the embodiment, maintaining a pH value of 8.0 is recommended. This invention adjusts the pH by adding NaHCO3 or KHCO3 to the culture system.

[0026] The cultivation temperature described in this invention is 25~27℃, such as 25℃, 26℃ or 27℃, and any temperature value between two values ​​in decimal or fractional form; and the cultivation requires light, with a light intensity of 12000~15000 Lux and a light-dark time of 12h / 12h.

[0027] The present invention also provides the application of the above-mentioned Scenedesmus XS1 or the Scenedesmus XS1 cultured using the above-mentioned culture method in the fixation of CO2 in flue gas.

[0028] In the embodiments of the present invention, it was found that the nitrogen-to-phosphorus ratio has a significant effect on the accumulation of Scenedesmus biomass. Under the cultivation conditions, CO2 in the flue gas can be fixed, and the volume concentration of CO2 in the flue gas is required to be no more than 30%.

[0029] The present invention also provides a bioreactor for fixing CO2 in flue gas, comprising the above-mentioned Scenedesmus XS1 or Scenedesmus XS1 cultured using the above-mentioned culture method.

[0030] This invention does not impose any special limitations on the structure and construction of the bioreactor. For example, the construction of the bioreactor in the embodiment is shown in Chinese Patent CN223249094U. This invention supplies light to the bioreactor at an intensity of 12000~15000 Lux, with light-dark periods of 12h / 12h. The bioreactor of this invention contains a flue gas inlet. In the embodiment, during the 15% CO2 flue gas simulation experiment, the total flow rate was set to 2L / min, including 0.3L / min of CO2 and 1.7L / min of air.

[0031] The present invention also provides a carbon fixation device comprising the above-described bioreactor.

[0032] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, provides a carbon-fixing algae and its cultivation method, carbon fixation method, and carbon fixation device provided by the present invention, but these descriptions should not be construed as limiting the scope of protection of the present invention.

[0033] Example 1: Isolation, purification and identification of dominant freshwater algal species (1) Sample source and pretreatment: Surface water samples were collected from a lake at Tianjin University of Technology, 1 meter from the south bank. The samples were mixed at a 1:3 ratio (water sample: BG-11 medium) and placed in sterile Erlenmeyer flasks. The mixture was then incubated for 3 weeks in an intelligent light incubator (27℃, 12h:12h light-dark cycle, 12000 Lux light intensity), with shaking 1-2 times daily, to obtain a yellow-green microalgae enrichment solution. After osmosis, the water was yellow-green with sediment at the bottom.

[0034] (2) Separation and purification process: 1. Plate preparation: Add 1.5% agar powder to BG-11 medium, sterilize it, and pour it into sterile plates to make solid culture medium.

[0035] 2. Gradient dilution coating: Take the enriched solution and perform 10... -1 Up to 10 -7 Serial dilutions were performed, with 0.5 mL of each dilution spread onto plates, and incubated for 14 days (under the same conditions as enrichment culture). Results showed that 10 -7 The diluted algae on the plate are clearly separated, making them easy to pick up.

[0036] 3. Streak purification: Select a single algal colony (large in size, dark in color, and with obvious protrusions) and streak it on a BG-11 plate for 2 weeks.

[0037] 4. Antibacterial culture: Add 100 mg / L gentamicin sulfate to the culture medium and repeat the streak step to inhibit bacterial growth; at the same time, set up a control group without gentamicin sulfate and perform the same experiment.

[0038] The results are as follows Figure 1 As shown, the algal colonies on the untreated plate were contaminated with other bacteria (REF _Ref28784 \h \). MERGEFORMAT Figure 1 (a) After adding gentamicin, the algal colony has high purity and is free of contaminants. Figure 1 (b). Furthermore, under 40x magnification, the purified algal solution showed a significant reduction in contaminating algae and bacteria. Figure 2 ).

[0039] 5. Expanded culture: The purified algal colonies were inoculated into 96-well plates (0.5 mL of BG-11 medium per well) and cultured for 10 days before being transferred to Erlenmeyer flasks for expanded culture.

[0040] (3) Algal species identification: Take high-density algal solution (OD) 680Total DNA was extracted using the Ezup column-based bacterial genomic DNA extraction kit (=0.6), and 18S rRNA PCR amplification was performed. The PCR products were sequenced, and the obtained sequences were compared with the NCBI database using BLAST to construct a phylogenetic tree.

[0041] PCR reaction system (25 μL): 12.5 μL MgSO4 (50 mM), 1 μL each of forward and reverse primers (10 μM), 1 μL DNA template and 9.5 μL ddH2O; The primer sequences are designed as follows: TAReuk454FWD1 (SEQ ID No. 1): CCAGCASCYGCGGTAATTCC; 2.TAReukREV3 (SEQ ID No. 2): ACTTTCGTTCTTGATYRA.

[0042] The 18S rRNA sequence showed 99.59% similarity to Scenedesmus sp. (FJ608099.1) in NCBI. Phylogenetic analysis results are as follows: Figure 3 As shown, the algal species was confirmed to be of the genus *Scenedesmus* and named *Scenedesmus XS1*.

[0043] Example 2: Optimization Experiment of Nitrogen-Phosphorus Ratio in Scenedesmus Culture Medium (1) Culture medium preparation BG-11 was used as the basal culture medium, with a fixed initial inoculum size of 15% (OD of the algal stock solution). 680 =0.6), pH=7, by adjusting the ratio of NaNO3 (fixed concentration 0.5 g / L) to K2HPO4, five nitrogen-to-phosphorus (N / P) gradients were set: N-1: N / P=4:1(K2HPO40.768g / L); N-2: N / P=8:1(K2HPO40.384g / L); N-3: N / P=16:1(K2HPO40.192g / L); N-4: N / P=32:1(K2HPO40.096g / L); N-5: N / P=64:1(K2HPO40.048g / L).

[0044] (2) Cultivation and Detection Each group had three replicates, which were cultured for 21 days in a light incubator (27℃, light-dark ratio 12h:12h, 12000 Lux). OD was measured daily. 680 Establish algal solution concentration (y, g / L) and OD 680 The linear equation for the value (x) is: y = 0.198x + 0.0016, R0 2 =0.9914, and use this as the standard curve to calculate the algal solution concentration; the increase in algal solution concentration is used to represent the biomass accumulation, and the biomass accumulation is calculated after the culture is completed.

[0045] Growth trend as Figure 4 As shown, the growth curves of each N / P group are similar, while the initial concentration of the N-4 group (32:1) is slightly higher, which may be related to the pH adjustment process.

[0046] On day 21, the biomass accumulation statistics are as follows: Figure 5 As shown, the accumulation amount in group N-1 was relatively low, group N-2 increased slightly, group N-3 increased further, group N-4 had the highest accumulation amount (approximately 0.089 g / L), while the accumulation amount in group N-5 decreased.

[0047] In summary, the nitrogen-to-phosphorus ratio (N / P) has a significant non-linear effect on the biomass accumulation of *Scenedesmus*. The highest biomass accumulation is observed when the N / P ratio is 32:1, indicating that this ratio is most favorable for *Scenedesmus* growth and carbon assimilation. Both excessively high and low N / P ratios inhibit algal growth; therefore, it is recommended to use N / P = 32:1 as the baseline parameter in subsequent processes.

[0048] Example 3: BBD Optimization Experiment The Box-Behnken design method in Design-Expert 13 software was used, with the initial nitrogen-to-phosphorus ratio (A), pH value (B), and initial inoculum size (C) selected as independent variables, and the biomass accumulation Rz of Scenedesmus as the response value for Box-Behnken response surface methodology analysis. Three levels of high (+1), medium (0), and low (-1) were selected for the above three factors to design Box-Behnken response surface experiments.

[0049] The influencing factors and level settings of the Box-Behnken response surface methodology are shown in Table 1.

[0050] Table 1. Factors influencing the Box-Behnken Design experiment and level settings.

[0051] A total of 17 experimental groups were generated. The OD (dose distribution) of the algal solution was dynamically monitored using ultraviolet spectrophotometry. 680 The value represents biomass accumulation. Each treatment group was replicated three times. All test data were standardized and the arithmetic mean was used for importing into the analysis system. The Box-Behnken response surface methodology and response value results are shown in Table 2.

[0052] Table 2 Box-Behnken Design Test Scheme and Response Value Results

[0053] The response results in the table were subjected to multiple regression analysis, and the regression model established is as follows: R Z =0.0896+0.0007A-0.0038B-0.0004C-0.0034AB-0.006AC-0.0004BC-0.0065A 2 -0.0122B 2 -0.0024C 2 In the formula, A represents the initial nitrogen-to-phosphorus ratio of the culture system; B represents the pH value of the culture system; and C represents the initial inoculum size of *Scenedesmus* in the culture medium. The results of the model variance analysis are shown in Table 3. The regression model... PA value < 0.0001 indicates that the model is highly significant and statistically significant. The results of the model's lack-of-fit test show that... P The value is 0.2821 ( P A value greater than 0.05 indicates that the lack-of-fit term in the model is not significant, suggesting that factors not considered outside the model have a relatively small impact on the experimental results. From the coefficients of the model... P The values ​​show that, under the interaction of various factors, the regression model contains pH (B), initial nitrogen-phosphorus ratio, and pH (AB), as well as the squares (A, B, C, and D) of the three influencing factors: initial nitrogen-phosphorus ratio, pH, and initial inoculum size. 2 B 2 C 2 The effect on the biomass accumulation of Scenedesmus was extremely significant. P The influence of <0.01) indicates that these three factors are related to the biomass accumulation R of Scenedesmus. z The distribution of these factors along the regression curve was significant. The initial inoculum size (C) of the culture system had no significant impact on the biomass accumulation of *Scenedesmus* compared to the other two groups. The F-values ​​of each coefficient in the regression model indicate the strength of the influence of factors on the biomass accumulation of *Scenedesmus*; the larger the F-value, the stronger the influence. Therefore, the order of influence of each factor on the biomass accumulation of *Scenedesmus* is: pH (B) > initial nitrogen-to-phosphorus ratio (A) > initial inoculum size (C). Regarding pairwise interactions, the square of each influencing factor had a significant impact on the biomass accumulation of *Scenedesmus*.

[0054] Table 3. Analysis of Variance of the Model

[0055] The fitting statistics of the Box-Behnken response surface regression model are shown in Table 4. The coefficient of determination (R²) of the regression model is shown in Table 4. 2 The coefficient of determination (R²) for the regression model is 0.9975, close to 1, indicating that the model has high accuracy and can accurately reflect the influence of various factors on the biomass accumulation of Scenedesmus. The adjusted R² for the regression model is 0.9944, indicating that the model can explain 99.44% of the biomass accumulation of Scenedesmus. The model signal-to-noise ratio (Adeq Precision) is 53.9488 > 4, indicating that the model has high precision, strong response signal, and can provide a reasonable prediction of the biomass accumulation of Scenedesmus.

[0056] Table 4 Statistical Results of Model Fit

[0057] In summary, the Box-Behnken response surface model exhibits good fit and can be used as a predictive model for the biomass accumulation of *Scenedesmus* under different culture conditions. Based on the Box-Behnken Design, the biomass accumulation of *Scenedesmus* was measured and calculated, and the growth differences of *Scenedesmus* under different initial nitrogen-to-phosphorus ratios, pH values, and initial inoculum sizes were compared. Using Design Expert 13.0 software, the relationship between the interaction of the three experimental influencing factors and the response values ​​was further obtained, thus yielding the response surface and contour plots of the pairwise interactions of initial nitrogen-to-phosphorus ratio (A), pH value (B), and initial inoculum size (C) on the biomass accumulation of *Scenedesmus*.

[0058] The results are as follows Figure 6 , Figure 7 and Figure 8 As shown, the effects of four factors on the biomass accumulation of *Scenedesmus* in pairwise interactions are illustrated. Among them, the interaction between the initial nitrogen-to-phosphorus ratio (A) and pH (B) has the greatest impact on the biomass accumulation of *Scenedesmus*, consistent with the model results. When the initial nitrogen-to-phosphorus ratio (A) is low, the measured biomass accumulation Rz of *Scenedesmus* first increases and then decreases with the increase of the pH (B) of the culture system. When the initial nitrogen-to-phosphorus ratio (A) is high, the measured biomass accumulation Rz of *Scenedesmus* first increases and then decreases. This response surface has a high slope and a steep gradient, and the contour lines are elliptical, indicating that the interaction between the initial nitrogen-to-phosphorus ratio (A) and pH (B) has a significant impact on the biomass accumulation of *Scenedesmus*. The optimal conditions for Scenedesmus biomass accumulation were determined through regression equations: an initial nitrogen-to-phosphorus ratio of 42.358:1 (presumably 42.4:1), a pH of 7.983 (presumably 8), and an initial inoculum size of 9.648% (presumably 9.65%). Under these conditions, the predicted biomass accumulation was 92.37 mg / L. Based on these optimal conditions, experimental verification was performed, and the biomass accumulation of Scenedesmus was found to be 89.963 mg / L.

[0059] Example 4: Carbon fixation process for cultivating Scenedesmus using 15% CO2 simulated flue gas (1) Construction of the culture system A 5L photobioreactor (PBR) was used, equipped with an LED light source, a constant-temperature circulating water jacket (27°C), and an aeration system. The culture medium was configured according to the response surface methodology parameters of Example 3: N / P = 42.4:1, pH = 8, and inoculum size of 9.65%.

[0060] (2) Gas Condition Design 1. Experimental group: Simulated flue gas with 15% CO2 was introduced (total flow rate 2L / min, of which CO2 0.3L / min and air 1.7L / min).

[0061] 2. Control group: Pure air was introduced (2L / min).

[0062] (3) Operation and Monitoring The culture was carried out continuously for 57 days, with the following procedures performed daily: 1. pH adjustment: Maintain pH by pumping KHCO3 solution in at a rate of 0.2 mL / min.

[0063] 2. Sampling and testing: Daily sampling of algal solution to measure OD. 680 According to the standard curve (y=0.198x+0.0016, R), 2 =0.9914) Calculate the algal solution concentration; centrifuge and take the supernatant to determine total nitrogen and total phosphorus.

[0064] 3. Gas analysis: Collect gas from the inlet and outlet, measure CO2 concentration using gas chromatography (GC-2014C), and calculate daily carbon sequestration.

[0065] , where m CO2 Let Q be the daily fixed CO2 mass (g) and Q be the CO2 gas flow rate (m³). 3 / h), t is the ventilation time (h), ρ is the CO2 density (g / L); C in CO2 concentration (ppm) at the bioreactor inlet; C out The CO2 concentration (ppm) at the outlet of the bioreactor.

[0066] (4) Nitrogen and phosphorus supplementation strategies On day 40, a severe deficiency of nitrogen and phosphorus was detected (total nitrogen decreased by 75%, and total phosphorus decreased by 89.8%). NaNO3 and K2HPO4 were supplemented to the initial concentration.

[0067] Results of algal growth and carbon fixation efficiency are as follows Figure 9 and Figure 10 As shown, the algal concentration in the experimental group (15% CO2) continuously increased, reaching a maximum of 0.11842 g / L; the control group showed slow growth. The maximum daily carbon fixation of the experimental group reached 1520 mg / L / d, significantly higher than that of the pure air group.

[0068] The CO2 fixation rate results are as follows: Figure 11 As shown, the CO2 concentration at the system outlet dropped to a minimum of 6.1%, and the carbon sequestration rate reached 59.33%.

[0069] pH stability results are as follows Figure 12 As shown, the pH was stabilized between 8.1 and 8.15 by adjusting with KHCO3.

[0070] After day 20, the growth rate of the algal solution slowed down, and began to decline on day 30, corresponding to a continuous decrease in total nitrogen and total phosphorus. After nitrogen and phosphorus were replenished on day 40, the algal solution resumed growth, but at a lower rate than in the previous period. Figure 13 and Figure 14 ).

[0071] The analysis of daily variations yielded the following results: Figure 15 As shown, the daily concentration of algal solution was positively correlated with the daily CO2 fixation in the first 20 days; from day 20 to day 40, the concentration of algal solution decreased, but the CO2 fixation remained at a high level, indicating that the Scenedesmus still maintained carbon assimilation metabolism.

[0072] In summary, the Scenedesmus carbon fixation process using 15% CO2 simulated flue gas as the carbon source and KHCO3 as the pH adjuster is feasible. This carbon fixation system can achieve continuous and efficient carbon fixation (up to 1520 mg / L / d) under optimized culture conditions. Nitrogen and phosphorus are the key factors limiting long-term operation. Dynamic monitoring and real-time replenishment of nitrogen and phosphorus (recommended on day 20) are necessary measures to maintain stable system operation. This process has a high CO2 fixation rate and biomass output, demonstrating potential for industrial application.

[0073] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A carbon-fixing algae (Scenedesmus) Scenedesmus obliquus XS1, characterized in that, The Scenedesmus XS1 has been biologically preserved, with the accession number CGMCC NO.46955.

2. The method for cultivating Scenedesmus XS1 according to claim 1, characterized in that, The process includes the following steps: inoculating the Scenedesmus XS1 onto a culture medium for cultivation, wherein the mass ratio of N to P in the culture medium is 16~64:

1.

3. The cultivation method according to claim 2, characterized in that, The basal medium of the culture medium includes BG-11 medium, and the pH value of the culture medium is maintained at 7.5~8.

5.

4. The cultivation method according to claim 2 or 3, characterized in that, The mass ratio of N to P in the culture medium is 32-64:

1.

5. The cultivation method according to claim 2 or 3, characterized in that, The inoculum size of the Scenedesmus XS1 is 5-25%.

6. The application of the Scenedesmus XS1 of claim 1 or the Scenedesmus XS1 cultured using any one of the culture methods of claims 2 to 5 in the fixation of CO2 in flue gas.

7. The application according to claim 6, characterized in that, The volume concentration of CO2 in the flue gas does not exceed 30%.

8. A bioreactor for fixing CO2 in flue gas, characterized in that, Includes the Scenedesmus XS1 as described in claim 1 or the Scenedesmus XS1 cultured using any one of the culture methods described in claims 2 to 5.

9. The bioreactor according to claim 8, characterized in that, Light is supplied to the bioreactor at an intensity of 12,000 to 15,000 Lux, with light and dark periods of 12 hours and 12 hours, respectively.

10. A carbon fixation apparatus comprising the bioreactor of claim 8 or 9.

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