Bubble Column Photobioreactor Research Articles

Combined Production of Astaxanthin and β-Carotene in a New Strain of the Microalga Bracteacoccus aggregatus BM5/15 (IPPAS C-2045) Cultivated in Photobioreactor.

Simple SummaryMicroalgae are the richest source of natural carotenoids, valuable pigments, which are key components of functional food, cosmetics, drugs and animal feeding. To date, only two genera of green microalgae are widely used for mass production of carotenoids on an industrial scale, Haematococcus and Dunaliella. They produce astaxanthin and β-carotene, respectively, which are among the most useful carotenoids. In doing so one alga produces only one type of a pigment. In this paper we characterize a new strain of the green microalga Bracteacoccus aggregatus BM5/15 (IPPAS C-2045). It can simultaneously produce both carotenoids (up to 13.1 and 47.9% β-carotene and astaxanthin of cell dry mass, respectively). Growth parameters of the strain cultivated in glass bubble-column photobioreactors for commercial cultivation of microalgae were obtained. We also provide data of microscopic observations, pigment and fatty acid profile of the microalga, which are important biotechnological characteristics. Collectively, new data makes B. aggregatus BM5/15 suitable for industrial production of β-carotene, a pro-vitamin A, and astaxanthin, the most powerful antioxidant.Carotenoids astaxanthin and β-carotene are widely used natural antioxidants. They are key components of functional food, cosmetics, drugs and animal feeding. They hold leader positions on the world carotenoid market. In current work, we characterize the new strain of the green microalga Bracteacoccus aggregatus BM5/15 and propose the method of its culturing in a bubble-column photobioreactor for simultaneous production of astaxanthin and β-carotene. Culture was monitored by light microscopy and pigment kinetics. Fatty acid profile was evaluated by tandem gas-chromatography–mass spectrometry. Pigments were obtained by the classical two-stage scheme of autotrophic cultivation. At the first, vegetative, stage biomass accumulation occurred. Maximum specific growth rate and culture productivity at this stage were 100–200 mg∙L−1∙day−1, and 0.33 day−1, respectively. At the second, inductive, stage carotenoid synthesis was promoted. Maximal carotenoid fraction in the biomass was 2.2–2.4%. Based on chromatography data, astaxanthin and β-carotene constituted 48 and 13% of total carotenoid mass, respectively. Possible pathways of astaxanthin synthesis are proposed based on carotenoid composition. Collectively, a new strain B. aggregatus BM5/15 is a potential biotechnological source of two natural antioxidants, astaxanthin and β-carotene. The results give the rise for further works on optimization of B. aggregatus cultivation on an industrial scale.

Irradiance Optimation for Growing Spirulina fusiformis: Biomass, Phycocyanin, and Protein Production

The optimization of cyanobacterium microalgae cultivation technology to provide the need for food or feedstocks has recently attracted many investigators. An optimum operation on microalgae cultivation is important to reduce the excessive workload on the aquatic environment. Therefore, this study describes how the varied irradiance (2000 lux, 4000 lux, 6000 lux, 8000 lux, and 10,000 lux) treatments on a bubble column photobioreactor system affected biomass production, phycocyanin, and protein from cyanobacterium Spirulina fusiformis. The objective of this study was to obtain the optimum irradiance for producing maximum biomass, phycocyanin, and protein simultaneously. The results demonstrated some findings those were: 1) irradiance 10,000 lux made doubling time of growth earliest (only 24 hours) while 2,000 lux doubled within five days later; 2) light response curve showed that the increase of biomass concentration was linear with the increasing of irradiance; 3) a predictive model (Response Surface Method) proof that the most optimum quantity of the biomass (0.58 ±0.035 gL-1 dry weight), chlorophyll-a (0.090 ±0.023 % dry weight), and phycocyanin (2.44 ±0.00 gL-1 dry weight) were obtained on 10,000 lux, while protein contents of 79.18±5.47 % dry weight attained on the irradiance of 6000 lux. The maximum productivity of the biomass, chlorophyll-a, phycocyanin, and protein was ~Pbiomass of 24.95 mgL-1day-1; Pchl-a of 2.25E-02 mgL-1day-1; Pphycocyanin of 1.88E-02 mgL-1day-1; and Pprotein of 17.56 mgL-1day-1. Enhancement of irradiance up to 5 folds lead to the increasing of biomass chlorophyll-a, phycocyanin, and protein productivity, attained to 1.7, 5.01, 4.13, and 2.81 folds, respectively. The irradiance had a significant influence on the production of the metabolites; therefore, the irradiance must be optimized.

A comparative evaluation of design factors on bubble column operation in photosynthetic biogas upgrading

Studies attempting to optimise photosynthetic biogas upgrading by simultaneous investigation of the bubble column-photobioreactor setup have experienced considerable variability in results and conclusions. To identify the sources of such variation, this work quantitatively compared seven design factors (superficial gas velocity; liquid to gas flow rate (L/G) ratio; empty bed residence time; liquid inlet pH; liquid inlet alkalinity; temperature; and algal concentration) using the L16 Taguchi orthogonal array as a screening design of experiment. Assessments were performed using the signal to noise (S/N) ratio on the performance of CO2 removal (CO­2 removal efficiency, CO2 absorption rate, and overall CO2 mass transfer coefficient) and O2 stripping (O2 concentration in biomethane and O2 flow rate in biomethane). Results showed that pH and L/G ratio were the most critical design factors. Temperature and gas residence times had minimal impact on the biomethane composition. The interactive effect between pH and L/G ratio was the most impactful, followed by the interactive effects between superficial gas velocity and L/G ratio and pH on CO2 removal efficiency. The impact of L/G ratio, algal concentration, and pH (in that order of impact) caused up to a 90% variation in oxygen content in biomethane. However, algal concentration had a diminishing role as the L/G ratio increased. Using only the statistically significant main effects and interactions, the biomethane composition (CO2% and O2%) was predicted with over 95% confidence through regression equations for superficial gas velocity up to 0.2 cm/s.

Design, Commissioning, and Performance Assessment of a Lab-Scale Bubble Column Reactor for Photosynthetic Biogas Upgrading with Spirulina platensis.

The two-step bubble column-photobioreactor photosynthetic biogas upgrading system can enable simultaneous production of biomethane and value-added products from microalgae. However, due to the influence of a large number of variables, including downstream processes and the presence of microalgae, no unanimity has been reached regarding the performance of bubble column reactors in photosynthetic biogas upgrading. To investigate this further, the present work documents in detail, the design and commissioning of a lab-scale bubble column reactor capable of treating up to 16.3 L/h of biogas while being scalable. The performance of the bubble column was assessed at a pH of 9.35 with different algal densities of Spirulina platensis at 20 °C in the presence of light (3–5 klux or 40.5–67.5 μmol m–2 s–1). A liquid/gas flow (L/G) ratio of 0.5 allowed consistent CO2 removal of over 98% irrespective of the algal density or its photosynthetic activity. For lower concentrations of algae, the volumetric O2 concentration in the upgraded biomethane varied between 0.05 and 0.52%, thus providing grid quality biomethane. However, for higher algal concentrations, increased oxygen content in the upgraded biomethane due to both enhanced O2 stripping and the photosynthetic activity of the microalgae as well as clogging and foaming posed severe operational challenges.

Sustainable Production of Reclaimed Water by Constructed Wetlands for Combined Irrigation and Microalgae Cultivation Applications

Considering the increasing pressure on freshwater resources due to the constant increase in water consumption and insufficient wastewater control and treatment, recovering wastewater is a path to overcoming water scarcity. The present work describes the potential of reusing treated wastewater (reclaimed water) for irrigation and production of microalgae biomass in an integrated way, through experimental evaluation of plant and microalgae growth, and creation of an application model. First, two parallel experiments were conducted to evaluate the use of reclaimed water produced by a constructed wetland filled with a mix of solid waste: the irrigation of a set of small pots filled with soil and planted with Tagetes patula L., and the cultivation of microalgae Chlorella sp. and a mixed microalgae population with predominant species of the genus Scenedesmus sp. in shaken flasks and tubular bubble column photobioreactors. Results indicated no negative effects of using the reclaimed water on the irrigated plants and in the cultivated microalgae. The growth indicators of plants irrigated with reclaimed water were not significantly different from plants irrigated with fertilized water. The growth indicators of the microalgae cultivated with reclaimed water are within the range of published data. Second, to apply the results to a case study, the seasonal variability of irrigation needs in an academic campus was used to propose a conceptual model for wastewater recovery. The simulation results of the model point to a positive combination of using reclaimed water for the irrigation of green spaces and microalgae production, supported by a water storage strategy. Water abstraction for irrigation purposes can be reduced by 89%, and 2074 kg dry weight microalgae biomass can be produced annually. Besides the need for future work to optimize the model and to add economical evaluation criteria, the model shows the potential to be applied to non-academic communities in the perspective of smarter and greener cities.

Observation of Spirulina platensis cultivation in a prototype household bubble column photobioreactor during 107 days

Fresh Spirulina is more favorable than dried one, yet its ease of deterioration necessitates production of biomass that can be immediately consumed. We developed a prototype household photobioreactor and studied the semi-continuous cultivation and harvest conditions within 107 days. Three growth phases were observed featuring different growth rate and recovering time after harvest. Nutrients were consumed at rates of Fe > N > P > Mg > K. The pH mounted rapidly when below 9 and varied slowly between 9 and 10, whose variation positively correlated with that of biomass concentration. Bacterial load was at a constant level of about 2 × 104 CFU, indicating good sanitary condition. Harvesting efficiency improved with greater biomass and filtration sack mesh number until reaching 3.5 g·L−1 and 200, respectively. We hope this study can help the method development of fresh Spirulina cultivation in miniaturized systems.

Multiscale integration of mixotrophic microalgal cultivation, lipid synthesis, rapid biomass harvesting, and nutrient recycling in pilot-scale photobioreactors

This work presents an acetic acid mediated energy-efficient process that integrates mixotrophic cultivation of extremophilic microalga Chlorella sorokiniana at the photobioreactor (macro) scale, with algal lipid accumulation at the molecular (micro) scale, and rapid biomass harvesting at the algal particle (meso) scale, followed by multiple recycling of nutrient-rich harvested broth. Chlorella sorokiniana is grown mixotrophically in Tris-Acetate-Phosphate medium using Tris buffer as nitrogen source, CO2 and acetic acid as inorganic and organic carbon sources, respectively, at light intensities of 5600–11,000 lx and an optimized photoperiod of 18:6 (Light: Dark) in 25-l bubble-column photobioreactors for 138 h. Acetic acid is used as an organic carbon source to integrate the processes occurring at the three scales; acetic acid ionizes to acetate ions in the culture media, which are enzymatically assimilated inside the alga's cytosol to acetyl-CoA that enhance fatty acid synthesis at the molecular scale and biomass yield at the reactor scale. The excess acetate ions in the culture medium react with the ions formed by the hydrolysis of potash alum to form complexes that react with the ions on algal cell surfaces to facilitate rapid flocculation at the meso (particle) scale. This multiscale integration results in maximum biomass and overall productivity 4.16 g/L and 0.70 g/L/day, respectively, with 25.8% lipid content, obtained at 2% CO2 and 11,000 lx, while reducing the harvesting time to 18–28 min, at a harvesting efficiency and cost of 98%, and 0.064$ per kg of dry biomass, respectively. The first and the second recycles of nutrient-rich broth lower the biomass yield by 9.8% and 14.2%, respectively, while increasing the harvesting time by 8.2% and 15.3%, respectively, as compared to fresh broth. Such multiscale integration of algal growth, macromolecular synthesis and biomass harvesting, followed by broth recycling, offers a novel, cost-effective technology for mixotrophic mass cultivation of extremophilic microalgae.

Biomass Production and Synthesis of Biodiesel from Microalgae Synechococcus HS-9 (Cyanobacteria) Cultivated Using Bubble Column Photobioreactors

Biomass Production and Synthesis of Biodiesel from Microalgae Synechococcus HS-9 (Cyanobacteria) Cultivated Using Bubble Column Photobioreactors

Economic analysis of microalgae biodiesel production in a small-scale facility

Industrial production and commercialization of biodiesel from microalgae have become a good alternative to conventional feedstock. Microalgae show high growth rate and carbon sequestration and can be easily cultivate in fresh and/or marine water, using non-arable soil. This study aims to analyze the technical and economic feasibility of biodiesel production from Phaeodactylum tricornutum, using an algae biomass production scaled-up scenario, considering local reality prices and available technologies. The model assumes 80,000 m3 of microalgae cultivation, in a set of bubble column photobioreactors installed on 15.247 ha of land, reaching a total of 1,811 tons of microalgae biomass and 171,705 L of biodiesel per year. The production cost estimated for microalgae biomass is 2.01 €kg−1 and for biodiesel is 0.33 €L−1. The ROI calculated for the project is 10% with a 10 years’ payback time and an EBITDA of 588,139 €year−1. Despite the project’s viability in the medium term, the cost of producing microalgae biodiesel remains high when compared to fossil fuels. Thus, unless greater technological maturity is achieved to make the process more economical, it will not be viable in the short term.

Performance evaluation of bubble column photobioreactor along with CFD simulations for microalgal cultivation using human urine

Optimization of microalgae cultivation to reduce the associated costs is one of the major objectives in a biorefinery model. The present study optimized the microalgal cultivation using 4.5–8.5 % v/v of DHU (diluted human urine) as a cost-effective resource, in a bubble column photobioreactor (BCPBR) under real-time conditions. Media with 5.5 % DHU and 4% CO2 showed maximal biomass productivity of 0.14 g L−1 day−1 with a final concentration of 1.06 g L−1. Phosphate and ammonium removal of 90.70 % and 84.10 % respectively was achieved. The biofixation of CO2 obtained for 6 days, during the cultivation in 5.5 % DHU, by supplying 4% of CO2 enriched air was 0.29 g L-1 d-1. Computational fluid dynamics (CFD) simulations were used to study the effects of velocity magnitude, shear stress, turbulent kinetic energy, and irradiance on the microalgal growth inside the BCPBR. The developed kinetic model predicted the biomass concentration and phosphate removal up to 98 % and 82 % accuracy respectively. Such studies would aid in comprehending the large scale commercial cultivation and thereby facilitate the application of microalgae in the future.

Semicontinuous system for the production of recombinant mCherry protein in Chlamydomonas reinhardtii.

Biotechnology advances have allowed bacteria, yeasts, plants, mammalian and insect cells to function as heterologous protein expression systems. Recently, microalgae have gained attention as an innovative platform for recombinant protein production, due to low culture media cost, compared to traditional systems, as well as the fact that microalgae such as Chlamydomonas reinhardtii are considered safe (GRAS) by the Food and Drug Administration (FDA). Previous studies showed that recombinant protein production in traditional platforms by semicontinuous process increased biomass and bio product productivity, when compared to batch process. As there is a lack of studies on semicontinuous process for recombinant protein production in microalgae, the production of recombinant mCherry fluorescent protein was evaluated by semicontinuous cultivation of Chlamydomonas reinhardtii in bubble column photobioreactor. This semicontinuous cultivation process was evaluated in the following conditions: 20%, 40%, and 60% culture portion withdrawal. The highest culture withdrawal percentage (60%) provided the best results, as an up to 161% increase in mCherry productivity (454.5 RFU h-1 - Relative Fluorescence Unit h-1 ), in comparison to batch cultivation (174.0 RFU h-1 ) of the same strain. All cultivations were carried out for 13 days, at pH 7, temperature 25°C and, by semicontinuous process, two culture withdrawals were taken during the cultivations. Throughout the production cycles, it was possible to obtain biomass concentration up to 1.36 g L-1 .

Cultivation of Chlorella vulgaris in anaerobically digested gelatin industry wastewater

Abstract This work aimed to study the effect of using anaerobically digested gelatin industry wastewater as a culture medium for the cultivation of Chlorella vulgaris microalgae in bubble column photobioreactors (PBRs). Batch experiments were carried out to determine the growth kinetics by inoculating microalgae in wastewater prepared with different dilutions and supplemented with Bold's Basal Medium (BBM). From the values of the saturation constants (KS = 50.25 mgN-NH4+·L−1) and substrate inhibition (KI = 28.12 mgN-NH4+·L−1) obtained in the adjustment to the Andrews kinetic model (R2 = 0.817), the PBRs achieved specific maximum growth rates (μmax) of 0.343 d−1, biomass productivity of 0.141 g·L−1·d−1, lipid content of 12.45%, lipid productivity of 17.63 mg·L−1·d−1 and instantaneous ammoniacal nitrogen consumption rates of 20.06 and 14.22 mg·L−1·d−1. The addition of wastewater to the culture medium provided an increase in biomass productivity of 57.45% in relation to the negative control. The results obtained demonstrate the high efficiency of C. vulgaris in the removal of nitrogenous compounds and the potential of using anaerobically digested gelatin industry wastewater in the production of microalgae biomass.

Direct brackish water desalination using Chlorella vulgaris microalgae

The objective of this study was to investigate the suitability of direct use of Chlorella vulgaris for brackish water desalination as a new conceptual technique. First, the adaptation of Chlorella vulgaris in saline water was performed, and then the living microalgae cells were utilized for the desalination process using a bubble column photobioreactor. The effect of culture medium, time, salinity and initial inoculum on the microalgae growth and salinity removal was investigated and the optimum conditions were obtained by RSM−CCD method. To assure the consumption of sodium chloride (NaCl) content of water by microalgae, the BG11 culture medium was modified by substituting its chloride and sodium containing salts by nitrate, calcium and potassium containing minerals. The results indicated that the enhancement of microalgae growth and salt removal efficiency were more pronounced in the modified-BG11 (MBG11) culture medium. Using Chlorella vulgaris microalgae in the MBG11 culture medium, the decrease in brackish water electrical conductivity for different NaCl concentrations between 1000 and 5000 ppm, was between 80 % and 40 %, respectively. Atomic absorption and flame photometry analyses confirm the hypothesis of adsorption of Na+ ions on the Chlorella vulgaris cell surface.

An Integrated Strategy for Nutraceuticals from Haematoccus pluvialis: From Cultivation to Extraction.

The aim of this study was to develop an effective integrated cultivation system for Haematococcus pluvialis as a source of bioactive compounds such as astaxanthin, lutein, proteins, and fatty acids (FAs). The Chlorophyta H. pluvialis was cultivated in a vertical bubble column photobioreactor (VBC-PBR) under batch mode, allowing switching from green to red phase for astaxanthin induction. The combined effect of light intensity and nutrients on bioactive compound formation was investigated. Results showed that growth under lower nutrients availability and light intensity led to a higher concentration of biomass. Growth under high light intensity with an appropriate concentration of nitrate, sulfate, phosphate and magnesium led to ~85% and ~58% higher production of total carotenoids and fatty acids, respectively. Under high stress conditions, ~90% nitrate and phosphate consumption were observed.

Enhancing the lipid content of Scenedesmus obtusiusculus AT-UAM by controlled acidification under indoor and outdoor conditions

This work explores the influence of controlled acidification on lipid accumulation in S. obtusiusculus AT-UAM under N-deplete conditions. The protocol included determination of the acidification procedure (CO2 or HCl) and the application chronology in flat panel photobioreactors, operated under controlled conditions. The highest lipid content and productivity of 60% glipids gDCW−1 and 85 mg L−1 d−1, respectively, were obtained when controlled acidification to pH of 5.5 was applied after 80 h of operation under N-depletion. The strategy was also applied successfully in a larger scale using different configurations such as bubble-column photobioreactors and raceway ponds, operated outdoors, yielding a maximum lipid content of 45% glipids gDCW−1 in both systems. Globally, the lipid content increased almost twice the value obtained without acidification in indoor and outdoor conditions. The analysis revealed that no major changes in fatty acid profile occurred, suggesting a high specificity of the microalga toward lipid production; however, significant changes in the ultrastructure of the subcellular components and the cell wall were observed.

Cultivation of Chlorella vulgaris using sequential-flow bubble column photobioreactor: A stress-inducing strategy for lipid accumulation and carbon dioxide fixation

Biological CO2 fixation by microalgae coupled with value-added product creation appears to be a sustainable approach in microalgae-based industry. However, the major constraint of this process is the low solubility of CO2 in water which limits CO2 fixation ability by the microalgae. Therefore, the current work aimed to improve the CO2 fixation efficiency of Chlorella vulgaris through the introduction of sequential-flow bubble column photobioreactor system. The influence of various cultivation parameters towards the growth, carbon fixation efficiency, lipid accumulation, and fatty acid profile of C. vulgaris were explored. Experimental results showed that microalgae cultivated under optimized conditions attained the highest biomass productivity (0.83−0.86 g/L/day) as compared to the control conditions. Meanwhile, the highest lipid content (50.4 % for SFB-PBR1) was recorded when the microalgae were cultivated in the spent medium. In addition, the CO2 fixation efficiency by microalgae in the sequential-flow photobioreactor system under the optimized condition was 3.78-fold higher than a single column mode (control). In short, the present work had demonstrated that cultivation conditions and photobioreactors configuration were equally important for an effective carbon capture process via microalgae cultivation.

A theoretical analysis of the hydrodynamic influence on the growth of microalgae in the photobioreactors with simple growth kinetics

This work presents a theoretical analysis for understanding the influence of hydrodynamics on the growth of microalgae in the photobioreactor (PBR). In the analysis, it is assumed that the growth rate is determined by the instantaneous light intensity and the light distribution is not influenced by the hydrodynamics. It is proved that the average growth rate over the tracked particles and the volume-averaged growth rate are the same if the average spatial distribution function (SDF) of the particles is included. In addition, the fluid kinematics shows that the SDF is related to the Jacobian or volumetric change ratio of the particle trajectories. For single-phase flows, the SDF should be uniform. The analysis justifies the conclusion that if the PBR is well-mixed and the dynamic growth kinetics are not included, the growth rate is only influenced by the light condition and the geometry of the PBR, but is not influenced by the hydrodynamics. The theoretical analysis is validated by the CFD simulations of the average growth rates of Taylor vortex PBR with single-phase flows, bubble column PBR and airlift PBRs with two-phase flows. It is also found that the particles tend to accumulate near the wall or boundary regions in the Lagrangian particle tracking method. This artificial effect is contrary to the theoretical analysis and can generate errors when predicting the growth rate. Therefore, further validations and examinations are needed for the numerical models.

Evaluation of cell growth performance of microalgae Chlorella minutissima using an internal light integrated photobioreactor

Microalgae have received special attention due to the biotechnological potential of their biomass, which can be used to produce biofuels, food formulations and pharmaceutical products. In order to improve biomass productivity, the present work proposes an internal light integrated photobioreactor (ILI-PBR), which integrates two configurations of photobioreactors (PBRs) already consecrated and widely used (tubular and bubble column) in a single system, combining the benefits of each configuration in a single PBR. To evaluate the applicability of ILI-PBR, a comparative test was conducted with the internal light bubble column photobioreactor (ILBC-PBR); both PBRs were illuminated with blue light-emitting diodes (LED).The PBR’s performance was evaluated in terms of specific growth rate (μmax) and cell productivity (PX) of the microalgae Chlorella minutissima. The μmax and PX in ILI-PBR were at least 42.85 and 58.06 % higher than ILBC-PBR, respectively. ILI-PBR was 36 % more efficient in terms of electricity consumption than ILBC-PBR.

In Situ Transesterification of Marine Microalgae Biomass via Heterogeneous Acid Catalysis

Microalgae have been widely considered as a promising alternative to renewable feedstock to biofuel production. Considering the many oleaginous strains of microalgae, this work assessed the potential of two species, Chlorella minutissima and Nannochloropsis gaditana, to be tested as raw material for ethyl esters production of biodiesel value. This work demonstrates an efficient pilot-size photoautotrophic growth of the two strains using 40-L bubble-column photobioreactors, providing lipid productivities of around 15.2 and 8.7 mg L−1 day−1 for C. minutissima and N. gaditana, respectively. The lipid-bearing biomass, which presented fatty acids composition similar to vegetable oils, such as soybean, rich in palmitic, oleic, and linoleic acids, was then assayed in direct trans/esterification reactions using ethanol as acyl donor, lipid extracting and solvent for the liquid phase in a pressurized reactor. The reactions, which were catalyzed by a heterogeneous acid catalyst (12-molybdophosphoric acid supported onto aluminum oxide), demonstrated an efficient route for producing a product mixture containing ester contents greater than 96.5 wt%, total conversion of triacylglycerols, and low levels of mono- and diacylglycerols, promoting an ethyl ester mixture with possible integration within the biodiesel market specifications.

Potential microalgal strains for converting flue gas CO2 into biomass

A screening method using 15% CO2 (v/v) as screening stress and a spotting plate method was developed to isolate microalgae with the potential to convert flue gas CO2 to biomass. A total of six microalgal strains, belonging to the genera Chlorella, Heynigia, Desmodesmus, and Scenedesmus, were isolated from ponds near metallurgical/cement/power plants. The growth of these isolated strains was dramatically promoted at 5 to 15% CO2 when they were cultivated in bubble column photobioreactors aerating with 0.03%, 5%, 10%, and 15% CO2. The growth of Heynigia riparia SX01 in particular showed substantial improvement with the increase of CO2 concentrations from 5 to 15%. Furthermore, the maximum biomass, overall biomass productivity, maximum biomass productivity, and maximum CO2 fixation rate of these microalgal strains greatly increased at 5 to 15% CO2 as well. Chlorella sorokiniana GS03 showed the highest values in maximum biomass productivity (0.36 g L−1 day−1) and maximum CO2 fixation rate (0.66 g L−1 day−1) at 5% CO2. Heynigia riparia SX01 exhibited the highest values of maximum biomass (3.28 g L−1), overall biomass productivity (0.27 g L−1 day−1), maximum biomass productivity (0.39 g L−1 day−1), and maximum CO2 fixation rate (0.71 g L−1 day−1) at 15% CO2. This study provides not only an efficient screening method obtaining microalgae with wide CO2 tolerance but also microalgal strains utilizing high levels of CO2 up to 15% to produce biomass, which contributes to further exploration in converting real flue gas CO2 into biomass feedstock.