Flat-plate Photobioreactor Research Articles

Pollution control and biodiesel production with microalgae: new perspectives on the use of flat panel photobioreactors regarding variation in volume application rate.

In the present study, the microalga Arthrospira platensis DHR 20 was cultivated in vertical flat-plate photobioreactors (FPBRs) to bioremediate anaerobically digested cattle wastewater (ACWW) and used as a growth substrate. The final objective was to evaluate the properties of the oil extracted from this biomass to determine its potential for biodiesel production. The process was divided into five phases, varying the volume of the applied substrate: 1 L (Phase I), 5 L (Phase II), 10 L (Phase III), 15 L (Phase IV), and 20 L (Phase V). Dry biomass reached a maximum of 5.7g L-1, and productivity peaked at 0.74g L-1d-1. The highest rate of CO2 biofixation was 1213.5mg L-1day-1, showing good potential for purifying the air. The highest specific maximum growth rate (μmax) and the shortest doubling time (Dt) were found during Phase I. The removal of pollutants and nutrients during the experimental phases ranged from 65.8% to 87.1% for chemical oxygen demand (COD), 82.2% to 85.8% for total organic carbon (TOC), 91% to 99% for phosphate (PO43-), 62.5% to 93% for nitrate (NO3-), 90.4% to 99.7% for ammoniacal nitrogen (NH4+), and 86.5% to 98.5% for total nitrogen (TN). The highest lipid production recorded was 0.172g L-1day-1. The average cetane number recorded in Phase IV of 51 suggests that the fuel will ignite efficiently and consistently, providing smooth operation and potentially reducing pollutant emissions. The analysis of fatty acids revealed that the produced biodiesel has the potential to be used as an additive for other low-explosive biocombustibles, representing an innovative and sustainable approach that simultaneously offers bioremediation and carbon sequestration.

Application of computational fluid dynamics in optimizing microalgal photobioreactors

Developing more efficient microalgal photobioreactors (closed cultivation systems) is impelled by increasing interest in microalgal cultivation to produce high-value products. Compared to open cultivation systems closed photobioreactors (PBRs) offer several advantages, including the potential for high productivity in a small footprint, ability to maintain a controlled environment, and their scalability for commercial production. Computational Fluid Dynamics (CFD) provides a powerful tool to simulate flow conditions of microalgal cultivation systems and analyze operational parameters which may affect cultivation key factors such as light (wavelength, intensity, and period of exposure), accessibility to nutrients, and mixing. Besides, geometric modifications employing CFD can accelerate the design process and considerably reduce the need for a thorough, empirical exploration of reactor configurations and the associated costs. This paper provides a comprehensive review of recent updates on the application of CFD in various microalgal cultivation systems with special focus on different geometry optimization of flat plate photobioreactors.This review examines recent studies that have employed various multiphase and turbulence methods within the CFD framework to simulate fluid flow and turbulence within reactors, aiming to improve flow characteristics and enhance microalgal productivity. Specifically, the application of CFD in optimizing flat plate photobioreactors is explored, with researchers investigating a range of baffles and sparger configurations to enhance microalgal productivity. Additionally, the advantages of adopting CFD are discussed, and the potential future applications of CFD in microalgal cultivation are outlined.

A comprehensive review on effective parameters on microalgae productivity and carbon capture rate

Rising carbon emissions caused by population growth and industrialization is a significant environmental challenge in various countries. To combat this issue, Renewable Energy (RE) and Carbon Capture and Storage (CCS) technologies should be commercialized to reduce Greenhouse Gas (GHG) emissions and generate carbon-free energy. One such technology is the use of microalgae, which can directly capture CO2 from the air through photosynthesis and potentially produce biofuels due to their high energy content. However, the carbon capture rate of microalgae varies globally due to numerous parameters and variables affecting microalgae productivity. Additionally, microalgae productivity and carbon capture formulas yield different results worldwide, especially in outdoor industrial-scale cultivation. This research aims to comprehensively review the effective variables and parameters in carbon capture by microalgae based on microalgae productivity and carbon capture formulas. The research also ranked countries based on CO2 production in four different categories to determine whether the biggest carbon producer countries could exhibit suitable weather conditions for microalgae cultivation. Findings reveal optimal ranges of critical variables in the microalgae growth formula, including temperature, solar radiation intensity, Photon Flux Density (PFD), and sunlight duration. The study also analyzes microalgae cultivation, carbon capture, and oxygen production formula in different systems such as Open Ponds (OP), Tubular Photobioreactors (TPBR), and Flat Plate Photobioreactors (FPPBR), while discussing other influential parameters. In conclusion, emphasizing the adjustment and utilization of optimal values of effective parameters in microalgae cultivation not only holds promise for future carbon capture by microalgae but also pushes human beings toward sustainable development goals.

Development and evaluation of low-cost flat plate photobioreactors for microalgae and cyanobacteria cultivation with biotechnological potential.

The high performance of biomass and metabolite biosynthesis by photosynthetic microorganisms is directly influenced by the cultivation system employed. Photobioreactors (PBRs) stand out as controlled and fundamental systems for increasing the production of biocompounds. However, the high costs associated with these systems hinder their viability. Thus, a more practical and economical approach is necessary. Accordingly, this study aimed to design and evaluate low-cost flat-panel photobioreactors on a laboratory scale for the cultivation of photosynthetic microorganisms, using economical materials and instruments. Additionally, internal optimization of the low-cost system was aimed to maximize growth and biomass production. The PBRs were designed and built with uniform dimensions, employing 4 mm translucent glass and agitation through compressors. The internally optimized system (PBR-OII) was equipped with perforated acrylic plates used as static mixers. To evaluate the performance of the low-cost PBR-OII, a comparison was made with the control photobioreactor (PBR-CI), of the same geometry but without internal optimization, using a culture of Synechocystis sp. CACIAM 05 culture. The results showed that the PBR-OII achieved maximum biomass yield and productivity of 6.82 mg/mL and 250 mg/L/day, respectively, values superior to the PBR-CI (1.87 mg/mL and 62 mg/L/day). Additionally, the chlorophyll concentration in the PBR-OII system was 28.89 ± 3.44 µg/mL, while in the control system, the maximum reached was 23.12 ± 1.85 µg/mL. Therefore, low-cost photobioreactors have demonstrated to be an essential tool for significantly increasing biomass production, supporting research, and reducing costs associated with the process, enabling their implementation on a laboratory scale.

Comparison of Growth of Chlorella vulgaris in Flat-Plate Photobioreactor Using Batch, Fed-Batch, and Repeated Fed-Batch Techniques with Various Concentrations of Walne Medium

Chlorella vulgaris was autotrophically grown in a Flat-Plate Photobioreactor (FPPB) using batch (BC), fed-batch (FB), and repeated fed-batch (RPF) cultivations. BC stage was done in the 20 L of working volume. During FB stages, 20 L of fresh medium was added to reach the final volume of 60 L. In the RPF stages, 20 L of broth was harvested, and then a similar volume of fresh medium was added to keep the working volume. This study aimed to evaluate the effect of Walne media (with various concentrations of composition) and cultural techniques on algal growth. Three different concentrations of Walne medium (original [coded as ´1], double [coded as ´2], and triple [coded as ´3] in concentrations of the original medium) was used for cultivations. Not only culture techniques but also various media affected biomass and chlorophyll productivity. RPF (with ´2 cultivation) gave the highest biomass productivity. However, RPF (with ´1 cultivation) gave the highest chlorophyll productivity. So, this study showed much fundamental information for the industrial production of Chlorella vulgaris biomass using flat-plate photobioreactors.

Polyhydroxyalkanoate production in a biofilm by mixed culture phototrophic bacteria

Anoxygenic purple phototrophic bacteria (PPB) were utilised in an 80 L biofilm flat plate photobioreactor to generate polyhydroxyalkanoate (PHA) over 44 cycles, with acetate as feed. Over the cycles, net PHA yield (growth + accumulation) averaged 21% while accumulation yield averaged 55%. Average PHA content was 35 wt% volatile solids (VS), with the majority (>80%) being harvested from the biofilm at 100 gTotal solids (TS) L−1. The PPB microbial population averaged 45% of total population. Detailed cycle studies indicated that PHA content (and yield) peaked at 0.5–1 d into the accumulation stage (peak of 53 wt% VS), suggesting that cycle time optimisation could improve both yield and selection of PHA accumulators. The resulting polymeric material was comprised of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with 95.5 mol% 3-hydroxybutyrate and 4.5 mol% 3-hydroxyvalerate content, but the molecular weight, at >1090 kDa, is unusually high for extracted, microbially produced PHA and a feature of this work.

Progressive pollution abatement in raw dairy wastewater induced by the algae Poterioochromonas malhamensis with a high-value biomass yield

This work aimed to systematically abate in batch mode organic pollutants from raw dairy wastewater (DW) with high values of chemical oxygen demand (COD, ∼10.3 g L−1), total organic carbon (TOC, ∼2.4 g L−1), and total nitrogen (TN, ∼0.28 g L−1) by using the Poterioochromonas malhamensis algae strains. In this regard, variables such as fractions of DW (40–100%, v/v), mineral nutritional inoculum addition (0–100%, w/v) and CO2-enriched air (2–8%) were proposed to address a study in optimizing conditions with new insights on algae production. As controlled photobioreactors (PBR), a set of tubular PBRs and a pair of flat-plate PBRs (FP-PBR) surrounded by fluorescent lamps and pumped by CO2-enriched air at a flow rate of 1.4 L min− 1 per litre were used. A Box-Behnken design (BBD) for algal growing was applied using the set of tubular PBRs to get a better reduction in TOC, TN and COD, defining an optimized condition. On the best tubular PBRs-based outcome and including a holed baffles system for hydrodynamically providing a flashing light state, 9-day kinetic experiments based on a pair of FP-PBRs were performed to provide more insights on how to enhance the algal yield and COD, TN and TOC reduction. A biomass yield rate of 1.1 g L−1 per day was attained using FP-PBRs, being comparatively 10% better than tubular PBRs. Additionally, the organic pollution abatement in DW was highly significant, with a decrease of about 98%, 95%, and 92% in COD, TN and TOC, respectively, besides changing the initial bacteria diversity to another less harmful one.

Stimulating carbon and nitrogen metabolism of Chlorella pyrenoidosa to treat aquaculture wastewater and produce high-quality protein in plate photobioreactors

Wastewater treatment by microalgae is the economical and environmentally friendly strategy, but is still challenged with the strict discharge standards and valuable biomass exploitations. The carbon and nitrogen metabolism of Chlorella pyrenoidosa was improved by the red LED light and starch addition to treat Tilapia aquaculture wastewater (T-AW) and produce protein simultaneously in a plate photobioreactor. The red LED light was applied to improve the nutrient removals at an outdoor temperature, but the concentrations except total nitrogen did not satisfy the discharge standards. After starch addition, the removal efficiencies of total phosphorus, total nitrogen, chemical oxygen demand, and total ammonia nitrogen were 85.15, 96.96, 88.53, and 98.01 % in a flat-plate photobioreactor, respectively, which met the discharge standards and the protein production reached 0.60 g/L. At a molecular level, the metabolic flux and transcriptome analyses showed that red light promoted carbon flux of the Embden-Meyerhof-Pranas pathway and tricarboxylic cycle, and upregulated the levels of genes encoding α-amylase, glutamine synthetase, glutamate dehydrogenase, nitrate transporter, and ammonium transporter, which facilitated nutrients removal and provided nitrogen sources for protein biosynthesis. The harvesting C. pyrenoidosa possessed the 62 % essential amino acids and great lipid composition for biofuels. This study provided a new orientation for outdoor wastewater treatment and protein production by collaboratively regulating the carbon and nitrogen metabolism of microalgae.

Resource recovery using enriched purple phototrophic bacteria in an outdoor flat plate photobioreactor: Suspended vs. attached growth

Purple phototrophic bacteria (PPB) can produce single-cell protein from wastewater at high yields. Growing in a biofilm vs suspended can improve product quality and consistency. This study compares suspended and attached growths of enriched PPB cultures in an outdoor flat plate photobioreactor treating poultry-processing wastewater. Attached growth had lower VFA removal efficiencies (95 ± 2.7 vs 84 ± 6.4 %) due to light limitations and low substrate diffusion rates. Nevertheless, similar overall treatment performances and productivities were achieved (16 ± 2.2 and 18 ± 2.4 gCOD·m−2·d−1 for attached and suspended) at loading rates of 1.2–1.5 gCOD·L−1·d−1. Biofilms had higher quality than suspended biomass, with lower ash contents (6.9(0.6)% vs 57(16)%) and higher PPB abundances (0.45–0.67 vs 0.30–0.45). The biofilm (20–50 % of the total biomass) might be used as feed and the suspended fraction as fertiliser, improving the economics of the process. Semi-continuous PPB growth outdoors as biofilm is technically feasible, obtaining a superior product without jeopardising performance.

Simultaneous photoautotrophic production of DHA and EPA by Tisochrysis lutea and Microchloropsis salina in co-culture

Marine microalgae have received much attention as a sustainable source of the two health beneficial omega-3-fatty acids docosahexaenoic acid (DHA, C22:6) and eicosapentaenoic acid (EPA, C20:5). However, photoautotrophic monocultures of microalgae can only produce either DHA or EPA enriched biomass. An alternative may be the photoautotrophic co-cultivation of Tisochrysis lutea as DHA-producer with Microchloropsis salina for simultaneous EPA production to obtain EPA- and DHA-rich microalgae biomass in a nutritionally balanced ratio. Photoautotrophic co-cultivation processes of T. lutea and M. salina were studied, applying scalable and fully controlled lab-scale gas-lift flat-plate photobioreactors with LED illumination for dynamic climate simulation of a repeated sunny summer day in Australia [day–night cycles of incident light (PAR) and temperature]. Monocultures of both marine microalgae were used as reference batch processes. Differences in the autofluorescence of both microalgae enabled the individual measurement, of cell distributions in co-culture, by flow cytometry. The co-cultivation of T. lutea and M. salina in artificial sea water with an inoculation ratio of 1:3 resulted in a balanced biomass production of both microalgae simultaneously with a DHA:EPA ratio of almost 1:1 (26 mgDHA gCDW−1, and 23 mgEPA gCDW−1, respectively) at harvest after depletion of the initially added fertilizer. Surprisingly, more microalgae biomass was produced within 8 days in co-cultivation with an increase in the cell dry weight (CDW) concentration by 31%, compared to the monocultures with the same amount of light and fertilizer. What is more, DHA-content of the microalgae biomass was enhanced by 33% in the co-culture, whereas EPA-content remained unchanged compared to the monocultures.Graphical

Modified closed flat-plate photobioreactor for optimizing CO2 bio-fixation by the cyanobacterium Synechococcus elongatus

Modified closed flat-plate photobioreactor for optimizing CO2 bio-fixation by the cyanobacterium Synechococcus elongatus

Integrated Model for Design, Optimization, Scale-Up, Culture Scheme, and Production Evaluation of a Bioreactor and Its Application for Improving Algal Biomass and Carbon Fixation in Bioreactors

A comprehensive numerical model system for the bioreactor design, structure and cultivation condition optimization, scale-up, and carbon fixation performance evaluation was proposed. Three basic models of computational fluid dynamics, particle and mass transfer, and two improved models of algae growth and light accumulation were integrated innovatively. The algae growth model directly predicted the algal production performance of the bioreactor, and the error was less than 15% compared with the experimental results. The light accumulation model was proposed to simulate the spatial distribution of light utilization with the changes of algal concentration and light intensity. The model system was applied to scale up the flat plate photobioreactor with inclined baffles, and the results showed that the photobioreactor with 9 cm light path had a maximum ideal areal productivity (505.94 g/m2) and better performance. Based on the light accumulation model, the strategy of changing the surface light intensity during the cultivation was proposed to maintain the light utilization and increase the production. Under the optimized surface light intensity, the maximum algal concentration and the average carbon fixation rate of the bioreactor were 43.41 and 248.35% higher than those of the constant light intensity. The proposed model system is a reliable and efficient experimental alternative tool for algal production evaluation and carbon fixation application of the bioreactor.

Modeling Effect of Bubbles on Time-Dependent Radiation Transfer of Microalgae in a Photobioreactor for Carbon Dioxide Fixation

Microalgae are considered one of the most efficient and environmentally friendly ways for carbon dioxide fixation. The bubbles play an important role in analyzing the radiation transfer in photobioreactors during microalgae growth. Herein, Chlorella sp. and Scenedesmus obliquus were cultured in the airlift flat plate photobioreactor and evaluated for the temporal evolution of radiation characteristics. A one-dimensional model of bubbles on time-dependent radiation transfer in a photobioreactor was proposed, and it was well verified with the experimental result. The results indicated that with the increase of bubble volume fraction or the decrease of bubble radius, the local irradiance increased at the illuminated surface of the microalgal culture and was attenuated more rapidly along with the radiation transfer. The average specific growth rate of microalgae decreases as bubble volume fraction increases or bubble radius decreases. The volume fraction of 0.003 and a radius of 3.5 mm are the optimal operating conditions in this study for microalgae growth and carbon dioxide fixation. The presented analysis would facilitate the design and optimization of the optical and aeration configurations of photobioreactors for carbon dioxide fixation.

Maximizing unsaturated fatty acids production by using sugarcane agroindustry wastes in cultivation of Desmodesmus sp. in a flat plate photobioreactor

Microalgae lipid accumulation can be accomplished by different strategies rather than naturally reaching the stationary phase. Many studies employ nitrogen (N) depletion to improve lipid production; however, this approach might not be a suitable alternative when growth in wastewater is attempted. Agro-industry effluents in particular can have high concentrations of N, so nutrient removal is also required. This study evaluated two possibilities of achieving stress conditions in Desmodesmus sp. cultivation: light intensity and CO2 concentration. The culture medium also included liquid and solid residues from the sugarcane agro-industry: vinasse and a biofertilizer produced from bagasse biochar. Optimization of growth in a flat plate photobioreactor was conducted by combining a two-level factorial design and simplex methodology. Both the highest biomass and polyunsaturated fatty acid productivities (150.2 and 21.4 mg L−1 day−1, respectively) were achieved near the central points (5% CO2 in air and 1000 μmol m−2 s−1 light intensity). These results show the possibility of microalgae growth in a sustainable medium coupled with high-value lipid production, e.g., omegas-3, − 6, and − 9.

The synergy of light/fluid flow and membrane modification of a novel membrane microalgal photobioreactor for direct air carbon capture

In this paper, a novel microalgal attached membrane photobioreactor based on the modified polyvinylidene difluoride (PVDF) / polyvinyl pyrrolidone (PVP) composite membrane for microalgae direct air carbon capture is developed and optimized. The Computational Fluid Dynamics (CFD) simulation, molecular dynamic study (MDS) and experimental study are adopted to investigate the synergy between light transmission and fluid flow, CO2 transmission mechanism inside the membrane and microalgae cells. The modified composite membrane is proposed and processed to improve the carbon sequestration rate of the microalgal attached membrane photobioreactor (AM-PBR). First, the synergy angle between the light transmission direction and fluid flow direction of the flat-plate photobioreactor (FP-PBR) is analyzed. To improve the synergy of light and fluid flow, the AM-PBR is proposed. Secondly, for the MDS part, the models of PVDF membrane and polytetrafluoroethylene (PTFE) membrane are developed. A three-layer simulation model is proposed to reveal the transmission mechanism of CO2 from the gas-liquid layer to the microalgae cell membrane layer. Several parameters including CO2 diffusion coefficient, CO2 concentration profile and velocity profile of CO2 are analyzed to compare the performance of different membranes and working conditions. Then, for verification of the simulation work, AM-PBR experiments are designed. To further enhance the CO2 transmission and microalgae attached performance, different PVDF/PVP composite membranes are assessed. The carbon sequestration rate of the modified membrane is improved according to the experiments. Finally, the novel microalgae membrane photobioreactor with the modified PVDF/PVP membrane is developed and the carbon sequestration rate of the PBR system is improved. The results showed that the best ratio for PVDF and PVP is 2:1 with 20 wt% solution, and with this modified membrane the carbon sequestration rate of the PVDF/PVP-based AM-PBR is 18.61% higher than the original PVDF-based AM-PBRs. The proposed novel AM-PBR is especially useful for low-concentration CO2 direct air carbon capture.

Seasonal variation in the growth, lipid accumulation, and fatty acid composition of Chlorella sp. GN1 cultured in flat plate photobioreactors outdoors

Seasonal variation in the growth, lipid accumulation, and fatty acid composition of Chlorella sp. GN1 cultured in flat plate photobioreactors outdoors

Outdoor demonstration-scale flat plate photobioreactor for resource recovery with purple phototrophic bacteria

To make purple phototrophic bacteria (PPB)-based technologies a reality for resource recovery, research must be demonstrated outdoors, using scaled reactors. In this study, a 10 m long PPB-enriched flat plate photobioreactor (FPPBR) with a volume of 0.95 m3 was operated for 253 days, fed with poultry processing wastewater. Different operational strategies were tested, including varying influent types, retention times, feeding strategies, and anaerobic/aerobic conditions in a novel mixed metabolic mode concept. The overall results show that regardless of the fermented wastewater fed (raw or after solid removal via dissolved air flotation) and the varying environmental conditions (e.g., light exposure and temperatures), the FPPBR provided effective volatile fatty acids (VFAs), N, and P removals (average efficiencies of >90%, 34–77%, and 28–45%, respectively). The removal of N and P was limited by the availability of biodegradable COD. Biomass (C, N and P) could be harvested at ∼90% VS/TS ratio, 58% crude protein content and a suitable amino acid profile for potential feed applications. During fully anaerobic operation with semicontinuous/day-only feeding, the FPPBR showed biomass productivities between 25 and 84 g VS m−2 d−1 (high due to solid influx; the productivities estimated from COD removal rates were 6.0–24 g VS•m−2•d−1 (conservative values)), and soluble COD removal rates of up to 1.0 g•L−1•d−1 (overall average of 0.34 ± 0.16 g•L−1•d−1). Under these conditions, the relative abundance of PPB in the harvested biomass was up to 56%. A minimum overall HRT of 2–2.4 d (1.0–1.2 d when only fed during the day) is recommended to avoid PPB washout, assuming no biomass retention. A combined daily-illuminated-anaerobic/night-aerobic operation (supplying air during night-time) exploiting photoheterotrophy during the day and aerobic chemoheterotrophy of the same bacteria at night improved the overall removal performance, avoiding VFA accumulation during the night. However, while enabling enhanced treatment, this resulted in a lower relative abundance of PPB and reduced biomass productivities, highlighting the need to balance resource recovery and treatment goals.

Novel bioreactor with inclined baffles in cost-efficiently increasing algal biomass and carbon fixation

We assess the cultivation of microalgae and possible improvements of photobioreactor (PBR) design and operation. A systematic method based on numerical modeling and experiments was proposed to guide the study of reactor performance. Taking the novel flat plate photobioreactor (FPPBR) with inclined baffles (IBs) as an example, the method was applied to investigate an effective way to improve the cultivation potential of the reactor. To obtain good mass transfer and light utilization, the optimal ratio of baffle opening gap to bioreactor width was 0.25. The algal biomass in the FPPBR with IBs at 3% CO2 aeration and an aeration rate of 0.05 vessel volume per minute (vvm) was 27.08% and 48.34% higher than that of FPPBR without baffles under the same cultivation conditions and higher air aeration rate of 0.15 vvm. The maximum carbon fixation rate increased by 106% when using the IBs under the same 3% CO2 aeration condition. The installation of the optimal IBs made it possible to achieve highly efficient cultivation under low energy aeration input, and it is also a cost-efficient way to increase carbon fixation in the bioreactor.

Optimization of Culture Conditions for Total Carotenoid Amount Using Response Surface Methodology in Green Microalgae / Ankistrodesmus convolutus

Commercial carotenoids of green microalgae have become significant especially for their applications in the cosmetic, pharmaceutical, food and feed industries. Effects of physical and chemical parameters on carotenoid contents in isolated microalgal species have been investigated. The variables of shaking rate, nitrogen concentration and light intensity affect biomass production and the synthesis of carotenoids in the green microalgae were investigated using the statistical design by Box-Behnken (BBD) employing Response Surface Methodology (RSM). Furthermore, the optimized cultivation conditions using BBD for Chlorella vulgaris, Ankistrodesmus convolutus, Dunaliella salina, Tetraselmis striata were determined using the spectrophotometric method to enhance carotenoid concentration. A. convolutus within the green algae was detected with the highest carotenoid concentration. The optimum conditions results indicated that the growth of A. convolutus (0.55 mg/L) and production of total carotenoids (25.1138 mg/g biomass) were found at the stirrer rate of 100 rpm under the light intensity of 100 μE/m2 s, and in the nutrient component of 8.82 mM NaNO3 . These conditions were validated experimentally for total carotenoid yield (24.13 mg/g biomass). After that the production was performed in a flat-plate photobioreactor with a volume of 6L based on the optimized conditions and the carotenoid profile was defined by HPLC-DAD using standards such as violaxanthin, astaxanthin and β-carotene. This study proposes that the RSM approach can be used to define optimal conditions for large-scale production of carotenoids by A. convolutus. 

Development a novel hexagonal airlift flat plate photobioreactor for the improvement of microalgae growth that simultaneously enhance CO2 bio-fixation and wastewater treatment

A novel hexagonal airlift flat plate (HAFP) photobioreactor was designed to improve microalgae growth rate and compared with traditional flat plate (TFP) photobioreactor. The computational fluid dynamics (CFD) simulation was used to determine hydrodynamic parameters and optimal aeration rate in the photobioreactors. Additionally, the capability of the HAFP photobioreactor to enhance microalgae based CO2 bio-fixation and wastewater treatment were investigated. The results of CFD simulation indicated that the HAFP photobioreactor could improve hydrodynamic parameters of turbulence kinetic energy (TKE), average fluid velocity, dead zone (DZ), and water shear stress (WSS) up to 78 %, 41 %, 44 % and 40 %, respectively, under optimal aeration rate of 0.6 vvm. The proposed HAFP photobioreactor showed a drastic improvement in microalgae growth (up to 61 %). The maximum CO2 removal of 53.8 % and bio-fixation of 0.85 g L−1 d−1 were achieved in the HAFP photobioreactor which were approximately 70 % more than that in the TFP photobioreactor. The results suggested that the HAFP photobioreactor could accelerate nutrients removal and achieve remarkably higher efficiencies of 91 %, 99 %, 97 % and 93 % of ammonia (NH3), nitrate (NO3−), phosphate (PO43−) and chemical oxygen demand (COD) within seven days of cultivation.