Photosynthetic performance of a helical tubular photobioreactor incorporating the cyanobacterium spirulina platensis

The photosynthetic performance of a helical tubular photobioreactor ("Biocoil"), incorporating the filamentous cyanobacterium Spirulina platensis, was investigated. The photobioreactor was constructed in a cylindrical shape (0.9 m high) with a 0.25-m(2)basal area and a photostage comprising 60 m of transparent PVC tubing of 1.6-cm inner diameter (volume = 12.1 L). The inner surface of the cylinder (area = 1.32 m(2)) was illuminated with cool white fluorescent lamps; the energy input of photosynthetically active radiation(PAR, 400 to 700 nm) into the photobioreactor was 2920 kJ per day. An air-lift system ncorporating 4%CO(2) was used to circulate the growth medium in the tubing. The maximum productivity achieved in batch culture was 7.18 g dry biomass per day [0.51 g . d biomass/L . day, or 5.44 g . d biomass/m(2)(inner surface of cylindrical shape)/day] which corresponded to a photosynthetic (PAR) efficiency of 5.45%. The CO(2) was efficiently removed from the gaseous stream; monitoring the CO(2) the outlet and inlet gas streams showed a 70% removal of CO(2) from the inlet gas over an 8-h period with almost maximum growth rate. (c) 1995 John Wiley & Sons, Inc.     

Productivity of Spirulina in a strongly curved outdoor tubular photobioreactor

 The effect of different flow rates (from 0.18 m∣s to 0.97 m∣s) on the productivity of Spirulina grown outdoors in a strongly curved tubular photobioreactor (CTP) was studied. The results were compared to those obtained with a conventional photobioreactor made with straight tubes to form a loop (STP). The cultures were operated at a biomass concentration of 10 g/l dry weight. The productivity of the culture increased by about 39% and 29% in the CTP and STP respectively when the flow rate of the culture was increased from 0.18 m/s to 0.75 m/s. A further increase of the flow rate did not result in any increase of the productivity in either of the photobioreactors. The better performance of the culture observed in the CTP was attributed to an intermittent illumination pattern resulting from a secondary flow motion generated in the bends. The power required for the induction of the same flow rate inside the two types of photobioreactor changed significantly. At a Reynolds number of 4000, the power absorbed by the CTP was 25% higher than that required for water recycling in the STP and rose by more than 40% at a Reynolds number of 20000. Received: 3 July 1995 / Received revision: 16 October 1995 / Accepted: 24 October 1995     

Comparative analysis of the outdoor culture of Haematococcus pluvialis in tubular and bubble column photobioreactors

The present paper makes a comparative analysis of the outdoor culture of H. pluvialis in a tubular photobioreactor and a bubble column. Both reactors had the same volume and were operated in the same way, thus allowing the influence of the reactor design to be analyzed. Due to the large changes in cell morphology and biochemical composition of H. pluvialis during outdoor culture, a new, faster methodology has been developed for their evaluation. Characterisation of the cultures is carried out on a macroscopic scale using a colorimetric method that allows the simultaneous determination of biomass concentration, and the chlorophyll, carotenoid and astaxanthin content of the biomass. On the microscopic scale, a method was developed based on the computer analysis of digital microscopic images. This method allows the quantification of cell population, average cell size and population homogeneity. The accuracy of the methods was verified during the operation of outdoor photobioreactors on a pilot plant scale. Data from the reactors showed tubular reactors to be more suitable for the production of H. pluvialis biomass and/or astaxanthin, due to their higher light availability. In the tubular photobioreactor biomass concentrations of 7.0 g/L (d.wt.) were reached after 16 days, with an overall biomass productivity of 0.41 g/L day. In the bubble column photobioreactor, on the other hand, the maximum biomass concentration reached was 1.4 g/L, with an overall biomass productivity of 0.06 g/L day. The maximum daily biomass productivity, 0.55 g/L day, was reached in the tubular photobioreactor for an average irradiance inside the culture of 130 microE/m2s. In addition, the carotenoid content of biomass from tubular photobioreactor increased up to 2.0%d.wt., whereas that of the biomass from the bubble column remained roughly constant at values of 0.5%d.wt. It should be noted that in the tubular photobioreactor under conditions of nitrate saturation, there was an accumulation of carotenoids due to the high irradiance in this reactor, their content in the biomass increasing from 0.5 to 1.0%d.wt. However, carotenoid accumulation mainly took place when nitrate concentration in the medium was below 5.0mM, conditions which were only observed in the tubular photobioreactor. A similar behaviour was observed for astaxanthin, with maximum values of 1.1 and 0.2%d.wt. measured in the tubular and bubble column photobioreactors, respectively. From these data astaxanthin productivities of 4.4 and 0.12 mg/L day were calculated for the tubular and the bubble column photobioreactors. Accumulation of carotenoids was also accompanied by an increase in cell size from 20 to 35 microm, which was only observed in the tubular photobioreactors. Thus it may be concluded that the methodology developed in the present study allows the monitoring of H. pluvialis cultures characterized by fast variations of cell morphology and biochemical composition, especially in outdoor conditions, and that tubular photobioreactors are preferable to bubble columns for the production of biomass and/or astaxanthin.     

Improvement of mass transfer characteristics and productivities of inclined tubular photobioreactors by installation of internal static mixers

The feasibility of improving mass transfer characteristics of inclined tubular photobioreactors by installation of static mixers was investigated. The mass transfer characteristics of the tubular photobioreactor varied depending on the type (shape) and the number of static mixers. The volumetric oxygen transfer coefficient ( k(L)a) and gas hold up of the photobioreactor with internal static mixers were significantly higher than those of the photobioreactor without static mixers. The k(L)a and gas hold up increased with the number of static mixers but the mixing time became longer due to restricted liquid flow through the static mixers. By installing the static mixers, the liquid flow changed from plug flow to turbulent mixing so that cells were moved between the surface and bottom of the photobioreactor. In outdoor culture of Chlorella sorokiniana, the photobioreactor with static mixers gave higher biomass productivities irrespective of the standing biomass concentration and solar radiation. The effectiveness of the static mixers (average percentage increase in the productivities of the photobioreactor with static mixers over the productivities obtained without static mixers) was higher at higher standing biomass concentrations and on cloudy days (solar radiation below 6 MJ m(-2) day(-1)).     

Hydrogen production by cyanobacteria in an automated outdoor photobioreactor under aerobic conditions

The possibility of hydrogen production by a hydrogenase impaired mutant strain of Anabaena variabilis in outdoor culture was studied. A computer-controlled rooftop (outdoor) tubular photobioreactor (4.35 L) was assembled. H(2) production rates by A. variabilis PK84 grown in CO(2) + air in the photobioreactor were measured together with other parameters such as temperature, irradiance, pH, dry biomass weight, and pO(2), and Chl a concentrations during summer months of 1998 and 1999. Efficiencies of light energy bioconversion to H(2) energy and energy accumulated in biomass were calculated. The influence of irradiance, temperature, and mode of cultivation on H(2) production and efficiency of light energy bioconversion were evaluated. The culture produced up to 1.1 L H(2) day(-1) PhBR(-1). The efficiency of light energy to H(2) energy bioconversion on some days was 0.094%. However, the conditions for maximum H(2) photoproduction and for maximum efficiency of light energy to H(2) energy bioconversion were not the same. A. variabilis PK84 could produce hydrogen for prolonged periods (up to 40 days) without injection of fresh inoculum. During this period photobioreactor produced 24.5 L of H(2). Possibilities for increasing the efficiency of light energy conversion are discussed.     

Growth characteristics of Arthrospira platensis cultured inside a new close-coil photobioreactor incorporating a mandrel to control culture temperature

The aim of this study was to investigate Arthrospira growth inside a new CCP incorporating a mandrel for culture temperature control. Some hydrodynamic aspects and photobioreactor performances were investigated as well. The bioreactor incorporated A. platensis grown under batch and semicontinuous conditions. Two systems were used to recycle Arthrospira cultures: a peristaltic pump and an airlift system. When the pump recycled the culture, we achieved a very high Dean number (De=3,950), which decreased a great deal when the pump was replaced with the airlift system. During outdoor Arthrospira batch growth, a cell concentration of 16.4 g (DW)l-1 was reached after 9 days. However, the maximum chlorophyll content of the biomass (2.0% of DW) was achieved on the fifth and sixth days. The highest daily biomass output rate was obtained using the airlift system, when the CCP was operated under a semicontinuous regime: the gross output rate was 2.85+/-0.37 g (DW) l-1 d-1 and the net was 2.32+/-0.11 g (DW) l-1 d-1. The advantages of the airlift system may be due to the low concentration of oxygen built up inside Arthrospira culture and the lack of cell damage due to the pump system. Thus, oxygen and pump stress may have been avoided.     

Evaluation of a vertical flat-plate photobioreactor for outdoor biomass production and carbon dioxide bio-fixation: effects of reactor dimensions, irradiation and cell concentration on the biomass productivity and irradiation utilization efficiency

Outdoor culture of the thermophilic cyanobacterium Synechocystis aquatilis SI-2 with a vertical flat-plate photobioreactor (VFPP) was studied during the period of January to August of 1999 in the northern region of Japan (Kamaishi, Iwate, 39 degrees N, 142 degrees E). The aim of this study was to investigate the CO2 fixation ability of the VFPP device under various irradiation conditions. An average biomass productivity of over 30 g m(-2) day(-1), which corresponds to a CO2 fixation rate of 50 g m(-2) day(-1), was achieved during this period with a 192-l scale culture. The effects on biomass productivity of the light path, height of the reactor, cell concentration and irradiation were also investigated. Variation of the optimal cell concentration to achieve the highest productivity for outdoor operation is discussed. A cell concentration of 1-2 g l(-1) was found to be most suitable for the irradiation range of 1-12 MJ m(-2) day(-1) under the experimental conditions used.     

Tubular photobioreactor design for algal cultures.

Principles of fluid mechanics, gas-liquid mass transfer, and irradiance controlled algal growth are integrated into a method for designing tubular photobioreactors in which the culture is circulated by an airlift pump. A 0.2 m(3) photobioreactor designed using the proposed approach was proved in continuous outdoor culture of the microalga Phaeodactylum tricornutum. The culture performance was assessed under various conditions of irradiance, dilution rates and liquid velocities through the tubular solar collector. A biomass productivity of 1.90 g l(-1) d(-1) (or 32 g m(-2) d(-1)) could be obtained at a dilution rate of 0.04 h(-1). Photoinhibition was observed during hours of peak irradiance; the photosynthetic activity of the cells recovered a few hours later. Linear liquid velocities of 0.50 and 0.35 m s(-1) in the solar collector gave similar biomass productivities, but the culture collapsed at lower velocities. The effect of dissolved oxygen concentration on productivity was quantified in indoor conditions; dissolved oxygen levels higher or lower than air saturation values reduced productivity. Under outdoor conditions, for given levels of oxygen supersaturation, the productivity decline was greater outdoors than indoors, suggesting that under intense outdoor illumination photooxidation contributed to loss of productivity in comparison with productivity loss due to oxygen inhibition alone. Dissolved oxygen values at the outlet of solar collector tube were up to 400% of air saturation.     

Impact of ammonia concentration on Spirulina platensis growth in an airlift photobioreactor

Spirulina platensis was cultivated in a bench-scale airlift photobioreactor using synthetic wastewater (total nitrogen 412 mg L(-1), total phosphorous 90 mg L(-1), pH 9-10) with varying ammonia/total nitrogen ratios (50-100% ammonia with balance nitrate) and hydraulic residence times (15-25 d). High average biomass density (3500-3800 mg L(-1)) and productivity (5.1 g m(-2) d(-1)) were achieved when ammonia was maintained at 50% of the total nitrogen. Both high ammonia concentrations and mutual self-shading, which resulted from the high biomass density in the airlift reactor, were found to partially inhibit the growth of S. platensis. The performance of the airlift bioreactor used in this study compared favorably with other published studies. The system has good potential for treatment of high strength wastewater combined with production of algae for biofuels or other products, such as human and animal food, food supplements or pharmaceuticals.     

A model for light distribution and average solar irradiance inside outdoor tubular photobioreactors for the microalgal mass culture

A mathematical model to estimate the solar irradiance profile and average light intensity inside a tubular photobioreactor under outdoor conditions is proposed, requiring only geographic, geometric, and solar position parameters. First, the length of the path into the culture traveled by any direct or disperse ray of light was calculated as the function of three variables: day of year, solar hour, and geographic latitude. Then, the phenomenon of light attenuation by biomass was studied considering Lambert-Beer's law (only considering absorption) and the monodimensional model of Cornet et al. (1900) (considering absorption and scattering phenomena). Due to the existence of differential wavelength absorption, none of the literature models are useful for explaining light attenuation by the biomass. Therefore, an empirical hyperbolic expression is proposed. The equations to calculate light path length were substituted in the proposed hyperbolic expression, reproducing light intensity data obtained in the center of the loop tubes. The proposed model was also likely to estimate the irradiance accurately at any point inside the culture. Calculation of the local intensity was thus extended to the full culture volume in order to obtain the average irradiance, showing how the higher biomass productivities in a Phaeodactylum tricornutum UTEX 640 outdoor chemostat culture could be maintained by delaying light limitation. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 701-714, 1997.     

Dilution of solar radiation through "culture" lamination in photobioreactor rows facing south-north: a way to improve the efficiency of light utilization by cyanobacteria (Arthrospira platensis)

Efficient utilization of solar radiation for the photoautotrophic production of cyanobacterium biomass was achieved, using small pipes (ID = 0.01 m) arranged in rows in two photobioreactors facing south-north. A high Arthrospira yield of 47.7 g m(-2) (installation area) d(-1) was attained under outdoor conditions in a tubular undulating row photobioreactor (TURP-10r). During the summer, under a semicontinuous culture regime, the optimal biomass concentration (OBC) in TURP-5r was 6.0 g L(-1): it was 5.0 g L(-1) in TURP-10r. These OBCs made it possible to produce a biomass output rate of 2.7 +/- 0.2 g L(-1) d(-1) in the former and 2.1 +/- 0.1 g L(-1) d(-1) in the latter. When Arthrospira was grown at a preset dilution rate (0.3 d(-1)), sunrise cell density (SrCD) variations were not proportional to the drop of solar radiation. The SrCD was comparatively high at high solar radiation and decreased abruptly with decreasing solar radiation. There was a tendency to stabilize at low solar radiation. In both photobioreactors, the chlorophyll content of the Arthrospira biomass (% of the dry weight) was higher at sunrise than at sunset. A comparison of the chlorophyll biomass content in the TURPs showed no significant differences. Night biomass losses were very high (> 30% of the daylight productivity) when the culture temperature was kept constant at 31 +/- 1.0 degrees C: these losses fell to < 20% of the daylight productivity, when the night temperature of the cultures decreased according to the environmental temperature. Dilution of solar radiation was carried out using two quasi-laminated bioreactors. The rows of S-N facing bioreactors showed a very high growth yield in TURP-10r [about 2.1g (d.w.) MJ(-1)]. In TURP-10r, the high photic ratio (R(f) = 6), the high surface-to-volume ratio (S(ill)/V = 400 m(-1)) and the S-N facing of the rows (better than an E-W orientation) allowed for good results.     

产油嗜碱绿球藻MC-1的烟气适应性

为了降低微藻产油成本和减少温室气体的排放,利用煤炭烟气培养一株具有pH快速漂移和高碱适应特性的产油微藻Chlorococcum alkaliphilus MC-1.首先于15L光生物反应器中分三组(空白组、CO2组和烟气组)进行小体积培养实验,然后在24 m2开放式跑道池中进行放大培养,研究了微藻MC-1对烟气培养的适应性.结果表明,在光生物反应器培养实验中,烟气组的最高生物量浓度、生长速率、藻体总脂含量和CO2固定速率分别为:(1.02±0.07) g/L、(0.12±0.02) g/(L·d)、(37.84±0.58)％和(0.20±0.02) g/(L·d),比CO2组分别提高了36％、33.33％、15.34％和33.33％.在开放式跑道池培养实验中,烟气与纯CO2的培养效果相似,烟气培养下的最高生物量浓度、生长速率、藻体总脂含量和CO2固定速率分别为:147.40 g/m2、14.73 g/(m2·d)、35.72％和24.01 g/(m2·d);烟气培养产出的藻粉中有毒重金属Pb、As、Cd和Cr的含量均低于国家限量标准.实验同时测定了烟气培养下藻液对烟气中CO2、NO和SO2的吸收效果,结果显示,在光生物反应器和开放式跑道池培养中此三种气体的平均吸收率均高于以往研究结果.上述结果说明,该藻能适应烟气培养条件,耦合微藻MC-1产油与烟气减排的室外放大培养是可行的.     

用管式光生物反应器培养螺旋藻的研究

微藻大规模培养主要有敞开式大池培养和封闭式光生物反应器培养两种主要方式。管式光生物反应器是封闭式光生物反应器的主要类型之一。与其它类型相比,管式光生物反应器放大较易,成本较低。国外关于管式光生物反应器已有不少研究［１～３］但关于管式光生物反应器产率与光强和光暗比的关系等方面的研究尚未得出明确的结论。国内管式光生物反应器的研究较少［４］,尚未见有关管式光生物反应器中微藻悬浮液流变特性基础参数和产率影响因素的报道。螺旋藻是丝状体蓝藻,螺旋藻蛋白质含量高,其蛋白质所含必需氨基酸丰富,是国内外大规模商业…     

Photosynthetic production of the filamentous cyanobacteriumSpirulina platensis in a cone-shaped helical tubular photobioreactor

The photosynthetic productivity of the filamentous cyanobacteriumSpirulina platensis was investigated in a cone-shaped helical tubular photobioreactor. A laboratory-scale photobioreactor was constructed with a 0.255-m² basal area and a conical shape (0.64 m high × 0.57 m top diameter). The photostage comprised transparent reinforced polyvinyl chloride (PVC) tubing with spirally wound, metal-wire reinforcing in the tubing wall (31 m in length and 1.6 cm internal diameter with 0.25 cm wall thickness; total volume = 6.23 l). The inner surface of the photostage (0.651 m²) was illuminated with compact fluorescent cool white lamps; the photosynthetically active radiation (400–700 nm) energy input into the photobioreactor was 1249 KJ day^–1 (12 h day/12 h night). The operation of an air-lift photobioreactor with CO₂-enriched air (4%) at a flow rate of 0.3 l min^–1 showed a maximum daily photosynthetic efficiency of 6.83% under batch-culture conditions. This corresponded to a production rate of 15.9 g dry biomass m^–2(basal area) day^–1 or 0.51 g dry biomass l medium^–1 day^–1.     

Pilot-plant-scale outdoor mixotrophic cultures of Phaeodactylum tricornutum using glycerol in vertical bubble column and airlift photobioreactors: studies in fed-batch mode

Pilot-scale (0.19 m column diameter, 2 m tall, and 60 L working volume) outdoor vertical bubble column (BC) and airlift photobioreactors (a split-cylinder (SC) and a draft-tube airlift device (DT)) were compared for fed-batch mixotrophic culture of the microalga Phaeodactylum tricornutum UTEX 640. The cultures were started photoautotrophically until the onset of a quasi-steady-state biomass concentration of 3.4 g L(-)(1). After this, the cultures were supplemented with organic nutrient (glycerol 0.1 M) and a reduced nitrogen source, resulting in an immediate growth rate boost, which was repeated with successive additions of nutrients in all three photobioreactors. During this period the biomass productivity was enhanced compared to photoautotrophic cultures in the three reactors, although differences were found among them. These could be attributed to the different hydrodynamic behavior influencing the transport phenomena inside the cultures. A 25.4 g L(-)(1) maximum biomass concentration was attained in the SC. Further additions of nutrients did not promote any more growth. The consumption of glycerol was quantitative in the first additions but slowed at high biomass concentration, suggesting that a minimum amount of light is needed to sustain growth. No significant effect of the supplied organic nutrient on carotenoids and chlorophylls content was observed, although it had a profound effect on the fatty acid composition. Eicosapentaenoic acid (EPA) content was increased up to 3% (DW) in mixotrophic growth, giving a productivity of 56 mg L(-)(1) d(-)(1), a significant increase compared to the photoautotrophic control, which yielded a maximum EPA content of 1.9% (DW) and a productivity of 18 mg L(-)(1) d(-)(1). The maximum biomass and EPA volumetric yields obtained in this work are comparable with those reported for commercial photoautotrophic monoculture of large quantities of P. tricornutum in closed continuous-run tubular loop bioreactors with tubes that are typically less than 0.08 m in diameter. When the comparison is established in terms of productivities based on the land area occupied, the vertical airlift and bubble-column bioreactors are extraordinarily more productive.     

Design and performance of an α-type tubular photobioreactor for mass cultivation of microalgae

Ab α-shape tubular photobioreactor was designed and constructed based on knowledge of algal growth physiology using sunlight. The algal culture is lifted 5 m by air to a receiver tank. From the receiver tank, the culture flows down parallel polyvinyl-chloride tubes of 25 m length and 2.5 cm internal diameter, placed at an angle of 25 ° with the horizontal to reach another set of air riser tubes. Again the culture is lifted 5 m to another receiver tank, then flows down parallel tubes connected to the base of the first set of riser tubes. Thus, the bioreactor system looks like the symbol α. As there is no change in the direction of the liquid flow, high liquid flow rate and Reynolds Number can be achieved at relatively low air flow rate in the riser tubes. Due to the high area-volume ratio of the bioreactor, and equable photosynthetically available radiance and culture temperature, biomass density of exceeding 10 g dry weight L^-1 and daily output rate of 72 g dry weight m^-2 land d^-1 were achieved.     

THE FISH POND EXPERIMENT: CHAPTER TWO

A tubular photobioreactor for outdoor cultivation of Spirulina platensis was successfully operated for the last two years. The reactor was made of transparent 2.4-cm diameter tubes with a total length of approximately 101-m and a volume of 124-liter. Flow was induced using an airlift pumping system. To optimize the system further, a larger tube diameter was also tested. Preliminary results have suggested that a larger tube diameter might provide increased output with reduced surface area requirements. Results of experiments comparing the productivity of the same culture volume in tubes of 2.4 cm and 5.0 cm will be presented which show a small decrease in productivity by volume, but a large increase in areal productivity. This suggests that the larger tube diameter would be an appropriate choice for larger scale systems. Additionally, data will be presented demonstrating the effectiveness of an on-line surface scatter turbidimeter for accurate measurement of Spirulina density when correlated to manual dry weight measurements.     

Microalgal biomass production and on-site bioremediation of carbon dioxide, nitrogen oxide and sulfur dioxide from flue gas using Chlorella sp. cultures

The growth and on-site bioremediation potential of an isolated thermal- and CO?-tolerant mutant strain, Chlorella sp. MTF-7, were investigated. The Chlorella sp. MTF-7 cultures were directly aerated with the flue gas generated from coke oven of a steel plant. The biomass concentration, growth rate and lipid content of Chlorella sp. MTF-7 cultured in an outdoor 50-L photobioreactor for 6 days was 2.87 g L?1 (with an initial culture biomass concentration of 0.75 g L?1), 0.52 g L?1 d?1 and 25.2%, respectively. By the operation with intermittent flue gas aeration in a double-set photobioreactor system, average efficiency of CO? removal from the flue gas could reach to 60%, and NO and SO? removal efficiency was maintained at approximately 70% and 50%, respectively. Our results demonstrate that flue gas from coke oven could be directly introduced into Chlorella sp. MTF-7 cultures to potentially produce algal biomass and efficiently capture CO?, NO and SO? from flue gas.     

Pigment production in Spirulina fussiformis in different photophysical conditions

The present investigation makes a comparative investigation of individual light source on the different commercially important pigments in Spirulina fussiformis in photobioreactor culture condition. Continuous culture system was carried out throughout the experimental condition. Initially, seed culture, corresponding to 0.2 g/L on dry weight basis was cultivated in Zarrouks medium with different colored light source in reactor. Maximum daily biomass productivity, 0.8 g/L, 0.75 g/L and 0.69 g/L in white light (WL), blue light (BL) and green light (GL), respectively, conditions was noticed. Pigment content during WL treatment showed the highest accumulation (5.5 microg/mL) of chlorophyll whereas, other pigments roughly remained constant without much change, implying WL intensity is better for chlorophyll synthesis. On the other hand, chlorophyll and phycocyanin content gradually increased up to 7 microg/mL and 2 mg/mL, respectively, at BL intensity. The response to GL was negative to all pigments studied except for phycocyanin; in this case a highest production (2.5 mg/mL) was seen during 18 days experimental period. Additionally, when yellow light (YL) treatment experiments were conducted, the rate of production gradually decreased from 6th day onward in all pigments demonstrating the photobleaching effect of YL. The average rate of pigments production did not show significant accumulation in red light (RL) light treatment except phycoerythrin which showed an increasing trend of production. It is worth to mention here that higher light intensity is better for production of phycocyanin and phycoerythrin in Spirulina.     

A novel low-cost thin-film flat plate photobioreactor for microalgae cultivation

In this study, a novel thin-film flat plate photobioreactor (FPPBR) mounted with baffles and a 61.2 m² (2,000 L) photobioreactor system based on the FPPBR were developed. The flow of the fluid in the thinfilm photobioreactor was investigated by means of computational fluid dynamics (CFD). The cultivation of Chlorella sp. and Scenedesmus dimorphus in the thin-film FPPBR was carried out outdoors. The results showed that the flow of culture medium in different channels was uniform. In outdoor cultivation, the biomass productivity in the FPPBR with baffles was 25.2% higher than that in the FPPBR without baffles. In the pilot-scale FPPBR system, the maximum area productivity of Scenedesmus dimorphus reached 21.9 g/m²/day. When the service time of the photobioreactor was 1 and 3 years, the capital cost of the photobioreactor was 4.72 and 2.45 $ kg_algae, respectively. The results demonstrated that the thin-film FPPBR was cost effective, and it has the potential to be used for mass cultivation of microalgae.