Abstract 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. employed (PBRs biocompounds However viability Thus necessary Accordingly lowcost low cost flatpanel flat panel instruments Additionally dimensions compressors PBROII PBR OII (PBR-OII mixers PBROII, OII, PBRCI, PBRCI CI , (PBR-CI) sp 0 682 6 82 6.8 mgmL mg mL 25 mgLday L day mg/L/day respectively 1.87 187 1 87 (1.8 mg/L/day. . mg/L/day) 2889 28 89 28.8 344 3 44 3.4 µgmL µg µg/mL 2312 23 12 23.1 185 85 1.8 Therefore research process (PBR-CI 68 8 6. 2 18 (1. 288 28. 34 3. 231 23. 1. (1 (

Resumen Las microalgas juegan un rol muy importante en la cadena alimenticia de la acuicultura, ya que estas son utilizadas en la nutrición y cría de moluscos, camarones y peces en sus diferentes etapas de crecimiento. Tetraselmis sp., es una microalga reconocida por sus aplicaciones como alimento vivo en acuicultura y sus parámetros de crecimiento pueden variar de acuerdo a las condiciones de cultivo. En este sentido, fueron evaluadas diferentes condiciones de crecimiento como medio de cultivo empleado, fertilizante comercial, fotoperiodo (12:12 y 24:0) y salinidad (0-55 gL-1) para obtener diferentes parámetros cinéticos de crecimiento. Las mejores condiciones de cultivo se alcanzaron con un fertilizante comercial, un fotoperiodo 12:12, salinidad del 35 gL-1, una velocidad específica de crecimiento de 1,071 d-1, tiempo de duplicación de 0,64 días, rendimientos (Yx/s) de biomasa respecto al consumo de nitrato, fósforo y amonio de 4,3; 37,7; 10,5 (gg-1) respectivamente, con un contenido de proteínas del 55% (p/p). Adicionalmente, se evaluó el modelo de Gompertz para la producción de biomasa presentando un buen ajuste (r2=0,9) entre el modelo y los resultados experimentales.

Abstract Microalgae play a very important role in the food chain of aquaculture, they have already been used in the nutrition and breeding of mollusks, shrimps and fish in their different stages of growth. Tetraselmis sp. is a recognized microalgae for its applications as live feed in aquaculture and its grow could vary according to the culture conditions. In this sense, different growing conditions such as culture medium, comercial fertilizer, photoperiod (12:12 and 24:0) and salinity (0-55 gL-1) were evaluated to obtain different growth kinetic parameters. The best growing conditions were achieved with a commercial fertilizer, a 12:12 photoperiod, salinity of 35 gL-1, a specific growth rate of 1.071 d-1, doubling time of 0.64 days, yields (Yx/s) of biomass with respect to the consumption of nitrate, phosphorus and ammonium of 4.3; 37.7; 10.5 (gg-1) respectively, with a protein content of 55% (w/w). In addition, the Gompertz model for biomass production was evaluated, presenting a good fit (r2 = 0.9) between the model and the experimental results.

Resumo As microalgas são muito importantes na dieta alimentar da acuicultura, são aquelas que são utilizadas na nutrição e cría de moluscos, camarões e peças em diferentes fases de crescimento. Tetraselmis sp. é uma microalga reconhecida por suas aplicações como ração viva na aquicultura e sus parámetros de crescimento podem variar de acordo com as condiciones de cultivo. Neste sentido, foram avaliados diferentes condiciones de crescimento como meio de cultivo em fertilizante comercial, fotoperíodo (12:12 y 24: 0) e salinidade (0-55 gL-1) a fim de obter diferentes parâmetros cinéticos de crescimento. As melhores condições de cultivo foram obtidas com fertilizante comercial, fotoperíodo 12:12, salinidade de 35 gL-1, taxa de crescimento específico de 1,071 d-1, tempo de duplicação de 0,64 dias, rendimento (Yx/s) biomassa em relação ao consumo de nitrato, fósforo e amônio de 4,3; 37,7; 10,5 (gg-1) respectivamente, porcentagem de proteína 55% (p/p). Adicionalmente, o modelo de Gompertz foi avaliado para produção de biomassa apresentando um bom ajuste (r2 = 0,9) entre o modelo e os resultados experimentais.

ABSTRACT The work was carried out in the Laboratory of Antibodies and Experimental Biomodels (LABEX) with the objective of evaluating the cultivation system of the microalgae Porphyridium cruentum. Bubble column photobioreactor was used in the experiments to obtain biomass. This allows introducing a new product to the market with a positive impact on the National Health System. Kinetic parameters of 0,29 d-1 and 2,37 d, were reached for the specific maximum growth rate and the doubling time respectively. The system is characterized as a low volumetric productivity with 0,09 g·L-1·d-1 and cellular density of 5,2 g·L-1 of wet biomass. Gompertz and Logistic models were evaluated for biomass description. Residual Sum of Squares (RSS), Akaike's Information Criterion Test (AIC) and coefficient R-Square were used as selection criteria. Logistic model described microalgal growth under the conditions used in this research with 0,9836 R2 coefficient.

RESUMEN La presente investigación se desarrolló en el Laboratorio de Anticuerpos y Biomodelos Experimentales (LABEX) teniendo como objetivo realizar una evaluación del sistema de cultivo de la microalga Porphyridium cruentum. Para la producción de biomasa se empleó un fotobiorreactor tipo columna de burbujeo. El desarrollo de esta tecnología permitirá introducir un nuevo producto al mercado, con un impacto positivo en el Sistema Nacional de Salud. Se alcanzaron parámetros cinéticos de 0,29 d-1 y 2,37 d para la velocidad específica de crecimiento máxima y el tiempo de duplicación respectivamente. El sistema resulta de baja productividad volumétrica con valor de 0,09 g·L-1·d-1 y densidad celular de 5,2 g·L-1 de biomasa húmeda. Se evaluaron los modelos matemáticos Gompertz y Logístico para la descripción de la formación de biomasa. Como criterios de selección se emplearon la suma de cuadrados de los residuos (SCR), el criterio de información de Akaike (AIC) y el coeficiente R2. El modelo Logístico es el que describe el crecimiento microalgal bajo las condiciones empleadas en esta investigación, con un coeficiente R2 de 0,983 6.

ABSTRACT • The cultivation of microalgae has important interests from the economic point of view with the production of medicines, antiseptics, protein-vitamin supplements and biofuels such as hydrogen, ethanol and biodiesel, as well as for bio remediation of the environment contributing to the mitigation of CO2 in the atmosphere and wastewater treatment. In this work, a dynamic model is presented that describes the symbiotic growth of the microalgae Chlorella vulgaris and bacteria, in an open-air thin-film photobioreactor of 3,500 m2, used for the treatment of liquid pig waste. A novel procedure is developed to estimate the pH value and a new kinetic equation for the growth of microalgae is proposed. MATLAB software R2009b was used to develop a program that allows estimating the temperature of the culture suspension and the variation of the process parameters (concentration of algae and bacteria, concentration of organic matter in terms of biochemical oxygen demand, pH, concentration of dissolved oxygen, dissolved carbon dioxide concentration, dissolved ammonia nitrogen concentration, and dissolved ortho-phosphates). The correlation between the experimental process parameters and those obtained with the program is demonstrated, with an error of less than 10% in all cases. The productivity per unit of cultivation area obtained with the program is compared with the real data obtained and the maximum error is ± 4%.

RESUMEN • El cultivo de microalgas tiene intereses importantes desde el punto de vista económico con la producción de medicamentos, antisépticos, suplementos proteico-vitamínicos y biocombustibles como hidrogeno, etanol y biodiesel, así como para bio-remediación del medio ambiente contribuyendo a la mitigación del CO2 en la atmósfera y al tratamiento de aguas residuales. En este trabajo se presenta un modelo dinámico que describe el crecimiento simbiótico de la microalga Chlorella vulgaris y bacterias, en un fotobiorreactor de capa fina a cielo abierto de 3500 m2 de área, utilizado para el tratamiento de residuales líquidos porcinos. Se desarrolla un procedimiento novedoso para estimar el valor del pH y se propone una nueva ecuación cinética de crecimiento de las microalgas. Se empleó MATLAB sofware R2009b para desarrollar un programa que permite estimar la temperatura de la suspensión de cultivo y la variación de los parámetros de proceso (concentración de algas y bacterias, concentración de materia orgánica en términos de demanda bioquímica de oxígeno, pH, concentración de oxígeno disuelto, concentración dióxido de carbono disuelto, concentración de nitrógeno amoniacal disuelto y orto-fosfatos disueltos). Se demuestra la correlación existente entre los parámetros experimentales de proceso y los obtenidos con el programa, con un error inferior a un 10% en todos los casos. La productividad por unidad de área de cultivo obtenida con el programa, es compara con los datos reales obtenidos y el error máximo es de ± 4%.

Resumen La viabilidad económica y energética de procesos basados en el uso de biomasa de microalgas requiere un sistema de cultivo eficiente. La obtención de biomasa algal se genera con base en la capacidad para crecer relativamente rápido, recolectarse a diario y cultivarse en estanques de tierra o fotobiorreactores cerrados que ocupan tierras de cultivo marginales. El objetivo del presente trabajo fue producir biomasa algal en un fotobiorreactor discontinuo a escala laboratorio. El equipo contó con 15 litros de capacidad, lámparas LED de 841.91 Lx distribuidos en 6 cilindros de acrílico. El cultivo se realizó por tres semanas. Los primeros tres cilindros contuvieron cepas de Chlorella vulgaris los otros tres Scenedesmus sp. Para el control de tiempo de exposición a la luz, se usó un temporizador, programado en fotoperíodos de 12 horas luz y 12 horas de oscuridad, se suministró dióxido de carbono (CO2) atmosférico al cultivo a través de una bomba de aire con un caudal de 0.0378 cm³ de CO2 /s, se realizaron también controles diarios de pH, ajustándolo a un rango entre 7.5 y 8.5, al igual que los valores de absorbancia, medidos a 750 nm, para evaluar el crecimiento de las microalgas. La biomasa fue sedimentada en recipientes de 20 litros, el sobrenadante fue retirado, la biomasa húmeda se centrifugó por 6 minutos a 840 rpm, conservando únicamente el pellet. Como resultado, las muestras liofilizadas conservaron las propiedades de la biomasa seca: 6.59 g de C. vulgaris y 9.74 g de Scenedesmus sp., las 2 muestras se guardaron en refrigeración, se concluyó que existe que hubo mayor producción de C. vulgaris frente a Scenedesmus sp.

Abstract The economic and energetic feasibility of microalgae-based processes requires an efficient cultivation system. Algal biomass is generated based on the ability to grow relatively fast, be harvested daily and cultivated in earthen ponds or closed photobioreactors that occupy marginal farmland. The objective of the present work was to produce algal biomass in a laboratory-scale batch photobioreactor. The equipment had a capacity of 15 liters, LED lamps of 841.91 Lx distributed in 6 acrylic cylinders. The culture was carried out for three weeks. The first three cylinders contained strains of Chlorella vulgaris and the other three Scenedesmus sp. For the control of light exposure time, a timer was used, programmed in photoperiods of 12 hours of light and 12 hours of darkness, atmospheric carbon dioxide (CO2) was supplied to the culture through an air pump with a flow rate of 0. 0378 cm³ of CO2 /s, daily pH controls were also performed, adjusting it to a range between 7.5 and 8.5, as well as absorbance values, measured at 750 nm, to evaluate the growth of the microalgae. The biomass was sedimented in 20liter containers, the supernatant was removed, the wet biomass was centrifuged for 6 minutes at 840 rpm, keeping only the pellet. As a result, the freeze-dried samples retained the properties of the dry biomass: 6.59 g of C. vulgaris and 9.74 g of Scenedesmus sp., the 2 samples were kept refrigerated, it was concluded that there was a higher production of C. vulgaris compared to Scenedesmus sp.

RESUMEN Se evaluó la capacidad de algas Chlorophyta aisladas de la laguna Limoncocha para remover materia orgánica en aguas residuales del Camal Municipal del cantón Shushufindi, Provincia de Sucumbíos - Ecuador. Se utilizó un fotobiorreactor tubular para aplicar seis tratamientos de 1.8 L, con cinco repeticiones cada uno. Los tratamientos dirigidos a evaluar el crecimiento de las algas consistieron en el uso del medio de cultivo Nitrofoska Foliar, con y sin aireación; para las pruebas de reducción de materia orgánica se aplicaron cuatro tratamientos con dilución de 1:3 del agua residual: dos unidades experimentales inoculadas con algas Chlorophyta, con y sin aireación; y dos unidades experimentales sin inoculación de algas, con y sin aireación. El fotoperiodo fue de 12 horas a 22.38°C y un pH de 8.45. El tratamiento más eficiente para la remoción de DBO5 (83.1%), fosfatos (58.9%), nitrógeno total Kjeldahl (63.1%), corresponde al cultivo aireado de algas Chlorophyta en agua residual diluida, presentando además mayor productividad celular (41944 células/L/día) en comparación al crecimiento en el medio de cultivo. La remoción más eficiente de sulfatos (58.9%) se obtuvo mediante el cultivo de algas Chlorophyta en agua residual diluida sin aireación.

ABSTRACT In this study, the capacity of isolated Chlorophyta algae from Limoncocha lagoon to remove organic matter in wastewater from the Shushufindi municipal slaughterhouse (Province of Sucumbios - Ecuador) was evaluated. Six different treatments of 1.8 L, with five replicates each, were applied in a tubular photobioreactor. The treatments aimed at assessing algae growth consisted of using of Nitrofoska foliar culture medium, with and without aeration; while for the organic matter reduction tests, four treatments were applied at a 1:3 dilution of the litter wastewater: two experimental units inoculated with Chlorophyta algae, one with aeration and one without aeration; and two experimental units without algae inoculation, with and without aeration. The photoperiod was 12 hours at 22.38°C and a pH value of 8.45. The most efficient treatment for the BOD5 (83.1%), phosphate (58.9%), and total Kjeldahl nitrogen (63.1%) removal was the aerated cultivation of Chlorophyta algae in diluted bed wastewater, showing higher cell productivity (41944 cells/L/day) compared to the growth in the culture medium. The most efficient sulfate removal (58.9%) was obtained by Chlorophyta algae culture in diluted, non-aerated, farmyard wastewater.

Abstract Microalgae research has attracted interest worldwide and in order to advance algal biotechnology in Brazil, government has been funding several projects. In the last 10 years, two main funds were provided by the National Council of Scientific and Technological Development (CNPq) agency to researchers in Brazil, who study the potential uses of microalgae for biomass, bioproducts and biofuels production. These funded projects addressed aspects of algal strain identification, development of algal cultivation techniques, designing photobioreactors and raceway ponds, modeling harvesting and dewatering process, maximizing biomass and oil productivities, characterizing chemical composition with different extractions systems and determining physiochemical properties of biodiesel. This review presents the state of art of algal research conducted by Brazilian institutions. Special attention is given to the recent progress on microalgal cultivation, high-value products extracted from microalgae and potential biofuels production. This review may serve as a policy instrument for planning next steps for algal research in Brazil as well as for attracting attention from international researchers who work with microalgae and would like to pursue a future partnership on algal research with Brazilian research institutions.

RESUMEN En este artículo exponemos el problema de diseño de un FotoBioRreactor (FBR) tubular helicoidal basado en la minimización del consumo de energía por medio del radio de curvatura para el cultivo de microalgas. En el cual, a través del estudio del cambio de dirección en el flujo de la tubería se busca diseñar una configuración de la tubería con mínimo consumo de energía. Se ha utilizado dinámica de fluidos computacional para evaluar el consumo de energía en diferentes configuraciones, encontrando que la forma como cambia la dirección del flujo tiene un efecto sobre el consumo de energía. Adicionalmente, se ha encontrado que el radio de curvatura tiene efecto sobre la caída de presión en la tubería del FBR, por lo que se ha desarrollado una función de costo que ha permitido resolver un problema de optimización para encontrar el radio de curvatura óptimo y obtener un diseño de un FBR helicoidal con bajo consumo de bombeo.

ABSTRACT In this paper we present the design problem of helical tubular PhotoBioReactors (PBR) based on energy consumption minimization, using the radius of curvature for the cultivation of microalgae. Computational Fluid Dynamics (CFD) is used to design a configuration of the helical pipeline with minimum energy consumption. We determined how flow direction changes affect energy consumption. Additionally, it was found that the radius of curvature affects the pressure drop in the PBR's pipe, so a cost function has been developed to solve an optimization problem seeking to obtain the optimum radius of curvature and a helical tubular PBR design with low pumping rates.

Resumen El presente trabajo de investigación tiene como objetivo determiner el efecto de la relación Carbono/Nitrógeno en la producción de biomasa y carotenoides totales en una cepa de Scenedesmus sp. Inicialmente, se evaluaron tres fuentes de carbono diferentes (carbonato de sodio, bicarbonato de sodio y acetato de sodio) bajo diferentes concentraciones de una fuente de nitrógeno (nitrato de sodio) en reactores tubulares de 250 ml. Los reactores fueron operados a 25° C durante 40 días en un ciclo de luz:oscuridad de 12:12 horas y un flujo continuo de aire. De acuerdo con los resultados se encontró que mediante el ajuste de la concentración de la fuente de carbono y nitrógeno, es posible aumentar la concentración de biomasa hasta 0.8 g/L. Por otra parte, mediante la regulación de la concentración de carbonato de sodio y nitrato de sodio, el contenido final carotenoides totales se incrementó dos veces (de 0.3 a 0.66% p/p). Los resultados de este estudio muestran que, al ajustar las concentraciones de la fuente de carbono y de nitrógeno es posible obtener un aumento interesante en la biomasa final y la concentración de carotenoides totales. Finalmente, es importante resaltar que se debe estudiar el efecto de otras estrategias como la luz, la salinidad y el pH, junto con la relación C/N para obtener un método adecuado que lleve a las celulas hacia un estress metabolico y mejore así la síntesis de carotenoides en Scencedesmus sp.

Abstract This study investigates the effect of C/N ratio on the production of biomass and total carotenoids on a Scenedesmus sp. Initially, three different carbon sources (sodium carbonate, sodium bicarbonate and sodium acetate) were tested under different concentrations of a nitrogen source (sodium nitrate) in 250 mL tubular air-lift reactors. The reactors were operated at 25° C for 40 days. in light:dark cycle of 12:12, under a continuous flow of air. Results showed that by the adjustment of the concentration of the carbon and nitrogen source, it is possible to increase the concentration of biomass up to 0.8 g/L. However, by the regulation on the concentration of sodium carbonate and sodium nitrate, the final content of total carotenoids was increased two times (from 0.3 to 0.66 % w/w). Results from this study shows that an specific ratio between the carbon source employed and the concentration of the nitrogen source shows that an outstanding increase on the final biomass and the concentration of total carotenoids that can be produced. Finally, the effect of well-known strategies such as light, salinity and pH, coupled with C/N ratio must be studied to achieve a proper method to stress the cell culture and enhance the synthesis of carotenoids in Scenedesmus sp.

Abstract To develop a biorefinery concept applied in the brewery industry, Chlorella pyrenoidosa and a consortium of associated bacteria were cultivated mixotrophically in a continuous photobioreactor using brewery low-value subproducts as an integrative process. Beer production residues were biochemically characterized to assess the most promising options to be used as a nutrient source for microalgal cultivation. Due to its physical and chemical properties, pre-treated weak wort was used to prepare an organic complex culture medium for microalgal biotransformation. Filtration and nitrogen supplementation were necessary to improve nutrient removal and biomass productivity. Maximal removal of nitrate and phosphate obtained were 90% and 100% respectively. Depending on operation conditions, total carbohydrates depuration ranged from 50 - 80%. The initial concentration of total carbohydrates of the weak wort must be adjusted to 2 - 4g/L to maintain a stable equilibrium between microalgal and bacterial growth. The biochemical composition of produced biomass varied depending on the cultivation conditions as well as on its final use. Upon continuous mixotrophic conditions evaluated in this study, C. pyrenoidosa was composed mainly of carbohydrates and protein.

Abstract Diatoms are the major group of microalgae which have been utilized by the potential applications as food industries, aquatic feeds, cosmetics, biofuels, and pharmaceuticals. In this study, current approaches were made in order to determine growth rate, biomass productivity, protein, carbohydrate, lipid and fatty acid composition for Nanofrustulum shiloi cultures using both aeration and mixing conditions in flat-plate photobioreactor (PBR). Physical (the intensity of aeration, mixing, light intensity etc.) and chemical (nutritional materials) factors are affecting the growth and bioproduct contents of a diatom. Biomass and lipid productivities of N. shiloi were measured as 31.29 and 36.9622±0.0598 mg L-1 day-1 in flat-plate PBR having the combination of aeration and stirring system, respectively. A slightly higher amount of saturated fatty acids was detected in PBR having only bubbling system while the increase of mono- and poly- unsaturated fatty acids were found in PBR having the combination of aeration and stirring system. Flat-plate PBR design was also investigated for improving not only biomass but also the lipid productivity of N. shiloi.

Abstract In this study, usage possibility of the dried Porphyridium cruentum type microalga biomass in the chewing gum formulation as a natural colorant was investigated. For this aim, the effect of different spray dryer inlet temperatures (150-200 °C) on pigment (total carotenoid and chlorophyll-a) quantities and color properties ( L*, a*, b* and C*) of Porphyridium cruentum type microalga biomass were examined. P. cruentum were cultured using the tubular photobioreactor and harvested by centrifugation. The dried microalga was then added to chewing gum at different concentrations (0.5% and 1.0% w:w) as a natural red colorant. The amount of the total carotenoids in dried biomass ranged from 112.6 to 419.9 μg g -1 and chlorophyll-a from 511 to 1513 μg g-1. Considering sensorial analysis, algal taste increased with increasing microalga concentration ( p < 0.05). The studied factors had no significant effect on cohesiveness, (0.186-0.254), springiness (0.713-0.806) and resilience (0.014-0.015) parameters in chewing gums ( p < 0.05). However, a* value in chewing gum samples increased with drying temperature and usage amount (from 10.5 to 18.7) which increased red color intensity. According to the findings of the present study, it can be concluded that P. cruentum biomass had a potential use in chewing gum matrix.

Resumen La producción de microalgas ha tomado importancia en los últimos años, debido a sus diversos usos en la producción de biocombustibles, alimentación tanto humana como animal, y en biorremediación; es por ello que, la optimización de las tecnologías destinadas a su producción resulta necesaria. En el presente trabajo se implementó y comparó un fotobiorreactor tubular helicoidal con un sistema abierto tradicional para la producción de Nannochloropsis oculata en el Parque Marino del Pacífico, Puntarenas, Costa Rica. En la construcción del fotobiorreactor se utilizó 100 metros de manguera transparente de 1” con un volumen total de 55 L, una estructura cilíndrica metálica (diámetro 0,67 m y 1,90 m de altura), un colector (0,12 m diámetro y 1,25 m de altura) de 15 L de volumen, un desgasificador para eliminar los excedentes de oxígeno, se instaló un aireador para la mezcla del medio de cultivo y finalmente se colocaron ocho lámparas de 32 W alrededor de la estructura metálica. Mientras que el sistema abierto estaba conformado por tanques de fibra de vidrio de 2 m3 de volumen y una manguera para la aireación. Se obtuvo como resultado que con el fotobiorreactor tubular se logró aumentar la densidad algal de 7,5 a 134x 106 cel/mL, la microalga logró permanecer en este sistema hasta 20 días mientras que, con el sistema abierto común solamente de 4 a 5 días, redujo el área requerida para la producción de la microalga en un 91% y al reducir las horas hombre necesarias para su funcionamiento logró reducir en un 18% los costos económicos.

Abstract Microalgae production has become important in recent years due to its diverse uses in the industry (biofuels, human and animal feeding, and bioremediation), because is important the optimization of the technologies destined to its production is necessary. A tubular photobioreactor with a traditional open system for production of Nannochloropsis oculata in the Parque Marino del Pacífico, Puntarenas, Costa Rica, was compared. In the construction of the photobioreactor was used 100 meters of transparent hose 1 “with a total volume of 55 L, a cylindrical structure (diameter 0, 67 m and 1, 90 m height), a manifold (0, 12 m diameter and 1, 25 m height) of 15 L of volume, a degasser to remove excess oxygen, an aerator was installed for the corresponding mixing of the culture medium and finally eight lamps of 32 W were placed around the metallic structure. While the open system consisted of glass fiber tanks 2 m3 and a hose for aeration. Results showed with tubular photobioreactor it was possible to increase the algal density from 7, 5 to 134 x 106 cells / mL, the microalga managed to remain in the system for up to 20 days while with the common open system only 4 to 5 days, the new equipment reduced the area required for microalgae production by 91% and by reducing the man hours required for its operation managed to reduce economic costs by 18%.

ABSTRACT Spirulina is a microalgal genre that has the capacity to produce various bioproducts with applications in several areas including the energy sector. The study aimed to assess the ability of CO2 biofixation, biodiesel and other biocompounds production by Spirulina sp LEB 18 cultured in air-lift photobioreactor. The microalgae presented a rich macronutrient composition: protein (47.3%), carbohydrates (13.4%) and a high lipid content (32.7%) in a media with nitrogen reduction, CO2 using air-lift photobiorector. Furthermore, 160 mg.L.d-1 of CO2 was biofixed, generating a maximum biomass yield of 0.02 g.L.d-1. The lipids evaluated for biodiesel production presented a theoretical yield of 19.8% for in situ transesterification and 47.9% for conventional transesterification. The microalgal biomass has potential for producing biodiesel that can be applied instead or in mixture with traditional diesel fuel. The study of obtaining energy associated with the production of other high value-added biocompounds from the microalgal biomass is of high importance because in this way, the viability of biofuel production by this microorganism can be increased.

RESUMEN Hoy en día, existen fotobiorreactores (PBRs de su sigla en inglés) a escala piloto funcionales, que presentan serios desafíos al momento de realizar un proceso de escalamiento para una aplicación industrial. Este trabajo propone evaluar el diseño de varios fotobiorreactores continuos de placa plana conectados en serie con recirculación desde la última unidad hasta la primera, para analizar la viabilidad del escalado de la productividad a partir de la adición de más unidades en lugar de incrementar el volumen del fotobiorreactor. Para esto, se ha construido un modelo matemático basado en los balances de masa y ecuaciones constitutivas de la literatura, en las cuales se integran los efectos de la iluminación y la transferencia de masa en la cinética de crecimiento de las microalgas. Desafortunadamente, se obtiene un modelo que es muy complejo para evaluar por medios convencionales. Adicionalmente, presenta problemas al evaluarse por métodos numéricos ya que se obtienen resultados que no tienen explicación física y la solución tiene una gran dependencia de las condiciones iniciales. Por lo tanto, este artículo presenta un método sencillo para el análisis del diseño de este tipo de sistema continuo. El método permite obtener los parámetros de diseño del sistema de fotobiorreactores y soluciones con sentido físico de una forma sencilla, sin tener que tantear las posibles soluciones del sistema. Adicionalmente se muestra que el sistema de fotobiorreactores continuos en serie con recirculación proporciona una buena productividad de microalgas.

ABSTRACT Nowadays, there are functional pilot scale PhotoBioReactors (PBRs), which present serious challenges when performing a scaling up process for an industrial application. The aim of this research was to evaluate the design of several continuous flat plate PBRs connected in series, while allowing constant circulation from the last to the first unit. Scaling up feasibility using the adjunction of new units, instead of PBRs volume increase is analyzed. An ad hoc mathematical model based on mass balances and constitutive equations from literature was constructed; the model integrates the illumination and mass transfer effects on microalgae growth kinetics by a complete model solution. Unfortunately, the model is too complex to be analyzed by conventional methods. Furthermore, it presents problems when evaluated by numeric methods as the results do not have physical meaning and the initial condition has strong effect on the final solution. Hence, this paper presents a simple method to analyze the design of this kind of continuous system. The method allows the design parameters calculation of PBRs system resulting physically in a simple way without having to guess possible system solutions. Moreover it is also shown that the continuous PBRs in series with a recirculation system obtain good amount of microalgae productivity.

RESUMO Atualmente existem fotobioreatores de escala piloto funcionais, porém trazem sérias complicações para executar um processo de escalonamento para uma implementação industrial. Este trabalho propõe avaliar a concepção de vários fotobioreatores contínuos de placa plana conectados em série com recirculação desde a última unidade até a primeira, para analisar a viabilidade do escalonamento da produtividade a partir da adição de mais unidades em vez de aumentar o volume do fotobioreator. Para este propósito um modelo matemático foi construído baseado nos balanços de massa e equações constitutivas da literatura, nas quais se integram os efeitos da iluminação e a transferência de massa na cinética de crescimento das microalgas. Infelizmente, obtém-se um modelo que é muito complexo para ser avaliado através de meios convencionais. Além disso, apresenta problemas ao ser avaliado com métodos numéricos, há que se obtêm resultados que não têm explicação física e a solução tem uma grande dependência das condições iniciais. Portanto, este artigo apresenta um método simples para a análise do desenho deste tipo de sistema contínuo. O método permite obter os parâmetros do desenho do sistema de fotobioreatores e soluções com sentido físico de forma simples, sem ter que tentar possíveis soluções do sistema. Além disso, mostra-se que o sistema de fotobioreatores contínuos em série com recirculação oferece uma boa produtividade de microalgas.