Las microalgas son capaces de producir biomoléculas que poseen diversidad de aplicaciones relacionadas con la agricultura, alimentos y medicina. En la presente investigación se evalúan tres variables de proceso para determinar su incidencia e interacciones en la producción de biomasa y exopolisacáridos. El efecto de la intensidad de la luz, la agitación y la concentración de carbono sobre el crecimiento y la producción de exopolisacáridos en Scenedesmus obliquus (UTEX 393) es evaluada aplicando un diseño experimental factorial 23 por metodología de Screening. Se evalúa el efecto en simultáneo de la variación de tres variables experimentales en tres niveles (Intensidad de luz: 80, 130, 180 μE m-2 s-1, Agitación: 0, 600, 1200 rpm, concentración de carbono: 0, 2, 4% v/v Air-CO2). El coeficiente específico de crecimiento y la concentración de exopolisacáridos son las variables de respuesta seleccionadas. Los resultados muestran condiciones óptimas para las dos variables de respuesta en los niveles máximos de las variables experimentales (180 μE m-2 s-1, 4% mezcla CO2-aire y 1200 rpm), obteniendo una coeficiente específico de crecimiento 0.64 d-1 y una concentración de exopolisacáridos de 24,7 mg L-1. Se muestra una marcada influencia de la interacción entre variables que repercuten directamente sobre el crecimiento celular y la producción de exopolisacáridos, está ultima favorecida por los regímenes de flujo turbulentos (máximo nivel de agitación) que se asocia a una mayor disponibilidad y mejor distribución de la fuente de energía (luz) y carbono. La validación de los modelos polinómicos en montajes adicionales, certifica la representatividad de los análisis realizados.

Microalgae are capable of producing biomolecules that have a wide variety of applications in agriculture, food industry, and medicine. In this study, three process variables are evaluated in order to determine its incidence on biomass and exopolysaccharides production. The effect of light intensity, agitation and carbon concentration on Scenedesmus obliquus (UTEX 393) growth and expolysaccaharides production is evaluated using 2³ factorial design through the screening methodology. The simultaneous effect of level variation for three different experimental variables is examined in the present study in three levels for each parameter (Light intensity: 80, 130, 180 μE m-2 s-1, Agitation: 0, 600, 1200 rpm, carbon concentration 0, 2, 4% v/v Air-CO2). Specific growth rate and the exopolysaccharides concentration are the selected response variables. Results show that the optimal conditions for the two response variables correspond to the maximum levels of the three experimental variables (180 μE m-2 s-1, 4% air-CO2, and 1200 rpm), obtaining a specific growth rate of 0.64 d-1 and a exopolysaccharides concentration of 24.7 mg L-1. A significant interaction between the variables is observed, which has direct effects on cellular growth and exopolysaccharides production. The EPS production is facilitated by the turbulent flow (agitation maximum level), which is associated with a higher availability and better distribution of energy sources (light) and carbon dioxide. The validation of polynomials models verifies the relevance of the analysis performed.

O acido indolacético (IAA) é uma auxina natural e um dos principais reguladores do crescimento de plantas superiores. A quantidade de ácido indolacético extracelular produzida pela cultura de microalga verde Scenedesmus obliquus foi estabelecida por cromatografia líquida de alta eficiência (HPLC). Avaliou-se o efeito de três variáveis de processo na produção de IAA extracelular nestas culturas usando planejamento fatorial 2³ para uma metodologia de screening. As variáveis de planejamento experimental foram agitação, iluminância (intensidade do fluxo luminoso) e fonte de carvão (mistura CO2/air v/v (%)) em três diferentes níveis. A concentração de IAA e a taxa de crescimento específico foram usadas como variáveis de resposta. As análises de HPLC mostraram que em condições experimentais, a quantidade de IAA que foi liberada no meio pela alga S. obliquus depende somente da variável iluminância. Os efeitos da luz e as concentrações de carvão no meio de cultura foram significantes (p < 0.05) para uma taxa de crescimento específico.

The indoleacetic acid (IAA) is a natural auxin and one of the main growth regulators in higher plants. The extracellular indoleacetic acid (IAA) amount produced by the green microalga Scenedesmus obliquus culture was detected by high performance liquid chromatography (HPLC). It was evaluated the effect of three process variables in the extracellular IAA production in these cultures using 2³ factorial design for screening methodology. The experimental design variables were agitation, illuminance (intensity of luminous flux) and carbon source (CO2/air v/v (%) mixture) at three different levels. The IAA concentration and the specific growth rate were used as response variables. The HPLC analyses showed that under experimental conditions, the IAA amount that is released to the medium by S. obliquus depends only on the illuminance variable. The light effects and the carbon concentrations in culture medium were significant (p < 0.05) for specific growth rate.