The behavior of cyanobacteria and its potential use for biofuel production in scale-up conditions is a topic of growing importance. The aim of our work is to study the effects of illumination, stirring, and different growth phases on the cultivation of the cyanobacteria Spirulina platensis in 10 L raceways. The cultivations were carried out in a greenhouse under measured, but not controlled, illumination and in agitated raceways with stirring speeds varying from 0.1 to 0.4 m s-1, using culture media with nutrient depletion. At the end of the stationary phase (SP) and decline of culture, the biomass was harvested and used to determine the chemical composition. The stirring rate and the growing phase influenced the carbohydrate concentration. In both phases of cultivation, compared to high-speed stirring, stirring at lower speeds produced fewer carbohydrates in the culture. Biomass grown until the end of the SP with a stirring speed of 0.35 m s-1 had a carbohydrate content of 72%, which is very high compared to that reported in the literature.
Keywords: Carbohydrate; bioethanol; cell growth; cyanobacteria; extracellular carbohydrates.