Abstract

Microalgae can serve as a source of biocompound with high nutritional and commercial potential, such as fatty acids, vitamins and pigments. The microalgae composition is influenced by the physical and chemical conditions of the culture medium and environment in which they are grown, and the composition can be manipulated to produce specific biomolecules. The lack of stirring or the employment of stirring inefficient in the microalgae cultivation, limits the development of the culture because may have areas of stagnant culture, in which the cells do not receive light, which affects photosynthesis and cellular growth. The biomass concentration too is directly influenced by concentration of each nutrient culture medium. Hence, the need to add macronutrients and micronutrients in the ideal concentration and correct form as regards mass concentration and absorption availability. The objective of this study was to assess the growth of the microalgae Cyanobium sp. and Chlorella sp. in different culture media and stirring settings. For this, the cultures were carried out in Erlenmeyer flasks and Raceway type bioreactors, respectively, for 10 days at 30°C, with illumination of 41.6 µmol m^-2 s^-1, and with a 12 h light/dark photoperiod. The maximum biomass concentrations (0.56 and 0.66 g L^-1), specific growth rate (0.30 and 0.17 d^-1) and productivities (0.12 and 0.09 g L^-1 d^-1), were observed in Cyanobium and Chlorella, respectively, when they were grown in BG11 medium with 0.40 g L^-1 NaHCO₃. Regarding the stirring, the best responses were obtained when the assays were carried out with stirring by two submersible pumps, with maximum biomass concentrations of 1.21 g L^-1 for the Cyanobium sp. and 0.93 g L^-1 for the Chlorella sp.                                                                                                                        

Key words: BG11 medium, H/2 medium, ASM medium, Raceway, submersible pump.