GROWTH AND CONTENT OF SPIRULINA PLATENSIS BIOMASS CHLOROPHYLL CULTIVATED AT DIFFERENT VALUES OF LIGHT INTENSITY AND TEMPERATURE USING DIFFERENT NITROGEN SOURCES

The effects of light intensity and temperature in S. platensis cultivation with potassium nitrate or urea as nitrogen source were investigated, as well as the biomass chlorophyll contents of this cyanobacteria, through the Response Surface Methodology. Experiments were performed at temperatures from 25 to 34.5 degrees C and light intensities from 15 to 69 mu mol photons m(-2) s(-1), in mineral medium. In cultivations with both sources of nitrogen, KNO3 and urea, statistic evaluation through multiple regression, no interactions of such independent variables were detected in the results of the dependent variables maximum cell concentration, chlorophyll biomass contents, cell and chlorophyll productivities, as well as in the nitrogen-cell conversion factor. In cultivation performed with both sources of nitrogen, it was possible to obtain satisfactory adjustments to relate the dependent variables to the independent variables. The best results were achieved at temperature of 30 degrees C, at light intensity of 60 mu mol photons m(-2)s(-1), for cell growth, with cell productivity of approximately 95 mg L-1 d(-1) in cultivations with urea. For the chlorophyll biomass content, the most adequate light intensity was 24 mu mol photons m(-2) s(-1).