CHANGES IN THE GROSS CHEMICAL-COMPOSITION OF MASS-CULTURES OF THE MARINE MICROALGA DUNALIELLA-TERTIOLECTA WITH DIFFERENT AERATION RATES

The effect of different aeration rates, in the range 0-6.51 l of air m in(-1) l of culture(-1), and CO2 supply on the biochemical composition of mass cultures of the marine microalga Dunaliella tertiolecta was s tudied The biochemical composition of D, tertiolecta was strongly affe cted by the aeration rate. There was a negative correlation between st ationary-phase protein cellular content and air flow. Carbohydrate cel lular content also decreased with aeration rate, a minimum being reach ed with 0.93 l of air min(-1) l of culture (-1) Maximum carbohydrate p er volume unit was achieved with maximum aeration as the increase of c arbohydrates per mi was directly proportional to airflow and therefore to CO2 availability. Maximum protein per mi was achieved with 1.86 l of air min(-1) l of culture(-1), keeping stable with higher airflows. The cultures supplied with CO2 showed carbohydrate and protein concent rations similar to the cultures with 1.86 l of air min(-1) l of cultur e(-1), indicating a correlation between available CO2 and not only car bon but also nitrogen metabolism. Different factors seemed to limit ce ll division and nitrogen metabolism as maximum nitrogen transformation rate was achieved with an air flow of 1.86 l of air min(-1) l of cult ure(-1), lower than the 3.72 l of air min(-1) l of culture(-1) needed for maximum cell density.