Effect of temperature on yield and night biomass loss in Spirulina platensis grown outdoors in tubular photobioreactors.

Outdoor experiments carried out in Florence, Italy (latitude 43.8° N, longitude 11.3 ° E), using tubular photobioreactors have shown that in summer the average net productivity of a Spirulina platensis culture grown at the optimal temperature of 35 C was superior by 23 % to that observed in a culture grown at 25 C. The rates of night biomass loss were higher in the culture grown at 25 C (average 7.6 % of total dry weight) than in the one grown at 35 C (average 5%). Night biomass loss depended on the temperature and light irradiance at which the cultures were grown, since these factors influenced the biomass composition. A net increase in carbohydrate synthesis occurred when the culture was grown at a low biomass concentration under high light irradiance or at the suboptimal temperature of 25 C. Excess carbohydrate synthesized during the day was only partially utilized for night protein synthesis.