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-degrees-N, longitude 11.3-degrees-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-degrees-C was superior by 23% to that observed in a culture grown at 25-degrees-C. The rates of night biomass loss were higher in the culture grown at 25-degrees-C (average 7.6% of total dry weight) than in the one grown at 35-degrees-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-degrees-C. Excess carbohydrate synthesized during the day was only partially utilized for night protein synthesis.