Physiological and biochemical responses of dinoflagellate Symbiodinium sp. to the different light intensities

Symbiotic dinoflagellates produce bioactive valuable compounds such as carotenoids and lipids used in various industrial fields. However, a small amount of their biomass can be produced with a suspension-based closed photobioreactors. In the present study, we attempted to obtain a high lipid and total carotenoid contents from Symbiodinium sp. by creating optimal light intensity conditions using a Twin-layer photobioreactor. The growth rate, biomass, chlorophyll a concentration, as well as total carotenoid and lipid contents were examined at the light intensities of 50, 100 and 250 μmol m-2 s-1 for 16 days. Based on the results, biomass productivities ranged from 35.7, to 72.0 g m-2 at 50 and 250 µmol photons m-2 s-1, respectively. The highest linear growth rates were obtained 2.03, 3.27, and 5.85 g m−2 d−1 between 12 and 16 days at light intensity of 50, 100, and 250 μmol m−2 s−1, respectively. The highest values of total carotenoids, chlorophyll a, and percentage of total lipid were 0.85 g m-2, 0.96 g m-2, and 27.77% at light intensity of 250 μmol m-2 s-1, respectively. The findings proved that immobilization of algal cells in the photobioreactor biofilm resulted in high production of biomass and total carotenoids and lipids.