Cultivation of two thermotolerant microalgae under tropical conditions: Influences of carbon sources and light duration on biomass and lutein productivity in four seasons

Biomass and lutein productivities of two thermotolerant microalgae were assessed in tropical outdoor conditions in all four seasons. Generally, addition of bicarbonate at 0.2 g/L every two days or 2% CO2 did not enhance the productivities compared to the controls, and the productivities in the spring were higher than in the fall. Durations of effective irradiance positively correlated to the productivity of Coelastrella sp. F50 well, but not for Desmodesmus sp. F2. The ineffective light intensity was below 5000 lux (about 106 μmol/m2s). The productivities produced in the 17 cm diameter bottles were 1.5- to 1.9-fold higher than that in the 27 cm ones. Lutein content, about 0.5% in biomass on average, did not change significantly grown in different carbon sources or seasons. The annual productivities of the microalgal biomass and lutein in one hectare were estimated to be 33 tons and 180 kg, respectively, using the non-optimized photobioreactor cultivation.