Effect of temperature on the oxygen production capacity and growth of scenedesmus almeriensis

The optimal temperature and irradiance to maximise oxygen production were 39.3 °C and 512.5 μmol photons·m⁻²·s⁻¹, respectively. These values were obtained by photorespirometry, which is a quick method to measure the photosynthetic and respiration rates of microalgae at a laboratory scale. With these conditions, the global oxygen production rate of S. almeriensis was 246.23 mg_oxygen·g_biomass⁻¹·h⁻¹. When the culture temperature was controlled at 39.3 °C for 1 h per day, the daily oxygen production capacity of S. almeriensis increased from 3129.5 mg_oxygen·g_biomass⁻¹ to 3778.5 mg_oxygen·g_biomass⁻¹. However, keeping the temperature at 39.3 °C for a longer time period caused a damage to the photosynthetic apparatus. This was validated using laboratory-scale bubble columns. The damage was reversible when heating the cells for <2 h, but keeping the temperature of the culture at 39.3 °C for 3 h led to an irreversible damage and a 6 % decrease in the photosynthetic performance. Controlling the overheating of microalgal cultures is crucial to maximise growth. In addition, the duration of the exposure to high temperatures should also be included into growth and taken in consideration.