Effect of the temperature, pH and irradiance on the photosynthetic activity by Scenedesmus obtusiusculus under nitrogen replete and deplete conditions

Abstract

This paper evaluates the effect of the irradiance, pH and temperature on the photosynthetic activity (PA) of Scenedesmus obtusiusculus under N-replete and N-deplete conditions through oxygen measurements. The highest PA values were 160mgO2gb−1h−1 at 620μmolm−2s−1, 35°C and pH of 8 under N-replete conditions and 3.3mgO2gb−1h−1 at 100μmolm−2s−1, 28.5°C and pH of 5.5 for N-deplete conditions. Those operation conditions were tested in a flat-panel photobioreactor. The biomass productivity was 0.97gbL−1d−1 under N-replete conditions with a photosynthetic efficiency (PE) of 4.4% yielding 0.85gbmolphoton−1. Similar biomass productivity was obtained under N-deplete condition; and the lipid productivity was 0.34gLL−1d−1 with a PE of 7.8% yielding 0.39gLmolphoton−1. The apparent activation and deactivation energies were 16.1 and 30kcalmol−1, and 11.9 and 15.3kcalmol−1, for N-replete and N-deplete conditions, respectively.