Figure 3From: Achieving pH control in microalgal cultures through fed-batch addition of stoichiometrically-balanced growth mediapH instability from nitrogen metabolism in Chlamydomonas reinhardtii . Photoautotrophic Chlamydomonas reinhardtii cultures were grown in 1.5-L loop air-lift photobioreactors on 5% CO2 (v/v) in air and 0-9% nitrogen from ammonium (0 to 0.027 gN-NH4+/L) with the balance nitrogen as nitrate. The optical density was measured at 550-nm to monitor culture growth and converted to biomass density using the conversion factor of 0.52 gDW/L/OD550 determined experimentally (A). The culture pH was monitored online continuously with samples averaged every 5Â minutes to monitor nitrogen utilization (B). The nitrate concentration was measured offline using an ion selective electrode (C).Back to article page