High concentrations of dissolved oxygen can inhibit the growth of photosynthetic microorganisms in microalgal culture systems. Not taking into account this parameter can also affect the reliability of mathematical models predicting biomass productivity. This study investigates the impact of high dissolved oxygen concentrations (C O₂) on biomass productivity. The eukaryotic microalgae Chlorella vulgaris was cultivated in a torus-shaped photobioreactor in chemostat mode at constant light and for different C O₂. Results showed a loss of biomass productivity at C O₂ ≥ 31 g•m −3. By recalculating the specific rate of cofactor regeneration on the respiratory chain (J NADH 2), the kinetic growth model was able to predict the impact of C O₂. This improved model was then used to explain the discrepancy in performances between two photobioreactor geometries, highlighting the utility of regulating gas-liquid mass transfer via aeration for better optimization of photobioreactor performances.

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