Role of culture solution pH in balancing CO2 input and light intensity for maximising microalgae growth rate


  • Microalgae growth is governed by CO2 input and light intensity.
  • CO2 input & light intensity have an opposing impact on the culture pH.
  • Microalgae growth can be inhibited by excessive lighting or CO2 input.
  • Balancing CO2 input and light intensity is essential for CO2 fixation by microalgae.
  • CO2 fixation rate of 4.2 g/L by Scenedesmus sp. at optimised condition.


The interplay between CO2 input and light intensity is investigated to provide new insight to optimise microalgae growth rate in photobioreactors for environmental remediation, carbon capture, and biomass production. Little is known about the combined effect of carbon metabolism and light intensity on microalgae growth. In this study, carbonated water was transferred to the microalgae culture at different rates and under different light intensities for observing the carbon composition and growth rate. Results from this study reveal opposing effects from CO2 input and light intensity on the culture solution pH and ultimately microalgae growth rate. Excessive CO2 concentration can inhibit microalgae growth due to acidification caused by CO2 dissolution. While increasing light intensity can increase pH because the carboxylation process consumes photons and transfers hydrogen ions into the cell. This reaction is catalysed by the enzyme RuBisCO, which functions optimally within a specific pH range. By balancing CO2 input and light intensity, high microalgae growth rate and carbon capture could be achieved. Under the intermittent CO2 transfer mode, at the optimal condition of 850 mg/L CO2 input and 1089 μmol/m2/s light intensity, leading to the highest microalgae growth rate and carbon fixation of 4.2 g/L as observed in this study.

Aditya L., Vu H. P., Johir M. A. H., Mahlia T. M. I., Silitonga A. S., Zhang X., Liu Q., Tra V.-T., Ngo H. H. & Nghiem L. D., 2023. Role of culture solution pH in balancing CO2 input and light intensity for maximising microalgae growth rate. Chemosphere 343: 140255. doi: 10.1016/j.chemosphere.2023.140255. Article.

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