(330h) Environmental Microalgae Responses to Extreme pH at High CO2 Concentrations During Culture

Biological fixation of CO2 by microalgae has the potential to reduce the effect of industry gas emissions to the atmosphere. However, when these gases enter the proposed mitigation system, high concentrations of CO2 and other trace gases might acidify the growth medium to an intolerable pH for microalgae. We evaluate the effect of a range of CO2 concentrations (0.03-25% v/v) by continuously exposing microalgae to these atmospheres. One promising environmental strain of microalgae was grown in a 0.7 L bioreactor to determine the effect on growth of different CO2 atmospheres. Also, pH and pO2 were monitored. Results showed a drastic decrease in media pH that corresponded to CO2 concentration and type of medium used. However, the microalgae was able to tolerate the initial pH drop of the media without evident effects on growth or biomass productivity. At the highest CO2 concentration, extreme values of pH were observed during grow, i.e. 4.3 and 9.0, and 4.75 and 6.6, in MB3N and BG11 culture media, respectively. Our results suggest that the microalgae tested tolerates the harsh conditions imposed by these mitigation systems without further considerations on pH control and potentially demonstrating an advantageous condition to control contamination. However, how well a microalgae tolerates these conditions most likely is species-dependent. Therefore, our isolate might be an ideal species for this application.