Effects of nutrient ratios and carbon dioxide bio-sequestration on biomass growth of Chlorella sp. in bubble column photobioreactor.

Photobioreactor technology, especially bubble column configuration, employing microalgae cultivation (e.g., Chlorella sp.), is an ideal man-made environment to achieve sufficient microalgae biomass through its strictly operational control. Nutrients, typically N and P, are necessary elements in the cultivation process, which determine biomass yield and productivity. Specifically, N:P ratios have certain effects on microalgae's biomass growth. It is also attractive that microalgae can sequester CO2 by using that carbon source for photosynthesis and, subsequently, reducing CO2 emission. Therefore, this study aims to investigate the effect of N:P ratios on Chlorella sp.'s growth, and to study the dynamic of CO2 fixation in the bubble column photobioreactor. According to our results, N:P ratio of 15:1 could produce the highest biomass yield (3568 ± 158 mg L-1). The maximum algae concentration was 105 × 106 cells mL-1, receiving after 92 h. Chlorella sp. was also able to sequester CO2 at 28 ± 1.2%, while the specific growth rate and carbon fixation rate were observed at 0.064 h-1 and 68.9 ± 1.91 mg L-1 h-1, respectively. The types of carbon sources (e.g., organic and inorganic carbon) possessed potential impact on microalgae's cultivation.