Optimization of carbon dioxide fixation and starch accumulation by Tetraselmis subcordiformis in a rectangular airlift photobioreactor

Culture conditions are very important to CO(2) bio-fixation and carbohydrate accumulation in microalgae. The objective of this study was to optimize semi-continuous culture conditions of Tetraselmis subcordiformis in a rectangular airlift photobioreactor for obtaining maximized carbon dioxide fixation rate and intracellular starch productivity. The effects of the initial biomass concentration (0.13, 0.8, 1.8, 2.8 and 3.47 g L(-1)), the gas flow rate (0.03, 0.1, 0.2, 0.3 and 0.37 V V(-1) m(-1)) and different carbon dioxide concentrations (1.63, 5, 10, 15 and 18.37%) were considered using a central composite design. By using response surface methodology and the desirability function approach, the optimal CO(2) fixation rate of 55.15 mg L(-1) h(-1) and the intracellular starch productivity of 10.66 mg L(-1) h(-1) occurred when the initial biomass concentration was 1120 mg L(-1) and the air supplemental CO(2) concentration was 6.9% with a gas flow rate of 0.35 V V(-1) m(-1). These results suggest the potential of applying T. subcordiform to CO(2) mitigation and starch production.