(634b) Effects of Two-Stage Semi-Continuous Culture and CO2 Aeration On Cell Growth and Lipid Accumulation of Nannochloropsis Oculata

As a result of current high oil prices, depleting fossil oil reserves and growing concerns about increased levels of atmospheric carbon dioxide, algae have emerged as one of the most promising sources for biofuel production. In this paper, Nannochloropsis oculata culture was studied aiming at the impact evaluation of operational conditions over cellular growth and lipid production associated with the CO2 sequestration on focus. Concerning about nitrogen source effect, semi-continuous two-stage strategy was applied to obtain high biomass and lipid productivity. The first N-sufficient biomass production stage was followed by a lipid accumulation stage under N-deficient condition, and harvest culture volume (40%) in three-day replacement with N-deficient medium. The microalgal special growth rate and lipid productivity was 0.87d-1 and 0.33g/L, respectively. N. oculata were cultured with 1%, 5% and 10% CO2. With 1% CO2 aeration, the highest biomass concentration was 0.84g/L. Different CO2 concentrations have an apparent effect on lipid and other organic compounds content in microalgae. To optimize the condition for long-term biomass and lipid yield, N. oculata was suggested to grow in the semi-continuous two-phase system aerated with 1% CO2 and operated by three-day replacement.