Maximizing Productivity in Batch Reactors of Microalgae Nannochloropsis Gaditana

Biodiesel from algae is receiving more attention. Just recently, the United States Department of Energy (DOE) announced to fund around $85 million in the development of algae-based biofuels and advanced infrastructure-compatible biofuels. Compared to other terrestrial crops, such as soybean, sunflower, canola, palm, jatropha and others, algae has many advantages. It has high oil productivity, a short growth cycle and survives in a wide variety of water sources including high salinity and waste water.

Nutrients, salinity, pH, temperature, light intensity and aging of the culture can all affect on both lipid content and fatty acid profile. Usually nutrient stress is the easiest way to manipulate lipid composition and increase lipid content. In our research, microalgae Nannochloropsis Gaditana has been shown to have high lipid content (more than 40%) and quick growth rate (around 0.018hr^-1).  Current work focuses on how the harvest time and nitrogen sources affect on the lipid content and composition.

The cell growth, sodium nitrate concentration, and lipid content and profile are monitored as a function of time. Decreasing nitrogen concentration does stimulate lipid content increase with sacrificing growth rate. In contrast, increasing nitrogen concentration does not increase lipid content. Maximum lipid content is obtained in mid-exponential phase and is relatively constant from this point through stationary phase. Major lipid compounds are palmitic acid (16:0) and palmitoleic acid (16:1), and lipid profile does change significantly with time.