(674b) 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.