(62a) Optimization of a Louisiana Native Algal Co-Culture for Biofuel Production

Microalgae have been reported to possess significantly higher lipid productivity per unit area than traditional oil crops, a benefit for biofuel production.  Microalgal strains such as Nannochloropsis sp., Botryococcus braunii, and Chlorella vulgaris have been reported to contain high lipid/oil content. However, these results are mostly at the lab scale. In large-scale, commercial culture systems, tolerance to local environmental conditions and invasive algal species significantly affect lipid/oil production. Therefore, native microalgal strains with high lipid productivity are likely better options for large-scale biofuel production.

A native fresh water microalgae strain from Louisiana was investigated. This work measures the impacts of irradiance and nitrate levels on total lipid yield and the fatty acid profile of this strain. The culture was harvested in the late exponential-stationary phase to maximize the lipid content, and Soxhlet extraction with chloroform/ methanol (2:1, v/v) was used for total lipid content evaluation. Microwaves and nanoparticle assisted Folch’s extraction methods have been used to optimize lipid extraction. The fatty acid profiles of neutral lipids were analyzed by gas chromatography combined with mass spectrometry.

The results indicated the lipid yield and content at 400 and 800 mmol m^-2s^-1 was the highest and no significant differences (32.13 and 32.76 mg L^-1d^-1, 31% and 30%) between the two treatment levels were observed.Results also indicate that although the lower nitrate level increased lipid content, the increase did not compensate for a decrease in growth rate. The fatty acid profiles indicate the major components are 16- and 18-carbon fatty acids, and ~35% are saturated fatty acids. The fatty acid profiles do not vary significantly with the irradiance and nitrate levels.