Consideration for the use of microalgae as a feedstock for commercial biofuels production began in the 1970s. While high production costs and inefficiencies impeded private industry scale up to meet national energy needs, recent energy supply concerns and market instability has revitalized this alternative energy process. A key factor in using microalgae comes from efficiently harvesting algae oils which are chemically similar to fossil fuel oils. Technological advances have been made to genetically engineer microalgae to accumulate oils but these procedures are time consuming and expensive. Others have made progress in using natural processes in the environment to cause algae to produce oils. Considerable research has shown determining the appropriate mix of light, temperature and CO2 can foster oil accumulation in select microalgae strains. Using an experimental design, the freshwater algae, Chlorella pyrenoidosa and Ettlia sp. were subjected to various environmental conditions to investigate effects on oil production. When exposed to a higher irradiance level (400 μE), C. pyrenoidosa achieved a significantly higher cell count leading to an increase in lipid productivity. Under media manipulation effects, the cell count for nitrogen-limited cultures was significantly lower than that of cultures grown on replete medium. Nitrogen limitation seems to negatively impact lipid productivity under our experimental conditions. Supplementation with 2 % CO2, led to an increase in growth after seven days of incubation; however, growth decreased subsequently to a slower rate as compared to growth with air sparging after 12 days of incubation. There appeared to be a degree of variability with regards to lipid ratios, with increases in neutral lipids in cultures exposed to higher levels of irradiance, nitrogen limitation and additional CO2. Although analysis showed that environmental manipulation is feasible in terms of oil accumulation for these select strains, further study is warranted in investigating other oil-accumulating microalgae strains for commercial production.
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Vol. 84 • No. 1