Steven Baldassano, 2011, Chemical Engineering

Diatoms, a class of eukaryotic plankton, are under investigation as possible producers of lipid precursors to be used in biofuel production. Environmental stresses have been shown to alter the carbon composition of diatoms, often resulting in increased usable lipid (TGA) content. There were two aims of this experiment. The first was to determine the effect of nitrogen deprivation on the carbon budget and distribution of the diatom Phaeodactylum tricornutum. The second was to determine whether increases in specific carbon pools were due to a rearrangement of preexisting carbon in the cells or uptake of new carbon from the surroundings. Cells were grown into exponential phase in normal media, and then transferred to sealed containers without access to environmental carbon. The only carbon source from this point is labeled C13 bicarbonate. Also, half of the cells were placed in nitrogen deficient media. After several days, the lipid, protein, and carbohydrate content of the samples was measured. Nitrogen deprivation increased lipid and storage carbohydrate pools, while decreasing protein. Nitrogen deficient cells showed altered physical characteristics, becoming much larger and ovoid. Ongoing mass spectroscopy is being used to determine the fraction of labeled carbon in each pool. This measurement will indicate whether lipid and carbohydrate increase is due to de novo synthesis with new carbon uptake or rearrangement of preexisting carbon stores.