Our world today relies almost completely on fossil fuels, a resource which is depleting in supply, and negatively affecting our environment. For these reasons, a renewable, environmentally friendly fuel source must be found. The research presented, will explore the effects that nitrate concentrations (11.80 and 2.80 mM) will have on the cell density and lipid accumulation in the algae specie, <i>Nannochloris eucaryotum.</i> A suite of analytical techniques including: fluorescence spectroscopy, transmission electron microscopy (TEM), and gas chromatography coupled with mass spectrometry (GC/MS) will be used to qualitatively and quantitatively explore the extent of these effects on the lipid storage mechanism inside these cells. The binding nature of the fluorescent stain nile red was first explored with various lipid standards of polar (phosphoacylglycerides) and neutral (mono-, di-, and triacyclglycerides) lipids. There was an apparent blue shift in the lipid fluorescent peak when nile red bonded with phospholipids and there was a red shift starting with monoacylglycerides and steadly increasing to triacylglycerides. At early times in the algal growth cycle, it was observed with fluorescence spectroscopy that the stored lipids were primarily made up of phospholipids and associated with the phospholipid bilayer of the algal cells. As the algal cells began to become stressed, a steady migration of the nile red/lipid peak towards the triacylglycerides was observed. This effect was only more pronounced with algal cells grown under nitrogen deprivation conditions. Observing these algal cells with TEM, throughout the growth cycle, showed a direct correlation to the fluorescence data. However, these measurements do not reveal the exact chemical composition of these stored lipid bodies. To address this, GC/MS measurements revealed that the chemical makeup of these lipids includes four major fatty acids: stearic, palmitic, oleic, and linoleic acid. At earlier growth times, GC/MS revealed that the chemical makeup was primarily saturated fatty acids used in the phospholipid bilayer. At later time a more pronounced unsaturated fat chemical profile was observed for the stored lipids. This effect was observed earlier on with the nitrogen stressed algae and to a large extent. Understanding the fundamental chemistry behind increasing lipid storage in these algal systems will aid in the utilization of this renewable resource for future biofuel generation.

Effect of nitrogen medium concentration on cell growth and lipid composition of <i>Nannochloris eucaryotum</i>

256th National Meeting (2018)

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Effect of nitrogen medium concentration on cell growth and lipid composition of Nannochloris eucaryotum