<br/>The nutrient dense waters of agriculture and storm drain basins allow for many species of microalgae to flourish. This relationship can be utilized to grow specific algal strains for research and bypass the need to create a growth media. In this study, four algal strains known for their high lipid accumulation Chlorella sorokiniana (CS), Chlorella vulgaris (CV), Neochloris oleoabundans (NO), and Scenedesmus dimorphus (SD) were grown in water collected from surface recharging basins. The accumulation of lipids in the algal cells were monitored during the growth period and later extracted following its characterization. These lipids have the potential to serve as alternative sources of biodiesel, as algae is known to harbor lipids at higher concentrations than traditional-plant based biodiesel crops.<br/>Algal cultures were stained with the lipophilic dye BODIPY (505/515) to quantitatively and qualitatively measure the lipid accumulation over the 8-day growth period. Qualitative analysis was performed using fluorescence microscopy to take snapshots of the fluorescing cells every other day. A visual observation of brighter fluorescent cells on the last day translated to peak lipid accumulation. Quantitative lipid analysis was performed using an Attune NxT Flow cytometer. A set of stained and unstained cells were analyzed to account for autofluorescence. The fluorescence intensity of the stained cells were compared against those of unstained cells every other day. Algal lipids were also chemically extracted and analyzed using thin-layer chromatography (TLC) and gas chromatography-mass spectrometry (GC-MS). The neutral fatty acids were converted to the fatty-acid methyl esters (FAME) technique and analyzed using GC-MS. Total lipids extracted were analyzed by the TLC method. <br/>Lipid yields ranged between 10-20% in comparison with total wet culture, and the presence of polar and lipids nonpolar lipids, beta-carotene, tri-, di-, and monoglycerides were noted in the extracted oil. Flow cytometry analysis and fluorescence microscopy showed the highest lipid accumulation on the 8th day of the growth period as noted from fluorescence intensity of BODIPY stained cells compared to non-stained cells.

Tracking lipid accumulation and quantitation of microalgae grown in surface recharging basin water

ACS Spring 2022

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