The increase in the price of fossil fuel based products, such as gasoline and diesel fuel and the ever present reality of global climate change has brought an increased interest in the use of renewable sources of energy products. While initial efforts have focused on the fermentation of sugars obtained from sugar cane or corn, the use of food based sources has proved untenable for long term production of renewable fuels. While algae based products offer many potential advantages over the food based sources of energy, significant research is still required in order to make them an economically viable option. To date, algal research has not extensively utilized the tool of high throughput screening using microplates that has been successfully employed in fields such as drug discovery.
Microplate based screening and experimentation offers the ability to measure large numbers of samples in multiple experimental conditions rapidly and simultaneously. Here we describe the quantitation of algal cell growth under various growth media conditions using a microplate reader to make absorbance and fluorescent determinations. Light scatter absorbance measurements at 600 nm were used to monitor cell growth and Nile Red stain fluorescence monitored neutral lipid production under various nutrient deficient states. Algal cells grow to a 20-fold greater density in complete nutrient rich media than in either nutrient poor or nitrogen deficient media. However, despite the marked disparity in cell number, cultures grown in nitrogen deficient media exhibit more neutral lipid staining. On a per cell basis Chlorella vulgaris cultures grown in nitrogen deficient media have 15-fold more lipid than cells grown in complete media. When nutrient deprived cells are placed in complete media, lipid droplets are quickly reabsorbed and Nile red staining returns to basal levels. The use of microplates enables the rapid measurement of multiple samples and experimental conditions at the same time.