Abstract:
The demand for alternative energy has increased exponentially and algal-based biofuels are viewed as a viable alternative. This study examined the lipid producing capability of Isochrysis and the role of phosphorus depletion in stimulating lipid production. The main objective of this study was to determine the relationship between varying levels of phosphorus depletion and total lipid production in a suitable marine microalga. The ability of the microalgal strain to grow and produce lipid were examined under varying concentrations of phosphorus in the f/2 medium. Isochrysis exhibited log growth after 8 days of cultivation in the various dilutions of the phosphorus concentration recommended for f/2 medium. A stationary phase was observed when the microalgal cells depleted the surrounding medium of phosphorus. The phosphorus concentration of the various media was measured using a phosphorus colorimetric assay which revealed that the phosphorus concentration of the media progressively decreased from day 2 to day 24. However, there was no further uptake of phosphorus from the surrounding medium when the cells entered a stationary phase. The medium containing no phosphorus supplementation stimulated a lipid production of 57.75 % after 24 days which was attributed to the microalgae accumulating lipid under phosphorus deprivation. This was a result of continuous lipid synthesis combined with a low rate of cell division and photosynthesis. Therefore, allowing Isochrysis to deplete the medium of soluble reactive phosphorus resulted in increased lipid production. Furthermore, a relationship between phosphorus deprivation and lipid content was attained for sustained lipid production over time.
