Enhancing Starch and Lipid Content of Microalgae using a Two-Stage Cultivation Strategy: Effect of Dilution and Nitrogen Limitation

فاقد چكيده فارسي

Microalgae containing several intracellular materials such as starch, lipid, chlorophyll, carotenoid and protein play an important role in production of biofuels, pharmaceuticals and antioxidants. However, biofuel production from microalgae is not yet cost-effective as compared to fossil fuels. To make this process profitable, attempts have been made to increase starch and lipid contents of microalgae. In the present work, a two-stage cultivation strategy was used to grow microalgae where in the first stage cells were cultivated until mid-log phase. Cell dilution was then carried out to reduce self-shading by high cell levels. In the second stage, diluted cells were separately cultivated using both nitrate-containing and nitrate-free media. Considering the cessation of cell growth in nitrogen limitation due to the lack of cellular DNA synthesis, microalgae cells were forced to store valuable intracellular materials such as starch and lipid. The results show that the starch and lipid content has significantly increased because of nitrogen limitation, with dry cell weights of 49.371% and 42.046% for starch and lipid, respectively