Lipid production by Chlorella vulgaris after a shift from nutrient-rich to nitrogen starvation conditions

A two-stage process, composed of growth under nutrient-rich conditions followed by cultivation under nitrogen starvation and controlled conditions of phosphate, light intensity, aeration, and carbon sources was applied for lipid production by the green alga Chlorella vulgaris. Using conditions without addition of nitrogen, 2 mg/L PO4-P, light intensity of 100 μmol/m2/s and 0.25 vvm of air, about 43% of dry cell weight accumulated as lipids after 12 h, which equates to a lipid productivity of 77.8 mg/L/d. In a medium containing 5 mg/L NO3-N and 2 mg/L PO4-P, and at a light intensity of 100 μmol/m2/s and 0.25 vvm of 2% CO2, about 53% of dry cell weight consisted of lipids after 24 h, representing a lipid productivity of 77.1 mg/L/d. The low amount of nutrients, moderate aeration and light intensity were helpful for increasing lipid productivity.