Effect of nitrogen concentration, two‐stage and prolonged cultivation on growth rate, lipid and protein content of Chlorella vulgaris

BACKGROUND The effects of the initial nitrogen concentration, as well as of two‐stage and prolonged cultivation on the growth rate, lipid and protein content of Chlorella vulgaris were examined. Additionally, a kinetic model of specific growth rate in the exponential growth phase (µ exp ) was developed as a function of initial nitrogen concentration. RESULTS As the initial nitrogen concentration in the culture medium increased, the total biomass production and µ exp went through a maximum at 300 mg N L −1 and at 200 mg N L −1 , respectively. The lipid content was found to be highly dependent on the initial nitrogen concentration and increased from 9.0% to 29.6% as the nitrogen concentration varied from 800 to 10 mg N L −1 , respectively. Cultivation in two stages resulted in an increase of the lipid content of the biomass from 15.4% to 24.9%, while prolonged cultivation led to an increase of the lipid content from 15.4% to 23.0%. CONCLUSION Cultivation under optimum nitrogen concentration can lead to increased biomass production. In addition, optimization of lipid production can be carried out by a two‐stage cultivation mode or by prolonged cultivation.