BACKGROUNDThe 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 (mu(exp)) was developed as a function of initial nitrogen concentration. RESULTSAs the initial nitrogen concentration in the culture medium increased, the total biomass production and mu(exp) went through a maximum at 300mgNL(-1) and at 200mgNL(-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 10mgNL(-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%. CONCLUSIONCultivation 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. (c) 2018 Society of Chemical Industry