Effect of temperature and nitrogen concentration on the growth and lipid content of Nannochloropsis oculata and Chlorella vulgaris for biodiesel production

A possible source of biological material for the production of biodiesel is represented by microalgae, in particular by their lipid content. The aim of the present work was to study of the effects of temperature and nitrogen concentration on the lipid content of Nannochloropsis oculata and Chlorella vulgaris in view of their possible utilization as novel raw materials for biodiesel production. In addition, various lipid extraction methods were investigated. The extracted lipids were quantitatively and qualitatively analyzed by gravimetric and gas chromatographic methods, respectively, in order to check their suitability according to the European standards for biodiesel. The lipid content of microalgae was strongly influenced by the variation of tested parameters; indeed, an increase in temperature from 20 to 25 °C practically doubled the lipid content of N. oculata (from 7.90 to 14.92%), while an increase from 25 to 30 °C brought about a decrease of the lipid content of C. vulgaris from 14.71 to 5.90%. On the other hand, a 75% decrease of the nitrogen concentration in the medium, with respect to the optimal values for growth, increased the lipid fractions of N. oculata from 7.90 to 15.31% and of C. vulgaris from 5.90 to 16.41%, respectively.