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International audience; The first use of microalgae by humans dates back 2000 years to the Chinese, who used Nostoe to survive during famine. However, microalgal biotechnology only really began to develop in the middle of the last century. Nowadays, there are numerous commercial applications of microalgae. For example, (i) microalgae can be used to enhance the nutritional value of food and animal feed owing to their chemical composition, (ii) they play a crucial role in aquaculture and (iii) they can be incorporated into cosmetics. Moreover, they are cultivated as a source of highly valuable molecules. For example, polyunsaturated fatty acid oils are added to infant formulas and nutritional supplements and pigments are important as natural dyes. Stable isotope biochemicals help in structural determination and metabolic studies. Future research should focus on the improvement of production systems and the genetic modification of strains. Microalgal products would in that way become even more diversified and economically competitive.

International audience; Optimization of Nannochloropsis oculata growth was undertaken using the response surface method. A central composite design was defined to study the effects of temperature, pH, incident light intensity and aeration rate on the maximum growth rate of the microalga. Using statistical analysis, the first model calculated to fit results was twice improved. The final model obtained was used to clarify the effects of each factor and their interactions on the growth of Nannochloropsis oculata. The optimum growth conditions of this microorganism were also estimated as 21 degrees C, 52 mu mol photons m(-2) s(-1), pH 8.4 and 14.7 VVH of aeration rate. These conditions were tested and validated experimentally since the maximum growth rate achieved with these parameters, 0.0359 h(-1), is the best reported in this study.