Résumé:
Microalgae are arousing growing interest today, as the applications that converge
around these cells are numerous. From energy production, to human and animal nutrition,
through the treatment of anthropogenic waste, researchers and industrialists are investing in
these vast fields of application. Today there are a multitude of scientific and technological
barriers that deserve to be lifted.
The aim of this work was to assess the influence of two-step culture on biomass and
lipid productivity in the strain of microalgae Nannochloropsis gaditana. The first step was to
promote maximum biomass productivity via culture in a Guillard f / 2 culture medium. The
second is to allow maximum lipid accumulation through stress caused by phosphate and
nitrogen deficiency.
Growth was monitored by measuring the optical density with a spectrophotometer and
by counting the cells using the Malassez cell. Assays of the level of chlorophyll "a" and of the
lipid content were carried out.
In view of our results, it can be concluded that nitrogen and phosphate deficiency
conditions are indeed effective in stimulating lipid production. A compromise must therefore
be found between growth and richness in lipids.
Further studies will allow these levels to be optimized. Thus, in a first approach, the
culture of microalgae could be split into two phases: a phase of rapid growth in a favorable
rich medium and a phase of storage of lipids after a deficiency in phosphate and nitrogen.
