Etude de la croissance et de la composition biochimique de deux souches microalgale marine «Nannochloropsis gaditana» (Hibbred, 1998) et «Nannochloris sp.» (Naumann ,1921).

Abstract

Microalgae are currently generating a lot of enthusiasm and many start-ups are investing in this niche. In addition, much applied research is devoted to microalgae for the production of lipids to produce renewable energy (biofuels). The exploitation of microalgae also leads to the production of pigments; these pigments may have applications in certain medical, cosmetic and environmental fields. Nevertheless, there are still issues to be resolved, through upstream research, before expected yields and costs are actually achieved and these technologies cannot be realized on a large scale. The objective of our work was to study the evolution of the growth of the species Nannochropsis gaditana and Nannochloris sp., and their reaction in the culture medium Guillard f/2. The growth monitoring was carried out daily by measuring the optical density by a spectrophotometer and a count of the cells was made using the Malassez cell for the determination of the cell concentration. The growth parameters (concentration of initial and maximum biomass as well as the specific growth rate) and the volume productivity of the biomass were determined. For the study of the biochemical composition of the two species, chlorophyll «a» rate, Carotenoiid level and lipid content were measured. Our results show that Nannochloris sp. has a concentration of biomass (1956.69mg MES/L) and a specific growth rate (0.008 J-1) greater than that of Nannochloropsis gaditana (1644.97mgMES/L and 0.009 J-1, respectively). With regard to the production of metabolites; the lipid, chlorophyll a and carotenoid content, N.gaditana has a better production (45%, 21μg/m³, and 0,030μg/ml,respectively). In view of our results, we can conclude that the species richest in lipid, chlorophyll «a» and Carotenoiid is Nannochloropsis gaditana. However, the monitoring of growth parameters in Nannochloris sp. was better. The latter is quickly adapted to the environment and the experimental conditions.