CONICET | Buscador de Institutos y Recursos Humanos

The large-scale culture of microalgae has become a focus of interest for the biorefinery industry, combining the production ofbiofuels with that of other value-added bioproducts and thus increasing the profitability of the process. In order to evaluate itspotential as biodiesel feedstock under a biorefinery approach, the biomass, pigment, nutrient, total lipid and lipid fraction kineticsof the Argentinian Nannochloropsis oceanica CCALA 978 strain were analysed. The species was first cultivated under optimalconditions (f/2 medium) and then transferred to nutritional stress conditions (N-deprivation or P-deprivation media). Undercomplete f/2 medium, N. oceanica presented maximum growth rate (μ) and chlorophyll-a values and minimum values for lipidand carotenoid content. The high nutrient consumption rate (N or P) in this exponential phase was associated with increasing celldensity. Under both nitrate and phosphate deprivation, μ was drastically reduced but biomass production reached its highestvalues, indicating a phase of metabolite accumulation. Maximum values of total lipids (ca. 39% dw) and carotenoids (1100 ×10−3 ± 15 μg mL−1) were obtained under nitrate deprivation. In addition, total lipid composition was characterized by 92%neutral lipids, 0.7% phospholipids, a high percentage of C16:1 (ca. 37%of total fatty acids) and minimum values of PUFA (5.9%of total fatty acids). Biodiesel properties inferred from the fatty acid methyl ester profile of neutral lipids meet the standardsestablished by EN 14214 and ASTMD 6751-08. Although N and P deficiency both produced an increase in neutral lipids in thestudied strain, under a biorefinery approach, nitrate deprivation is considered to be a better method of stress induction thanphosphate deprivation for the purpose of co-producing neutral lipids for biodiesel and value-added pigments.