Outdoor pilot-scale production of Nannochloropsis gaditana: influence of culture parameters and lipid production rates in tubular photobioreactors.

This work studied outdoor pilot scale production of Nannochloropsis gaditana in tubular photobioreactors. The growth and biomass composition of the strain were studied under different culture strategies: continuous-mode (varying nutrient supply and dilution rate) and two-stage cultures aiming lipid enhancement. Besides, parameters such as irradiance, specific nitrate input and dilution rate were used to obtain models predicting growth, lipid and fatty acids production rates. The range of optimum dilution rate was 0.31-0.351/day with maximum biomass, lipid and fatty acids productivities of 590, 110 and 66.8 mg/l day, respectively. Nitrate limitation led to an increase in lipid and fatty acids contents (from 20.5% to 38.0% and from 16.9% to 23.5%, respectively). Two-stage culture strategy provided similar fatty acids productivities (56.4 mg/l day) but the neutral lipids content was doubled.

Marine microalgae selection and culture conditions optimization for biodiesel production.

Continuous cultures of Nannochloropsis gaditana, Tetraselmis chuii, Tetraselmis suecica and Phaeodactylum tricornutum were carried out at different dilution rates and culture media in order to check their influence on biomass productivity. N. gaditana attained maximum biomass productivity of 0.49 g/lday at a dilution rate of 0.421/day. The influence of nitrate concentration on biomass productivity was tested by continuous cultures of N. gaditana. At 8.0 mM nitrate and dilution rates ranging between 0.30 and 0.401/day, maximum biomass productivities were achieved. To enhance lipid accumulation, a two-stage culture strategy consisting in a first stage of nitrate-replete conditions followed by a nitrate-depleted phase was performed. The accumulated productivity was 51 mgFATTY ACIDS/l day. Results showed an important change in the fatty acids profile and an increase in the neutral lipids content, representing 73.1% of total lipids. Additionally, the combination of nitrogen depletion and light stress was proved to contribute to lipid enhancement.