Outdoor pilot production of Nannochloropsis gaditana: Influence of culture parameters and lipid production rates in flat-panel photobioreactors

This work is the last of a series of three papers. The previous ones were performed in tubular photobioreactors and raceways. In the present work, the outdoor continuous production of Nannochloropsis gaditana in flat-panel reactors is studied over a two-year period, analysing the influence of the dilution rate imposed in addition to the nitrate and phosphate supplied. Maximum biomass and lipid yields of 0.19 g/l day and 38.0 mg/l day were obtained when operating at a dilution rate of 0.35 1/day and concentrations of 10.0 mM NO3− and 0.8 mM PO43 − in the culture medium. By decreasing the specific nitrate input (below 2 mmol N/g day), and exposing the culture to moderate light availability and temperature, the volumetric productivity of saturated and monounsaturated fatty acids increased to 10.0 mg/l day. The specific nitrate input, together with other important parameters such as the average irradiance, temperature and dilution rate were used to develop a model describing this species' behaviour. The model is a powerful tool for further improvement and scaling-up of this technology.