Effect of nitrate depletion on lipid accumulation by the marine microalga Nannochloropsis oculata

Abstract

Nannochloropsis oculata is a marine algae with high lipid content, being a promising species for biofuel production. It is used also as food in aquaculture for larval fish and crustaceans due to its high nutritional value and compatible size with the larvae feeding. This study evaluated the lipid content in the biomass of N. oculata under nitrate depletion. The cultivation was carried out in 8 L bottles with three replications, at salinity 27, illuminance of 60 μE cm^-2 s^-1 and temperature 28°C. The levels of sodium nitrate used were 15; 30; 45; 60 and 75 mg L^-1, while maintaining constant the levels of all other nutrients of the Guillard f/2 medium. The growth curve was monitored every two days by spectrophotometry at 680 nm (DO_680nm) and cell counting in a Neubauer chamber. For separation of the culture medium from the cells, we used chemical flocculation method adding 2N NaOH. The higher lipid content in the biomass was obtained at the lowest level of nitrate in the culture medium.