ABSTRACT
A three-phase culture system combining blue (465â¯nm) light-emitting diode (LED) wavelength as the first phase, green (550â¯nm) as the second phase, and temperature stress as the third phase was applied to a Nannochloropsis oceanica culture in 14-L photobioreactors. Microalgal growth promotion parameters were optimized in the first phase, followed by green LED stress for lipid production in the second phase. Maximum biomass and lipid production values of 0.75â¯gdcwâ¯L-1 and 57.6% (w/w) were obtained at an aeration rate of 0.50â¯vvm, with a light intensity of 250⯵molâ¯m-2â¯s-1 and 24:0â¯hâ¯light/dark cycle. Culture temperatures of 15, 10 and 5⯰C were applied in the third phase, where temperature stress induced the production of monounsaturated and polyunsaturated fatty acid synthesis in N. oceanica. The production of α-linolenic acid, eicosapentaenoic acid and docosahexaenoic acid increased by 52% (w/w), 96% (w/w), and 77% (w/w), respectively, at 5⯰C in the third phase.