Enhancement of biomass, lipids, and polyunsaturated fatty acid (PUFA) production in Nannochloropsis oceanica with a combination of single wavelength light emitting diodes (LEDs) and low temperature in a three-phase culture system

•N. oceanica was cultured in 14-L photobioreactors using a three-phase culture system.•Maximum biomass was produced with 24 h blue LED light at an intensity of 250 µmol m−2 s−1.•Maximum lipid content was obtained with 24 h green LED light at an intensity of 250 µmol m−2 s−1.•SFAs were changed to MUFAs and PUFAs at low temperatures (15, 10, and 5 °C).•The highest PUFA content was obtained at a culture temperature of 5 °C. A three-phase culture system combining blue (465 nm) light-emitting diode (LED) wavelength as the first phase, green (550 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 0.75 gdcw L−1 and 57.6% (w/w) were obtained at an aeration rate of 0.50 vvm, with a light intensity of 250 µmol m−2 s−1 and 24:0 h 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.