Effects of wavelength mixing ratio and photoperiod on microalgal biomass and lipid production in a two-phase culture system using LED illumination

Abstract Blue and red light-emitting diodes (LEDs) were used to study the effects of wavelength mixing ratios, photoperiod regimes, and green wavelength stress on Nannochloropsis salina , Isochrysis galbana , and Phaeodactylum tricornutum cell biomass and lipid production. The maximum specific growth rates of I . galbana and P . tricornutum were obtained under a 50:50 mixing ratio of blue and red wavelength LEDs; that of N . salina was obtained under red LED. Maximum cell biomass for N . salina and P . tricornutum was 0.75 and 1.07 g dcw/L, respectively, obtained under a 24:0 h light/dark cycle. However, the maximum I . galbana biomass was 0.89 g dcw/L under an 18:6 h light/dark cycle. The maximum lipid contents for N . salina, I . galbana , and P . tricornutum were 49.4, 63.3 and 62.0% (w/w), respectively, after exposure to green LED. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were obtained 1% in P . tricornutum and 2% in I . galbana .