Lipid and unsaturated fatty acid productions from three microalgae using nitrate and light-emitting diodes with complementary LED wavelength in a two-phase culture system.

In this study, Pavlova lutheri, Chlorella vulgaris, and Porphyridium cruentum were cultured using modified F/2 media in a 1 L flask culture. Various nitrate concentrations were tested to determine an optimal nitrate concentration for algal growth. Subsequently, the effect of light emitted at a specific wavelength on biomass and lipid production by three microalgae was evaluated using various wavelengths of light-emitting diodes (LED). Biomass production by P. lutheri, C. vulgaris, and P. cruentum were the highest with blue, red, and green LED wavelength with 1.09 g dcw/L, 1.23 g dcw/L, and 1.28 g dcw/L on day 14, respectively. Biomass production was highest at the complementary LED wavelength to the color of microalgae. Lipid production by P. lutheri, C. vulgaris, and P. cruentum were the highest with yellow, green, and red LEDs' wavelength, respectively. Eicosapentaenoic acid production by P. lutheri, C. vulgaris, and P. cruentum was 10.35%, 10.14%, and 14.61%, and those of docosahexaenoic acid were 6.09%, 8.95%, and 11.29%, respectively.

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.

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.