Effects of green LED light and three stresses on biomass and lipid accumulation with two-phase culture of microalgae

The effects of wavelengths of light-emitting diode (LED), nitrate concentration, and salt concentration were evaluated for the two-phase culture of the microalgal species Phaeodactylum tricornutum, Dunaliella tertiolecta, and Isochrysis galbana on cell growth and lipid production. Blue LEDs produced the highest biomass of P. tricornutum at a nitrate concentration of 8 mg/L, reaching 0.97 g dcw/L with a specific growth rate (μ) of 0.047 h^?1, followed by I. galbana with 0.79 g dcw/L and μ = 0.040 h^?1 and D. tertiolecta with 0.55 g dcw/L and μ = 0.028 h^?1. Of the three microalgae, P. tricornutum had the highest specific growth rate of μ_max = 0.070 h^?1 and lowest saturation constant of K_s = 4.18 mg/L, resulting in fast cell growth. The highest lipid production was obtained under green LED wavelength stress on day 14, reaching 60.6% (w/w) of the dry cell weight among the three microalgae. The main fatty acids produced by the three microalgae were myristic acid (C14:0), palmitic acid (C16:0), oleic acid (C18:1), and arachidic acid (C20:0), which comprised 72.68%–84.16% (w/w) of the total fatty acids content under three stresses.