Effect of initial biomass-specific photon supply rate on fatty acid accumulation in nitrogen depleted Nannochloropsis gaditana under simulated outdoor light conditions

Triacylglycerol (TAG) accumulation in the microalgae Nannochloropsis gaditana is induced by nitrogen starvation and dependent on the light supplied. We studied under simulated outdoor light conditions the effect of supplied light on the TAG yield by varying the biomass-specific photon supply rate present at the onset of nitrogen starvation. High, intermediate and low average biomass-specific photon supply rates (26, 11 and 6 mu mol g(-1) s(-1)) were achieved by applying equal incident light intensity to different biomass concentrations (1.2, 2.9 and 5.4 g L-1). The intermediate biomass-specific photon supply rate resulted in the highest time-averaged TAG yield on light; 0.09 g(TAG)mol(ph)(-1). Sub-optimal yields were attributed to photosaturation, photoinhibition, light falling through reactor without being absorbed and high maintenance requirements. The biomass-specific photon supply rate is important to optimize TAG production by microalgae.