Nutrient starvation-induced oxidative stress-mediated lipid accumulation in Tetradesmus obliquus KMC24

A two-stage cultivation approach was employed to investigate the effect of nitrogen and/or phosphorus starvation on the morphology, biomass yield, photosynthetic activity, biochemical, and fatty acid composition of Tetradesmus obliquus KMC24. A two-day nitrogen-starved cells (-N2) were able to accumulate the maximum amount of lipid (39.93 ± 0.44%) without affecting the biomass yield (2.15 ± 0.04 g L−1). During nitrogen (-N) and phosphorus (-P) starvation, photosynthetically fixed carbon pool was diverted to lipid biosynthesis. Pearson’s correlation analysis suggested that stress-induced lipid accumulation is associated with an increased intracellular reactive oxygen species (ROS) level. The ROS fluorescence intensity was highest in -N2 cultures (17,051.49 ± 93.15 a.u.), suggesting highly oxidative stress-tolerant cells. A high degree of fatty acid saturation was obtained under nitrogen starvation as compared to other culture conditions. Biodiesel properties such as cetane number, saponification number, and iodine value improved under nitrogen starvation.