Oleaginous microalgae have been considered promising sources of
biodiesel due to their high
lipid content.
Nitrogen limitation/
starvation is one of the most prominent strategies to induce
lipid accumulation in microalgae. Nonetheless, despite numerous studies, the mechanism underlying this approach is not well understood. The aim of this study was to investigate the effect of
nitrogen limitation and
starvation on biochemical and morphological changes in the microalga Chlorella vulgaris FACHB-1068, thereby obtaining the optimal
nitrogen stress strategy for maximizing the
lipid productivity of microalgal biomass. The results showed that
nitrogen limitation (
nitrate concentration < 21.66 mg/L) and
starvation enhanced the
lipid content but generally decreased the biomass productivity, pigment concentration, and
protein content in algal cells. Comparatively, 3-day
nitrogen starvation was found to be a more suitable strategy to produce
lipid-rich biomass. It resulted in an increased biomass production and satisfactory
lipid content of 266 mg/L and 31.33%, respectively. Besides,
nitrogen starvation caused significant changes in cell morphology, with an increase in numbers and total size of lipid droplets and
starch granules. Under
nitrogen starvation,
saturated fatty acids (C-16:0, C-20:0, and C-18:0) accounted for the majority of the total
fatty acids (~80%), making C. vulgaris FACHB-1068 a potential feedstock for
biodiesel production. Our work may contribute to a better understanding of the biochemical and morphological changes in microalgae under
nitrogen stress. Besides, our work may provide valuable information on increasing the
lipid productivity of oleaginous microalgae by regulating
nitrogen supply.