Effect of light intensity and nitrogen starvation on CO2 fixation and lipid/carbohydrate production of an indigenous microalga Scenedesmus obliquus CNW-N

Engineering strategies were applied to improve the CO2 fixation rate and carbohydrate/lipid production of a Scenedesmus obliquus CNW-N isolate. The light intensity that promotes cell growth, carbohydrate/lipid productivity, and CO2 fixation efficiency was identified. Nitrogen starvation was also employed to trigger the accumulation of lipid and carbohydrate. The highest productivity of biomass, lipid, and carbohydrate was 840.57 mg L−1 d−1, 140.35 mg L−1 d−1. The highest lipid and carbohydrate content was 22.4% (5-day N-starvation) and 46.65% (1-day N-starvation), respectively. The optimal CO2 consumption rate was 1420.6 mg L−1 d−1. This performance is better than that reported in most other studies. Under nitrogen starvation, the microalgal lipid was mainly composed of C16/C18 fatty acid (around 90%), which is suitable for biodiesel synthesis. The carbohydrate present in the biomass was mainly glucose, accounting for 77–80% of total carbohydrates. This carbohydrate composition is also suitable for fermentative biofuels production (e.g., bioethanol and biobutanol).

► Scenedesmus obliquus CNW-N is a good candidate for CO2 fixation and biofuels production.
► A light intensity of 420 μmol m−2 s−1 favors CO2 fixation and lipid/sugar production.
► Carbohydrate/lipid production was enhanced by nitrogen starvation strategies.
► Accumulation of lipid/carbohydrate can be adjusted by the nitrogen starvation time.