Chiang Mai Journal of Science

     The green marine microalga Nannochloropsis oculata is rich in biochemicals and well known as a suitable source for dietary supplements and biodiesel feedstock. This study investigated the effects of CO₂ supplementation on N. oculata in terms of its biomass, biochemical composition, CO₂ fixation, and biodiesel qualities. Microalgae were cultivated in f/2 medium supplied with CO₂ at 0.04-6%. The culture supplemented with 6% CO₂ produced the highest biomass (1.64±0.04 g L⁻¹) and contents of carotenoids (0.93±0.00 μg g⁻¹), lipids (47.68± 2.80%), eicosapentaenoic acid (EPA; 28.45 mg g⁻¹ biomass), and docosahexaenoic acid (DHA; 22.43 mg g⁻¹ biomass); it also demonstrated the highest CO₂ fixation rate (74.62±2.55 kg m⁻³y⁻¹) and provided an algal oil with desirable biodiesel qualities, specifically high cetane (52.27-53.50) and low iodine (75.91-82.15 g I₂ 100 g⁻¹) values meeting the biodiesel specifi cations established by standards in the US (ASTM D6751) and Europe (EN 14214). In sum, CO₂ supplementation during N. oculata cultivation enhanced its production of high-value biomolecules, making this algal species a good source for production of dietary supplements and biodiesel.