Effect of CO2 Concentration on Growth, CO2 Fixation, and Biochemical Composition of the Microalga Nannochloropsis oculata

Abstract

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 specifications 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.