Biodiesel production from Nannochloropsis oculata cultured at stressful carbon dioxide concentration and light illumination

Abstract

Nannochloropsis oculata is a promising source of biodiesel due to the production of cellular lipid which can be converted to biodiesel through transesterification reaction. In this study, N. oculata cells were cultured under a medium light intensity and high CO₂ concentrations to improve cell growth and cellular lipid content. With an appropriate initial cell concentration, a 1.5-fold increase in cell number and a 4-fold increase in lipid content were achieved when N. oculata was cultured at a medium light intensity of 300 µEm⁻²s⁻¹ and 10-15% CO₂ compared to cells cultured at a low light intensity of 30 µEm⁻²s⁻¹ and 0.037% CO₂. The cultivation of N. oculata was further scaled up in a photobioreactor. When cultured with medium light intensity and high CO₂ concentration, N. oculata can obtain higher cell concentrations and lipid amounts. The microalgal biodiesel analyzed by gas chromatography revealed that high yield was achieved by culturing N. oculata under the combination of medium light illumination and high CO₂ concentration. When cultured in a scaled-up photobioreactor under stressful illumination and high CO₂ concentrations, N. oculata not only showed improved cell concentrations and lipid content, but also showed increased CO₂ depletion compared to cells cultured under low light and low CO₂.

Keywords:

• Nannochloropsis oculata
• photoinhibition
• CO₂ stress
• biodiesel
• lipid

Acknowledgments

The GC analysis was provided by Dr. Chan-Chiung Liu of Department of Food Science, National Pingtung University of Science and Technology, Pingtung, Taiwan.

Disclosure statement

No potential conflict of interest was reported by the authors.