Effects of temperature on the growth and eicosapentaenoic acid production of Nannochloropsis oceanica (Eustigmatophyceae)
Nannochloropsis oceanica has been recognized as a valuable source of eicosapentaenoic acid (EPA) for nutraceutical applications. In this study, the effects of temperature on the growth and fatty acid production of N. oceanica were investigated to determine the optimal conditions for maximizing both growth and EPA production. The growth responses of N. oceanica exhibited a wide temperature range of 5-30°C, with the maximum cell density at 25°C (35.9×105 cells mL-1). Biomass production, as measured by dry weight in N. oceanica culture, was the highest at 20°C (86.2 mg L-1). In N. oceanica cultures exposed to relatively low temperatures (5-10°C), cells did not grow significantly; however, the proportion of polyunsaturated fatty acids including EPA (22.3, 26.0% of total fatty acid), was significantly high. These results indicate that the optimal temperature conditions for promoting growth and EPA accumulation of N. oceanica are different. Based on these results, a temperature-dependent two-stage cultivation strategy was proposed to optimize both biomass and EPA production in N. oceanica cultures, which included an initial phase at 20°C to achieve high biomass, followed by a second phase at 5-10°C to maximize EPA accumulation.