Orthogonal test design for optimization of lipid accumulation and lipid property in Nannochloropsis oculata for biodiesel production

In order to improve the property of Nannochloropsis oculata as biodiesel feedstock, a L9(34) orthogonal test on limited nitrogen supplementation (0, 0.22 and 0.44 mmol N L −1), high iron concentration (1.2 × 10−2, 1.2 × 10−1 and 1.2 mmol Fe L−1) and culture temperature (10, 20 and 30 °C) was conducted to select the most effective combinational measurement. Results showed that microalgae displayed the highest total lipid content (60.44 ± 0.68%), the highest neutral lipid proportion (90.74 ± 0.18%), the highest lipid yield (152.70 ± 7.40 mg L−1) and the largest cetane number (CN, 64.34 ± 0.13) under different combined conditions. There were significant interaction among nitrogen supplementation, iron concentration and culture temperature on the lipid yield and CN of N. oculata. Nitrogen supplementation, followed by iron concentration and temperature orderly, was the most influential factor in lipid yield. It is therefore suggested that the combination of 0.44 mmol N L−1, 1.2 × 10−1 mmol Fe L−1 and 20 °C was the best measurement for improving the property of N. oculata as biodiesel feedstock.