Optimization of one-step extraction and transesterification process for biodiesel production from the marine microalga Nannochloropsis sp. KMMCC 290 cultivated in a raceway pond

Biodiesel production from microalgal biomass by a one-step direct process was investigated, and optimal conditions for this process were determined. The one-step direct process comprises the extraction of lipids from microalgae and the simultaneous transesterification of the unpurified lipids with methanol. The lipid content of Nannochloropsis sp. KMMCC 290, which was cultivated in a raceway pond, was determined to be 16.1% by pretreatment using a bead beater and conventional lipid measurement by the Bligh and Dyer method. Among the combinations of catalysts and organic extraction solvents evaluated, sulfuric acid with chloroform showed the highest lipid extraction efficiency and biodiesel conversion. Contrary to previous reports, the effect of shaking on lipid extraction and biodiesel conversion during biodiesel production was not significant. The optimal temperature and reaction time were determined to be 70°C and 90 min, respectively. Under the optimal conditions, the biodiesel conversion based on the total lipid content and the convertible lipid content was 84.2 and 96.7%, respectively. The highest biodiesel production was 155.7 mg/g-dry cell.