A novel process on lipid extraction from microalgae for biodiesel production

To promote microbial oils as the feedstock for biodiesel preparation, developing an advanced cell treatment technology, especially suitable for treating water-containing microbial feedstock is very important. A novel method based on using formic acid assisted with small amounts of hydrochloric acid, to treat water-containing microalgae and extract lipid subsequently, is proposed in this paper. Effect of several factors on mixed acid treatment of Chlorella protothecoides was investigated systematically. It was found that the dosage of formic acid and hydrochloric acid, liquid/solid (l/s) ratio and temperature had a significant influence on lipid extraction from water-containing microalgae. Under the optimum condition of formic acid dosage 5.57 g/g (based on the weight of dried microalgae cell, the same below), hydrochloric acid dosage 0.1 g/g, liquid/solid (l/s) ratio10:1 and temperature 100 °C, the total lipid yield and FAME (Fatty Acid Methyl Ester) yield reached 45.6% and 85.8% respectively. This process allowed water content of wet biomass reaching 82.1%. Further study revealed that the process was suitable for the treatment of different microalgae materials. The results indicate that this mixed acid treatment is very promising for using wet microalgae as the feedstocks for biodiesel production.