High-density fermentation of microalga Chlorella protothecoides in bioreactor for microbio-diesel production

Applied Microbiology and Biotechnology
Volume 78, Number 1 / February, 2008 p:29-36

Wei Xiong, Xiufeng Li, Jinyi Xiang and Qingyu Wu1

Abstract
Agal-fermentation-based microbio-diesel production was realized through high-cell-density fermentation of Chlorella protothecoides and efficient transesterification process. Cell density achieved was 16.8 g l−1 in 184 h and 51.2 g l−1 in 167 h in a 5-l bioreactor by performing preliminary and improved fed-batch culture strategy, respectively. The lipid content was 57.8, 55.2, and 50.3% of cell dry weight from batch, primary, and improved fed-batch culture in 5-l bioreactor. Transesterification was catalyzed by immobilized lipase, and the conversion rate reached up to 98%. The properties of biodiesel from Chlorella were comparable to conventional diesel fuel and comply with US standard for Biodiesel. In a word, the approach including high-density fermentation of Chlorella and enzymatic transesterification process were set up and proved to be a promising alternative for biodiesel production.

Keywords
Agal-fermentation-based microbio-diesel (AFMD) - Chlorella protothecoides - Fed-batch - High-density fermentation - Immobilized lipase