Integrating Fermentation of Chlamydomonas Mexicana by Oleaginous Lipomyces Starkeyi and Switchable Ionic Liquid Extraction for Enhanced Biodiesel Production

Abstract

The biodiesel production from microalgal biomass is an attractive, ecofriendly, and sustainable process. However, the limited lipid content in microalgal cells (7 to 65% of cell mass), and requirement of expensive downstream process for bioconsituents’ extraction is a bottleneck in this technology. The fermentation of microalgal biomass using oleaginous yeast would be a holistic approach as it can increase ultimate lipid yield by utilizing other constituents (carbohydrates and proteins) of microalgae during fermentation. Nevertheless, the rigid cell wall structures of microalgae and yeast interfere with the extraction. This study is an attempt to develope an integrated process to enhance the production and extraction of lipids through oleaginous yeast fermentation of microalgal biomass and utilize permeable and switchable ionic liquid (IL) for lipid extraction to achieve economic efficiency of biorefinery. The oleaginous yeast L. starkeyi effectively utilized the carbohydrates (92%) and proteins (91%) of C. mexicana and produced excessive lipids (163%) in comparison to the original microalgal lipid (12.6 g/L), and yielded 2.2 times higher biodiesel than the conventional process. The IL extraction required a shorter process time (1.5 h) and had better efficiency (99%) than the conventional lipid extraction method (8 h, 87%). The IL was recovered and recycled for >5 times, while maintaining an efficiency of >80% after five cycles. The outcomes of this study provides a economic and sustainable model to overcome the existing limitations of biodiesel production from microalgal biomass.

Keywords: ionic liquid, biodiesel, Microalgal biomass, Oleaginous yeast, fermentation