Study on hydrothermal liquefaction for cell disruption and lipid extraction from Rhodosporidium toruloides

Abstract

Oleaginous yeast is a promising microorganism for producing lipids to replace fossil fuels. Current technology to derive lipids involves two steps: disrupting the cell wall and then extracting lipids. Cell walls are disrupted using physical, chemical, and enzymatic methods, and lipids are extracted using organic solvents. Yet, lipid extraction with current methods requires considerable energy, and such methods are complex and bad for the environment. Here, we propose a method that uses hydrothermal liquefaction (HTL) to disrupt cell walls and extract lipids from oleaginous yeast (Rhodosporidium toruloides) in a single step. We investigated the main parameters of HTL: reaction temperature, solid–liquid ratio, retention time, and solvent type. The results showed that with a temperature of 160 °C, a solid–liquid ratio of 5/100 g mL⁻¹, retention time of 60 min, and ethanol solvent, the bio-oil yield reached 62.4 ± 1.8%. Thin layer chromatography indicated that the bio-oil contained triacylglycerol, free fatty acid, diacylglycerol, and monoacylglycerol. Gas chromatography–mass spectrometry analysis of the fatty acid composition of triacylglycerol showed oleic acid, palmitic acid, stearic acid, linoleic acid, myristic acid, and palmitoleic acid. Scanning electron microscopy analysis revealed that the cells were shriveled after HTL. Taken together, our results indicate that the proposed HTL method is an efficient way to extract lipids from Rhodosporidium toruloides.