Hydrothermal treatment of oleaginous yeast for the recovery of free fatty acids for use in advanced biofuel production

• Oleaginous yeast was hydrothermally treated as pre-processing for biofuels.
• This technology avoids dewatering and facilitates fatty acid extraction.
• Yeast fatty acids were extracted from hydrolysates to be used in a patented process.
• Recovered fatty acids were free of sulfur and low in salts and nitrogen.

Microbial oils hold great potential as a suitable feedstock for the renewable production of biofuels. Specifically, the use of oleaginous yeasts offers several advantages related to cultivation and quality of lipid products. However, one of the major bottlenecks for large-scale production of yeast oils is found in the lipid extraction process. This work investigated the hydrothermal treatment of oleaginous yeast for hydrolysis and lipid extraction resulting in fatty acids used for biofuel production.The oleaginous yeast, Cryptococcus curvatus, was grown in 5 L bioreactors and the biomass slurry with 53 ± 4% lipid content (dry weight basis) was treated at 280 °C for 1 h with an initial pressure of 500 psi in batch stainless steel reactors. The hydrolysis product was separated and each of the resulting streams was further characterized. The hexane soluble fraction contained fatty acids from the hydrolysis of yeast triacylglycerides, and was low in nitrogen and minerals and could be directly integrated as feedstock into pyrolysis processing to produce biofuels.The proposed hydrothermal treatment addresses some current technological bottlenecks associated with traditional methodologies such as dewatering, oil extraction and co-product utilization. It also enhances the feasibility of using microbial biomass for production of renewable fuels and chemicals.