Two-step process for production of biodiesel blends from oleaginous yeast and microalgae

• Two-step process developed to generate biodiesel blends from microbial biomass.
• FAME extraction up to 82.6% for microalgae and 93.0% for yeast is achieved.
• Up to 99% of chlorophyll and 96% of carotenoids are excluded from the blends.
• B20 blend produced from yeast biomass passes key fuel requirements.
• Two-step process reduces the NER by 25% compared to traditional solvent extraction.

Biodiesel produced from oleaginous microorganisms shows promise in displacing use of petroleum diesel fuel, however, low biodiesel yields and rigorous processing have thwarted large-scale commercialization. Here, we report a simple and efficient two-step process for generating biodiesel blends from microbial biomass, which eliminates the need for solvent extractions, distillations, or additional purifications. In the present work, diesel fuel was utilized to extract biodiesel produced from direct transesterification of the yeast, Cryptococcus curvatus, and microalgae, Scenedesmus dimorphus, thus generating a blend of microbial biodiesel and diesel fuel. Up to 93% and 83% of the produced biodiesel is extracted from both yeast and microalgae, respectively, whereas the majority of pigments are excluded. A B20 blend produced from yeast meets key ASTM fuel requirements including flash point, viscosity, sulfur, oxidation stability, and acid number. Integration of experimental data into system models reveals a 25% reduction in the net energy ratio (NER) with the process presented here compared to traditional solvent extraction.