Investigations on cell disruption of oleaginous microorganisms: Hydrochloric acid digestion is an effective method for lipid extraction

Abstract

Cell disruption is an important step used to substantially increase lipid recovery prior to extraction. This is the first study exploring the effects of cell disruption methods on lipid recovery from different oleaginous microorganisms. Specifically, we examined the effects of cell disruption methods, including autoclaving, bead-beating, microwaving, sonication, acid digestion, and Soxhlet extraction on the yeast Cryptococcus curvatus, the fungus Mortierella isabellina and the microalga Chlorella sorokiniana. Although lipid recovery by cell disruption methods varied with microbial species, autoclaving and microwaving resulted in the lowest lipid contents for all tested strains. The Soxhlet method achieved the highest lipid content of 63.4% for M. isabellina and 12.8% for C. sorokiniana, followed by acid digestion. The highest lipid content of C. curvatus was achieved at 47.3% through acid digestion, compared to sonication, bead-beating and Soxhlet methods. This study suggests that acid digestion may be the most simple and effective method for lipid recovery from the tested species in terms of time and reaction temperature. Moreover, fatty acid profile analysis revealed that lipids extracted by acid digestion were similar to those from untreated microbial cells, indicating a favorable feedstock for use in biodiesel production. Practical applications: An effective cell disruption method is critical for not only enhancing the lipid recovery in a large scale but also reporting the accurate values of lipid contents of microorganisms in a lab scale. Different cell disruption methods have different effects on lipid extraction from different microorganisms. In this work, for the first time, we performed comparative investigations among yeast, fungus, and microalga to reveal the lipid recovery yields by cell disruption methods for microbial lipid extraction from different oleaginous microorganisms and identified their most effective methods for analytical lipid determination.