The effect of pretreating the microalga C. sorokiniana (Fig. 3) was similar to that of N. gaditana (Fig. 2). A higher lipid content was extracted when using a cell disruption method rather than not pretreating the sample. Among the compared methods, the steam explosion treatment showed the highest efficiency, with 18.4% lipid extraction, while the efficiencies of ultrasound, microwave and autoclaving were comparable and just above 14%.