Characterization of wet microalgal cells pretreated with steam for lipid extraction

Abstract

• Steam pretreatment employed to disrupt microalgal cells for lipids extraction. • Maximum curvature of cell increased from 1.88 × 10 −6 to 1.43 × 10 −7 m −1 after treatment. • Fractal dimension of microalgal cells increased from 1.25 to 1.47 after treatment. • Lipid recovery from wet microalgal cells increased 2.1-fold after treatment. Steam pretreatment was employed to disrupt microalgal cells for lipids extraction. Effects of steam pretreatment on microstructure of microalgal cells were investigated through scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Effect of treatment on lipid extraction was also studied. Microalgal cell walls were distorted after steam pretreatment due to the hydrolysis of organic macromolecules contained in cell wall. Maximum curvature was increased from 1.88 × 10 −6 m −1 to 1.43 × 10 −7 m −1 after treatment with the steam at 130 °C. The fractal dimension of microalgal cells increased from 1.25 to 1.30 after pretreatment for 15 min, and further increased to 1.47 when the pretreatment time was increased to 60 min. Increased steam pretreatment temperature and time enhanced the hydrolysis of organic macromolecules, and finally destroyed microalgal cell walls at pretreatment temperature of 130 °C and pretreatment time of 60 min. Lipid extracted from wet microalgal was significantly increased (2.1-fold) after pretreatment.