Physicochemical characterization of wet microalgal cells disrupted with instant catapult steam explosion for lipid extraction

•Wet microalgal cells were disrupted through instant catapult steam explosion (ICSE).•Fractal dimension of exploded cells increased with the prolonged preheat time.•Mean size of exploded cells decreased with the reduced filling ratio of microalgae.•ICSE decreased carbohydrate content and increased lipid content in exploded biomass.

Instant catapult steam explosion (ICSE) was employed to disrupt wet microalgal cells for efficient lipid extraction. Physicochemical properties of exploded cells were investigated through SEM, TEM, FTIR, and TGA. The exploded cells increased in fractal dimension (1.53–1.65) when preheat time was prolonged from 0 min to 5 min and in surface pore area when steam pressure was increased. Meanwhile, the exploded cells decreased in mean size (1.69–1.44 μm) when the filling ratio of wet microalgal biomass in the preheat chamber decreased (75–12.5%). Flash evaporation and volume expansion exploded the cell walls and released the cytoplasm of the microalgal cells. These phenomena decreased the carbohydrate content and increased the lipid content in the exploded biomass. However, ICSE treatment did not change the lipid compositions in the microalgal cells. Using isopropanol as a cosolvent significantly increased the yield of lipids extracted with hexane from the exploded wet microalgal biomass.

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