Flash hydrolysis of microalgae (Scenedesmus sp.) for protein extraction and production of biofuels intermediates

Abstract The present study on flash hydrolysis under subcritical water medium capitalizes on the difference in reaction kinetics of algae polymeric components and fractionates proteins in liquid phase in seconds of residence time. All the experiments were conducted using flocculated Scenedesmus sp. cultivated in the laboratory using photobioreactors. The effect of temperature and residence time on protein hydrolysis to water-soluble fractions (algal hydrolyzate) and yield of lipid-rich solids (biofuels intermediate) was studied using a lab-scale continuous flow reactor. More than 60 wt% of the total nitrogen content (dry basis) in Scenedesmus sp. was extracted within 10 s of residence time above 240 C. The ion chromatography and NMR spectra of the algal hydrolyzate showed that the extracted proteins were present both as free amino acids and peptides. The carbon content of biofuels intermediate increased up to 66 wt% making it lipid- and energy-dense feedstock suitable for biofuels production. The scanning electron microscope image of biofuels intermediate indicated that the solids were globular and smaller in size as compared to the untreated microalgae.