Computer-aided solvent screening for the fractionation of wet microalgae biomass

Abstract

Microalgae have enormous potential as producers of fine and platform chemicals. However, sophisticated, energy-efficient separation strategies for fractionating the algal biomass are still under research and no economically viable biorefinery process exists to date. An obstacle for the feasibility of microalgal biorefineries is the energy-intense drying step. By fractionating wet algae biomass into the carbohydrate, protein, lipid, and pigment fractions, all valuable target molecules would be available for further purification and conversion while simultaneously eliminating energy expenses for biomass drying. This study presents a computational screening of more than 8000 molecules as solvent candidates for wet extraction and fractionation of microalgae using Phaeodactylum tricornutum as a model organism. In order to eliminate potentially hazardous solvents, environmental, health, and safety properties were considered. Our screening aimed at solvents being partially miscible with water in order to promote accessibility of the solvent to the target molecules contained in the algal cells and phase separation after extraction. Finally, green solvents identified by the computational approach were validated in extraction experiments. The proposed approach is a new computational method for solvent selection in biorefineries. In addition, it is the first study exploiting the water miscibility of solvents for biomass fractionation and wet extraction. 2-butanol was identified as highly effective, green solvent for the wet extraction of algae biomass and outperformed the typically used toxic solvent hexane.