Abstract: The present application relates to an expression system for multigene overexpression in microalgae, which expression system comprises at least two nucleic acid expression cassettes, wherein each expression cassette comprises a promoter operably linked to three or more transgenes connected to one another by at least one sequence encoding a 2A peptide (i.e. a multicistronic construct). Also disclosed herein are vector systems comprising said expression systems, host cells transformed with said expression systems or comprising said vector systems, methods for producing these host cells, as well as their use for biosynthesis.