Abstract: Biosynthesis of a desired macromolecule includes inserting a promoter that encodes for an endogenously produced inducible macromolecule in a Chlorella cell into a DNA vector to form a first recombinant DNA vector. A cDNA sequence that encodes for the desired macromolecule is inserted into the first recombinant DNA vector to form a second recombinant DNA vector, which is then incorporated into the microalgae cell genome to form a transformed microalgae cell. Transcription and translation of the cDNA sequence are induced in the transformed microalgae cell to biosynthesize the desired macromolecule. Control of the method is achieved with the use of a mechanism effective in repressing an expression of the endogenously produced inducible macromolecule. Then, when desired, expression of the cDNA sequence may be induced by removing the repressing agent, thereby inducing a biosynthesis of the desired macromolecule.