Advances in the metabolic engineering of Escherichia coli for the production of serotonin and its precursor, tryptophan

Serotonin, a monoamine neurotransmitter, participates in signal transduction in the nervous systems of organisms. It is essential in the coordination of movement and regulation of mood. As the production of serotonin via chemical synthesis and tissue extraction is limited, production by microorganisms has attracted considerable attention in recent years. Tryptophan is an essential precursor for serotonin biosynthesis; this amino acid can be converted to serotonin through hydroxylation and decarboxylation. In vivo, the tryptophan regulatory network and synthetic pathway are complex. This paper discusses existing methods of serotonin production and introduces the metabolic pathway of serotonin biosynthesis by microorganisms. Additionally, metabolic strategies for the efficient production of tryptophan in Escherichia coli are summarised. Strategies for serotonin synthesis by engineered E. coli are identified. Finally, suggestions for constructing additional efficient serotonin-producing strains are presented.