Metabolic engineering of Escherichia coli for production of salvianic acid A via an artificial biosynthetic pathway

Salvianic acid A, a valuable derivative from L-tyrosine biosynthetic pathway of the herbal plant Salvia miltiorrhiza, is well known for its antioxidant activities and efficacious therapeutic potential on cardiovascular diseases. Salvianic acid A was traditionally isolated from plant root or synthesized by chemical methods, both of which had low efficiency. Herein, we developed an unprecedented artificial biosynthetic pathway of salvianic acid A in E. coli, enabling its production from glucose directly. In this pathway, 4-hydroxyphenylpyruvate was converted to salvianic acid A via D-lactate dehydrogenase (encoding by d-ldh from Lactobacillus pentosus) and hydroxylase complex (encoding by hpaBC from E. coli). Furthermore, we optimized the pathway by a modular engineering approach and deleting genes involved in the regulatory and competing pathways. The metabolically engineered E. coli strain achieved high productivity of salvianic acid A (7.1 g/L) with a yield of 0.47 mol/mol glucose.