Chromosome engineering of Escherichia coli for constitutive production of salvianic acid A

Abstract

BACKGROUND: Salvianic acid A (SAA), a valuable natural product from herbal plant Salvia miltiorrhiza, exhibits excellent antioxidant activities on food industries and efficacious therapeutic potential on cardiovascular diseases. Recently, production of SAA in engineered Escherichia coli was established via the artificial biosynthetic pathway of SAA on the multiple plasmids in our previous work. However, the plasmid-mediated system required to supplement expensive inducers and antibiotics during the fermentation process, restricting scale-up production of SAA. Microbial cell factory would be an attractive approach for constitutive production of SAA by chromosome engineering. RESULTS: in module 3, which then was inserted at the position between nupG and speC on the chromosome of strain BAK11. The final strain BKD13 produced 5.6 g/L of SAA by fed-batch fermentation in 60 h from glucose without any antibiotics and inducers supplemented. CONCLUSIONS: The plasmid-free and inducer-free strain for SAA production was developed by targeted integration of the constitutive expression of SAA biosynthetic genes into E. coli chromosome. Our work provides the industrial potential for constitutive production of SAA by the indel microbial cell factory and also sets an example of further producing other valuable natural and unnatural products.