Modular optimization of synthetic pathway for improving 3-dehydroshikimate production in Escherichia coli

3-dehydroshikimate (DHS) is a key metabolic intermediate for aromatic compound production. It could be a potent antioxidant and important feedstock for producing a variety of important industrial chemicals, such as muconate and adipate with great commercial value. In the previous study, Escherichia coli was always engineered to produce DHS by deleting aroE and overexpressing several key genes via plasmid under the control of inducible promoters. This would result in the genetically instability of the engineered E coli and the additional supplement of minor shikimate or aromatic amino acids in the fermentation medium for cell growth, thus affect the future industrial production of DHS. Hence, it is greatly necessary to construct the genetically stable strain as well as adaptable to simple synthetic media with any supplementation for higher and efficient production of DHS. Here, in this study, the synthetic regulatory parts with different strength were used for combinatorially regulating the different modules of DHS synthetic pathway for facilitating glucose transport, enhancing and balancing the supply of precursors, and blocking the degradation of DHS. These modifications further increased the production of DHS in the simple mineral salt media without supplementing shikimate or aromatic acids by about 40 fold. The metabolically engineered strain produced DHS in 7-L fed-batch fermentation with more than 50% yield (mol/mol) from D-glucose, which is the highest reported yield so far for DHS production form glucose. Our study implicated modular optimization would be very useful for engineering microorganisms for higher and efficient production of biobased chemicals.