Green and aromatic future: Expanding the biosynthetic repertoire of aromatic chemicals via shikimate pathway

The aromatic chemicals are a large number of industrially important products with a range of industrial applications as organic solvents, dyes, and precursors for the synthesis of numerous products employed in the food, pharmaceutical, and chemical industries. Recently, an increasing array of aromatic chemicals were produced via many microbes directly from renewable, biomass-derived feedstocks. In this study, we engineered and expanded shikimate pathway in Escherichia coli for efficient production of about ten aromatic chemicals. Firstly, the synthetic regulatory parts with different strength were used for combinatorially regulating the different modules of 3-dehydroshikimate (DHS) synthetic pathway for facilitating glucose transport, enhancing and balancing the supply of precursors, and blocking the degradation of DHS. These modifications enabled the production of DHS in the simple mineral salt media without supplementing shikimate or aromatic acids. The metabolically engineered strain produced about 50g/L DHS in 7-L fed-batch fermentation with 23% yield (mol/mol) from D-glucose. With the strain for DHS production as the chassis cell, other nine aromatic chemicals, including 3-dehydroquinate, quinate, shikimate, protocatechuate, protocatechuic aldehyde, protocatechuic alcohol, catechol, vanillate, vanillyl alcohol and vanillin were then produced with different titer and yield by intercepting, guiding or expanding the pathway based on introducing the suitable exogenous enzymes or/and deleting some endogenous genes. Of Which, about 110g/L 3-dehydroquinate was produced in 7-L fed-batch fermentation with 35% yield (mol/mol) from D-glucose, and this is the highest reported titer and yield so far for 3-dehydroquinate production form glucose. Our study laid important foundation for biomanufacturing of many useful aromatic chemicals.