4-Hydroxybenzoate (4HBA) is a valuable platform intermediate for the production of commodity and fine chemicals, including protocatechuate, cis,cis-muconic acid, adipic acid, terephthalic acid, phenol, vanillin, and 4-hydroxybenzyl alcohol glycoside (gastrodin). Here we describe rational engineering of the shikimate and related pathways in Corynebacterium glutamicum ATCC13032 for over-producing 4HBA. As an approach to increase the carbon flux to 4HBA, we first introduced a mutated chorismate-pyruvate lyase (CPLpr) and feedback-resistant 3-deoxy-d-arabinoheptulosonate-7-phosphate synthases encoded by ubiCpr and aroFfbr/aroGfbr, respectively, from Escherichia coli along with blockage of carbon flux to the biosynthetic pathways for aromatic amino acids and the catabolic pathway for 4HBA by deletion of the genes trpE (encoding anthranilate synthase I), csm (chorismate mutase), and pobA (4HBA hydroxylase). In particular, CPLpr less sensitive to product inhibition was incorporated into the microorganism to enhance the conversion of chorismate to 4HBA. The subsequent steps involved expression of aroE (shikimate kinase) and aroCKB in the shikimate pathway and deletion of qsuABD coding for enzymes involved in the quinate/shikimate degradation pathway. Finally, to reduce accumulation of pathway intermediates, shikimate and 3-dehydroshikimate, shikimate-resistant AroK from Methanocaldococcus jannaschii was introduced. The resulting strain was shown to produce 19.0 g/L (137.6 mM) of 4HBA with a molar yield of 9.65% after 65 h in a fed-batch fermentation. The engineered strain can also be effectively applied for the production of other products derived from the shikimate pathway.
Keywords: 4-Hydroxybenzoate; Corynebacterium glutamicum; Metabolic engineering; Shikimate; Shikimate pathway.
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