P165: Renewable production of benzaldehyde and benzyl alcohol in engineered Escherichia coli

Benzaldehyde and benzyl alcohol are petroleum derived aromatic commodity chemicals with diverse applications, particularly in the flavor and fragrance industries. For the first time, the biosynthetic production of benzaldehyde and benzyl alcohol directly from renewable sugar has been achieved using engineered Escherichia coli. The biosynthetic pathway utilizes phenylpyruvate, produced via the shikimic acid pathway, as the endogenous precursor. From the initial demonstration of pathway functional, a multitude of approaches were implemented to systematically improve product titers and yields, including through pathway deregulation and deletion of competing pathways to increase and preserve precursor availability.  For example, as E. coli was found to possess numerous native alcohol dehydrogenases of broad substrate specificity capable of converting benzaldehyde to benzyl alcohol, their deletion from the wild-type background was ultimately necessary for producing benzaldehyde as the major end-product.  At last, pathway flux was enhanced through the use of optimized protein scaffold designs which co-localized pathway enzymes.  As a result of these and other efforts, multi-fold improvements in product titer and yield, as well as improved control over product purity have been realized.  Here we report on the latest highlights of this research.