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Production of Aromatic Compounds by Metabolic Engineering

Lixuan Huang, Zhixiong Xue, Quinn Zhu, Michael McCluskey, Keith Cantera, Sharon Haynie, Arie Ben-Bassat, and Sima Sariaslani. CR&D, Biochemical Sciences and Engineering, DuPont, DuPont Experimental Station, E173/203, Wilmington, DE 19880

Aromatics derived from the phenylpropanoid pathway provide many opportunities for industrial as well as nutrition & health applications. We have demonstrated microbial production of the UV protectant para-hydroxycinnamic acid (pHCA) and resveratrol, a compound with cardio-protection and anticancer properties. Microbial production of pHCA was achieved through conversion of tyrosine by the phenylalanine/tyrosine ammonia lyase (PAL/TAL) enzyme from Rhodotorula glutinis. Advantageous application of the high pH optimum of this enzyme allowed achieving high titers of pHCA. Resveratrol, which is found in grapes, peanuts and other plants, belongs to the stilbene family of compounds that use pHCA-CoA (coumaroyl CoA) as a common precursor. It is formed by decarboxylative condensation of three molecules of malonyl-CoA and one molecule of coumaroyl CoA. The recombinant microbial cells that converted tyrosine to resveratrol contained PAL/TAL, coumaroyl CoA ligase, and stilbene synthase. Engineering of microbial strains for production of these chemicals presented several challenges, e.g., enzyme expression and product toxicity. Approaches to overcome these challenges will be discussed.