Improving Azelaic Acid Production in Escherichia coli via Adaptive Laboratory Evolution

Abstract

Azelaic acid, a medium-chain dicarboxylic acid (DCA) with nine carbons, has been used in plastics and acne medication. Its use in cosmetics is emphasized as it is known as a tyrosinase inhibitor that reduces melanin synthesis and for its antibacterial and anti-inflammatory effects which lead to improvement of the skin. Azelaic acid has been produced from grains such as wheat, rye, and barley. In general, wild-type Escherichia coli cannot effectively uptake the medium-chain fatty acids. In this study, we constructed an E. coli MG1655 mutant in order to improve the uptake of medium-chain fatty acids by with fadR deletion to retain gene expression of β-oxidation pathway. Then we obtained an E. coli strain that grows faster than the wild type on nonanoic acid (C9 fatty acid), which is the precursor to produce azelaic acid through ω-oxidation pathway, by evolutionary engineering. According to previous studies, ω-hydroxyacids were converted to dicarboxylic acids by the action of an engineered ω-oxidation pathway. Using this approach, the Pseudomonas putida alkane monooxygenase system, encoded by alkBGT, was introduced to the evolutionary engineered E. coli with fadE deletion to produce the C9 DCA. The mutant strain showed approximately 3-fold increased production of azelaic acid in comparison with wild type strain.