(96e) Engineering Auto-Regulatory Genetic Circuits for Production of Hydroxycinnamic Acid-Derived Chemicals

In the biological production of chemicals, inducers such as arabinose and IPTG are often used. Artificial induction in many cases is less favorable due to high economic cost of inducers, inducer toxicity, and incompatibilities with industrial scale-up. Hence, in this study, we have attempted to engineer E. coli that is capable of auto-inducing and self-regulating its enzyme expressions by applying control theory through the introduction of a genetic bio-sensor with a time-delay element. Implementation of control theory in enzyme expression not only eliminates the need for artificial inducers, it also allows optimal performance in dynamic biological systems and achieving system stability through corrective actions. As a proof of concept, we forward engineered E. coli to detect ferulic acid and convert it to vanillin, a key compound for vanilla aroma which is used in food, cosmetic and pharmaceutical industries. To ensure that the host cells would not be induced at the early stage of growth, we installed a time-delay element to the ferulic acid sensor. Together, our engineered E. coli attained a much improved growth rate, and reached maximum vanillin production in a highly efficient manner.  We envision that our auto-regulation approach can be readily extended to improving production of a range of chemicals derived from hydroxycinnamic acid.