(532g) Engineering Escherichia coli to Utilize New C2-C3 Feedstocks

In the past few years, my research group has led developing a set of Escherichia coli strains that could grow on the following C2-C3 molecules as sole or major carbon source: ethanol, ethylene glycol (EG), glycine, and 1,3-propanediol. In the future, these molecules may be cost-effectively derived from major waste streams such as CO₂ and plastics. In this presentation, I plan to summarize the key findings of these studies and highlight the unique features we have observed in their metabolism. Many of these strains were challenged by toxic aldehyde intermediates and reactive oxygen species (ROS). RNA sequencing revealed that many improved strains obtained through adaptive laboratory evolution deployed strategies to reduce accumulation of these two classes of toxic species. Despite of these challenges, two strains (the ethanol strain and the EG strain) could be engineered to efficiently produce aromatic amino acids, even outperforming the control strain growing on glucose under similar conditions (e.g., 2 g/L L-tyrosine can be produced from 10 g/L EG). I will discuss our preliminary investigations into how the metabolism was rewired to achieve these unexpected results (the pathways from these C2 molecules to the aromatic amino acids are longer than that from glucose), and end the presentation by sharing my thoughts on the potential applications of these strains.