Creation of CO2 Emission Suppressed E. coli By Combination of CO2 Transporter/Fixation-Enzyme Introduction and Directed Evolution

Effective CO₂ fixation from the air is urgent issue for preventing global climate change. Especially the CO₂ transformation into high value-added chemicals by synthetic biology is considered to be one of the promising solutions with economic viability. In the synthetic biology, Escherichia coli is widely utilized as a platform cell because of its established genetic engineering methods and possible high-density culture. We constructed the genetically engineered E.coli cell transformed with CO₂ transporter (bicA) and phosphoenolpyruvate carboxykinase (pck) for the subsequent CO₂ fixation process. On the other hand, we applied the wild type to the directed evolution process, in which UV-irradiated E. coli cells were cultured under high CO₂ environment and survived clones were selected. We evaluated the characteristics of those cells by our created measurement system for the CO₂ concentration in sealed container. As a result, the engineered (bicA/pck) and evolved (high CO₂) cells exhibited lower CO₂ emissions than that from the wild type. When the evolved cells were transformed with bicA and pck, those cells showed more suppressed CO₂ emission than the engineered and the original evolved cells. Both engineered and evolved cells showed lower CO₂ emission than that from the wild type, suggesting that the both cells incorporated CO₂ to some extent, and assimilated CO₂ to the other metabolite in the cells. In order to elucidate the genetic mechanism behind, genetic analysis of evolved cells are now under investigation. We would like to report our preliminary study on our directed evolution method and its effectiveness in creating novel characteristics of bacterial cells.