Liliana Calzadíaz Ramírez

Project title: Rational in vivo exploration of microbial formate dehydrogenases for bioelectrocatalytic CO₂ reduction

Host Institution: Technical University of Denmark (DTU)

Host Supervisor: Professor Anne S. Meyer

Co-host Institution: École Polytechnique Fédérale de Lausanne (EPFL)

Co-host Supervisor: Professor Xile Hu

Summary project: Increased carbon dioxide (CO₂) emissions are the direct cause of global warming and climate change, and identification of novel solutions to capture and utilize CO₂ is a worldwide priority. Microbial formate dehydrogenases (FDHs) can catalyze the reduction of CO₂ to formate/formic acid, thus providing a first step for utilizing CO₂ to produce high-in-demand chemicals that are currently produced from fossil fuels. CO2FDH-21 project aims to identify FDHs that efficiently reduce CO₂ to formate and to obtain novel engineered FDH variants that have unprecedentedly high catalytic activity (target: 1000 times improved k_cat). To reach this aim, we will construct large libraries of FDH genes and select the best variants using a formatotrophic microbial strain as biosensor. In this biosensor, formate assimilation is coupled to CO₂ reduction, which allows a high-throughput in vivo selection of efficient FDHs by growth assessment in a CO₂ atmosphere (with CO₂ as the only carbon source), as growth indicates efficient FDH-dependent CO₂-reduction to formate. The kinetics and robustness of the best engineered FDH variants obtained will be characterized and the performance of the 10 best enzymes will be examined in the co-host’s lab at EPFL and Nano-bio-TECHNION using a bioelectrocatalytic system for CO₂ reduction based on direct transfer of electrons from the electrode to the enzyme. This project will establish a multidisciplinary strategy to efficiently obtain engineered enzymes from a large enzyme library space to deliver efficient FDHs for in vivo or in vitro applications for reduction of CO₂.