(620bi) Elucidate Robust Redox Metabolism of Clostridium Thermocellum (Rapid Fire)

Consolidated bioprocessing (CBP) is a potentially feasible route for sustainable production of bio-based fuels that condenses multiple steps of biomass degradation and sugar fermentation into a single step. Clostridium thermocellum is an anaerobic, gram positive, thermophilic bacterium that is capable of degrading cellulosic biomass directly into ethanol. Despite its growing popularity, the complete understanding of C. thermocellum central metabolism is still lacking with atypical glycolysis, incomplete pentose phosphate pathway and Krebs cycle, and complex redox pathways. In this study, a predictive metabolic model of C. thermocellum has been developed for metabolic flux quantification and rational strain design. We experimentally validated the model and investigated the range of phenotypes of C. thermocellum in response to significant perturbation of energy and redox pathways. The result revealed a complex, robust redox metabolism of C. thermocellum. By incorporating experimental data into the model, we identified redox bottlenecks hindering high-yield ethanol production in C. thermocellum. Furthermore, we show the model’s rationale for why previous metabolic engineering strategies had low target ethanol yields, and provide different metabolic engineering strategies for reaching the target yield.