S145: Metabolic reconstruction of butanol-producing Clostridium beijerinckii

Butanol is a higher carbon alcohol with lower water affinity and vapor pressure than ethanol, and hence holds great promise as a liquid fuel alternative. Clostridium beijerinckii has the potential to make butanol economically competitive because it naturally produces butanol as a product of its metabolism and co-ferments pentoses and hexoses. The challenge with this bacterium is that its butanol concentration during fermentation remains below the threshold needed to maximize profitability. A systems biology approach to this challenge allows for exploration of phenotype modifications using a genome-scale computational model. In this work, the application of metabolic reconstruction for the enhancement of a particular characteristic trait is demonstrated on C. beijerinckii NCIMB 8052. Genome annotation databases (e.g. Kyoto Encyclopedia for Genes and Genomes), published in silico models, and available literature on C. beijerinckii were used as a basis for metabolic network reconstruction. Constraint-based analysis on the metabolic model provides information needed to rationally align the natural objectives of the organism (selection pressure for growth) with the industrial objectives of the engineer (butanol production). This allows for identification of key modifications in metabolic pathways that are predicted to enhance butanol production. The current model, containing 824 reactions and 778 metabolites, therefore serves as a guide to experimentally engineer C. beijerinckii to the network state needed to make it an economically competitive fermentation organism.