(6cs) Automating Development of Genome-Scale Metabolic Networks: Clostridium Acetobutylicum, a Known Singularity and Biofuel Production

Solventogenic non-pathogenic clostridia are of major importance for the production of biofuels through the acetone, butanol and ethanol (ABE) fermentation. However, much is still not understood by the scientific community regarding the molecular events that lead to a cascade of clostridial sigma factor-modulated regulatory programs. These programs generally include acidogenesis during vegetative growth followed by solventogenesis and multiple stages of cellular differentiation (sporulation). To investigate metabolic flux re-routing in response to clostridial regulatory programs, and to develop targets for further metabolic engineering, a genome-scale metabolic network was constructed for Clostridium acetobutylicum ATCC 824 using novel semi-automated technology. Multiple biochemical reaction, enzymatic and transporter databases were interfaced with genomic information and a technique of reverse metabolic network engineering to create a specialized metabolic network for this organism. For example, in spite of an ?incomplete? TCA cycle, C. acetobutylicum ATCC 824 can biosynthesize all L-amino acids due to heavy incorporation of the urea cycle and a specialized function of the acetylornithine transaminase (ArgD, e.c. 2.6.1.11, CAC2388). In further development of the network, genetic algorithms were imposed with a known membrane protein selectivity criterion to address a singularity of the metabolic network concerning acetate and butyrate uptake in the production of acetone.