(629d) Instating the Wood-Ljungdahl Pathway for Carbon Dioxide Fixation into the Solventogenic Clostridium Acetobutylicum

Atmospheric CO₂ has increased largely due to the burning of our depleting fossil fuel resources. Decreasing CO₂ emissions has become an increasingly appealing topic, and much research has been dedicated to understanding the biological CO₂ fixation route naturally found in acetogens. Acetogenic bacteria capture and utilize CO₂ along with electron sources such as H₂ or CO using the Wood-Ljungdahl pathway. This pathway has been shown to be the most energy efficient pathway for the production of both biomass and metabolic products[1]. Of particular interest is the production of butanol, a great alternative to current transportation fuels. Most acetogens primarily produce acetate as a primary fermentation product, and butanol titers, if at all exist, are much lower than those reported in Clostridium acetobutylicum [2, 3]. Therefore, we have investigated CO₂ sequestering enzymes found in the Wood-Ljungdahl Pathway by heterologous expression of these complex proteins in C. acetobutylicum. This presentation will focus on the expression of the two core carbon sequestering enzymes that form the CODH/ACS complex (carbon monoxide dehydrogenase and acetyl-CoA synthase) through in vivo and in vitro studies and assays. This will allow us to directly study activity and determine the feasibility of combining carbon sequestration with solvent production. The combination of the native solvent producing and the heterologous carbon sequestration abilities aims to create a strain capable of producing chemicals from cheap and abundant, renewable carbon resources.

[1] Fast, A. G. & Papoutsakis, E. T. Stoichiometric and energetic analyses of non-photosynthetic CO₂-fixation pathways to support synthetic biology strategies for production of fuels and chemicals. Curr. Opin. Chem. Eng.1, 1–16 (2012).

[2] Papoutsakis, E. T. Engineering solventogenic clostridia. Curr. Opin. Biotechnol. 19, 420–9 (2008).

[3] Bruant, G., Lévesque, M.-J., Peter, C., Guiot, S. R. & Masson, L. Genomic analysis of carbon monoxide utilization and butanol production by Clostridium carboxidivorans strain P7. PLoS One 5, e13033 (2010).