title: Metabolic modeling of synthesis gas fermentation in bubble column reactors.
abstract: BACKGROUND
  A promising route to renewable liquid fuels and chemicals is the fermentation of synthesis gas (syngas) streams to synthesize desired products such as ethanol and 2,3-butanediol. While commercial development of syngas fermentation technology is underway, an unmet need is the development of integrated metabolic and transport models for industrially relevant syngas bubble column reactors.
  
  
  RESULTS
  We developed and evaluated a spatiotemporal metabolic model for bubble column reactors with the syngas fermenting bacterium Clostridium ljungdahlii as the microbial catalyst. Our modeling approach involved combining a genome-scale reconstruction of C. ljungdahlii metabolism with multiphase transport equations that govern convective and dispersive processes within the spatially varying column. The reactor model was spatially discretized to yield a large set of ordinary differential equations (ODEs) in time with embedded linear programs (LPs) and solved using the MATLAB based code DFBAlab. Simulations were performed to analyze the effects of important process and cellular parameters on key measures of reactor performance including ethanol titer, ethanol-to-acetate ratio, and CO and H2 conversions.
  
  
  CONCLUSIONS
  Our computational study demonstrated that mathematical modeling provides a complementary tool to experimentation for understanding, predicting, and optimizing syngas fermentation reactors. These model predictions could guide future cellular and process engineering efforts aimed at alleviating bottlenecks to biochemical production in syngas bubble column reactors.
authors.affiliation: Department of Chemical Engineering, University of Massachusetts, Amherst, MA 010003 USA.
authors.forename: Jin
authors.initials: J
authors.lastname: Chen
authors.affiliation: Process Systems Engineering Laboratory, Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 USA.
authors.forename: Jose A
authors.initials: JA
authors.lastname: Gomez
authors.affiliation: Process Systems Engineering Laboratory, Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 USA.
authors.forename: Kai
authors.initials: K
authors.lastname: Höffner
authors.affiliation: Process Systems Engineering Laboratory, Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 USA.
authors.forename: Paul I
authors.initials: PI
authors.lastname: Barton
authors.affiliation: Department of Chemical Engineering, University of Massachusetts, Amherst, MA 010003 USA.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Henson
keywords: Bioprocess engineering; Ethanol production; Metabolic modeling; Microbial fermentation