Optimization of process parameters and medium components for carbon monoxide bioconversion with Clostridium autoethanogenum

Clostridium autoethanogenum is a model microbe capable of converting carbon monoxide (CO) into bioethanol and useful biochemicals. Successful process optimization when using CO as the primary carbon source requires an understanding of the influence of process parameters and growth medium components on cell growth and end-product formation. We conducted a full factorial analysis of the effects of CO total pressure, pH, yeast extract (YE), and cysteine concentrations on acetic acid, ethanol, and biomass production utilizing C. autoethanogenum with CO as the primary substrate. Maximum ethanol production of 0.71 g L^–1 was obtained at a pH of 4.5, yeast extract concentration of 0.5 g L^–1 , CO pressure of 1.8 atm, and cysteine concentration of 1.5 g L^–1. There was a tenfold enhancement when the pH was lowered from 6 to 4.5 and the YE concentration was reduced to 0.5 g L^–1. Response optimization using the reduced gradient algorithm confirmed these results. The information presented in this study could prove valuable for process engineering design by assisting with the selection of parameters that yield syngas blends specifically intended for increased ethanol production.