Medium Compositions for the Improvement of Productivity in Syngas Fermentation with Clostridium autoethanogenum

The cost of culture media represents a considerable portion of the overall cost in syngas fermentation. Yeast extract is an expensive ingredient among the medium components required to prepare the culture medium. In this study, we evaluated the effectiveness of replacing yeast extract with relatively low-cost nutrient supplements such as corn steep liquor, malt extract, and vegetable extract in improving the feasibility of the syngas fermentation process in Clostridium autoethanogenum culture. The use of corn steep liquor, malt extract, and vegetable extract as nutrient supplements at a concentration of 0.5 g/L resulted in optical densities of 1.44, 1.37, and 1.71, and produced ethanol concentrations of 2.24, 3.37, and 3.76 g/L, respectively. The microbial growth and ethanol production in syngas fermentation with yeast extract alternatives was comparable with the results of fermentation with yeast extract (optical density of 1.48 and ethanol concentration of 2.16). Moreover, the use of malt and vegetable extracts showed considerable improvement (69% and 51%, respectively) in the specific ethanol productivity compared to yeast extract.