초록
The effects of CO<SUB>2</SUB> on propionic acid production and cell growth in glycerol or glucose fermentation were investigated in this study. In glycerol fermentation, the volumetric productivity of propionic acid with CO<SUB>2</SUB> supplementation reached 2.94g/L/day, compared to 1.56g/L/day without CO<SUB>2</SUB>. The cell growth using glycerol was also significantly enhanced with CO<SUB>2</SUB>. In addition, the yield and productivity of succinate, the main intermediate in Wood-Werkman cycle, increased 81% and 280%, respectively; consistent with the increased activities of pyruvate carboxylase and propionyl CoA transferase, two key enzymes in the Wood-Werkman cycle. However, in glucose fermentation CO<SUB>2</SUB> had minimal effect on propionic acid production and cell growth. The carbon flux distributions using glycerol or glucose were also analyzed using a stoichiometric metabolic model. The calculated maintenance coefficient (m<SUB>ATP</SUB>) increased 100%, which may explain the increase in the productivity of propionic acid in glycerol fermentation with CO<SUB>2</SUB> supplement.