FIG 5.

CO concentration affects CO oxidation and metabolite distribution. C. acetobutylicum expressing the CODH enzyme was grown on defined medium in the presence of various amounts of ¹³CO (balance He) in the headspace (20 lb/in² total) during high-cell-density low-glucose-concentration experiments (5 g/liter glucose). (A) Concentration of ¹³CO₂ (in micromoles) formed per gram dry weight (gDW) of cells (n = 2). The large error bar for the experiments with 5% CO is largely due to the difficulty of precisely charging the gas phase with low partial pressures of CO, combined with the gas mixing and solubility and the biological variability. (B) Metabolite profile (shown as change in metabolite concentration [ΔConc.] from 0 to 24 h) of cultures in the presence of various CO concentrations. The ethanol data have been corrected for the evaporation of ethanol upon charging the culture with gas. The initial ethanol was ca. 49 mM, since ethanol is used to dissolve the antibiotic for plasmid maintenance. Error bars indicate the standard error of two biological replicates.