FIGURE 2.

Continuous gas fermentation of C. ljungdahlii with CO₂ and H₂ in standard PETC medium at different periods in a priliminary experiment (bioreactor 1/2/3). Mean values of triplicates with standard deviation (n = 3) for pH and OD₆₀₀ (A), and for acetate and ethanol production rates in mmol-C L^–1 d^–1 (B). Standard PETC medium containing 18.7 mM ammonium chloride as sole N-source was used. The horizontal dotted lines indicate the continuous process in which medium of different pH was fed to each bioreactor. Period: I, pH = 6.0; II, pH = 5.5, III, pH = 5.0; and IV, pH = 4.5.