Fig. 5

Characterization of hydrogen-dependent CO₂ reduction by whole cells of T. kivui. a Resting cells of T. kivui (1 mg/mL) were incubated in anoxic buffer (50 mM Imidazole, 20 mM KCl, 20 mM MgSO₄, 2 mM DTE, 4 µM Resazurin, pH 7.0) with H₂ + CO₂ (80:20%, 2 × 10⁵ Pa) in the presence of 300 mM KHCO₃. Shown is the temperature profile for formate production by whole cells at the temperature indicated. b The influence of the cell density on formate production by resting cells was determined by applying a final concentration of 0.5–4 mg mL⁻¹ in anoxic serum bottles at a temperature of 60 °C. 300 mM KHCO₃ was added to the cell suspension and the experiments were started by replacing the gas phase with H₂ + CO₂ (80:20%, 2 × 10⁵ Pa). The initial formate production rates (squares) and the volumetric production rates (triangle) were plotted against the cell density used in the experiment