Fig. 7

Closed-batch fermentation for hydrogen-dependent CO₂ reduction to formic acid. aT. kivui was grown on 28 mM glucose in a defined mineral medium in a shaking water bath at 66 °C. At the time point indicated b 300 mM KHCO₃, c H₂ + CO₂ (80:20%, 2 × 10⁵ Pa) or d H₂ + CO₂ (80:20%, 2 × 10⁵ Pa) + 300 mM KHCO₃ were added to the growing culture. The optical density of the culture was between 0.3 and 0.4. Squares, OD₆₀₀; diamonds, acetic acid; triangles, formic acid