Fig. 5
Schematic illustration of the experimental setup of the gas mixing system. Change of the (a) CO2 or (b) O2 concentration in the gas supply. In case of (b), the dilution of N2 and CO2 by O2 remains very low. Four mass flow controllers (MFC) were used with following ranges, for (a): MFC 1 & 3: 50–500 mL/min (calibrated with N2), MFC 2: 5–50 mL/min (calibrated with O2), MFC 4: 0.5-5 mL/min (calibrated with N2) and for (b): MFC 1: 5–50 mL/min (calibrated with O2), MFC 2 & 3: 50–500 mL/min (calibrated with N2) and MFC 4: 2–20 mL/min (calibrated with N2). This setup was chosen, as experiments at two different gas compositions can be performed with four shake flasks each