Fermentation graphs of a repeated batch cultivations of Chondromyces strain SBCm007. CO2 was kept at 0.3, 0.6 and 1.4% and pO2 at 20%. Both concentrations were maintained with the method described in this study. The steps in CO2 concentration indicate medium exchanges. The graph illustrates the calculated value OCQ, pO2, stirrer speed, flow, concentration of CO2 in the gas phase, and airflow (overall amount of air pumped through the bioreactor). The reduced flow rate at higher CO2 values led to ‘flow pulses’ because flow rate dropped below 0.2 l/min, the limit of the mass-flow controller which did not affect functionality. The belly of the OCQ value in the first batch, which was expected to be constant, is due to a lower operational limit of the stirrer and illustrates the sensitivity of the calculated OCQ value because deviations in the CO2 concentration caused by this are not yet obvious but already indicated by the OCQ.