Online monitoring of critical process parameters, such as oxygen and carbon dioxide, is often essential for further process steps. Information on biomass, product formation or substrate source and consumption provide important information on the status of the culture. In addition to the transfer rates (OUR, OTR, CTR), the oxygen and carbon dioxide values can also be used to determine the respiratory quotient that is often required. In addition, the calculated values can be used for control processes, for example. The gas analysis can therefore not only be used to monitor metabolic processes, but can also be seen as a tool for process and yield optimization.