Meßmethoden in Fermentern unter sterilen Bedingungen

Measuring methods for fermentations under sterile conditions . In process development as well as in industrial production it is necessary to obtain information about the state of the process by the measurement of characteristic variables. This is true for bioengineering in the same way as for chemical processes in general. Characteristic variables to be taken into consideration include temperature, pressure, masses and mass‐flow rates, operating parameters such as liquid level and impeller speed, and especially the concentrations of reactants, intermediates, and products. In contrast to other processes, a particular problem exists in fermentation because introduction of microorganisms, into the system by the measurement has to be prevented. Since taking samples from the reactor is hardly suitable for controlling the process for various reasons (amount of work, loss of time), this review considers only those methods which can be used for measurements directly in the fermentor. Essentially these are physical and physico‐chemical methods, e. g. for concentrations (O 2 and CO 2 in gas and liquid phase, pH, biomass). Of special interest for future development are spectroscopic and enzymatic methods for fast determination of substrates and of important intermediates and products. Here the sterility required entails special problems in the case of enzyme electrodes. Important information on the state of the process can, of course, also be obtained from physical variables, such as gas hold‐up, bubble size, viscosity, and turbulence properties of the medium. These variables are less critical with regard to sterility.