In large-scale processes of several hundred cubic meters, sensors are mounted at a fixed position in an reactor, due not give representative description of the (micro) environment for a cell. The concentration of gasses, pH regencies, cell density, cellular population substrate, product and byproduct concentrations do not only differ during the course of a cultivation, but also in the volume broth.
Sensors for the experimental gradient detection are needed, which can be placed at various positions inside a bioreactor and provide stable data throughout a cultivation process.
We use a multi-parameter-sensor with miniaturized electrodes for pH, temperature, redox potential, dissolved oxygen and carbon dioxide concentration for the investigation of gradients. A novel sampling devices, which allows to take  multiple samples at defined time points is used.