Shaken bioreactors are widespread in the field of biotechnology. Especially, microtiter plates are increasingly used as bioreactors in the early stages of process development. Microtiter plates allow for the investigation of numerous parallel experiments within a short period of time. Furthermore, microtiter plates offer economic advantages compared to larger systems due to reduced material consumption. When used as a bioreactor, microtiter plates are mostly used as bioreactor in combination

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... h shakers with an orbital shaking movement. Due to the orbital shaking movement, the centrifugal force acts on the culture broth and leads to the formation of a rotating liquid sickle. In addition to mixing of the culture broth, the motion of the liquid also increases the gas-liquid exchange surface, which increases the supply of oxygen to microorganisms.However, the full potential of small-scale systems is only guaranteed if (online) monitoring for each bioreactor is available. BioLector technology, an optical monitoring system based on fluorescence and scattered light measurements, allows for the online monitoring of various process parameters such as biomass, NADH and flavin levels during cultivation in orbitally shaken microtiter plates. pH value and dissolved oxygen tension (DOT) are also important biotechnological process parameters. Unfortunately, these parameters cannot be determined directly by fluorescence measurements. Sensitive fluorescent dyes are available for both measurements; these dyes change their fluorescence behavior depending on the respective concentrations. In microtiter plates, these sensitive fluorescent dyes are commonly immobilized at the well bottom. These optical sensor spots are also called optodes. However, previous studies have found interferences between biogenic fluorescence and the fluorescent dyes, leading to erroneous results.In the present work, an alternative measurement system for DOT monitoring in orbitally shaken microtiter plates based on a fluorescent dye was established. The fl [...]