Abstract: A device for determining and monitoring the physiological state of microbial cultures in each individual microbioreactor of a microtiter plate, wherein a gas space of each microbioreactor of the microtiter plate is accessible via an inlet opening and outlet opening, includes means for shaking the microtiter plate and a gas supply system suitable for purging the gas space of each microbioreactor with a stream of purge gas in a purging phase. A shut-off device is arranged directly on each microbioreactor for interrupting the stream of purge gas. The flow resistances in the gas supply system and the flow resistance of each microbioreactor are configured so that the stream of purge gas in the purging phase is substantially equal in all of the microbioreactors. The device includes a measuring device configured to detect the physiological state of the microbial culture in each individual microbioreactor.