A device for determining and monitoring the physiological state of microbial cultures in each individual microbioreactor of a microtitre plate, wherein a gas space of each microbioreactor is accessible via an inlet and outlet opening (23, 24), comprising: - means for shaking the microtitre plate, wherein the means comprise a shaker and a shaker tray, - a gas supply system suitable for purging the gas space of each microbioreactor with a stream of purge gas in a purging phase, which comprises a purge gas feed-in and a gas distribution system (11, 12), - a shut-off means arranged directly on each microbioreactor and suitable for interrupting the stream of purge gas, wherein the shut-off means comprise an inlet valve comprising a valve seat surrounding the inlet opening as well as a pneumatically actuated shut-off membrane for opening and closing the inlet opening, wherein the inlet opening at the same time forms the flow resistance of each microbioreactor, - wherein the gas distribution system (11, 12) adapted to deliver the fed-in purge gas and to remove the purge gas from each microbioreactor has a central delivery line which extends from the purge gas feed-in to a subdistributor for the purge gas arranged on the microtitre plate and - the flow resistances in the gas supply system and the flow resistance of each microbioreactor are adapted in such a manner that the stream of purge gas in the purging phase is substantially equal in the technical sense in all the microbioreactors, and - a measuring device adapted to detect the physiological state of the microbial culture in each individual microbioreactor in a measuring phase whilst the stream of purge gas is interrupted. - means for shaking the microtitre plate, wherein the means comprise a shaker and a shaker tray, - a gas supply system suitable for purging the gas space of each microbioreactor with a stream of purge gas in a purging phase, which comprises a purge gas feed-in and a gas distribution system (11, 12), - a shut-off means arranged directly on each microbioreactor and suitable for interrupting the stream of purge gas, wherein the shut-off means comprise an inlet valve comprising a valve seat surrounding the inlet opening as well as a pneumatically actuated shut-off membrane for opening and closing the inlet opening, wherein the inlet opening at the same time forms the flow resistance of each microbioreactor, - wherein the gas distribution system (11, 12) adapted to deliver the fed-in purge gas and to remove the purge gas from each microbioreactor has a central delivery line which extends from the purge gas feed-in to a subdistributor for the purge gas arranged on the microtitre plate and - the flow resistances in the gas supply system and the flow resistance of each microbioreactor are adapted in such a manner that the stream of purge gas in the purging phase is substantially equal in the technical sense in all the microbioreactors, and - wherein the gas distribution system (11, 12) adapted to deliver the fed-in purge gas and to remove the purge gas from each microbioreactor has a central delivery line which extends from the purge gas feed-in to a subdistributor for the purge gas arranged on the microtitre plate and - the flow resistances in the gas supply system and the flow resistance of each microbioreactor are adapted in such a manner that the stream of purge gas in the purging phase is substantially equal in the technical sense in all the microbioreactors, and - a measuring device adapted to detect the physiological state of the microbial culture in each individual microbioreactor in a measuring phase whilst the stream of purge gas is interrupted.