Practices of shake-flask culture and advances in monitoring CO2 and O2.

About 85 years have passed since the shaking culture was devised. Since then, various monitoring devices have been developed to measure culture parameters. O2 consumed and CO2 produced by the respiration of cells in shaking cultures are of paramount importance due to their presence in both the culture broth and headspace of shake flask. Monitoring in situ conditions during shake-flask culture is useful for analysing the behaviour of O2 and CO2, which interact according to Henry's law, and is more convenient than conventional sampling that requires interruption of shaking. In situ monitoring devices for shake-flask cultures are classified as direct or the recently developed bypass type. It is important to understand the characteristics of each type along with their unintended effect on shake-flask cultures, in order to improve the existing devices and culture conditions. Technical developments in the bypass monitoring devices are strongly desired in the future. It is also necessary to understand the mechanism underlying conventional shake-flask culture. The existing shaking culture methodology can be expanded into next-generation shake-flask cultures constituting a novel culture environment through a judicious selection of monitoring devices depending on the intended purpose of shake-flask culture. Construction and sharing the databases compatible with the various types of the monitoring devices and measurement instruments adapted for shaking culture can provide a valuable resource for broadening the application of cells with shake-flask culture.