Abstract
Shake flasks are commonly used for process development in biotechnologyindustry. For this purpose a lot of information is required from the growth conditions duringthe fermentation experiments. Therefore, Anderlei et al. developed the RAMOS technology[1, 2], which proviedes on-line oxygen and carbondioxide transfer rates in shake flasks.Besides oxygen consumption, the pH in the medium also plays an important role for thesuccessful cultivation of micro-organisms and for process development. For online pHmeasurement fiber optical methods based on fluorophores are available. Here a combinationof the on-line Oxygen Transfer Rate (OTR) measurements in the RAMOS device with anon-line, fiber optical pH measurement is presented. To demonstrate the application of thecombined measurement techniques, Escherichia coli cultivations were performed and on-line pH measurements were compared with off-line samples. The combination of on-lineOTR and pH measurements gives a lot of information about the cultivation and, therefore, itis a powerful technique for monitoring shake flask experiments as well as for processdevelopment.
Highlights
Up to now shaking bioreactors are the most commonly used reaction vessels in microbiology and biotechnology [3]
To demonstrate the application of the combined measurement techniques, Escherichia coli cultivations were performed and online pH measurements were compared with off-line samples
The combination of on-line Oxygen Transfer Rate (OTR) and pH measurements gives a lot of information about the cultivation and, it is a powerful technique for monitoring shake flask experiments as well as for process development
Summary
Up to now shaking bioreactors are the most commonly used reaction vessels in microbiology and biotechnology [3]. Several thousand shake flask experiments are carried out annually for strain development, screening processes and media optimization in large companies [4, 8] For such applications, especially for media optimization, monitoring of cultivation parameters is essential. To determine the actual pH in the solution the fluorescence intensities of both fluorophores are measured and with the ratio of both values the pH is calculated [12] Another method for the fiber optical pH measurement in small scale fermentation processes is the dual lifetime referencing (DLR). Kensy et al demonstrated the application of the technology for on-line monitoring of dissolved oxygen and pH in continuous shaken E. coli cultivations performed in 24-well micro titer plates [13]. The successful combined application of both measurement techniques were demonstrated in E. coli cultivations
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