Development Of A Partly Controllable System At Shake Flask Scale

The main objective of this study was to develop an easy to handle and partly controllable process cultivation system at shake flask scale. First, it was investigated how isturbances, like taking the flasks out of the incubator for feeding and sampling, affect culture conditions and results. An adapter was constructed that allowed automated feed in the shake flasks. Online monitoring of oxygen partial pressure (pO2) and pH were performed with the SFR Shake Flask Reader by PreSens, so limitations could be detected and adjustments made in time. This "semi-controlled" system clearly reduced the workload and minimized the disturbance variables, thus more reliable and representative data could be obtained for further scale-up processes.

In bioprocess development small scale systems are used to pick appropriate cell lines, media, and feeds before applying more expensive, controlled cultivation systems at larger scale. Comparability is still an issue as process developments still have to rely on data generated in uncontrolled small scale cultivation systems.

A commonly used small scale format for mammalian suspension cell cultures are shake flasks. Incubators providing a suitable environment by carbon dioxide (CO2) supply and humidity control are used to ensure sufficient oxygen transfer and homogenization of cell suspension by appropriate mixing. In order to match scale-up parameters power inputs are adjustable by adaptation of the shaking frequency and eccentricity of the shaking movement, or the working volume of the shake flasks. As no reliable system for automated feeding and sampling at shake flask scale is available so far, it is necessary to take the flasks out of the incubator. These disturbances might have an effect on metabolism and overall performance of the cultivated cells. Every disturbance might possibly decrease comparability to controlled systems, where those interferences are excluded.

This is why in this study the influence of different disturbances on the cultures as well as the culture environment in the incubator was tested. To avoid the necessity of removing the shake flasks from the incubator and thus minimize the amount of disturbance variables a prototype adapter was developed. It allows automated feed in the flasks by continuous pump or syringe based dosing systems. Moreover online monitoring of pH and pO2 was conducted with the SFR Shake Flask Reader by PreSens. This system allows the non-invasive measurement of the two parameters in several shake flasks in parallel without taking them out of the incubator.