Using one unified single-use cell culture platform for facilities that require culture of different types of cells can significantly reduce equipment costs, the risk of cross-contamination, and the requirement for training, cleaning, sterilization, and validation. Here, a bioreactor platform consisting of a presterilized, flexible, disposable plastic bag on a rocking platform and filled with media and a gas mixture is shown to support the growth of E. coli, Chinese hamster ovary (CHO) cells, and hybridoma cells as measured by the daily cell density, nutrient consumption, and production of metabolites.
There are several options for disposable, scalable bioprocess bags for completing upstream processing steps. The design of a cell culture system will affect the shear forces experienced by cells as well as the mass transfer of gases, and different types of cells will have different sensitivities to these parameters. Generally, mammalian cells are more sensitive to shear forces than bacteria, but bacteria are more sensitive to oxygen limitation. The following studies demonstrate that the Wave Bioreactor (GE Healthcare Chalfont St. Giles, UK) effectively supports the growth and productivity of different types of cells, and the versatility of the platform is further demonstrated by the flexibility of feed strategies and scalability of the systems.
BIOREACTOR SET UP
Each bioreactor consists of a presterilized, flexible, disposable, plastic Cellbag that is placed on a rocking platform and filled with up to half of the bag volume with media. The bioreactors used in these studies were the System20/50EH, System200, and System1000 (GE Healthcare) with maximum culture volumes of 25, 100, and 500 L of media, respectively. The following naming convention will be used to identify the culture set up: the volume of media in a Cellbag of a certain volume, e.g., 100/200 L indicates 100 L of media in the System200 bioreactor.
The remaining volume of the Cellbag is inflated with a process gas mixture, composed of carbon dioxide (CO2) and oxygen (O2), which is mixed with air in a controlled manner. These gases are added using a sterile inlet filter that is pre-attached to the bag. Continuous airflow provides oxygenation and gas exchange for pH control and CO2 removal. Exhaust air passes through another sterile filter and a backpressure control valve. The backpressure control valve ensures that the Cellbag is always fully inflated at any airflow and prevents overinflation.
Liquid mixing and mass transfer of gases are achieved by rocking the Cellbag back and forth at a user-determined rocking angle and frequency. The waves generated by the rocking motion greatly increase surface area to enhance gas transfer. The wave motion also promotes bulk mixing and off-bottom suspension of cells and particles without any damage to the cells. Temperature is controlled by a heater located in the base plate of the unit that warms the underside of the bag. The heater is regulated by a noninvasive temperature sensor that is also in the base plate of the unit.