What does a bioreactor need to do?
In order to successfully expand cells without any trouble, a reactor must meet these requirements:
- Operate aseptically: The reactor must be sealed and sterilised so that contamination will not occur during the process. This is important as contaminants not only compete with your cells for nutrients but also can harm your customer if it is in the final product. Contaminated cell cultures must be discarded according to regulatory bodies.
- Agitate and aerate effectively: Cells need oxygen to survive, hence effective aeration is needed. Effectively agitated broths produce homogeneous flow: where all the liquid has the same concentrations of oxygen, nutrients, pH buffer, etc. This is important as we want all cells to be exposed to the same conditions so that they grow and proliferate in the same way e.g. if a region of the liquid has too little oxygen all the cells in that region will die.
- Control: We must be able to control the conditions in the reactor (temperature, pH, air flow rate) not only so that the cells are growing in conditions we know optimise survival and growth, but to ensure that we have an idea of what conditions the cells are in and therefore predict how are cells will proliferate and grow.
- Minimise evaporation: We don’t want the liquid in the reactor evaporating since it contains cells and useful nutrients. Evaporation also means that our predictions of what is happening inside the reactor won’t be accurate.
- Allow monitoring/ sampling: So that we can analyse and understand what is happening in the culture.
- Minimise labour: More labour = more staff. Staff cost money!
- Maximise computer control: Also to reduce cost of staff. Automation can also reduce human error.
- Geometric similarity for scale-up: The reactor dimensions (i.e. height of vessel to diameter of vessel ratio, number of impellers, impeller diameter to vessel diameter etc. ) affect the conditions inside the reactor and thus cell growth. Therefore it is much simpler to scale-up cell expansion by maintaining the same reactor dimensions throughout upstream processing.
- Flexible operation: In case of reactor failure, change of cell culture, fermentation modes or reactor types (see Fermentation modes and Types of reactors), a process must be flexible and allow easy changes. One example is to increase the number of reactors you have.
If you have any questions, please leave a comment below and I will get back to you as soon as possible!
Bioprocessing Explained 