Growing cells in vitro in an artificial environment requires optimal physiochemical conditions. To ensure peak cell growth and proliferation, it’s crucial to select an appropriate growth medium. Cell culture media contain nutrients and other factors that support cell growth. Cells grown for production of pharmaceuticals are housed in bioreactors, which are operated in three broad categories: batch, fed-batch, and perfusion cell culture. Perfusion systems are used in the latter case.
In batch processes, all nutrients – including serum if it’s needed – are included at the start, and no supplements are added during the process. Because no nutrients or feed supplements are added, batch cultures are easy to manage. However, as key nutrients are depleted and not replaced, the growth medium can’t keep pace with the metabolic needs of the cells.
With fed-batch processes, specific nutrients are added as needed during cell culture. It’s possible to produce higher product quantities than with a batch process. In controlled growth conditions, cells grow rapidly and consume the nutrients in the culture medium. As the number of cells grows, more and more nutrients are needed. Fed-batch processes extend the period during which cells can continue to make the product of interest. Fed-batch culture is commonly used in the production of pharmaceuticals like monoclonal antibodies (mAbs) and other recombinant proteins in CHO cells.
In cell culture perfusion, fresh medium is continuously added during the culture. The fresh medium supplies a steady source of the nutrients cells need to maintain viability while removing toxic waste products that would otherwise accumulate and inhibit cell growth. As a result, the cell culture can potentially grow for a longer period of time than is possible with a batch of fed-batch process. One of the key needs is to avoid excessive cell loss as media leaves the system. Cells are either retained or added back. Perfusion systems are used for perfusion culture to produce biologics.
Perfusion bioreactor systems FAQs
Here are answers to some frequently asked questions about perfusion systems.
What are the advantages of perfusion culture?
Perfusion mode is used to improve productivity of cultures, so that a greater amount of the target product is made compared with batch and fed-batch cultures. It may also improve the stability and consistency of the product and allow higher facility utilization. Perfusion can be used to support continuous manufacturing processes.
What are the disadvantages?
Perfusion cultures are more complex to develop than other modes of operation. Because media is added continuously, a much larger volume is used compared with batch or fed-batch modes. This increase in reagents adds cost to the production process. It’s important to optimize the perfusion rate to give the cells the nutrients they need while keeping the volume of media as low as possible.
What is a perfusion system?
Perfusion systems are vessels used to maintain optimal physiochemical conditions during culture. Cytiva’s Xcellerex™ Automated Perfusion System (APS) seamlessly integrates with Xcellerex™ single-use bioreactors. The APS operates using hollow fiber filters for tangential flow filtration and is designed to minimize cell shear. The system automatically switches filters and containers to minimize hands-on time. The single-use flow path and other single-use components are disposed after each run.