Stirred Vessel Bioreactors : Key Technology in Vaccine Development and Manufacturing
By Shaliza Ibrahim
FEATURE
Stirred vessel bioreactors play a vital role in the development and production of vaccines , amongst a wide range of other applications in which this versatile reactor configuration can serve . Whether operated batch-wise or continuously , in either the disposable or reusable version , whether cells are free growing or attached to microbeads , the stirred vessel affords volume and provides a controlled environment that serves the purpose of biological cultures . The suitable selection of impeller-to-tank geometry , rotational speed , and other operating variables for a given specification of the bioreactor input and output , is critical in ensuring successful performance .
The Covid-19 pandemic has led to heightened efforts in making vaccines available for the world population to combat the spread of the disease . Vaccines , as we know , are either an inactivated or attenuated ( weakened ) virus , or fragments of the virus , which when inoculated into the body , trigger our immune system to build antibodies . In order to get sufficient quantities of these vaccines , the virus has to be proliferated in large amounts . Flu vaccines have for 80 years been mass produced using chicken eggs which act as hosts to grow the virus in large quantities 1 . Imagine the number of chicken eggs needed to produce enough vaccine for a country ! Biotechnological advancement has replaced the chicken eggs technique with cultured animal or microbial cells as hosts known as cell substrates . 2
In a race against time , Pfizer and Moderna rolled out their messenger ( m ) RNA vaccine , which is the first of this type to be approved . The uniqueness of this novel vaccine is that the body produces the viral proteins itself when injected with strands of mRNA . Compared with traditional vaccines , mRNA takes less time to produce and with much higher output in a cell-free biochemical process using synthetic enzymes . 3
In any case , manufacturing large quantities of vaccines is achieved by employing sophisticated bioreactor systems that provide the right environment in which to grow or replicate cells and biological components . Among bioreactor configurations , the stirred vessel , also known as stirred tank reactor ( STR ) or agitated vessel , is most commonly used . This article highlights important aspects of the stirred vessel bioreactor design and operation , and parameters that affect its performance in producing the desired outcome .
Bioreactors , the Heart of the Process
Typical of any process line , biopharmaceutical production comprises a series of unit operations — reactors for media preparation , storage and transfer , bioreactors for cultivation , filtration units , ultracentrifuges and separators for the
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