Abstract
The use of bioreactors coupled to membrane-based perfusion systems enables very high cell and product concentrations in vaccine and viral vector manufacturing. Many virus particles, however, are not stable and either lose their infectivity or physically degrade resulting in significant product losses if not harvested continuously. Even hollow fiber membranes with a nominal pore size of 0.2 µm can retain much smaller virions within a bioreactor. Here, we report on a systematic study to characterize structural and physicochemical membrane properties with respect to filter fouling and harvesting of yellow fever virus (YFV; ~50 nm). In tangential flow filtration perfusion experiments, we observed that YFV retention was only marginally determined by nominal but by effective pore sizes depending on filter fouling. Evaluation of scanning electron microscope images indicated that filter fouling can be reduced significantly by choosing membranes with (i) a flat inner surface (low boundary layer thickness), (ii) a smooth material structure (reduced deposition), (iii) a high porosity (high transmembrane flux), (iv) a distinct pore size distribution (well-defined pore selectivity), and (v) an increased fiber wall thickness (larger effective surface area). Lowest filter fouling was observed with polysulfone (PS) membranes. While the use of a small-pore PS membrane (0.08 µm) allowed to fully retain YFV within the bioreactor, continuous product harvesting was achieved with the large-pore PS membrane (0.34 µm). Due to the low protein rejection of the latter, this membrane type could also be of interest for other applications, that is, recombinant protein production in perfusion cultures.
Highlights
Viral vaccine and viral vector production can be intensified by cultivating animal cells in perfusion mode
Filter fouling was monitored in real time using transmembrane pressure sensors, and virus particle, DNA, and protein concentrations were measured in the permeate flow to relate membrane structure measurements to process performance
The small‐pore modified PES (mPES) (0.09 μm) and PS (0.08 μm) membranes retained more than 99% of the infectious virus material, whereas almost 90% of the infectious material was retained by mid‐pore PES (0.18 μm) and mixed ester (ME) membranes (0.25 μm)
Summary
Viral vaccine and viral vector production can be intensified by cultivating animal cells in perfusion mode. Concentration polarization and boundary layer resistances should be reduced to increase mass transfer coefficients This can be achieved by increasing the cross‐flow velocity (resulting in higher Reynolds numbers) in the filter lumen (e.g., higher flow rate and smaller hollow fiber diameter) or by reducing the transmembrane flux (e.g., lower permeate flow rate and increased membrane area). Two pore sizes (based on nominal cutoff) were investigated to either retain or harvest the virus particles over the cultivation period and to understand filter fouling in dependence of the pore size This resulted in a sample set of eight hollow fiber modules. Filter fouling was monitored in real time using transmembrane pressure sensors, and virus particle, DNA, and protein concentrations were measured in the permeate flow to relate membrane structure measurements to process performance. Where Cp is the YFV (PFU/ml), DNA or protein concentration (μg/ml) in the permeate flow, and Cv (PFU/ml or μg/ml) the respective concentration in the bioreactor vessel
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
