Screening of Media Supplements for High-Performance Perfusion Cultures by Design of Experiment

Model predictive control for steady-state performance in integrated continuous bioprocesses

Perfusion bioreactors are commonly used for the continuous production of monoclonal antibodies (mAb). One potential benefit of continuous bioprocessing is the ability to operate under steady-state conditions for an extended process time. However, the process performance is often limited by the feedback control of feed, harvest, and bleed flow rates. If the future behavior of a bioprocess can be adequately described, predictive control can reduce set point deviations and thereby maximize process stability. In this study, we investigated the predictive control of biomass in a perfusion bioreactor integrated to a non-chromatographic capture step, in a series of Monte-Carlo simulations. A simple algorithm was developed to estimate the current and predict the future viable cell concentrations (VCC) of the bioprocess. This feature enabled the single prediction controller (SPC) to compensate for process variations that would normally be transported to adjacent units in integrated continuous bioprocesses (ICB). Use of this SPC strategy significantly reduced biomass, product concentration, and harvest flow variability and stabilized the operation over long periods of time compared to simulations using feedback control strategies. Additionally, we demonstrated the possibility of maximizing product yields simply by adjusting perfusion control strategies. This method could be used to prevent savings in total product losses of 4.5–10% over 30 days of protein production.

Functional Trimeric SARS-CoV-2 Envelope Protein Expressed in Stable CHO Cells

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a β-coronavirus, is the causative agent of the COVID-19 pandemic. One of the three membrane-bound envelope proteins is the spike protein (S), the one responsible for docking to the cellular surface protein ACE2 enabling infection with SARS-CoV-2. Although the structure of the S-protein has distinct similarities to other viral envelope proteins, robust and straightforward protocols for recombinant expression and purification are not described in the literature. Therefore, most studies are done with truncated versions of the protein, like the receptor-binding domain. To learn more about the interaction of the virus with the ACE2 and other cell surface proteins, it is mandatory to provide recombinant spike protein in high structural quality and adequate quantity. Additional mutant variants will give new insights on virus assembly, infection mechanism, and therapeutic drug development. Here, we describe the development of a recombinant CHO cell line stably expressing the extracellular domain of a trimeric variant of the SARS CoV-2 spike protein and discuss significant parameters to be considered during the expression and purification process.