Real-time monitoring of protein precipitation in a tubular reactor for continuous bioprocessing

- Flow behavior in flowcells follow laminar flow in pipes model.
- Continuous precipitation measured by pH, conductivity, turbidity and image processing.
- Steady state is important during product collection for higher product quality.
- Turbidity signals are lumped values of floc properties.
- Quasi continuous image processing can measure flocs by area, size and count.

Real time monitoring is critical to apply continuous bioprocesses successfully. This requires the integration of flow cells into continuous reactors. Potential continuous steps include protein precipitation, used in plasma purification, antibody enrichment and virus inactivation. Consequently we developed real-time monitoring of protein precipitation in a tubular reactor by pH, conductivity, turbidity and image processing. Feasibility studies were then performed for each monitoring method. Since integrated flow cells can affect time to reach steady state due to its inherent residence time distribution (RTD) property, we first determined flow behavior in flow cell is best described by laminar flow in pipes model, in order to find acceptable levels of volumetric flowrates that is not impractically high. Separately, we found pH highly important for protein precipitation while conductivity has high sensitivity to changes in buffer content. Turbidity signals are lumped values of floc properties while image processing can separately measure flocs by area, size and count. Also, the time and behavior to reach steady state amid changing precipitating conditions was investigated, to select for correct collection times to ensure high product quality. Lastly, we report the technical considerations in reactor design, construction and operation.

152