We recently finished our Ask the Expert discussion, “Ask the Expert – Addressing Shear Stress in Bioreactors”. During this Ask the Expert session, we had questions that covered topics including factors that contribute to shear, analyzing and modeling shear stress in a bioreactor, and how to use a shear protectant to protect against shear. In addition, we had several questions related to Poloxamer 188 implementation, best practices, cell lines, qualification and media concentration level.

Poloxamer 188 became a standard ingredient in cell culture media for commercial production as an effective tool in protecting against shear. However, as cell culture technology improved including process intensification, which increased cell densities and productivities in fed-batch and perfusion modes, issues with poloxamer were reported. We recently published a Cool Tool, “Improved, High Quality Poloxamer 188 Produces Consistent Performance in Cell Culture, “ that discusses how MilliporeSigma addressed this issue by developing proprietary analytical and biological methods to identify the critical properties of Poloxamer 188. These methods were based on a reference library of over 100 blinded customer and supplier samples.

This Ask the Expert session was hosted by Jochen Sieck, Head of Perfusion Systems Lab, Life Science, BioProcessing R&D, Merck. Jochen has more than 10 years of experience in mammalian cell culture, upstream process development, bioreactor characterization and scale-up. He studied Biotechnology and received his PhD in bioprocess engineering from ETH Zurich, working on Scale-Down Models of CHO fed-batch processes at Novartis. He stayed at Novartis for 2 years of Postdoc, working on perfusion process and medium development, before joining Merck in 2014. Since then, his team’s focus is perfusion medium development for customer as well as catalog products. Furthermore, his team investigates specific critical cell culture ingredients for their quality and impact on mammalian cells, targeting increase of reproducibility, reduced variability and improved quality. He has authored several journal articles and a textbook chapter on medium development for perfusion processes. Also, he is in the final stages of his MBA focusing on Innovation and Technology Management.

Below is a sneak peek of the discussion, for a full transcript, please see – Ask the Expert – Addressing Shear Stress in Bioreactors

Question:

Can you tell me what are the advantages of using a protectant over managing mixing speed, impeller choice etc. to control shear?

The Answer:

Poloxamer 188 is commonly used in the biopharmaceutical industry as a cell culture media additive to protect cells from the turbulent environment of sparged bioreactors. It has been demonstrated that Poloxamer 188 can function as highly effective shear protectant as it decreases physical damage to suspensions of animal cell cultures by physical and biochemical means. Managing mixing time and speed, impeller choice, agitation, gas entrance velocities etc. in typical culture conditions can support sparging-associated cell damage. Nevertheless achievable cell densities and thereby process productivity are limited without a shear protectant especially with regard to the industry trend towards higher cell densities e.g. perfusion processes. From our view there is currently no real alternative to the addition of a shear protectant.

Question:

Do you have a recommendation for concentration level of poloxamer in the media, is it different for different cell lines and is there any reason to optimize?

The Answer:

The typical concentration in chemically defined cell culture media is usually 1-2g/L but this is always dependent on the cell line, the media composition, the process, etc. We also had some applications where we could reduce the concentration to 0,5g/L thanks to our improved Poloxamer 188 and still had full shear protection in our model system and with our cell line. It may be worth trying to reduce Poloxamer concentration as it contributes to foaming and impacts oxygen transfer. However, the main function in the media is the shear protection effect and this should not be put at risk.

Question:

Do we need Poloxamer 188 in seed train?

The Answer:

Yes, Poloxamer 188 in seed trains is needed to adapt the cells to the media composition and to protect the cells from shear. Especially after thaw, cells are very sensitive.