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Hydrodynamic shear stress in hollow filter for perfusion culture of human cells
KTH, School of Engineering Sciences (SCI). KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Industrial Biotechnology. (Cell Technology Group (CETEG))
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Industrial Biotechnology.
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Protein Science, Protein Technology.ORCID iD: 0000-0003-1763-9073
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

High cell density perfusion process is an economical way to produce biopharmaceuticals at high yield. To achieve high density of healthy cells, the cell culture conditions should be free from mechanically detriment. Human embryonic kidney (HEK) K293 cells, interesting for the production of therapeutic glycoproteins, are known as shear sensitive. In order to obtain the optimal hydrodynamics conditions with reduced mechanical damage, we investigated the fact of the shear stress compatible with HEK293 cells. We reviewed hollow filter based tangential flow filtration strategies, tangential flow filtration (TFF) and alternating tangential flow filtration (ATF). We studied shear stress introduced by these two flow filtration methods. By theoretical study, we obtained that lower shear stress introduced by alternating tangential flow filtration result in lower average shear stress comparing to tangential flow filtration with same flow rate.  In our experimental runs, we achieved different shear stress levels by applying different flow rates. 5-Days batch cultivations were performed to examine the influence of shear stress on cell growing and metabolic behaviour. We identified that the shear stress potentially reduce the growth rate and productivity of HEK293 cells and found the cell metabolism associated with shear stress levels. By documenting these cell responses to shear stress, we confirmed our theoretical results and could further optimize the hydrodynamic conditions for perfusion process of HEK 293 cells. 

Keywords [en]
shear stress, perfusion, HEK293 cells, tangential flow filtration
National Category
Industrial Biotechnology
Identifiers
URN: urn:nbn:se:kth:diva-252020OAI: oai:DiVA.org:kth-252020DiVA, id: diva2:1317559
Note

QC 20190523

Available from: 2019-05-23 Created: 2019-05-23 Last updated: 2019-05-27Bibliographically approved
In thesis
1. Hydrodynamics considerations in cells systems from ocean flow to perfusion cultivation process
Open this publication in new window or tab >>Hydrodynamics considerations in cells systems from ocean flow to perfusion cultivation process
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Microorganisms and animal cells are grown surrounded by fluid, which is providing them with nutrients and removing their waste products. In nature and industry processes, cells/microbes can be subject to aggressive environments, such as turbulent flow or shear flow. Hydrodynamics force generated in these flows can affect the distribution of cells/microbes and even lead to cell damage. Understanding the mechanism and exploring the effect of hydrodynamic force in these environments could make the prediction of cells’ hydrodynamic response more systematic. In pharmaceutical industry, perfusion process is recognized as an attractive option for biologics production due to its high productivity. However, there are still some challenges and limitations for further process improvement due to lack of information of cell response to hydrodynamic force and nutrients. In both cases, hydrodynamics plays an important role and similar tool can be used to achieve a deeper understanding of these processes. This thesis is mainly aiming to elucidate the influence of hydrodynamic forces on microorganisms or cells in nature and during bioprocesses. In particular, shear stress in a natural environment and in a bioreactor operated in perfusion mode is studied.

This work mainly investigates hydrodynamics in nature and bioprocess including three flow cases. The first study investigates the effect of turbulence on marine life by performing direct numerical simulations (DNS) of motile micro-organisms in isotropic homogeneous turbulence. The clustering level of micro-organisms with one preferential swimming direction (e.g. gyrotaxis) is examined. The second study uses Computation Fluid Dynamics (CFD) to simulate the fluid flow inside a Wave bioreactor bag. The phenomenon of mixing, oxygen transfer rate and shear stress in nine different operating conditions of rocking speeds and angles are discussed. In the third study, the cellular response to shear force including growth and metabolism in a cell retention device such as hollow fiber filters during a perfusion process is analyzed. Theoretical calculations and experiment validation is performed to compare two filtration modes, tangential flow filtration (TFF) or alternating tangential flow filtration (ATF). Further optimizations regarding mixing and feeding are performed in a screening scale of in a perfusion system of stirred tank bioreactor with cell separation device.

The main findings can be summarized as that spherical gyrotaxis swimmers show significant clustering, whereas prolate swimmers remain more uniformly distributed due to their large sensitivity to the local shear. These results could explain how pure hydrodynamic effects can alter the ecology of micro-organisms for instance by varying shape and their preferential orientation (paper I). The simulations of Wave bioreactors show that the mixing and shear stress increase with the rocking angle but that increasing rocking speeds are not systematically associated with increasing mixing and shear stress. A resonance phenomenon is responsible for the fact that the lowest studied rocking speed generates the highest fluid velocity, mixing and shear stress (paper II). Theoretical velocity profile-based calculations suggested a lower shear stress for ATF by a factor 0.637 compared to TFF. This is experimentally validated by cultures of HEK (human embryonic kidney) 293 cells subjected to shear stress by a perfusion system that affects growth and metabolism using these cell separation devices (paper III). Thanks to optimization of mixing and oxygen transfer in a screening system for perfusion process, very high cell densities above 100 x 106 cells/mL of mammalian cells were achieved (paper IV).

Place, publisher, year, edition, pages
Stockholm, Sweden: KTH Royal Institute of Technology, 2019. p. 57
Series
TRITA-CBH-FOU ; 35
Keywords
Microorganism, cells, hydrodynamics, turbulence, numerical simulation, CFD, Resonance, Wave bioreactor, ATF, TFF, perfusion, design feeding strategy
National Category
Industrial Biotechnology
Research subject
Biotechnology
Identifiers
urn:nbn:se:kth:diva-252023 (URN)978-91-7873-233-3 (ISBN)
Public defence
2019-06-14, FA32, Albanova, Department of Mechanics, Royal Institute of Technology, Stockholm, 13:00 (English)
Opponent
Supervisors
Funder
AstraZenecaKnut and Alice Wallenberg Foundation
Note

QC 2019-05-23

Available from: 2019-05-23 Created: 2019-05-23 Last updated: 2019-05-23Bibliographically approved

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Zhan, CaijuanMalm, MagdalenaRockberg, JohanChotteau, Véronique

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