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Yannick Manon, Dominique Anne-Archard, Jean-Louis Uribelarrea, Carole Molina-Jouve, Luc Fillaudeau
Physical and biological study of cell cultures in a bioreactor: on-line and off-line rheological analyses

Appl. Rheol. 21:3 (2011) 35167 (11 pages)

Rheological behaviour of culture broth stands as a fundamental parameter in bioprocess performances because it affects simultaneously the heat and mass transfer as well as the flow pattern. On-line measurements of rheological behaviour are hardly compatible with the operating condition with respect to accurate and stringent conditions imposed by cell culture strategy. Our scientific and technical objectives are (i) to develop and identify an experimental device enabling on-line rheometry and (ii) to discuss and compare on-line and off-line measurements. In this aim, a bioreactor was equipped with a derivation loop including a specific on-line rheometric device as well as additional physical and biological measurements (specific density, mass flow rate, electrical conductivity, pH,pO2 and temperature) during microbial cell cultures. In a first time, friction curves of calibrated ducts were established with Newtonian and non-Newtonian shear-thinning fluids. In a second time, axenic cultures with two microorganisms (bacteria and yeast exhibiting different sizes) were investigated in pure oxidative culture in order to produce biomass under high cell concentrations: ~ 40 to 110 gCDW/l for E. coli (bacteria) and ~ 75 to 105 gCDW/l for Y. lipolytica (yeast). Cell broths exhibited Newtonian behaviour for E. coli and shear-thinning behaviour for Y. lipolytica, which were both dependant on biomass concentration. On-line and off-line rheological measurements are consistent for E. coli and Y. lipolytica, but significantly differed. On-line estimated viscosity appears higher than off-line apparent viscosity. Several assumptions in relation with microorganism physiology and metabolism (size, morphology, surface properties, concentration, biological activity) could be formulated in agreement with scientific literature. On-line rheology brings new insight to investigate complex interaction between physical and biological phenomena.

Cite this publication as follows:
Manon Y, Anne-Archard D, Uribelarrea J, Molina-Jouve C, Fillaudeau L: Physical and biological study of cell cultures in a bioreactor: on-line and off-line rheological analyses, Appl. Rheol. 21 (2011) 35167.

M. Marouche, D. Anne-Archard, H.C. Boisson
A Numerical Model of Yield Stress Fluid Dynamics in a Mixing Vessel

Appl. Rheol. 12:4 (2002) 182-191

A numerical study is conducted on the behaviour of yield stress fluids in a mixing vessel equipped with anchor agitator in laminar regime. It is shown that extending a standard Carreau model of shear thinning fluid is a suitable practice. Validations versus Couette flow analytical solution are satisfactory. Main features of local hydrodynamics and global power consumption are described for a 2D flow. Significant changes in the flow pattern are observed for low inertia and high yield stress and the results are considered as guidelines for further laboratory experiments.

Cite this publication as follows:
Marouche M, Anne-Archard D, Boisson HC: A Numerical Model of Yield Stress Fluid Dynamics in a Mixing Vessel, Appl. Rheol. 12 (2002) 182.

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