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Modelling and advanced understanding of unsteady‐state gas transfer in shaking bioreactors
Author(s) -
Amoabediny Ghassem,
Büchs Jochen
Publication year - 2007
Publication title -
biotechnology and applied biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.468
H-Index - 70
eISSN - 1470-8744
pISSN - 0885-4513
DOI - 10.1042/ba20060120
Subject(s) - mass transfer , laboratory flask , bioreactor , chemistry , thermodynamics , spark plug , volume (thermodynamics) , plug flow , mechanics , partial pressure , oxygen , chromatography , physics , organic chemistry
In shaken bioreactors equipped with a sterile closure (e.g. a cotton plug), a realistic understanding and estimation of gas transfer is advantageous to avoid oxygen limitation or carbon dioxide inhibition of a microbial culture. Therefore, in the present study, an unsteady‐state gas‐transfer model for shake flasks was developed and experimentally investigated for a wide range of gas‐transfer resistances ( k plug ). The introduced approach is based on the model of Henzler and co‐workers [Henzler and Schedel (1991) Bioprocess Eng. 7, 123–131; Mrotzek, Anderlei, Henzler and Büchs (2001) Biochem. Eng. J. 7, 107–112], which describe the spatially resolved gas partial pressures inside the sterile closure, affecting the local gas diffusion coefficients and convective Stefan flow. For further easy processing the resulting total mass‐transfer resistance ( k plug ) is described as a function of the mass flow through the sterile plug ( OTR plug ) by an empirical equation. This equation is introduced into a simulation model which calculates the gas partial pressures in the head space of the flask. Additionally, the gas‐transfer rates through the sterile closure and gas/liquid interface inside the flask is provided. Simulations indicate that neglecting the oxygen in the head space volume of the flask under initial conditions (simple steady‐state assumption) may lead to an underestimation of the oxygen transfer into the liquid phase. The extension of error depends on the conditions. A good agreement between the introduced unsteady‐state model and experimental results for the sulfite oxidation as a chemical model system confirmed the validity and usefulness of the proposed unsteady‐state approach.