title: Insights into large-scale cell-culture reactors: II. Gas-phase mixing and CO₂ stripping.
abstract: Most discussions about stirred tank bioreactors for cell cultures focus on liquid-phase motions and neglect the importance of the gas phase for mixing, power input and especially CO(2) stripping. Particularly in large production reactors, CO(2) removal from the culture is known to be a major problem. Here, we show that stripping is mainly affected by the change of the gas composition during the movement of the gas phase through the bioreactor from the sparger system towards the headspace. A mathematical model for CO(2)-stripping and O(2)-mass transfer is presented taking gas-residence times into account. The gas phase is not moving through the reactor in form of a plug flow as often assumed. The model is validated by measurement data. Further measurement results are presented that show how the gas is partly recirculated by the impellers, thus increasing the gas-residence time. The gas-residence times can be measured easily with stimulus-response techniques. The results offer further insights on the gas-residence time distributions in stirred tank reactors.
authors.affiliation: Center for Bioprocess Engineering, Martin-Luther-University Halle-Wittenberg, Halle, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Sieblist
authors.forename: Oliver
authors.initials: O
authors.lastname: Hägeholz
authors.forename: Mathias
authors.initials: M
authors.lastname: Aehle
authors.forename: Marco
authors.initials: M
authors.lastname: Jenzsch
authors.forename: Michael
authors.initials: M
authors.lastname: Pohlscheidt
authors.forename: Andreas
authors.initials: A
authors.lastname: Lübbert
mesh_terms: D000818:Animals; D019149:Bioreactors; D002245:Carbon Dioxide / Q000737:chemistry*; D018929:Cell Culture Techniques / Q000295:instrumentation* / Q000379:methods; D003198:Computer Simulation; D008954:Models, Biological; D008956:Models, Chemical; D055585:Physical Phenomena; D010865:Pilot Projects; D015203:Reproducibility of Results
chemical_list: D002245:Carbon Dioxide