title: The impact of pH inhomogeneities on CHO cell physiology and fed-batch process performance - two-compartment scale-down modelling and intracellular pH excursion.
abstract: Due to high mixing times and base addition from top of the vessel, pH inhomogeneities are most likely to occur during large-scale mammalian processes. The goal of this study was to set-up a scale-down model of a 10-12 m3stirred tank bioreactor and to investigate the effect of pH perturbations on CHO cell physiology and process performance. Short-term changes in extracellular pH are hypothesized to affect intracellular pH and thus cell physiology. Therefore, batch fermentations, including pH shifts to 9.0 and 7.8, in regular one-compartment systems are conducted. The short-term adaption of the cells intracellular pH are showed an immediate increase due to elevated extracellular pH. With this basis of fundamental knowledge, a two-compartment system is established which is capable of simulating defined pH inhomogeneities. In contrast to state-of-the-art literature, the scale-down model is included parameters (e.g. volume of the inhomogeneous zone) as they might occur during large-scale processes. pH inhomogeneity studies in the two-compartment system are performed with simulation of temporary pH zones of pH 9.0. The specific growth rate especially during the exponential growth phase is strongly affected resulting in a decreased maximum viable cell density and final product titer. The gathered results indicate that even short-term exposure of cells to elevated pH values during large-scale processes can affect cell physiology and overall process performance. In particular, it could be shown for the first time that pH perturbations, which might occur during the early process phase, have to be considered in scale-down models of mammalian processes.
authors.affiliation: Research Division Biochemical Engineering, Institute of Chemical Engineering, Vienna University of Technology, Vienna, Austria.|CD Laboratory on Mechanistic and Physiological Methods for Improved Bioprocesses, Vienna University of Technology, Vienna, Austria.
authors.forename: Matthias
authors.initials: M
authors.lastname: Brunner
authors.affiliation: Research Division Biochemical Engineering, Institute of Chemical Engineering, Vienna University of Technology, Vienna, Austria.|CD Laboratory on Mechanistic and Physiological Methods for Improved Bioprocesses, Vienna University of Technology, Vienna, Austria.
authors.forename: Philipp
authors.initials: P
authors.lastname: Braun
authors.affiliation: Research Division Biochemical Engineering, Institute of Chemical Engineering, Vienna University of Technology, Vienna, Austria.|CD Laboratory on Mechanistic and Physiological Methods for Improved Bioprocesses, Vienna University of Technology, Vienna, Austria.
authors.forename: Philipp
authors.initials: P
authors.lastname: Doppler
authors.affiliation: Sandoz GmbH, Langkampfen, Austria.
authors.forename: Christoph
authors.initials: C
authors.lastname: Posch
authors.affiliation: Sandoz GmbH, Langkampfen, Austria.
authors.forename: Dirk
authors.initials: D
authors.lastname: Behrens
authors.affiliation: Research Division Biochemical Engineering, Institute of Chemical Engineering, Vienna University of Technology, Vienna, Austria.|CD Laboratory on Mechanistic and Physiological Methods for Improved Bioprocesses, Vienna University of Technology, Vienna, Austria.
authors.forename: Christoph
authors.initials: C
authors.lastname: Herwig
authors.affiliation: Research Division Biochemical Engineering, Institute of Chemical Engineering, Vienna University of Technology, Vienna, Austria.|CD Laboratory on Mechanistic and Physiological Methods for Improved Bioprocesses, Vienna University of Technology, Vienna, Austria.
authors.forename: Jens
authors.initials: J
authors.lastname: Fricke
mesh_terms: D000818:Animals; D061249:Batch Cell Culture Techniques / Q000379:methods*; D019149:Bioreactors; D016466:CHO Cells / Q000166:cytology*; D049109:Cell Proliferation; D006224:Cricetinae; D003412:Cricetulus; D005285:Fermentation; D006863:Hydrogen-Ion Concentration
keywords: Intracellular pH; Mammalian cell culture; Scale-down model; Two-compartment system; pH inhomogeneities