title: Physiological capacities decline during induced bioprocesses leading to substrate accumulation.
abstract: During the cultivation of E. coli for recombinant protein production, substrate accumulation is often observed in induction phase. Uncontrolled substrate accumulation leads to difficulties in transferring or scaling processes and even to failed batches. The phenomenon of metabolite/substrate accumulation occurs as a result of exceeding the physiological capacity to metabolize substrate (qScrit). In contrast to the common understanding of qScritas "static" value, we hypothesize that qScritessentially has a dynamic nature. Following the state of the art approach of physio logical strain characterization, substrate pulse experiments were used to quantify qScritin induction phase. The qScritwas found to be temperature and time dependent. Subsequently, qScritwas expressed through a linear equation, to serve as boundary for physiologically controlled experiments. Nevertheless, accumulation was observed within a physiologically controlled verification experiment, although the qScritboundary was not exceeded. A second set of experiments was conducted, by oscillating the qSset point between discrete plateaus during physiologically controlled experiments. From the results, we deduced a significant interrelation between the metabolic activity and the timely decline of qScrit. This finding highlights the necessity of a comprehensive but laborious physiological characterization for each strain or alternatively, to use physio logical feedback control to facilitate real time monitoring of qScrit, in order to effectively avoid substrate accumulation.
authors.affiliation: Christian Doppler Laboratory for Mechanistic and Physiological Methods for Improved Bioprocesses, Institute of Chemical Engineering, Vienna University of Technology, Vienna, Austria.
authors.forename: Wieland N
authors.initials: WN
authors.lastname: Reichelt
authors.affiliation: Christian Doppler Laboratory for Mechanistic and Physiological Methods for Improved Bioprocesses, Institute of Chemical Engineering, Vienna University of Technology, Vienna, Austria.
authors.forename: Markus
authors.initials: M
authors.lastname: Brillmann
authors.affiliation: Research Division Biochemical Engineering, Institute of Chemical Engineering, Vienna University of Technology, Vienna, Austria.
authors.forename: Peter
authors.initials: P
authors.lastname: Thurrold
authors.affiliation: Research Division Biochemical Engineering, Institute of Chemical Engineering, Vienna University of Technology, Vienna, Austria.
authors.forename: Peter
authors.initials: P
authors.lastname: Keil
authors.affiliation: Research Division Biochemical Engineering, Institute of Chemical Engineering, Vienna University of Technology, Vienna, Austria.
authors.forename: Jens
authors.initials: J
authors.lastname: Fricke
authors.affiliation: Christian Doppler Laboratory for Mechanistic and Physiological Methods for Improved Bioprocesses, Institute of Chemical Engineering, Vienna University of Technology, Vienna, Austria.|Research Division Biochemical Engineering, Institute of Chemical Engineering, Vienna University of Technology, Vienna, Austria.
authors.forename: Christoph
authors.initials: C
authors.lastname: Herwig
mesh_terms: D061249:Batch Cell Culture Techniques; D004926:Escherichia coli / Q000235:genetics / Q000502:physiology*; D011994:Recombinant Proteins / Q000378:metabolism*; D013696:Temperature; D013997:Time Factors
chemical_list: D011994:Recombinant Proteins
keywords: balancing approach; bioprocess control; dynamic experiments; physiological bioprocess development; physiological capacity; substrate accumulation