Implementation of proton transfer reaction-mass spectrometry (PTR-MS) for advanced bioprocess monitoring

• Published in: Biotechnology and bioengineering Vol. 109; no. 12; pp. 3059 - 3069
• Main Authors: Luchner, Markus, Gutmann, Rene, Bayer, Karl, Dunkl, Jürgen, Hansel, Armin, Herbig, Jens, Singer, Wolfgang, Strobl, Florian, Winkler, Klaus, Striedner, Gerald
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01.12.2012; Wiley Subscription Services, Inc
• Subjects: bioprocess monitoring; Bioreactors; Biotechnology - instrumentation; Cell Culture Techniques - instrumentation; Cells; E. coli fermentation process; Equipment Design; Escherichia coli; Escherichia coli - metabolism; Fermentation; Mass spectrometry; Mass Spectrometry - methods; Metabolites; on-line monitoring; Oxygen - metabolism; proton transfer reaction-mass spectrometry (PTR-MS); Protons; Reproducibility of Results; Sampling; Signal Processing, Computer-Assisted; VOCs; volatile organic compound (VOC); Volatile organic compounds; Volatile Organic Compounds - analysis; Volatile Organic Compounds - chemistry; Volatile Organic Compounds - metabolism
• ISSN: 0006-3592; 1097-0290
• DOI: 10.1002/bit.24579

We report on the implementation of proton transfer reaction‐mass spectrometry (PTR‐MS) technology for on‐line monitoring of volatile organic compounds (VOCs) in the off‐gas of bioreactors. The main part of the work was focused on the development of an interface between the bioreactor and an analyzer suitable for continuous sampling of VOCs emanating from the bioprocess. The permanently heated sampling line with an inert surface avoids condensation and interaction of volatiles during transfer to the PTR‐MS. The interface is equipped with a sterile sinter filter unit directly connected to the bioreactor headspace, a condensate trap, and a series of valves allowing for dilution of the headspace gas, in‐process calibration, and multiport operation. To assess the aptitude of the entire system, a case study was conducted comprising three identical cultivations with a recombinant E. coli strain, and the volatiles produced in the course of the experiments were monitored with the PTR‐MS. The high reproducibility of the measurements proved that the established sampling interface allows for reproducible transfer of volatiles from the headspace to the PTR‐MS analyzer. The set of volatile compounds monitored comprises metabolites of different pathways with diverse functions in cell physiology but also volatiles from the process matrix. The trends of individual compounds showed diverse patterns. The recorded signal levels covered a dynamic range of more than five orders of magnitude. It was possible to assign specific volatile compounds to distinctive events in the bioprocess. The presented results clearly show that PTR‐MS was successfully implemented as a powerful bioprocess‐monitoring tool and that access to volatiles emitted by the cells opens promising perspectives in terms of advanced process control. Biotechnol. Bioeng. 2012; 109: 3059–3069. © 2012 Wiley Periodicals, Inc. The present study describes the implementation and evaluation of PTR‐MS as a tool for on‐line monitoring of volatile organic compounds (VOCs) in the bioreactor headspace. The developed interface between bioreactor and PTR‐MS allows for non‐invasive, highly reproducible sampling and PTR‐MS facilitates online measurement of complex VOC mixtures from ppm down to the ppt level. VOCs are analytes closely related to cell metabolism and the obtained results open promising perspectives in terms of advanced bioprocess monitoring and control.