Thesis for Doctor of Philosophy

Bruno Sommer Ferreira
“Monitoring of Fermentations with Mass Spectrometry: Pitfalls and Achievements”
Ph. D. Biotechnology, IST, 2001
Supervisor: M. M. R. da Fonseca

Abstract

This thesis addresses the on line monitoring of fermentations with mass spectrometry.

Set up procedures to achieve proper performance of the mass spectrometer were implemented. An efficient calibration method was developed that allowed an important improvement in the accuracy of the measurements when compared with that obtained with methods described in the literature.

Propene, the carbon source of the system initially aimed to be studied, affected the overall mass spectrometer performance. An explanation for the effects of propene was suggested and supported by a simple mathematical model.

A microporous, hydrophobic hollow fibre membrane interface was developed to analyse dissolved gases and volatiles on liquid streams. The influence of membrane area and flow rates of the contacting streams on the measurements was studied. An attempt to measure consecutively gaseous and liquid streams was performed, however large transients resulted upon switching between streams.

Mass spectrometry was used to monitor the Pseudomonas putida growth on glutamic acid. Off-gas measurements allowed the estimation of biomass concentration, specific growth rate and oxygen volumetric mass transfer coefficient.

The information provided by mass spectrometry monitoring, together with off-line determined metabolite concentrations, allowed the understanding of the metabolism of a recombinant Saccharomyces cerevisiae strain producing cutinase from Fusarium solani pisi.

Keywords: Mass spectrometry; On-line analysis; Microporous hydrophobic hollow fibres; Fermentation monitoring ; Pseudomonas putida; Recombinant Saccharomyces cerevisiae