Flow injection/membrane introduction mass spectrometry for automated monitoring and control of bioreactors
Abstract
Membrane introduction mass spectometry with flow injection analysis (FIA) sampling has been utilized for on-line monitoring of the major products and volatile metabolites of fermentation by the Bacillus polymyxa and the Klebsiella oxytoca organisms. A flow injection sampling system has been developed to rapidly deliver fermentation broth or an external standard to the mass spectrometer. Both triple quadrupole and ion trap detector mass spectrometers have been combined with this FIA sampling system and shown to be effective for bioreactor monitoring. Analyte introduction occurred via a direct insertion membrane probe in which the aqueous solutions flowed past a membrane located either within the ion source of the triple quadrupole mass spectrometer or contiguous to the ion trap detector. For both organisms, concentrations of the liquid phase products acetic acid, acetoin, 2,3-butanediol and ethanol were monitored as a function of time after permeation through the membrane and ionization by chemical ionization. Tandem mass spectrometry confirmed that these measurements were made without interference. Off-line gas chromatography was utilized to test the accuracy of these measurements and excellent agreement was found. Dissolved oxygen in the fermentation broth was also monitored and carbon dioxide and oxygen were followed in the off-gases. The O$\sb2$ and CO$\sb2$ measurements were compared with other common measurement techniques (galvanic O$\sb2$ electrode, infrared absorption and paramagnetic O$\sb2$ analysis) and very good agreement was found. The use of tandem mass spectrometry has allowed the detection of additional compounds in the Klebsiella oxytoca and Bacillus polymyxa fermentation broths that were previously not known to be present in measurable amounts. Products of fermentation by the Clostridium acetobutyricum organism have also been examined. The entire FIA sampling system combined with a triple quadrupole mass spectrometer has been automated using a personal computer. This automated bioreactor monitoring system has been utilized to obtain real time product concentration information and for feedback control of Klebsiella oxytoca fermentations. Feedback control has been achieved via computer control of oxygen availability during the fermentations.
Degree
Ph.D.
Advisors
Cooks, Purdue University.
Subject Area
Analytical chemistry|Chemical engineering
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