AN ONLINE SAMPLING SYSTEM FOR FERMENTATION MONITORING USING MEMBRANE INLET MASS-SPECTROMETRY (MIMS) - APPLICATION TO PHENOXYACETIC ACID MONITORING IN PENICILLIN FERMENTATION

A sampling system for on-line monitoring of organic compounds of low v olatility in complex fermentation media uses membrane inlet mass spect rometry (MIMS). A syringe pump draws a continuous flow of microfiltere d broth from the reactor and circulates it after acidification through a membrane inlet, in which a membrane is the only interface between t he sample and the high vacuum of a mass spectrometer. All operations r un automatically, i.e., sampling, acidification, measurement, and cali bration. The on-stream acidification enables MIMS monitori ng of carbo xylic acids, as they must be undissociated in order to pass the hydrop hobic membrane. The performance of the monitoring system was tested by measurements of standard solutions of phenoxyacetic acid (POAA, the s ide chain precursor of penicillin-V) as well as on POAA during 200 h p enicillin-V fermentation. During the entire fermentation POAA was moni tored in low millimolar concentrations with high accuracy and fast res ponse to step changes in POAA concentration. Tandem mass spectrometry (MS/MS) allowed direct identification of peaks in the mass spectrum of the broth that were not accounted for by POAA. These peaks were ident ified as SO2 and SCO. (C) 1994 John Wiley & Sons, inc.