Tandem mass spectrometry for on-line fermentation monitoring

Membrane introduction mass spectrometry has been employed for on-line determination of the major products and volatile metabolites of Bacillus polymyxa fermentation. Samples were introduced into the mass spectrometer via a direct insertion membrane probe in which the aqueous solution flowed past a membrane located in the ion source of the mass spectrometer. Concentrations of the products 2,3-butanediol, acetoin, ethanol and acetic acid in fermentation broth were measured by tandem mass spectrometry after permeation through the membrane and ionization by chemical ionization. Dissolved CO sub(2) and O sub(2), as well as CO sub(2) in the off gases, were also monitored on-line by mass spectrometry. The use of tandem mass spectrometry has allowed the identification of products that were not previously known to be present in measurable amounts.