THE DYNAMIC BEHAVIOR OF YEAST-CELLS IMMOBILIZED IN POROUS-GLASS STUDIED BY MEMBRANE MASS-SPECTROMETRY

Membrane mass spectrometry (MMS) with reduced sample withdrawal has be en used to investigate the metabolic activity of yeast cells immobilis ed in porous glass. An adapted MS membrane inlet reactor with a polyet hylene terephthalate barrier membrane has been constructed for this pu rpose. In a first experiment, the mass transport of O-2 in a porous gl ass disc under well-defined experimental conditions has been studied b y determining the apparent effective diffusion coefficient. The behavi our of immobilised Saccharomyces cerevisiae has been monitored by the MMS measurement of O-2 and CO2 after applying a step in glucose concen tration. Free-cell kinetic parameters were used in a dynamic reaction- diffusion model to simulate the O-2 consumption curve. The theoretical and experimental curve showed comparable behaviour, which means that the immobilisation of yeast cells in porous glass has no substantial e ffect on its growth kinetics.