The dynamic behaviour of yeast cells immobilised in porous glass studied by membrane mass spectrometry.

Membrane mass spectrometry (MMS) with reduced sample withdrawal has been used to investigate the metabolic activity of yeast cells immobilised in porous glass. An adapted MS membrane inlet reactor with a polyethylene terephthalate barrier membrane has been constructed for this purpose. In a first experiment, the mass transport of O2 in a porous glass disc under well-defined experimental conditions has been studied by determining the apparent effective diffusion coefficient. The behaviour of immobilised Saccharomyces cerevisiae has been monitored by the MMS measurement of O2 and CO2 after applying a step in glucose concentration. Free-cell kinetic parameters were used in a dynamic reaction-diffusion model to simulate the O2 consumption curve. The theoretical and experimental curve showed comparable behaviour, which means that the immobilisation of yeast cells in porous glass has no substantial effect on its growth kinetics.