Assessing Viability of Recombinant Pichia pastoris in Fermentation Process with Flow Cytometry

This paper describes the establishment of flow cytometric methods to assess the viability for recombinant methylotrophic P.pastoris strains and its application to a lab scale high cell density fermentation.Using a recombinant strain expressing human reteplase(hrPA),the cell viabilities were measured with propidium iodide staining.The cell viability decreases significantly by 14% during the methanol(induction) phase,indicating there was a stress situation triggered by the fermentation conditions.These(data) demonstrate that cell viability is an important physiological parameter and flow cytometry is a power-(ful) tool for the analysis and optimization of recombinant protein production processes expressed with P.(pastoris.)