High-pressure CO2 inactivation and induced damage on Saccharomyces cerevisiae evaluated by flow cytometry

The cultivability, integrity and permeabilisation of Saccharomyces cerevisiae in saline solution after high-pressure CO2 treatment at 36 °C was assessed by using both conventional cultivation-based technique and flow cytometry. Conventional cultivation-based techniques do not allow the exact quantification of integer cells, which can be determined coupling the staining with propidium iodide and SYBR-Green I and the cell quantification by flow cytometry. A significant portion of cells injured by CO2 treatment is incapable of forming colonies but is still integer and potentially metabolically active. The yeast cell damage was demonstrated to be dependent on the conditions applied. In particular the influence of different operative parameters on integrity and permeabilisation of yeast cells was evaluated: pressure (50–100 bar), treating time (10–20 min) and stirring rate (500–10,000 rpm). After a 20 min treatment at 100 bar, 36 °C and 10,000 rpm more than 95% of cells result with completely permeabilised membrane.