FLOW CYTOMETRIC MONITORING OF RHODAMINE-123 AND A CYANINE DYE UPTAKE BY YEAST DURING CIDER FERMENTATION

Flow cytometry of rhodamine 123- or cyanine-stained cider yeast shows that the capacity for mitochondrial uptake of these cationic dyes is l ost early in the fermentation. Survival of prolonged anaerobiosis (for at least 22 days) at high ethanol concentrations (at least 11% v/v) d uring cider fermentation does not require the maintenance of a measura ble inner mitochondrial transmembrane electrochemical potential. Confo cal laser scanning microscopy of yeasts after exposure to either of th e cationic dyes confirms the lack of mitochondrial development and ina bility of the fermentative organisms to take up the fluorophores. Aera tion of samples taken from the fermentation vessels restores the ultra structure and the dye uptake capacity of the yeasts. This indicates th at the changes are reversible, and that the organisms have retained th eir viability.