Biomonitoring of working yeasts in practice in the fluorescence optical method .4. Cell cycle and 3 beta-hydroxysterol content

The main intercellular parameter of saccharomyces yeasts include the DNA content and the content of neutral lipids, enzymes and membrane-bound 3b-hydroxysterols. These have a great influence on the physiology of the working yeasts. In addition to proliferation controls, biomonitoring of the fermentation and maturing processes must also include the function of the yeast cells. The 3b-hydroxysterols have two key functions during the growth and proliferation of the yeast. The ''sparking function'' is regarded as the triggering moment for the proliferation process (cell cycle initiation) of the yeast cells. The ''bulk membrane function'' has an influence on the permeability, fluidity and stability of the yeast membrane. The interaction between the ambient conditions and the signal transfer by the yeast cells as to wether the specified conditions are adequate for starting a cell cycle of for stopping growth and proliferation, are of major significance for the fermentation process. Using optical fluorescence analyses the cell phase and the various cell statuses in a population can be determined statistically during the growth process.