Spiritual yeast Saccharomyces cerevisiae, are unicellular microorganisms belonging to the class of ascomycetes (marsupial fungi) and are intended for the fermentation of the sugars contained in saccharified wort into alcohol. The main requirement for yeast is its high fermentation activity. It is also necessary to create optimal conditions for their life: pH level, temperature, availability of nutrients (minerals, vitamins, amino acids). The question of the presence of pathogenic microflora, which affects the fermentation process itself and the amount of ethanol produced by yeast, is especially important.