Although there are hundreds of strains of yeast, only two main varieties are used in beer. 1. ale yeast . This is because they tend to flocculate at the surface of the beer in the begining of the fermentation process. A temperature range of 32 to 55 degrees F best suits this type of yeast. During this period, yeasts gain and store energy for reproduction and other activities.
Yeasts can gain energy from oxygen and sugar . .
Reproduction Yeasts are single cell organisms that reproduce through budding. During this part of the life cycle, yeast expends energy by converting sugars to alcohol, carbon dioxide and distinct flavor. At this time, the yeast is dispersed and in a state of suspension in order to obtain maximum contact with the liquid beer mixture. . At this stage, the yeast runs out of food and energy. It gathers and then settles, essentially shutting down all activity.