"What is yeast doing during beer fermentation? It is consuming wort sugars, and turning that sugar into new yeast cells, ethanol, CO2, and flavor compounds. Brewers are primarily concerned about flavor compounds. In order to maximize the correct flavor compounds, it is helpful to know how yeast ferments beer.
Ale fermentation of brewers wort follows three phases: lag phase for 3-15 hours, exponential growth phase for 1-4 days, and stationary phase of yeast growth for 3-10 days. Each of these phases will be described in terms of yeast behavior." [Read More]