alcohol-gcse chemWatch this thread
'describe the production of ethanol by fermentation of carbohydrates in aqueous solution, using yeast to provide enzymes'.
'explain how to obtain a concentrated solution ethanol by fractional distillation of the fermentation mixture'
Enzymes in yeast ferment glucose in anaerobic respiration to form CO2 and ethanol
As the fermentation reaction will take place in an aqueous solution, there will be water present. Use fractional distillation to remove the liquid with the lower boiling point. You have separated water and ethanol. As the ethanol will contain hopefully no water, it will be concentrated