The conversion of sugar (or any carbohydrate) into alcohol and carbon dioxide, by yeast, is just one example of fermentation. According to Wikipedia, fermentation is "[any] metabolic process that produces chemical changes in organic [substances] through the action of enzymes."
Other examples of fermentation given by Wikipedia include the production of lactic acid by mammalian muscles during periods of intense exercise, and the production of methane in the rumens (stomachs) of cattle.
© Macclesfield Quiz League 2021