The organism commonly used in fermentation processes is yeast, particularly species like Saccharomyces cerevisiae. Yeast is a type of fungus that converts sugars into alcohol and carbon dioxide through the metabolic process of fermentation. This process is vital in the production of various foods and beverages, such as bread, beer, and wine. By fermenting sugar, yeast not only contributes to flavor and texture but also acts as a leavening agent in baking and serves ecological roles in nutrient cycling.