Anaerobic fermentation is a process that occurs when microorganisms, like yeast and bacteria, break down sugars without the presence of oxygen. This process is essential for producing energy in environments where oxygen is scarce. One common example is the fermentation of grapes by yeast to create wine, where the sugars in the grapes are converted into alcohol and carbon dioxide. In addition to wine, anaerobic fermentation is also used in making bread and yogurt. In bread-making, yeast ferments the sugars in the dough, causing it to rise and develop a light texture. Similarly, in yogurt production, bacteria ferment lactose, the sugar in milk, resulting in a tangy and creamy product.