Which unicellular organism is used commercially in both brewing and baking?

Yeast is the correct answer because it is a unicellular fungus that plays a crucial role in both the brewing and baking industries due to its ability to ferment sugars. In brewing, yeast converts sugars from grains into alcohol and carbon dioxide through the process of fermentation, which is essential for producing beer and other alcoholic beverages. Similarly, in baking, yeast ferments sugars in the dough, producing carbon dioxide that helps bread rise, giving it a light and airy texture. Yeast's unique metabolic process enables these valuable commercial applications, making it an indispensable organism in these industries.