Yeasts are single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and today there are approximately 1,500 species in existence. These organisms are found in nearly every environment on Earth, from the polar regions to the hottest deserts. Yeasts are essential for many biological processes and have played a significant role in human history.
For thousands of years, humans have used yeasts for baking and brewing. In fact, breadmaking was one of the first biotechnologies developed by early civilizations. The ancient Egyptians were probably the first to use yeast fermentation in baking leavened breads around 1500 BCE. This process was later refined by the Greeks and Romans who developed different methods for making breads, cakes, and pastries using various types of flour and yeasts.
Yeast strains are also used in brewing beer and fermenting wine. The alcohol content in these beverages is a result of yeast fermentation; these microorganisms consume sugars present in grains or fruits and convert them into ethanol (alcohol) and carbon dioxide gas. In addition to their roles in food production, yeasts are also used to make pharmaceuticals such as antibiotics, vitamins, enzymes, and hormones. Some strains have even been genetically modified to produce fuel ethanol or other chemicals.
Despite their small size, yeasts play an important role in our world. They are essential for many biochemical processes and have greatly impacted human culture throughout history