The Untold Story of Humans and Yeast: What a Symbiotic Relationship.

Yeast and its incredibly important economic role

Yeast, a single celled fungus, is responsible for some of our most important foods and beverages, among other things. Bread, wine, beer, biofuel, and insulin are all made from yeast. We humans have been using yeast for thousands of years, and it has enabled our agricultural and geographical expansion.

From article, (Yeast has been used by humans for a very long time. Grinding stones and baking chambers for yeast-raised bread have been found in Ancient Egyptian ruins. So bread is actually thousands of years old. There has been evidence of 8,000 year old wine and 7,000 year old beer. However, it wasn’t until 1680 that Anton van Leewenhoek, a Dutch naturalist, first looked at yeast microscopically. He didn’t think that it was alive though. Later, in the 1840s, Theodor Schwann realized that yeast was a fungus and attributed fermentation to it. It was Louis Pasteur that figured out why dough rises and why the mix of hops and barley turns into a tasty beverage. In 1857, he proved that living yeast causes alcohol to ferment and that it was not simply a chemical reaction.

 In baking, yeast turns sugars in the dough into carbon dioxide. Little air bubbles then form which cause the dough to expand. When baked, the live yeast dies, but the air bubbles are kept, and give bread and other baked goods their soft, spongy texture. First, the yeast uses oxygen, and produces carbon dioxide and water. Then, when the oxygen is used up, it starts to ferment and produces ethanol but, luckily, this evaporates during baking.

Baking provides $311 billion of American GDP and 1.8 million jobs. Yeast is also used to produce foods which are not baked, such as cocoa beans for chocolate, sour cream, fish sauce, kimchi, miso, Tabasco, and vinegar.

The oldest evidence of beer comes from traces on pottery in present-day Iran, 7000 years ago. Beer production was also enabled by the cultivation of cereals and followed the discovery and use of yeast-bread. There is also ancient evidence of beer in Mesopotamia and China. It was useful, because beer was safer to drink than water since not much water purification went on then.

Different strains of yeast produce different types of beer. Top-fermenting yeasts, such as S. cerevisiae, start to foam at the top and are used to produce ales. Bottom-fermenting yeasts, such as S. pastorianus, are usually used to produce lager beers and ferment well at low temperatures.

The use of yeast in wine-making is perhaps not as obvious as for beer, but it is used to convert the sugars in grape juice into ethanol. Yeast is already on grape skins, but using this wild yeast is unpredictable and therefore not good for the commercial production of wine. Instead, a pure yeast culture is usually added which takes over the fermentation and produces wine reliably. Again, S. cerevisiae is the star, though different yeast strains are used, which affect the flavor of the wine.

Believe it or not, yeast also help millions of diabetics to lead normal lives. Insulin is produced using a genetically modified yeast. Other important medicines and vaccinations are also produced with yeast, such as the vaccine against the human papilloma virus and eye degeneration. Yeasts are also sold as probiotic treatments against a variety of ailments. Not to mention that yeast is used in laboratories all around the world as a genetic model organism. Different topics such as cell development, aging and cancer are studied.

Plant material can be fermented in the absence of oxygen for energy. The ethanol produced this way (about 5-10%) is blended with gasoline to create gasohol. It emits less carbon monoxide, nitrogen oxides and hydrocarbons than regular gasoline. It is also carbon neutral; the CO2 produced when ethanol is burned is offset by the amount taken in by the plants as they grow. Maize and palm oil are most often used for ethanol production. In light of these characteristics, the world ethanol production has increased recently. However, the conversion of natural habitats to palm oil or maize plantations is also not sustainable and a balance needs to be struck.)

For More Info