Some uses of yeast

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What Are Some Common Uses of Yeast?
Updated March 13, 2018
By Chris Rowling
Yeast is a single-celled organism that reproduces as3xually and has been used in baking and brewing for thousands of years. There are at least 1,500 species of yeast, all of which are technically living organisms. Yeast occurs naturally in the environment and is in the same biological family as fungi such as mushrooms.

The most common use of yeast has been in the making of bread. The yeast reacts with oxygen and helps leaven bread, or make it rise. During Passover, Jewish people will remove the yeast from bread to make flatbread. There is evidence the ancient Egyptians used yeast to make bread around 4,000 years ago.

Alcoholic Drinks
Brewing wine and beer has also used yeast for centuries to ferment the mixture to make it alcoholic. Different kinds of yeast are used to make ale, lager, spirits and wine. It makes alcohol by reacting with the sugars that naturally occur in these drinks.

Non-Alcoholic Drinks
Root beers and other soft drinks use yeast to add flavor, but the fermentation process is stopped before the drink becomes alcoholic. This means the drinks are much sweeter than their alcoholic counterparts and contain more carbon dioxide. They also normally have a very low alcohol content, although this is usually around 0.1 percent.

Scientific Research
Due to the cellular makeup of yeast, many scientists use it to learn more about human genetics. Studies of yeast cultures led directly to the mapping of the human genome.

Most recently yeast has been used in the production of biofuels. This is because the yeast turns sugar into ethanol which can be used as a diesel substitute in vehicles. The process it goes through is identical to that of making beer or wine.

Many of the probiotic drinks available now use yeast as a supplement. Many vegetarians use yeast as a supplement due to low protein and vitamin amounts in their normal diet.

Yeast Extract
Yeast can also be processed to create yeast extract. This is then used in a variety of food products such as Marmite and Vegemite.


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Denatured Alcohol Vs. Isopropyl Alcohol
Updated May 07, 2018
By Doug Johnson
Isopropyl alcohol and denatured alcohol share many similarities. However, their chemical structures, means of production, and toxicity vary. In science, the term alcohol refers to a broad range of organic compounds containing one or more hydroxyl – hydrogen and oxygen – groups. They have a long history of human use as cleaners and disinfectants, although the chemical group's biggest claim to fame can be found in liquor stores and bars: ethyl alcohol, or grain alcohol, finds use among humans as a recreational beverage or drug. However, isopropyl alcohol and denatured alcohol cannot be safely consumed by humans.

TL;DR (Too Long; Didn't Read)
Isopropyl and denatured alcohol share many similarities, but the means by which humans create them, their toxicity, and their purposes vary. Isopropyl alcohol and denatured alcohol cannot be safely consumed by humans.

Alcohol Production Methods
Humans make grain alcohol by fermenting fruits or grains, anything with a high starch content. Most often, alcohol that is created to be turned into denatured alcohol comes from sugarcane, beets and corn. After producers make the highly concentrated alcohol, they add a variety of substances to it to prevent humans from drinking it due to its poisonous nature or extremely bitter taste: benzene, formaldehyde and iodine, for example.

While ethyl alcohol isn't particularly harmful to humans before the denaturing process, ingesting isopropyl alcohol can cause vomiting, intestinal bleeding and, in severe cases, death. Producers make isopropyl alcohol through a reaction of propylene, a petroleum byproduct, and sulfuric acid, and then add water.

The two types of alcohol have different chemical formulas: ethanol (C2H6O) and isopropanol (C3H8O). Isopropyl alcohol can be found as a bittering agent in denatured alcohol.

Uses for Different Alcohols
After producers add bittering agents, denatured alcohol becomes more toxic than isopropyl alcohol. Additionally, some of the additive chemicals can harm a human's skin. As such, it rarely finds use in medical settings.

Isopropyl alcohol, on the other hand, can be found in most hospitals and medicine cabinets. It's relatively mild effect on human skin also means cosmetic makers add it to products like hand lotions. Similarly, isopropyl alcohol can be safely used to clean electronic components, unlike denatured alcohol.

When denatured alcohol evaporates, it leaves behind a residue that can affect the sensitive parts of a computer. Similarly, some of the other chemicals in denatured alcohol can be corrosive to plastics. Denatured alcohol can also be found in cosmetics, but most often it finds use as an industrial chemical. Denatured alcohol can be used as fuel for stoves and lamps. Both types of alcohols can be used as solvents and, in some cases, disinfectants.


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5 Uses of Fermentation
Updated March 01, 2020
By Lan Luo
Reviewed by: Lana Bandoim, B.S.
Fermentation is a chemical process by which carbohydrates, such as starch and glucose, are broken down anaerobically. Fermentation has many health benefits and is used in the production of alcoholic beverages, bread, yogurt, sauerkraut, apple cider vinegar and kombucha. It is also used in industry to generate ethanol as a source of biofuel.

A Brief History of Fermentation
Over the course of human history, different cultures have produced fermented beverages by leaving grains and fruits in covered containers, without understanding why the recipe worked.

It was not until Joseph Louis Gay-Lussac experimented with a method for keeping grape juice unfermented for a long time that he found yeast was indispensable for alcoholic fermentation. It was Pasteur, however, who demonstrated that yeast is responsible for the transformation of glucose to ethanol in fermented beverages. He also discovered microorganisms that cause milk to sour, which was later found to be the action of bacteria in lactic acid fermentation.

Definition of Fermentation
Fermentation is a metabolic process in which the activity of microorganisms brings about a desirable change to a food or beverage. For example, in the production of alcoholic beverages or acidic dairy products. In this chemical process, molecules such as glucose are broken down under anaerobic conditions.

The word “ferment” stems from the Latin word “fervere,” which means to boil. The science of fermentation is known as zymology, from Greek for “the workings of fermentation”, and is a study of the biochemical process of fermentation and its applications.

Fermentation occurs under anaerobic conditions (absence of oxygen), with the action of microorganisms (yeasts, bacteria and molds) that extract energy from the process.

Some species of yeast, such as Saccharomyces cerevisiae, prefers fermentation to aerobic respiration, even when oxygen is abundant, as long as there is an adequate supply of sugar. Fermentation is not limited to yeast but can also be carried out in muscles, in which the muscles catalyze the conversion of glucose to lactate.

Biochemical View
Glycolysis, which is the metabolic pathway that converts glucose to pyruvate, is the first step in fermentation. During the process of glycolysis, one molecule of glucose, a six carbon sugar, breaks down into two pyruvate molecules. This exothermic reaction releases energy for the phosphorylation of ADP to ATP and conversion of NAD+ to NADH.

In the presence of oxygen, the pyruvate may then be oxidized through the tricarboxylic acid cycle, a process known as aerobic respiration. Conversely, the pyruvate may be reduced to alcohol, lactic acid or other products in the absence of oxygen, in the fermentation process.

Types of Fermentation
There are many types of fermentation, distinguished mainly by the end products. Two of the most important and commonly used types are ethanol/alcoholic fermentation and lactic acid fermentation.

Ethanol fermentation is used in the production of alcoholic beverages. Lactic acid fermentation is used to flavor or preserve dairy and vegetables. Lactic acid fermentation also occurs in muscle cells under strenuous activity. In this case, muscles consume energy (ATP) faster than oxygen can be supplied, resulting in an anaerobic environment and thus lactic acid buildup and sore muscles.

There are other types of fermentation such as acetic acid fermentation, acetone-butanol-ethanol fermentation and mixed acid fermentation.

Ethanol Fermentation
Ethanol fermentation is defined as the biological process that turns sugar (glucose, fructose and sucrose) into ethanol, carbon dioxide and energy.

After the initial glycolysis step that converts one glucose molecule to two pyruvate molecules, the pyruvate molecules further break down into two acetaldehyde and two carbon dioxide molecules, a step catalyzed by pyruvate decarboxylase. Alcohol dehydrogenase then facilitates the conversion of the two acetaldehyde molecules to two ethanol molecules, utilizing the energy and hydrogen from NADH.

Ethanol fermentation
Lactic Acid Fermentation
Lactic acid fermentation is another type of fermentation and is described as the metabolic process that transforms sugar into the metabolite lactate and energy. It is the only respiration process that does not produce a gas and occurs in some bacteria (such as lactobacilli) and muscle cells.

This type of fermentation converts the two molecules of pyruvate from glycolysis to two lactic acid molecules and regenerates the NAD+ in the process, continuing the cycle. This redox reaction is catalyzed by lactic acid dehydrogenase.

Lactic acid bacteria can carry out either homolactic fermentation, where lactic acid is the major product, or heterolactic fermentation, where some lactate is further metabolized into ethanol, carbon dioxide and other byproducts.

Lactic acid fermentation
Importance and Benefits of Fermentation
Rich in probiotics, fermented foods contain microorganisms that can help maintain a healthy gut system, so it can extract nutrients from food more efficiently. They are beneficial for human health in a number of ways.

The probiotics, enzymes and lactic acid in fermented foods can facilitate the intake of vitamins and minerals by the body. Fermentation increases vitamins B and C and enhances folic acid, riboflavin, niacin, thiamin and biotin, making them more accessible for absorption.

Fermentation can also neutralize phytic acid, a substance in grains, nuts, seeds and legumes that causes mineral deficiencies. Phytates, the ionized form of phytic acid, also make starch, proteins and fats less digestible.

The microorganisms, or probiotics, in fermented food can help maintain a healthy gut in producing antibiotic, antiviral, antifungal and antitumor agents, as well as creating an acidic environment that pathogens do not thrive in.

Daily Uses of Fermentation
Fermentation is widely used for the production of alcoholic beverages, for instance, wine from fruit juices and beer from grains. Potatoes, rich in starch, can also be fermented and distilled to make gin and vodka.

Fermentation is also extensively used in bread making. When sugar, yeast, flour and water are combined to form dough, yeast breaks down the sugar and gives off carbon dioxide, which causes the bread to rise. Specialty bread such as sourdough uses both yeast and lactobacilli. This combination gives the dough its stretchy texture and distinctive sour taste.

Lactic acid fermentation is used to flavor or preserve dairy products and vegetables, for example yogurt, sauerkraut, pickles and kimchi.

Acetic acid fermentation can also be used to turn starches and sugars from grains and fruit into sour tasting vinegar and condiments including apple cider vinegar and kombucha.

Industrial Application of Fermentation
Fermentation is used in industry to generate ethanol for the production of biofuel. It is an attractive renewable resource because it originates from feedstocks including grains and crops such as corn, sugar cane, sugar beets and cassava. It can also come from trees, grasses, agricultural and forestry residues.

In the United States, which is the largest ethanol fuel producer, the main feedstock for ethanol fuel is corn given its abundance and low price. Approximately 0.42 liter of ethanol can be produced from one kilogram of corn. The second largest producer is Brazil, and most of its ethanol fuel comes from sugar cane. Most cars in Brazil run on pure ethanol or a blend of gasoline and ethanol.

Fermentation is also capable of producing hydrogen gas, for example in Clostridium pasteurianum, where glucose is converted to butyrate, acetate, carbon dioxide and hydrogen gas. In acetone-butanol-ethanol fermentation, carbohydrates such as starch and glucose are broken down by bacteria to produce acetone, n-butanol and ethanol. This process was developed by Chaim Weizmann as a primary method for making acetone in World War I.


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