Fermentation is a process carried out by certain unicellular organisms as part of their metabolism. It usually occurs from carbohydrates or carbohydrates that can occur, for example, in the form of glucose, sucrose, maltose and fructose, among others.

It is used by single-celled organisms to produce energy in the form of ATP to survive. Only facultative or strict anaerobic organisms that do not need oxygen can ferment. Oxygen is normally required as the final electron acceptor for energy production, which occurs in aerobic organisms. Still, anaerobes can use other compounds, as we will see below.

The process not only generates energy, but also produces organic compounds as a final result. For this reason, the process has been used by humans in industry, for example in food or pharmaceuticals. In addition, there are a large number of types of fermentation , but here we present the main ones.

This type of fermentation produces two molecules of ethanol and one of carbon dioxide from one molecule of glucose. It first releases CO2 from pyruvate and then uses acetaldehyde as the final electron acceptor instead of oxygen. It can occur by bacteria or by fungal yeasts .

wine production

To produce the wine, the yeast Saccaromyces cerevissae is present in the skin of the grapes and uses glucose and fructose to produce its energy. To begin the process, the must is made, a mixture of grape skins with juice that comes from pressing. From here they are taken to containers for fermentation to begin.

This fermentation has lactic acid as a final product from the oxidation of glucose. Here the pyruvate is reduced without previous steps to lactic acid. It can be:

• A homolactic fermentation: when this is the only product obtained.
• A heterolactic fermentation: when water and ethanol are also obtained.

yogurt production

Lactobacillus bulgaricus bacteria were discovered in ancient Thrace, today Bulgaria, 7 thousand years BC, and were used to ferment milk and produce yogurt, and even start renneting to make cheese. They were used to preserve food longer, since they prevent decomposition . They also have probiotic qualities for the intestinal microbiota that have a positive impact on the general health of the body. L. bulgaricus uses lactose, a form of milk sugar, for energy.

Muscle tissue

This fermentation not only occurs in microorganisms, but also occurs in muscle tissue. When due to excessive exercise, not enough oxygen reaches the muscle cells, they must do anaerobic respiration instead of aerobic, which is common. We experience this as a symptom of muscle pain and the accumulated lactic acid is processed in the liver.

This type of fermentation is done by Acetobacter bacteria , which form acetic acid from ethyl alcohol. This is a special type of fermentation, since it does require oxygen and is not generated from carbohydrates, unlike what the definition of fermentation dictates.

Balsamic vinegar

When wine production is not done properly and comes into too much contact with oxygen , it can be fermented to acetic acid. Here it is converted to vinegar.

In this case, lactose is converted to butyric acid and a gas. The odor that emerges from said reaction is the characteristic odor of putrefaction . Pyruvate and butyric acid is what originates after catabolizing sugar to generate energy. The bacteria that make this fermentation belong to the genus Clostridium spp.

Butyric swelling in cheese making

Butyric fermentation is useful for breaking down organic matter, but when it interferes with food it is harmful. A frequent case occurs in cheese factories with a phenomenon called late swelling or butyric swelling, where butyric acid forms voids within the cheese as the ripening time increases, causing them to swell, even in some cases causing them to explode and giving them a strong and Bad smell.

These bacteria are non-pathogenic, but they can reduce the nutritional quality of food. Contamination can be acquired when cows consume silage , that is, lactically fermented to preserve it and enhance its nutrients, but that was contaminated with too many butyric bacteria. By consuming it, cows produce milk with butyric bacteria.

Citric acid is the result of citric fermentation, created by filamentous fungi from carbohydrates.

food citric acid

Citric acid is widely used in the food industry because it prevents the deterioration of sensory qualities , such as color or flavor. It also provides a tangy flavor to multiple sweets, snacks or drinks. For industrial manufacturing, whey is usually used due to its lactose content together with Aspergillus niger, which is highly effective in producing citric acid in a short time.

This fermentation generates ammonia and carbon dioxide from the urea.

putrefaction of animal bodies

It usually occurs during the putrefaction of animal bodies, since the tissues are deprived of oxygen, the bacteria can begin to feed and fermentative transformations take place . The smell given off by this type of fermentation is a signal that attracts other decomposing organisms, mainly insects.