Glucose fermentation reaction. Types, significance and product of fermentation

Glucose fermentation is one of the main reactions by which it is possible to prepare spirits. It can be carried out in different ways, in each of which individual products are formed. This process plays a key role in many areas of our life, from cooking and cooking vodka to the reactions that take place in our body.

History

The process of fermentation of glucose and other sugars was used by ancient people. They ate a little fried food. This food was safer, because it contained alcohol, in the medium of which many harmful bacteria were killed. In ancient Egypt and Babylon, people already knew how to ferment many of the sugar-containing drinks and milk. When people at the end of the 18th century managed to better study this process, its types and possibilities for improvement, such industries as kvass, brewing and wine-vodka grew very qualitatively.

Types of fermentation

Strangely enough, this process is different. And distinguish between the types of fermentation of glucose in final products. Thus, there is lactic acid, alcohol, citric acid, acetone, oleic acid and several others. Let's talk a little about each type separately. Lactic acid fermentation of glucose is the main process in the preparation of products such as curdled milk, sour cream, kefir, cottage cheese. It is also used to conserve vegetables and performs a key function in our body: in conditions of lack of oxygen, glucose turns into the final product - lactic acid, which causes pain in the muscles at the time of training and a little after it.

Alcoholic fermentation is characterized by the fact that ethyl alcohol is formed as the final product. It occurs with the help of microorganisms - yeast. And plays a key role in cooking, because besides the main product, alcoholic fermentation of glucose releases carbon dioxide (this explains the fluffiness of the yeast test).

Lemon-acid fermentation occurs, as is not hard to guess, with the formation of citric acid. It occurs under the influence of a certain type of fungi and is part of the Krebs cycle, which ensures the breathing of all cells of our body.

Acetone-butyl fermentation is very similar to butyric acid. As a result, it forms oleic acid, butyl and ethyl alcohols, acetone and carbon dioxide. With oil-acid fermentation, only the acid and carbon dioxide corresponding to the name are formed.

Now we will look at all types in more detail, and start with the most basic - alcohol fermentation of glucose. All the reactions and nuances of their course will be analyzed in detail.

Alcoholic fermentation

We will tell a little more about glucose fermentation, the equation of which is: C ₆ H ₁₂ O ₆ = 2C ₂ H ₅ OH + 2CO ₂ . What can you learn from this reaction? We have two products: ethyl alcohol and carbon dioxide. Due to the latter, we observe the swelling of the yeast test. And due to the first, we have an opportunity to get an unforgettable taste of wine and wine. But in fact this is just a simplified equation. The complete reaction of glucose fermentation is more complicated, so let's take it a little deeper.

There is a process like glycolysis. Literally its name translates as "splitting sugar." It occurs in the body, and its by-product is pyruvic acid, and the main one is adenosine triphosphoric acid (ATP), which is formed during this reaction from another compound. It can be said that ATP is a carrier of energy in the body, and in fact glycolysis serves to provide our body with energy.

We have not in vain touched this process. In fact, fermentation is very similar to glycolysis, since the first stage is exactly the same for them. It can even be said that the reaction of alcoholic fermentation of glucose is a continuation of glycolysis. The pyruvate (pyruvic acid ion) formed during the latter is converted to acetaldehyde (CH ₃ -C (O) H), with the release of carbon dioxide as a by-product. After this, the resulting product is reduced by the coenzyme NADH contained in the bacteria. The reduction leads to the formation of ethyl alcohol.

Thus, the reaction of glucose fermentation to ethanol is as follows:

1) C ₆ H ₁₂ O ₆ = 2 C ₃ H ₄ O ₃ + 4 H ⁺

2) C ₃ H ₄ O ₃ = CH ₃ -COH + CO ₂

3) CH ₃ -COH + NADH + H ⁺ = C ₂ H ₅ OH + NAD ⁺

NADH serves as a reaction catalyst, and the NAD ⁺ ion plays a key role in the early stage of glycolysis, and, forming at the end of alcohol fermentation, returns to the process.

Let us pass to the next variety of the type of reactions being investigated.

Lactic Acid Glucose Fermentation

From alcohol this species differs in that it occurs not under the influence of yeast, but with the help of lactic acid bacteria. Therefore, we have completely different products. Lactic acid fermentation also occurs in our muscles at high loads and lack of oxygen.

There are two types of this process. The first is homofermentative fermentation. If you ever heard the prefix "homo", then for sure you understand what it means. Homofermentative fermentation is a process involving one enzyme. At the first stage, glycolysis occurs and pyruvic acid is formed. Then the resulting pyruvate (in the solution, this acid can exist only as ions) undergoes hydrogenation with NADH ⁺ H and lactate dehydrogenase. As a result, the product of reduction is lactic acid, which is about 90% of all products obtained during the reaction. This compound, however, can also be formed in the form of two different isomers: D and L. These types differ in that they are mirror reflections of each other and, therefore, differently affect our body. What isomer will be formed to a greater extent determines the structure of lactate dehydrogenase.

Let's pass to the second type of lactic fermentation - heterofermentative. In this process, several enzymes participate, and it goes along a more complex path. Because of this, more different products are formed during the reaction: in addition to lactic acid, we can find there acetic acid and ethyl alcohol.

So we looked at the lactic acid fermentation. This is the process by which we can enjoy the taste of cottage cheese, yogurt, ryazhenka and kefir. Let's summarize and write down in general the reaction of lactic acid fermentation of glucose: C ₆ H ₁₂ O ₆ = 2 C ₃ H ₆ O ₃ . Of course, this is a simplified scheme of the process of homofermentative fermentation, since even the scheme of the heteroenzymatic process will be very complicated. Chemists are still studying the milk fermentation of glucose and find out its full mechanisms, so we still have much to strive for.

Lemon-fermented fermentation

Reactions of this type of fermentation occur, as with alcohol, under the influence of fungi of a certain strain. The complete mechanism of this reaction has not yet been fully understood, and we can rely only on certain simplifications. However, there are suggestions that the initial stage of the process is glycolysis. Then the pyruvic acid turns in turn into various acids and comes to lemon. Owing to such a mechanism, other acids accumulate in the reaction medium, products of incomplete oxidation of glucose.

This process takes place under the influence of oxygen, and in general it can be written as the following equation: 2C ₆ H ₁₂ O ₆ + 3 O ₂ = 2C ₆ H ₈ O ₇ + 4H ₂ O. Before this type of fermentation was discovered, people extracted citric acid Solely squeezing the fruits of the corresponding tree. However, in the lemon of this acid no more than 15%, so this method proved to be inexpedient, and after the discovery of this reaction all the acid was started to be produced by fermentation.

Oily fermentation

Proceed to the next type. This type of fermentation occurs under the action of butyric acid bacteria. They are widespread, and the process that they cause, plays a key role in biologically important cycles. With the help of these bacteria, the decomposition of dead organisms takes place. Oily acid, formed during the reactions, attracts the scent of scavengers.

This type of fermentation is used in industry. As you might guess, they get oleic acid. Her esters are widely used in perfumery and have a pleasant smell, unlike her own. However, oil fermentation is not always beneficial. It can cause damage to vegetables, canned goods, milk and other products. But this can happen, if only the oil bacteria get into the product.

Let us analyze the mechanism of glucose oil fermentation. Its reaction is as follows: C ₆ H ₁₂ O ₆ → CH ₃ CH ₂ CH ₂ COOH + 2CO ₂ ↑ + 2H ₂ . As a result, energy is also produced, which ensures the life activity of the butyric acid bacteria.

Acetone-butyl fermentation

This type is very similar to butyric acid. Not only glucose, but also glycerin, and pyruvic acid can roam in this way. This process can be divided into two stages: the first (sometimes called acidic) is actually an oleic acid fermentation. However, in addition to the oil, acetic acid is also released. As a result of the fermentation of glucose in this way, we get products that go to the second stage (acetonobutyl). Since the entire process also occurs under the action of bacteria, then acidification of the medium (increase in the concentration of acids) gives rise to the release of special enzymes by bacteria. They induce a reaction for the conversion of glucose fermentation products to n-butanol (butyl alcohol) and acetone. In addition, some ethanol may be formed.

Other types of fermentation

In addition to these five types of this process, there are several more. For example, this is acetic fermentation. It also occurs under the action of many bacteria. This type of fermentation can be used for useful purposes when pickling. It protects food from pathogens and dangerous bacteria. Alkaline or methane fermentation is also distinguished. Unlike previous types, this type of fermentation can be carried out for most organic compounds. As a result of a large number of complex reactions, organic substances are split into methane, hydrogen and carbon dioxide.

Biological role

Fermentation is the oldest method of obtaining energy by living organisms. Some creatures produce organic substances, incidentally receiving energy, while others destroy these substances, while also receiving energy. Our whole life is built on this. And in each of us fermentation in one form or another proceeds. As we mentioned above, lactic fermentation occurs in muscles with intensive training.

What else to read?

If you are interested in the biochemistry of this very interesting process, it is worth starting with school textbooks on chemistry and biology. In many university textbooks so detailed material is set forth that after reading them you can become just an expert in this field.

Conclusion

So we came to the end. We have reviewed all types of glucose fermentation and general principles of these processes, which play a very important role both in the functioning of living organisms and in our industry. It is possible that in the future we will open several more types of this ancient process and learn how to use them for the benefit of ourselves, as did with those already known to us.