Fermentation of lactic acid: technology and necessary equipment. Heterofermentative lactic fermentation

Nature allows a person to enjoy those benefits that are in it. At the same time, people try to multiply these riches, create something new and learn something else. Bacteria are the smallest creatures of nature, which man has also learned to use for his own purposes.

But not only the harm associated with pathogenic processes and diseases, these prokaryotic organisms carry within themselves. They are still the source of an important industrial process, which has been used by people since ancient times - fermentation. In this article we will consider what this process represents and how lactic fermentation of substances is carried out.

History of the origin and use of fermentation

The first mention of the fact that the process of fermentation was used by people to obtain certain products, appeared even 5000 BC. It was then that the Babylonians used this method to obtain products such as:

• cheese;
• wine;
• Yogurt and other dairy products.

Later similar food began to be received also in Egypt, China, Sudan, Mexico and other ancient states. They began to bake yeast bread, ferment vegetable crops, there were first attempts to preserve.

The process of lactic acid fermentation has been used by people for millennia. Cheeses, kefir, yogurts were an important part of the meal at all times. All the healers and healers knew about the benefits of these products. However, the reasons for the possible transformation of this kind, for a long time remained unknown.

The fact that fermentation conditions require the presence of microorganisms, people could not even guess. In the middle of the XVII century, Van Helmont proposed to introduce the term "fermentation" for those processes of cooking, which are accompanied by the release of gas. Indeed, in translation, this word means "boiling." However, only in the XIX century, almost two hundred years later, the French microbiologist, chemist and physicist Louis Pasteur discovered the world the existence of microbes, bacteria.

Since then it became known that different fermentation requires the presence of various kinds of microorganisms invisible to the eye. Their study made it possible in time to control the fermentation and direct it to the right side of the person.

The essence of the processes of fermentation

If we talk about what the process of fermentation is, we should point out its biochemical nature. After all, at its core, it is simply the activity of bacteria, which extract their energy for life, while producing various by-products.

In general, fermentation can be designated in one word - oxidation. Anaerobic decomposition of a substance under the influence of certain bacteria, which leads to the formation of a number of products. What substance underlies, and also what will result as a result, is determined by the type of the process itself. There are several variants of fermentation, so there is a classification for these transformations.

Classification

There are three main types of fermentation.

1. Alcohol . It consists in the oxidation of the original carbohydrate molecule to ethanol, carbon dioxide, water and the ATP molecule (energy source). These transformations are carried out under the influence not only of bacteria, but also of fungi of different genera and species. It is in this way from time to time that products such as beer, wine, baker's yeast, alcohol are obtained. The energy that is released during the decomposition of the carbohydrate goes to ensure the processes of vital activity of the microorganism. This is the biological essence of the process.
2. Fermentation of lactic acid consists in the oxidation of carbohydrates to lactic acid with the release of a number of by-products. How it is carried out and what kinds of things are, let's take a closer look.
3. Oleaginous acid . This type of fermentation is important on a natural scale. It is carried out at the expense of the life of oil bacteria that live under anaerobic conditions at the bottom of bogs, river mud, and so on. Due to their work in nature, a huge amount of organic components is processed. Products are many substances, the main among them is butyric acid. Also excreted: acetone, isopropyl alcohol, carbon dioxide, acetic acid, lactic, ethyl alcohol and other compounds.

Each of the designated types is important both on a natural and industrial scale. The types of organisms that carry out such transformations have been well studied to date and many of them are cultivated artificially in order to obtain a large yield of the product.

Fermentation of lactic acid: a general concept

This type of fermentation is known since ancient times. Even before our era, the inhabitants of Ancient Egypt and other countries were able to make cheese, brew beer and wine, bake bread, sour fruit and vegetables.

Today, special ferments for fermented milk products are used, and strains of the necessary microorganisms are cultivated artificially. The process is modernized and brought to automatism, carried out with the help of complete equipment. There are many manufacturers that directly produce lactic acid fermentation.

The essence of the whole process can be stated in several paragraphs.

1. For the main product of the starting is taken carbohydrate - simple (fructose, glucose, pentose) or complex (sucrose, starch, glycogen and others).
2. Anaerobic conditions are created.
3. The product lumps strains of lactic acid bacteria of a certain type.
4. All necessary external factors that are optimal for the desired product are provided: illumination, temperature, availability of certain additional components, pressure.
5. After the fermentation process is completed, the product is processed and all the side compounds are isolated.

Of course, this is only a general description of what is happening. In fact, at every stage there are many complex biochemical reactions, because the process of lactic fermentation is the result of the vital activity of living beings.

The fundamentals of the process of lactic fermentation

From a chemical point of view, these transformations are a series of successive stages.

1. First, the original substrate changes, that is, the carbon chain of the substance (carbohydrate) changes. This leads to the appearance of intermediate compounds of a completely different nature, belonging to different classes. For example, if the initial substrate is glucose, then it is rearranged into gluconic acid.
2. Oxidation-reduction reactions, accompanied by the release of gases, the formation of by-products. The main unit during the whole process is lactic acid. It is it that is produced and accumulated during fermentation. However, this is not the only connection. So, there is a formation of molecules of acetic acid, ethyl alcohol, carbon dioxide, water, and sometimes other accompanying.
3. Energy output of the process in the form of adenosine triphosphate (ATP) molecules. There are 2 ATP molecules per molecule of glucose, if the initial substrate is more complex, for example cellulose, then three molecules of ATP. This energy is used by lactic acid bacteria for further life.

Naturally, if one understands biochemical transformations in detail, then all intermediate molecules and complexes should be indicated. Such, for example, as:

• Pyruvic acid;
• Adenosine diphosphate;
• Molecules of nicotinamide diphosphate as a carrier of hydrogen and others.

However, this issue deserves special attention and should be considered from the point of view of biochemistry, so we will not touch on this in this article. We will consider in more detail what is the technology of production of lactic acid products and what kinds of fermentation in question exist.

Homofermentative fermentation

Homoenzymatic fermentation of lactic acid implies the use of special forms of pathogens and differs from heterofermentative products and their quantity. It occurs on the glycolytic path inside the cell of the microorganism. The essence consists, as in the whole, of any fermentation, in the transformation of carbohydrates into lactic acid. The main advantage of this process is that the yield of the desired product is 90%. And only the remaining part goes to the side connections.

Bacteria of fermentation of this type are the following:

• Streptococcus lactis.
• Lactobacillus casei.
• Lactobacillus acidophilus and others.

What other substances are formed as a result of homofermentative fermentation? These are such connections as:

• ethanol;
• Volatile acids;
• carbon dioxide;
• Fumaric and succinic acid.

However, in industry this method of obtaining sour-milk products is practically not used. It is preserved in nature as the initial stage of glycolysis, it also occurs in the cells of the muscles of mammals under extensive physical exertion.

The technology of producing the right foods for human nutrition involves the use of such initial carbohydrates as:

• glucose;
• Sucrose;
• fructose;
• Mannose;
• Starch and some others.

And homofermentative bacteria are not able to oxidize many of these compounds, so their use as ferments during production is not possible.

Heterofermentative lactic fermentation

This method is precisely the industrially applicable, thanks to which the production of all sour-milk products is carried out, the conservation of vegetables is carried out, silage forage is being prepared for livestock.

The main difference from the previously described is that lactic fermentation pathogens are carried out with the formation of a larger number of by-products. Only 50% of sugar is processed by bacteria into lactic acid, the rest is spent on the formation of such molecules as:

• acetic acid;
• glycerol;
• carbon dioxide;
• Ethyl alcohol and others.

What is better and more profitable than the formation of 90% pure lactic acid with a homoenzymatic method? The thing is that when the main product is produced too much, the vital activity of many bacteria is suppressed altogether. In addition, the products lose many of the gustatory qualities that they gain through side-connections. For example, a pleasant aroma of canned vegetables is provided by acetic acid and isoamyl alcohol. If these compounds do not exist, the result of conservation will be completely different.

The yield of lactic acid in 50% is sufficient to suppress the development and vital activity of all extraneous fungi and microorganisms in the system. Because even 1-2% cause too much acidification of the environment, in which there can not exist any other organisms, except lactic acid bacteria. The entire process is carried out on the pentose-phosphate pathway.

The fermentation conditions for the heteroenzymatic method should be as follows:

• Good and fresh leaven, added at the initial stage;
• Optimal external conditions, which are selected for each product individually;
• High-quality and well-functioning equipment;
• All the necessary technical devices for the process.

Among the external conditions, the process temperature is of particular importance. It should not be too high, but the cold will dramatically slow down the entire course of fermentation.

Today there is a specialized fermentation tank, which automatically creates all the necessary conditions for the correct and comfortable work of microorganisms.

Necessary equipment

As we already noted above, among the most important attributes should be noted capacity for fermentation. If we talk about the home procedure, then we should pay attention to the purity of the used dishes when preserving, making yogurt and other products. One way to reduce the number of extraneous populations of microorganisms is to sterilize the containers before using them.

Which dishes are suitable for heterofermentative fermentation? This can be a glass or high-quality plastic (polypropylene, polyethylene) capacity, which can be tightly closed with a lid.

In the industry, special devices are used to decontaminate and clean containers before the fermentation process begins.

Bacteria used in the process

If we talk about the cultures of bacteria that are used to create canned and fermented milk products, we can identify several of the most common types of organisms.

1. Acidophilic Bulgarian wand.
2. Lactobacillus species Sporolactobacillus inulinus.
3. Bifidobacteria.
4. Leukonostok.
5. Lactic acid cocci.
6. Lactobacillus L. L. Casei.
7. Bacteria of the genus Streptococcus and others.

Based on the combination and pure cultures of the designated organisms, ferments are prepared for sour-milk products. They are in the public domain, they can be purchased by anyone. Most importantly, it is to comply with the conditions of the fermentation process in order to benefit from the resulting product.

What products are obtained as a result of this fermentation?

If we talk about what fermentation products can be obtained with the help of lactobacilli, then we can name a few basic categories.

1. Fermented milk products (fermented baked milk, yoghurts, varenets, kefir, cottage cheese, sour cream, butter, acidophilic products and others).
2. Silage-type forage for farm animals.
3. Lactic acid, which is used in the manufacture of non-alcoholic beverages, dressing fur skins and stuff.
4. Bakery, cheese production.
5. Preservation of vegetables and fruits.

All this proves the importance of bacteria of certain species in people's lives, their industrial activities.