The benefits and harms of lactic acid bacteria

Most often, when we imagine bacteria, images of thousands of small creatures that can harm our health pop up in our minds. But not all of them can harm a person. There are thousands of beneficial bacteria that humans can live on, such as lactic acid bacteria. They are found in the digestive system of humans and animals, are used in the food and pharmaceutical industries, as well as in agriculture in the production of animal feed.

Use beneficial features These microorganisms man became a few millennia ago, when no one suspected the existence of such a form of life. In ancient times, people began to use sourdough for cooking, as well as to give products a certain taste.

What are lactobacilli?

Lactic acid bacteria are microaerophilic gram-positive organisms that are capable of provoking fermentation processes. Most often, these microorganisms are represented by rods, less common are spherical organisms (cocci).

Reproduction of lactobacilli occurs by dividing the septum. Reproducing, they form chains. The most favorable conditions for their reproduction are created at temperatures from +15°С to +30°С. At high temperatures, lactic acid sticks die.

Most lactic acid bacteria are not aerobes, but they can also exist with access to oxygen, so they are considered to be aerotolerant anaerobes. Aerobes are organisms that can exist only with the access of molecular oxygen, while anaerobes, on the contrary, exist in an environment without air access.

With the access of oxygen, the type of respiration of lactic acid sticks does not change, and they can become aerobes. It is precisely the fact that lactic acid bacilli do not belong to aerobes, although they do not die with the access of oxygen, that their ability to survive in various conditions is due.

To obtain energy, lactobacilli use lactic acid fermentation, in which, unlike butyric fermentation, lactic acid is produced. With lactic acid fermentation, as with butyric fermentation, the process of fermentation of carbohydrates occurs, but various types of microorganisms are involved in these processes.

The shape of the colonies

The growth of cultures of most lactic acid bacteria is possible on milk, as well as nutrient media of various consistencies with the addition of nutrients derived from milk. They are not able to reproduce in a normal nutrient medium. For their development, a nutrient medium is needed with the addition of meat proteins, casein, flour and various amino acids.

Various types of bacteria of lactic acid fermentation are capable of forming colonies when they enter the nutrient medium. various forms. Lactic acid streptococci, getting into a vitamin-rich nutrient medium, create small dewy colonies on its surface, and in the thickness of the nutrient medium they are able to form small colonies in the form of boats. When cysteine, which has reducing properties, is added to the nutrient medium, lactic acid streptococci are able to form rough surface colonies. An exception is lactic streptococci Lac. Diacetilactis, which in a nutrient medium form deep colonies in the form of small lumps of cotton wool or spiders. In addition, certain types of streptococci are able to form stellate and mucous colonies.

Lactobacilli in production

Lactic acid bacteria produce lactic acid and are involved in the fermentation process. AT Food Industry they are used in:

• production of dairy products;
• canning (for example, sauerkraut);
• bakery;
• kvass production.

Today, in stores you can buy a wide variety of types of products based on cultures of lactic acid bacteria: yogurt, sour cream, kefir, cottage cheese, cheese, etc. Lactic acid bacteria that multiply in milk give it a sour taste. In order to obtain additional flavors or aromas, it is necessary that lactobacilli interact with other microorganisms or organic products of other strains of lactobacilli. For example, in the production of yogurt, a complex of bacteria Lactobacillus bulgaricus and Streptococcus Thermophilus is used, while each of these strains provokes the growth of the other. Lactic acid sticks, which are used in the production of yogurt, turn the product into a probiotic. A probiotic is a product that contains lactic acid fermentation bacteria. Such products are used to normalize the intestinal microflora, helping the intestinal bacteria to digest food.

Lactic acid bacteria are also used in the production of kvass. In the manufacture of kvass, two types of microorganisms are used: kvass yeast (Saccharomyces minor) and lactic fermentation bacteria (Lactobasillus fermenti). Kvass yeast starts the process of alcoholic fermentation, and lactobacilli - lactic acid. In the food industry for the production of kvass, ready-made sourdough is used, which contains the optimal ratio of these microorganisms, in which kvass acquires the necessary taste and aromatic qualities.

The well-known fermented milk drink kefir is a unique product that has a positive effect on human health. This product can be obtained through simultaneous alcoholic and lactic acid fermentation. The finished product contains lactic acid, carbon dioxide and a small amount of alcohol. Thanks to the processes of lactic acid and alcoholic fermentation, the amount of vitamins in kefir increases. The complex of microorganisms found in kefir has a positive effect on the human immune system, and also helps the body to accumulate nutrients.

All dairy products are produced using dry or liquid concentrate of lactic acid bacteria. To prepare a dry concentrate, concentrates of mesophilic lactic acid bacteria are most often used.

Lactobacillus and man

Until quite recently, no one could have imagined that lactic acid sticks bring great benefits to the human body, without them the existence of man and animals would be impossible. They can be found throughout the digestive tract, where they are involved in the process of digesting food. These organisms do not belong to aerobes, therefore they are able to survive well in the conditions of the intestine without access to oxygen.

The real defenders of human health are bacteria of the genus Lactobacillus. These bacteria are able not only to maintain human health, but also to resist infections, preventing the development of various diseases. Improper nutrition and uncontrolled intake of antibiotics lead to a decrease in the number of lactobacilli in the body, which, in turn, leads to a decrease in immunity. To return the intestinal microflora to a normal state, it is necessary to eat foods that contain lactobacilli in their composition (kefir, yogurt, etc.). Another advantage of probiotic products is that they are not capable of causing an allergic reaction.

The impact of lactobacilli on children's health

Lactic acid bacteria, entering the body, attach to the walls of the intestine and form small colonies. However, this colonization is temporary, so it is necessary to consume probiotics regularly to maintain normal microflora. Colonies of lactic acid bacteria do not allow pathogenic organisms to multiply in the intestines, and also protect the body from entering intestinal bacteria into the bloodstream.

If the intestinal microflora is disturbed, as well as against the background of taking antibiotics, candidiasis (thrush) can develop in children. This disease is most common in newborns and children who are breastfed. To combat candidiasis, antifungal drugs are prescribed in combination with probiotic products.

Studies show that children who regularly eat foods with Lactobacillus GG are less likely to develop tooth decay. In addition, eating such foods has a positive effect on the child's immune system.

It has been scientifically proven that in infants whose mothers during pregnancy and breastfeeding used probiotics, atopic diseases are much less common than in those children whose mothers consumed few products with Lactobacillus GG or did not use them at all.

Lactobacilli in the pharmaceutical industry

Science never ceases to study the world of bacteria, constantly discovering new types of them, as well as new properties of already known species. Many of the discovered properties have not yet received scientific confirmation, so this type of scientific research is quite promising. For example, it has recently been found that lactobacilli help patients with lactose intolerance to reduce the symptoms of the disease.

In pharmaceuticals, bacteria of the genus Lactobacillus are most often used for the production of drugs. For example, a species such as Lactobacillus Rhamnosus has been successfully used to make medicines for diarrhea. Recent scientific discoveries suggest that lactobacilli can prevent the onset of cancer.

Acidophilic bacteria are able to independently produce antibiotics that destroy dysentery bacteria, staphylococci, E. coli and salmonella, and also affect metabolism, which has a positive effect on human health. Forming their colonies in the intestines, these microorganisms prevent the processes of fermentation and putrefaction. In addition, acidophilus bacillus increases the body's ability to absorb milk protein, which promotes calcium absorption.

As a rule, for the production of drugs for the normalization of intestinal microflora, complexes of lactic acid bacteria are used. In order for their properties to be preserved in preparations for a long time, lyophilized lactobacilli are used in pharmaceuticals. In the lyophilization process, lactic acid bacteria are pre-frozen and then dried in a vacuum.

Freeze-dried microorganisms are insensitive to changes in storage temperature and can easily return to their original state when water or other solvents are added. Therefore, the lyophilisate of bacteria must be stored in sealed ampoules or vials in order to exclude their contact with moisture.

For example, the lyophilizate of lactic acid bacteria, which are resistant to antibiotics, is widely used for the production of medicines that regulate the balance of the human intestinal microflora even while taking antibiotics. Therefore, most often such drugs are prescribed to patients in combination with antibiotics in the treatment of bacterial infections in order to maintain the intestinal microflora in a normal state.

Today, lactic acid bacteria can be safely considered the hope of world medicine. Perhaps in a few years, thanks to lactobacilli, medicine will win in the fight against many serious diseases.

Not all bacteria are beneficial

Despite the many positive properties that most types of lactic acid sticks have, among them there are those that can harm a person or cause food spoilage. Not so long ago, scientists abroad announced that some of the lactic acid bacteria, for example, spore-forming bacteria B. anthracis and B. Cereus, are unsafe for humans.

Another species that can cause food spoilage is Micrococcaceae. These organisms are aerobes, but facultative anaerobes can also be found among them. Once on food, they can cause spoilage: stains on the surface of the cheese, rancid taste butter, thickening and bitter taste of milk. Reproducing in a favorable environment, they are able to form medium-sized round colonies.

Pathogenic organisms of the species Staphylococcus aureus, unlike Micrococcaceae, are mostly not strict aerobes. They can develop in an environment with access to oxygen and exist as aerobes, although when they enter an environment without air, they can change the type of respiration to anaerobic. These organisms can cause severe poisoning and can cause serious harm to human and animal health.

Dairy products can be spoiled not only by lactic fermentation bacteria, but also by butyric bacteria, which also do not belong to aerobes. In the process of butyric fermentation, dairy products acquire an unpleasant taste and smell.

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Ministry of Education and Science of the Russian Federation

Federal State Budgetary Educational Institution of Higher Professional Education "Moscow State Engineering University (MAMI)" (University of Mechanical Engineering)

ABOUT SCIENTIFIC RESEARCH WORK

lactic acid bacteria

Head Department of Doctor of Technical Sciences, Professor Biryukov V.V.

Project leader teacher

cafe EiPB. Samokhvalova N.S.

Moscow 2015

Introduction

2. Materials and methods

Conclusion

List of used literature

Introduction

Lactic acid bacteria are interesting microorganisms that interest scientists because of their functions and characteristics. The study of the presence of lactic acid bacteria in food products was one of the main tasks assigned to students in this research.

1. Analytical review of the literature

1.1 Species of bacteria, their morphology and characteristics

Lactic acid bacteria are represented by rods of various shapes: from short coccoid to long filamentous. The length of cells in different cultures of the same species depends on the composition of the medium, the presence of oxygen, and the method of incubation.

Most lactic acid bacteria are probiotic strains isolated from the intestinal flora of a healthy person (bifidobacteria and lactobacilli), which remain viable when passing through the gastrointestinal tract and have a beneficial effect on human health, which is confirmed by clinical trials. They are introduced into the composition of medicines, food supplements, and, more recently, fermented milk products.

Lactic acid bacteria, like all prokaryotes, do not have a nucleus. The carrier of hereditary information is a helical DNA strand localized in the cytoplasm. From the environment, the internal contents are limited by a shell and a thin cytoplasmic membrane.

Lactic acid bacteria multiply by septal division, which leads to the formation of chains. The ultrafine structure of the cells of these bacteria is in many respects similar to other gram-positive bacteria.

On agar media, lactic acid bacteria form small bacteria. Lactic acid bacteria are demanding on food sources; they grow on media containing vegetable decoctions, meat and yeast extracts, protein hydrolysates, since these bacteria need amino acids, vitamins, and a number of inorganic compounds.

In nature, lactic acid bacteria are found on the surface of plants, in milk, external and internal epithelial integuments of humans, animals, birds, and fish.

The genus Streptococcus (species Streptococcus Lactis) are 0.8-1.2 µm oval-shaped cocci that form chains of various lengths. When aging, the chain is crushed.

The genus Streptococcus diacetilactis is a smaller cocci with a diameter of 0.5-0.7 microns. They form chains of various lengths, the waste products of which give flavor to the product.

The genus Lactobacillus is a rod-shaped cells: 6-8 microns long, forming short chains. The best-known members of this genus are Lactobacillus bulgaricus and Lactobacillus acidophilus.

Lactobacillus bulgaricus - Bulgarian stick. The bacterium is named so because at one time it was isolated from the Bulgarian sour milk. Non-spore-free, immobile bacterium, reaching 20 m in length and often joining in short chains. It is thermophilic and grows best at temperatures above 40°C.

Lactobacillus acidophilus is a Gram-positive, anaerobic, non-spore-forming bacterium.

Lactobacillus leichmannii - this species is also included in the subgroup of thermobacteria. Bacterial cells are smaller, about 4 μm long and 0.6-1 μm wide, arranged singly or in chains. The presence of two or more grains of volutin in the cells is characteristic.

Lactobacillus plantarum ferments many sugars, including maltose and sucrose. It requires for its development rich media containing a variety of carbohydrates, vitamins, amino acids. The optimal temperature for its development is 30°C, however, it can grow in a fairly wide temperature range (15-38°C). Differs in alcohol resistance, maintaining alcohol concentration up to 20% vol. The species L. plantarum is constantly found in starter cultures and plays a major role in the process of acid accumulation.

Lactobacillus casei - this species also belongs to the subgroup of streptobacteria and is homofermentative in the nature of fermentation. According to morphological, cultural and physiological characteristics, it is very close to L. plantarum, and therefore it is difficult to distinguish from it. A significant difference is the ability of L. plantarum to grow in media containing 0.4% spool.

Lactobacillus brevis - the species belongs to the subgroup of beta bacteria. Ferments glucose with the formation of carbon dioxide. The cells are predominantly short (2/4X0.7/1 µm) without inclusions of volutin grains, arranged singly or in chains of different lengths. Colonies are small, convex, whitish, shiny. The optimum growth temperature is 30°C, but it can grow at more low temperatures(15°C).

Lactobacillus fermenti - This species is also heterofermentative. It has cells in the form of short rods (2/3X X0.5/1 µm) arranged singly or in chains. In terms of cultural and physiological properties, it is quite close to other types of the beta-bacteria subgroup. A distinctive feature of this species is that it does not grow on media containing 0.4% tipulus and its optimum growth temperature is much higher - in the range of 37-40°C. At 15°C no growth is observed. The species L. fermenti is often found in sourdoughs and seems to be specific to the bakery industry.

Lactobacillus buchneri - the species belongs to heterofermentative bacteria. The cells are very small - 0.74-4X0.35 microns, arranged singly, in pairs, often in long chains. Colonies are small, convex, opaque, yellowish. Grows in a wide range of temperatures - from 15 to 45°C. It differs from the species L. fermenti in the ability to grow in the presence of tipulus, and from the species L. brevis in the ability to ferment melecytosis. The species L. buchneri is described in starter cultures, but is found in them in small quantities. [Kvasnikov V. I., Nesterenko O. A. Lactic acid bacteria and ways of their use, "Nauka", 1975, pp. 1--384. ]

The first of the researchers who suggested that some bacteria are not at all harmful to humans, but, on the contrary, can have a positive effect on health, was the famous Russian scientist Ilya Ilyich Mechnikov. Even at the very beginning of the 20th century. he conducted research on the possibility of restoring the intestinal microflora with the help of lactic acid bacillus. As a result of serious and painstaking research, the scientists studied the properties of the bacterium, which he called the "Bulgarian stick" (in the modern classification - Lactobacillus bulgaricus), and also developed a recipe for a fermented milk drink - the prototype of modern yogurt. I.I. Mechnikov himself, his colleagues and acquaintances for many years regularly used this drink, which is also called "Mechnikov's curdled milk", and from their own experience they were able to verify its beneficial qualities.

Various positive effects of lactic acid probiotic bacteria are now known, confirmed by numerous clinical studies.

Dairy products are included in the diet of any person. Depending on the combination of genera and types of lactic acid bacteria, various fermented milk products are obtained from them. Over time, many questions arose about the qualitative composition and effect of fermented milk products on the human body. (Table 1). Qualitative composition of lactic acid products in accordance with GOST

	Their main microflora is made up of lactic acid bacilli, streptococci and yeast. They determine the specific taste and aroma of kefir, its nutritional properties. During the life of the kefir fungus, the microorganisms that make up its composition cause changes in milk. Under the influence of lactic acid streptococci and rods, lactic acid fermentation occurs, yeast causes alcoholic fermentation. Through these processes, the constituent elements of milk undergo changes, especially milk sugar.
	Cream is needed to make sour cream. In this case, pure bacterial cultures are used, which include lactic and creamy streptococci and aroma-forming bacteria.
	Cottage cheese is fermented with pure cultures of lactic acid streptococci and aroma-forming bacteria. The sourdough usually has a sour-milk taste, without any odors, gas formation, or protruding whey. Curd can't stand long-term storage, as lactic acid bacteria and molds quickly multiply in it.
	In yogurt, a variety of lactic acid bacteria discovered by I. I. Mechnikov, the Bulgarian stick, is used as a starter culture. When preparing yogurt, the starter consists of pure cultures of thermophilic streptococcus and Bulgarian bacillus, contained in equal proportions.

1.2 Technology for the production of lactic acid products

The production of dairy products in the food industry is based on fermentation processes. The basis of the biotechnology of dairy products is milk. Milk (the secret of the mammary glands) is a unique natural nutrient medium. It contains 82-88% water and 12-18% solids. The composition of the dry milk residue includes proteins (3.0-3.2%), fats (3.3-6.0%), carbohydrates (milk sugar lactose - 4.7%), salts (0.9-1% ), minor components (0.01%): enzymes, immunoglobulins, lysozyme, etc. Milk fats are very diverse in their composition. The main proteins of milk are albumin and casein. Due to this composition, milk is an excellent substrate for the development of microorganisms. Streptococci and lactic acid bacteria are usually involved in the fermentation of milk. By using the reactions that accompany the main process of lactose fermentation, other milk processing products are also obtained: sour cream, yogurt, cheese, etc. The properties of the final product depend on the nature and intensity of the fermentation reactions. Those reactions that accompany the formation of lactic acid usually determine the special properties of the products. For example, the secondary fermentation reactions that take place during the maturation of cheeses determine the taste of their individual varieties. Peptides, amino acids and fatty acids in milk take part in such reactions.

All technological processes for the production of products from milk are divided into two parts: 1) primary processing - the destruction of by-product microflora; 2) recycling. The primary processing of milk includes several stages. First, milk is cleaned of mechanical impurities and cooled to slow down the development of natural microflora. The milk is then separated (in the production of cream) or homogenized. After that, milk is pasteurized, the temperature rises to 80°C, and it is pumped into tanks or fermenters. Secondary processing of milk can go in two ways: using microorganisms and using enzymes. With the use of microorganisms, kefir, sour cream, cottage cheese, curdled milk, casein, cheeses, biofructolact, biolact are produced, with the use of enzymes - food hydrolyzate of casein, dry milk mixture for cocktails, etc. When microorganisms are introduced into milk, lactose is hydrolyzed to glucose and galactose, glucose is converted into lactic acid, the acidity of milk increases, and at pH 4-6, casein coagulates.

Lactic acid fermentation of glucose is the main process in the manufacture of starters, cheese and dairy products, and lactic acid bacteria are the most important group of microorganisms for the dairy industry.

Lactic acid fermentation is the process of anaerobic oxidation of carbohydrates, the end product of which is lactic acid. It got its name from its characteristic product, lactic acid. For lactic acid bacteria, it is the main pathway for the catabolism of carbohydrates and the main source of energy in the form of ATP. Also, lactic acid fermentation occurs in animal tissues in the absence of oxygen at high loads.

There are homofermentative and heterofermentative lactic acid fermentation, depending on the released products in addition to lactic acid and their percentage. The difference also lies in different ways of obtaining pyruvate during the degradation of carbohydrates by homo- and heterofermentative lactic acid bacteria.

In homofermentative lactic acid fermentation, the carbohydrate is first oxidized to pyruvate via the glycolytic pathway, then pyruvate is reduced to lactic acid NADH + H (formed at the stage of glycolysis during the dehydrogenation of glyceraldehyde-3-phosphate) using lactate dehydrogenase. The stereospecificity of lactate dehydrogenase and the presence of lactatracemase determine which enantiomer of lactic acid will prevail in the products - L-, D-lactic acid or DL-racemate. The product of homofermentative lactic acid fermentation is lactic acid, which makes up at least 90% of all fermentation products. Examples of homofermentative lactic acid bacteria: Lactobacillus casei, L. acidophilus, Streptococcus lactis12. Products of homofermentative fermentation: curdled milk, yogurt, acidophilic products, sour cream, cottage cheese and cottage cheese products.

For milk fermentation processes, pure cultures of microorganisms called starter cultures are used. The exception is starter cultures for kefirs, which represent a natural symbiosis of several types of lactic acid fungi and lactic acid bacteria. This symbiosis could not be reproduced in the laboratory, so a culture isolated from natural sources is maintained. When selecting cultures for starter cultures, the following requirements are adhered to:

The composition of starter cultures depends on the final product (for example, acidophilus bacillus is used to produce acidophilus, lactic streptococci are used to produce yogurt);

Strains must meet certain taste requirements;

Products must have an appropriate consistency, from brittle, granular to viscous, creamy;

Certain activity of acid formation;

Phage resistance of strains (resistance to bacteriophages);

The ability to syneresis (the property of a clot to give off moisture);

Formation of aromatic substances;

Compatibility of strains (without antagonism between cultures);

The presence of antibiotic properties, i.e. bacteriostatic action against pathogenic microorganisms;

Drying resistance.

Cultures for starter cultures are isolated from natural sources, after which site-directed mutagenesis and selection of strains that meet the above requirements are carried out.

Safety when sowing m / o in fermented milk products

The greatest potential danger in epidemiological terms is the production of fermented milk products. This is due to the fact that the process of production of fermented milk products takes a long time, during which there are favorable opportunities for the reproduction of microorganisms remaining after pasteurization, as well as those that have entered the milk as a result of secondary contamination.

After the introduction of the starter, the reproduction of most microorganisms is suppressed. However, under conditions of a slow increase in acidity as a result of a reduced activity of the starter, they can actively multiply, in particular, a bacteriophage develops intensively. Microbes also develop rapidly if milk is contaminated with small doses of antibiotics or other inhibitory substances.

Dairy products are not subjected to additional heat treatment. Therefore, all operations for the manufacture of fermented milk products should be subject to increased sanitary and hygienic and anti-epidemic requirements.

To obtain epidemiologically safe fermented milk products, the following is necessary: ​​only pasteurized raw materials should be used for the manufacture of fermented milk products; normalization and homogenization should be carried out before pasteurization: pasteurization of milk should be carried out under more stringent conditions than established by the technological instructions; to introduce the starter immediately after filling the container or in the process of filling; do not allow milk to be kept at the fermentation temperature without ferment; strictly control the quantity and quality of the ferment introduced, the duration of fermentation; to minimize the production of fermented milk products by the thermostatic method (completely switch to the reservoir method).

To develop the quality of fermented milk products guaranteed by sanitary indicators, strict adherence to hygienic rules and technological regimes is required in all areas of production.

Fermented milk products are mainly produced according to the general technological scheme - fermentation of pasteurized (or sterilized) milk with leaven. The production of individual products differs, as a rule, in the temperature conditions of some operations, the introduction of fillers and the use of starter cultures of various compositions.

Fermented milk products are produced by thermostatic and reservoir methods. With the thermostatic method, fermentation, cooling and maturation are carried out in bottles in thermostatic and cold chambers. With a reservoir - these processes occur in one container. After mixing the clot in the tank, the actually finished product is poured into the container, which must be further cooled. The tank method eliminates additional contamination of products, which is especially important in anti-epidemic terms.

For the production of fermented milk products, increased hygiene requirements are imposed on milk. The incoming milk is subjected to cleaning and normalization, after which it is sent for heat treatment. It is strictly forbidden to carry out normalization after pasteurization in order to avoid secondary contamination of milk.

Heat treatment is carried out under more stringent conditions than in production. drinking milk. Pasteurization of the mixture is carried out at high temperatures (87±2°C, 92±2°C) with an appropriate exposure (10-15, 2-8 min). For Ukrainian curdled milk, Varenets and some other fermented milk products, an even higher heat treatment of the mixture is required: 97 ± 2 ° C with an exposure of 60 ± 20 minutes. Such heat treatment not only completely destroys pathogenic microbes, but also reduces the amount of other microflora that can affect the activity of the starter.

The bacterial purity of milk is especially important, since during fermentation optimal temperature conditions are created for the development of the remaining microflora, which leads to deterioration sanitary indicators products and may cause the release of products that are unsafe in epidemiological terms.

The pasteurization process is controlled in the same way as in the production of drinking milk. After cooling to the fermentation temperature, the milk is sent to the tanks and the ferment is introduced into them. [ Kalinina L. V., Ganina V. I., Dunchenko N. I. Technology of whole milk products, St. Petersburg: Giord, 2008 ]

Phages found in all streptococci and many types of lactic acid bacilli are a serious danger in the production of lactic acid bacteria starter. If it is not required to isolate the bacterial mass after cultivation, then whole or skimmed milk can be used as the main one. In the latter case, the yield of lactic acid bacteria is 1.0-10 4-2.0-10 cells per 1 ml of medium.

Relationships between micro-organisms can also take many forms, and an example of a symbiotic relationship can often be observed. So, in kefir starter cultures there are yeast and lactic acid bacteria. Bacteria produce lactic acid, which creates an acidic environment favorable for yeast, and yeast enriches it with vitamins needed by lactic acid. Sometimes one group of microbes uses the waste products of another group, for example, in the biological treatment of pulp and paper wastewater, cellulose bacteria decompose the fiber of small wood fibers and form sugars and organic acids, and after them other groups of microorganisms, using these substances as food, oxidize them to carbon dioxide. gas and water.

Typical lactic acid fermentation is widely used for the manufacture of lactic acid products in dairies. Lactic acid bacteria are of great importance in the conservation of fresh feed by ensiling - Preservation of juicy feed mass is based on the fermentation of sugars contained in vegetable juice with the formation of lactic acid. Thanks to the environment, the development of putrefactive processes in the ensiled mass is prevented. In recent years, silage starters from lactic acid bacteria have been developed. The use of these starter cultures makes it possible to speed up and improve the process of maturation of silage, to avoid the formation of butyric acid.

Liquid sourdough is a semi-finished product, upon receipt of which mesophilic heterofermentative lactic acid bacteria and yeast, which got there spontaneously (for example, with flour) or made specially . When liquid starter cultures are used in the dough, not only alcohol, but also active lactic acid fermentation occurs, while the pH of the dough decreases to 4.7--4.8.

A good nutrient medium for the propagation of a lactic acid bacteria culture intended for drying is sterile skimmed milk with a high solids content (up to 16%), which is achieved by adding milk powder and 0.1% sodium citrate. The inoculum should be 1% of the volume of the medium. The process of reproduction of bacteria is carried out without aeration at a temperature of 30°C for 12-16 hours for lactic acid streptococci and at 40°C for 6 hours for lactic acid bacilli. Then the culture medium is neutralized with 20% sodium hydroxide solution to the initial acidity of sterile milk. [Ignatiev V.E. Kefir // Encyclopedic Dictionary of Brockhaus and Efron: In 86 volumes (82 volumes and 4 additional). -- SPb., 1890--1907.]

Fermentation and fermentation of milk are the most vulnerable stages of the technological process for the production of fermented milk products in hygienic and epidemiological terms. Therefore, careful observance of the fermentation and fermentation regimes should be given special importance. The most dangerous are those cases when conditions conducive to its reproduction are created for the potentially pathogenic or pathogenic microflora preserved after pasteurization or caught in the pasteurized mixture.

In order to timely identify the causes of existing violations, it is necessary to constantly note in the production logs the time of filling the containers and fermentation, the duration of fermentation, the activity of the starter, etc.

Of great importance is the use of starter cultures prepared by the direct method, and it is necessary to use only fresh starter culture made no later than a day before its consumption, preferably on sterilized milk. This is due to the fact that sterilization (or high-temperature pasteurization) completely destroys the microflora of milk, among which there may be heat-resistant microorganisms.

To obtain a hygienically high-quality product, the starter should be immediately added to the mixture cooled after pasteurization, and in the future, the course of the lactic acid process should be strictly monitored.

The quality of the starter is checked daily, determining the activity, the presence of foreign microflora by viewing a microscopic preparation in 10 fields of view of the microscope, the quality of the clot, taste and smell.

After fermentation, the process of fermentation of milk begins. In the thermostatic method, the fermented mixture is preliminarily poured into bottles (jars), corked, labeled and placed in thermostatic chambers. The duration of fermentation depends on the type of product being produced and ranges from 3 to 10 hours at a temperature of 35-42°C, depending on what type of ferment is used and what fermented milk product is produced.

Increasing the fermentation temperature is undesirable, as this leads to a more intensive development of bacteria of the Escherichia coli group. The end of fermentation is determined by the formation of a sufficiently dense clot and by acidity, which is 70-80°C for Varents, 75-85°C for yogurt, 65-70°C for ryazhenka. With the tank method, the fermentation process is carried out in tanks. They also carry out cooling of the finished product.

At the end of fermentation, fermented milk products are gradually cooled in a refrigerator to a temperature not exceeding 6 ± 2 ° C, during this period the product should acquire a dense homogeneous consistency. A number of fermented milk products after cooling (kefir, koumiss) withstand a certain time in refrigerators for maturation. At the end of maturation, the products are transferred for storage and sale. The air temperature in the storage chambers before the sale should not be higher than 6-8°C. Shelf life is not more than 18 hours. Compliance with the rules of cooling and storage is the most important hygienic requirement.

Finished products are controlled for the presence of bacteria of the Escherichia coli group and according to a microscopic preparation from one or two batches at least once every 5 days. microbiological indicators finished products should be at least 0.3 ml in titer.

Equipment that comes into direct contact with the product during the production process requires special attention. Before starting the technological process, a thorough sanitization of such equipment should be carried out. If the sanitary indicators of the finished product deteriorate, a thorough analysis and additional control of the technological process is carried out to establish the causes of secondary contamination of the product, the quality of the starter culture, as well as the sanitary and hygienic condition of the workshop are checked.

Today, yogurt is bought one and a half times more often than kefir. An important role here is played by fruit additives, a varied palette of flavors and convenient packaging. To get the product really High Quality- yogurt of the required consistency, viscosity, taste, smell, appearance, as well as free from syneresis - many factors must be taken into account in the production process. The selection and preparation of the raw material (i.e. the milk itself), the preparation of the sourdough, and most importantly, the correctly designed and optimally arranged production lines are decisive.

Only the highest quality milk is used to make yogurt. This means that it must have minimal amount bacteria and contaminants that will inhibit the development of the culture, such as antibiotics, bacteriophages, as well as cleaning solution residues.

The milk processing process includes several main technological stages, each of which is equally important for achieving the high quality of the final product. The basis for this is laid already at the stage of milk processing.

First, the milk is normalized according to the content of solids (SV). Increasing the total solids content, especially the ratio of casein to other whey proteins, results in a thicker yoghurt: thus reducing the tendency for whey to separate. Typical methods of normalization to TCO are evaporation (10--20% of the total volume of milk is usually evaporated), the addition of dry skimmed milk(usually up to 3% w/v) and the addition of concentrated milk. Typically, milk for making yogurt is normalized to a fat content of 0.1 to 3.5%, with the lower the percentage of fat in the milk, the more sensitive the yogurt curd is to processing. Taking this into account, TCO increases more often in the production of low-fat yogurt than whole. The air content of milk should be kept to a minimum. However, the presence of air in small quantities is still unavoidable, especially if the TCO is increased by adding milk powder at an early stage in the process. To remove the air contained in the original milk, the raw material enters the vacuum chambers for deaeration. Deaeration increases the stability and viscosity of the yoghurt; removes extraneous volatile odors and reduces fermentation time. In addition, the process improves the performance of the homogenizer and reduces the risk of sticking during cooking.

The next stage in the preparation of yogurt raw materials is homogenization. Its main purpose is to prevent the cream from settling during fermentation and to ensure an even distribution of fat in the milk. Homogenization also affects the stability and consistency of fermented milk products, even those with low fat content. To obtain a product of optimal quality, milk is recommended to be homogenized at a pressure of 200-250 atm. and temperature 65--70°C.

Next, the milk is subjected to heat treatment before the starter is added to it. This is done to improve the properties of the milk as a base for bacterial starter culture, as well as to ensure curd formation in the finished yoghurt and reduce the risk of whey separation in the final product. The most optimal mode of heat treatment is achieved at a temperature of 90--95°C and a holding time of about 5 minutes. This mode allows you to denature most of the proteins, providing them (and hence the clot) with the ability to bind water. The result is a yogurt with a firmer consistency. To achieve the best effect, the product must be kept at the required temperature in the holding tube. [ Yoghurts. General specifications GOST R 51331-99]

An equally important technological stage in the preparation of yogurt is the choice of starter culture and its preparation. Strict hygiene plays a decisive role here: the preparation of the sourdough must be carried out in a separate, specially equipped room in order to reduce the risk of contamination.

Yogurt starters usually consist of two types of bacteria: Lactobacillus bulgaricus and Streptococcus thermophilus. However, other types of bacteria are sometimes added to the base starter, such as Lactobacillus acidophilus and Bifidobacterium. Both types of bacteria grow together and produce lactic acid as the end product of airless fermentation of milk. Streptococcus thermophilus is mainly responsible for acid production, while Lactobacillus bulgaricus gives yogurt its distinctive flavor. The interaction between the two types of bacteria is affected by the amount of each type applied, as well as the temperature and time of ripening. [Kvasnikov V. I., Nesterenko O. A. Lactic acid bacteria and ways of their use, "Nauka", 1975, pp. 1--384.]

If we talk about the methods of reproduction of the working starter, then in recent years, concentrated forms have been mainly used - both for the reproduction of the working starter, and for direct introduction into the product. However, many dairies are increasingly breeding working starter cultures from mother cultures. At various stages of reproduction, cultures are called as follows:

The main starter - it is purchased in laboratories for the cultivation of starter cultures;

Uterine - is prepared from the main starter culture directly at the dairies;

Transfer - uterine culture in large quantities;

Working starter is a culture used to make yogurt.

Since the coagulum obtained as a result of fermentation is quite sensitive to mechanical stress, the design of the installation plays a decisive role. When producing tank-type yoghurt, it is very important that the pressure drop between the setter tanks and the packaging machine is as low as possible. Therefore, it is of paramount importance right choice type and size of pipes, valves, pumps, cooler, etc.

Cottage cheese - valuable dietary product, indispensable in the nutrition of children and adults, it is not only rich in vitamins, but also easily digestible. The proteins that make up the cottage cheese contain essential amino acids and can serve as a substitute for other proteins of animal origin for people for whom such proteins are contraindicated. Cottage cheese contributes to the formation of hemoglobin in the blood and the normalization of the nervous system, it is recommended for the prevention of metabolic diseases, strengthens bone and cartilage tissue.

Cottage cheese is a sour-milk concentrated protein product with a mass fraction of protein up to 15--20%. Cottage cheese has a pure sour-milk taste and smell without extraneous shades. The consistency is tender and homogeneous, slightly smearing for fatty cottage cheese, heterogeneous, crumbly with a slight release of whey is allowed for low-fat cottage cheese. The color is white, slightly yellowish with a creamy tint, uniform throughout the mass. According to microbiological indicators, the content of bacteria of the Escherichia coli group in 0.00001 g of the product and pathogenic microorganisms, including Salmonella in 25 g of the product, is not allowed in the curd. Dairy enterprises produce the following types of cottage cheese:

Bold - 18% fat and acidity 200--225 T;

Bold - 9% fat and acidity 210--240 °T;

Non-greasy -- acidity 220--270 T

Peasant - 5% fat and acidity 200 "T;

Table - 2% fat content and acidity 220 °T;

Dietary - 4% and 11% fat, non-greasy, acidity 210--220 ° T;

Dietary fruit and berry - 11, 9, 4% fat, low-fat, acidity 180-200 T;

With fruits -- 4% fat, low fat, acidity 200°T and other types of cottage cheese.

The technology for the production of cottage cheese is based on the fermentation of milk with sourdough in order to obtain a clot and its further processing. The clot is obtained by acid and acid-rennet coagulation of milk proteins. With acid coagulation, a ferment prepared on pure cultures of lactic streptococci is introduced into milk during fermentation. Acid-rennet coagulation involves the introduction of sourdough, calcium chloride and rennet. With acid coagulation, the clot is formed as a result of lactic acid fermentation and has a good consistency. However, when fermenting milk in the production of fatty cottage cheese, the resulting clot does not release whey well. Therefore, in practice, the method of coagulation of milk proteins is chosen depending on the quality of the feedstock, the type of curd produced, the equipment available, consumer orders, etc.

Production of cottage cheese in the traditional way

The technological process consists of the following operations: acceptance and preparation, separation of milk, normalization, pasteurization, cooling, fermentation and fermentation of normalized milk, curd cutting, whey separation and curd bottling, self-pressing and curd pressing, cooling, packaging, packaging, storage and transportation of curd .

Dairy raw materials intended for the production of cottage cheese are cleaned on separators - milk cleaners or filtered through three layers of gauze or other filter cloth. Purified milk is heated to 37 ± 2 ° C and separated on cream separators. In the manufacture of fat, semi-fat and peasant's cottage cheese, milk is normalized for fat, taking into account the mass fraction of protein in whole milk, so that a finished product with a given fat and moisture content is obtained. Skimmed or normalized milk is pasteurized at a temperature of 78 ± 2 ° C with a holding time of 15--20 s in plate or tubular pasteurization-cooling units or capacitive apparatus. After pasteurization, the milk is cooled to the fermentation temperature. If milk after pasteurization is not used immediately for processing, then it is cooled to 6 ± 2 ° C and stored for no more than 6 hours. After storage, the milk is heated again to the fermentation temperature. The starter is prepared on pure cultures of mesophilic lactic streptococci. For accelerated fermentation, a starter prepared on pure cultures of mesophilic and thermophilic streptococci is used. The temperature of milk during fermentation is 30 ± 2°C in the cold and 28 ± 2 °C in the warm season, with the accelerated method - 32 ± 2°C, when using the Darnitskaya starter - 26 ±2 and the Kaunas starter -- 24 ± 2 °С. Before adding to milk, the surface layer of the starter culture is carefully removed with a clean, disinfected ladle and removed. Then the starter is mixed to a homogeneous consistency with a clean whorl (when cooked in starter tubs) or a stirrer and poured into the prepared milk in an amount of 1--5% of the total mass. With accelerated fermentation, 2.5% of the ferment prepared on cultures of mesophilic streptococci and 2.5% of the ferment on cultures of thermophilic streptococci are added to milk. The duration of fermentation of milk is 10 hours, and with the accelerated method - 6 hours. An aqueous solution of calcium chloride (mass fraction of calcium chloride 30–40%) is added to milk after fermentation: 400 g per 1000 kg of fermented milk. It is necessary to restore the salt balance disturbed during pasteurization of milk. The preparation and preparation of a calcium chloride solution is carried out in accordance with the Instructions for technochemical control at the enterprises of the dairy industry. After adding a salt solution to fermented milk, a 1% solution of the enzyme is introduced at the rate of 1 g of the drug with an activity of 100,000 IU per 1000 kg of milk. Apply rennet, food beef or pork pepsin or enzyme preparation VNIIMS. With the activity of enzyme preparations below 100,000 IU, their number is increased.

Rennet powder or pepsin is introduced into milk in the form of a 1% aqueous solution prepared in boiled and cooled to 36 ± 3 ° C in water. To prepare a pepsin solution, it is recommended to use acid pasteurized and protein-free whey at a temperature of 36 ± 3 ° C 5-8 hours before use. The enzyme solution is introduced into the milk with constant stirring. 10-15 minutes after adding the enzyme solution, mixing is completed and the milk is left alone until a dense clot is formed with an acidity of 61 ± 5 ° T for cottage cheese of 9% and 18% fat content, 65 ± 5 °T for peasant and 71 ± 5°T for low-fat cottage cheese. The clot is checked for fracture and by the type of serum. If, when broken with a spoon or a removable ladle, a smooth edge with shiny smooth surfaces is formed, then the clot is ready for further processing. The serum released at the site of clot rupture should be transparent, greenish in color.

To process the clot, hand lyres are used, in which stretched thin stainless steel wire serves as knives. With such wire knives, the clot is cut into cubes measuring 2x2x2 cm. The clot is first cut along the length of the bath into horizontal layers, and then along the length and width into vertical ones. After this treatment, the clot is left for 40-60 minutes to separate the whey and increase the acidity. The separated whey is drained from the bath. The clot after draining the whey is poured into calico or lavsan bags measuring 40x80 cm. The bags are filled by about 70%, which is 7-9 kg of cottage cheese. The bags are then tied up and stacked one on top of the other in a self-pressing vat, a press trolley or a UPT unit for pressing and cooling the curds.

To speed up the separation of whey, as well as in case of poor whey release, the clot is heated by supplying steam or hot water. For uniform heating, the upper layers of the clot are moved with a wooden or metal plate (shovel) from one wall of the bath to another. The clot is heated to 40 ± 2 "C for 30--40 minutes for cottage cheese of 9% and 18% fat content, 35 ± 2 `C for 20--40 minutes for peasant and 36 ± 2 "C for 15-20 minutes for low-fat cottage cheese. When using the Darnitskaya starter, whey clots are heated to 34 ± 2 ° C with an exposure of 15-40 minutes.

Self-pressing of cottage cheese lasts at least 1 hour. When using the UPT installation, the duration of pressing, depending on the quality of the resulting clot and the coolant (brine, ice water), is 1-4 hours. Pressing is continued until curd is obtained with a mass fraction of moisture provided for by regulatory documentation. For cottage cheese of 18% fat content, it is 65%; 9% fat - 73; peasant - 74.5; canteen - 76; low-fat - 80; for dietary fruit 11% fat - 64, 9% fat - 66, 4% fat - 77 and non-fat - 79% moisture. When producing low-fat curd, curd dehydration can be carried out on a curd separator. After separation and pressing, the curd is cooled using various equipment. Packaged cottage cheese is cooled down to 6 ± 2 C, and the product is considered ready for sale.

Features of the production of cottage cheese in other ways

Moldovan way. The main feature of this method is that the bunch is cooled cold whey taken from other parties contact. Despite the faster cycle in production, it is used extremely rarely due to the rough and rubbery consistency of the finished product.

continuous way. Fermentation of normalized milk is carried out with sour whey or lactic acid. The whole process from the formation of a clot to the finished product is carried out in the inter-screw chambers of one large cylinder. The consistency of the finished product is flabby, has high acidity, and during production there are large losses of protein with whey. All this makes the production of cottage cheese in this way low-profit. On the line Ya9 - OPT. This is the only way where milk is homogenized. Calle (a clot with whey) is fed into the dehydrator, where, after certain manipulations, the finished product is formed. The quality of curd produced in this way corresponds to the quality of traditional curd.

Separate way. In the process of separation, milk is separated into skimmed milk and cream with an MJ of 50 - 55%. Then the usual manipulations are carried out with skimmed milk. The resulting mixture is sent to the curd separator, where the clot is separated from the whey. Ready low-fat cottage cheese mixed with cream to the required fat content. A separate method is used to produce soft dietary cottage cheese, as well as cottage cheese with fruit fillings.

membrane method. It is used in the production of children's curds. The essence of the process lies in the fact that the milk before fermentation is subjected to preliminary thickening in an ultra filtration plant. The fermented substrate is poured into consumer containers, where the final formation of the product takes place. The consistency of curd soufflé is figurative

Kefir is the national drink of the peoples of North Ossetia. It has been known in Russia and other countries of the world for more than a hundred years. The uniqueness of this product lies in the use of a special starter prepared on kefir fungi or specially selected pure cultures of microorganisms. Kefir is produced low-fat and with a mass fraction of fat 1; 2.5; 3.2 and 6%, solids 7.8; 8.1; 9.5 and 11%, as well as fruit, fortified and others with various original names. It is produced by reservoir and thermostatic methods. Kefir is a homogeneous liquid creamy product with a pure specific sour-milk taste, milky white or slightly creamy in color. Kefir is characterized by certain organoleptic properties. The consistency is homogeneous and without sludge with a broken clot, with a reservoir method of production and with an undisturbed clot with a thermostatic method of production. For low-fat kefir, as well as one percent gas formation is allowed in the form of separate eyes. On the surface of kefir, a slight separation of whey is allowed (no more than 2% of the volume of the product). The color is milky white, slightly creamy.

Kefir is obtained from pasteurized milk by fermenting fungi with sourdough. Starter cultures are prepared from kefir fungi. To do this, one part of dry fungi is placed in 40-50 parts of warm (19°C in summer and 21°C in winter) skimmed milk. It is pasteurized at 92-95°C with a holding time of 20-30 minutes. Kefir fungi filled with milk are kept at 19-21°C until a clot is formed for 20-24 hours. During this time, milk with fungi is mixed 1-2 times. When a clot forms, the fungi are separated and placed in warm (19-21°C) pasteurized milk. For one part of the fungus take 30-50 parts of milk. Next, fungi are cultivated as described above, usually 2-3 transplants are enough to revive the microflora of kefir fungi. Animated fungi float to the surface of the milk, they are used to obtain a fungal (working) starter. For this purpose, animated fungi are placed in pasteurized chilled milk (19-21 ° C), one part is taken for 30-50 parts of milk; at the fermentation temperature, the milk is kept for 15-18 hours, after which it is thoroughly mixed and left for another 5-7 hours. After that, the contents are mixed again, and then filtered through a sieve. The resulting fungal starter is used to ferment milk in order to obtain kefir, and the fungi are used to obtain a new batch of starter. The composition of the sourdough includes lactic acid streptococcus, lactic acid bacillus, yeast and acetic acid bacteria.

For the preparation of industrial (working) starter, fungal starter can also be used. It is prepared in the following way. In pasteurized and chilled milk (20-22°C) add 1-3% fungal starter; the fermentation process lasts 10-12 hours. In order to improve the taste and smell, the leaven is kept for 5-6 hours at 20-22°C. Sourdough, both kefir and fungal, is best used without cooling. If necessary, the starter is cooled to 3-10°C and stored for no more than 24 hours.

With the thermostatic method of obtaining kefir, 3-5% of industrial or 1-3% fungal sourdough is added to cooled milk, mixed for 15 minutes, and then poured into bottles or bags with continuous stirring, corked and kept in a thermostat for 8-12 hours at 18-21 ° With summer and 22-25C in winter. The end of fermentation is determined by the consistency of the clot: it should be dense, without gas bubbles and acidity 75-80T. Bottles with ready-made kefir are cooled in the refrigerator, where it matures for 8-13 hours. Ready kefir has an acidity of not more than 36 hours from the moment of its production. (one)

For the tank method of kefir production, it is fermented in tanks at 23-25°C. After introducing the starter (the same amount as in the thermostatic method), the mixture is stirred for 15 minutes, then left alone for 8-12 hours. at 23-25C. The finished clot has an acidity of 85-100T. At the end of fermentation, the milk clot is stirred for 10-30 minutes (to obtain a homogeneous consistency) and cooled to 20+-2°C, and then left alone to mature for 6 hours, after which it is cooled to 6°C, stirred for 2-5 minutes and bottled or packaged. The acidity of the finished kefir is 85-120T.

When producing fortified kefir, vitamin C is added to the starter 30-40 minutes before it is added to milk. Next, the starter is stirred for 10-15 minutes and incubated for 20-30 minutes. Vitamin C is added taking into account its content in the finished product, which is 110 g per 1000 kg of milk. The fermented milk is stirred. The duration of the first mixing is from 15 to 40 minutes, depending on the strength of the coagulum and the design of the agitator in the tank. When a homogeneous consistency is obtained, the stirrer is stopped for 30–40 minutes, and then it is periodically turned on for 5–15 minutes every hour. In kefir with a heterogeneous lumpy consistency, whey may separate during storage. After cooling and mixing, kefir is left alone for maturation, the duration of which is at least 24 hours from the moment of milk fermentation. After maturation, kefir is stirred again for 2-5 minutes and poured. Kefir after bottling is stored for 24 hours at a temperature not exceeding 8 °C.

So, dairy products have a high nutritional value. They contain proteins, fats, calcium, phosphorus, provitamin A - carotene and vitamin B2. Fermented milk products are also of great value from the point of view of nutritional physiology, since lactic acid bacteria, in addition to fermentation, also cause weak protein breakdown. Thus, the human body is offered already partially processed, easily digestible protein; the proportion of free amino acids increases. Through splitting and new synthesis, a rearrangement of vitamins occurs, which is well suited to human needs. Lactic acid arising from lactose promotes intestinal motility and calcium absorption; metabolism is activated. Many people who are intolerant to regular milk can take fermented sour milk drinks without any harm.

The value of fermented milk products also lies in the fact that they contain microorganisms and their metabolic products, which inhibit putrefactive bacteria in the human gastrointestinal tract. Lactic acid also contributes to this, which lowers the pH of the medium, and also prevents the activity of putrefactive microorganisms. At least some of the microorganisms used (eg Lactobacillus acidophilus, Bifidobacterium) have an antibiotic effect, so products made with their participation can be successfully used in certain digestive disorders. Sour-milk products have a positive effect on the nervous system, respiratory tract, stimulate appetite, have a pleasant, refreshing taste, and are used in the treatment of anemia, tuberculosis, and diseases of the gastrointestinal tract.

2. Materials and methods

lactic acid bacterium product probiotic

During the research, samples of fermented milk products were taken, such as kefir, sourdough, cottage cheese and fermented baked milk. Dilutions of lactic acid products and a suspension of cottage cheese were prepared. The declared amount of CFU was printed on the packages of the products. It was written on kefir that the amount of Lactobacillus rhamnosus was 1x CFU/g, on sourdough 1x CFU/g, on ryazhenka 1x CFU/g, on cottage cheese 1x CFU/g.

Various types of utensils and equipment were prepared for work. To be able to dilute to the indicated amount, sterile test tubes, 1 ml pipettes, 50 ml of sterile saline were prepared. MPA and MRS media were prepared for inoculation. Dilutions of kefir were prepared by introducing 1 ml of the product into 9 ml of saline, thus 7 dilutions were sequentially prepared, 5, 6 and 7 dilutions were planted on Petri dishes on both media. Dilutions of fermented baked milk were prepared, as well as 5, 6 and 7 planted on Petri dishes for both types of media. A suspension of cottage cheese was also prepared by adding 1 g of the product to 9 ml of water, stirring this solution until it is relatively homogeneous and then preparing 7 dilutions as described above. Dilutions 4, 5 and 6 were planted on Petri dishes on the above media. The starter was also diluted, dilutions 8, 9 and 10 were planted on nutrient media on Petri dishes. In the course of research, positive results were obtained only in experiments with kefir, colonies of lactic acid bacteria Lactobacillus rhamnosus, and 2 types of colonies of rods and cocci grew on the cup. During the sowing of cottage cheese on the MPA medium, a mold colony grew. During the sowing of sourdough and fermented baked milk, negative results were obtained, the cups were empty.

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lactic acid bacteria(syn. lactobacilli) - gram-positive rod-shaped bacteria belonging to the genus Lactobacillus (Beijerinck, 1901), fam. Lactobacillaceae.

M. b. are represented by rods of various shapes: from short coccoid to long filiform (Fig.). The length of cells in different cultures of the same species depends on the composition of the medium, the presence of oxygen, and the method of incubation. M. multiply. division by a septum, which leads to the formation of chains. Ultrafine structure of M.'s cells. in many ways similar to other gram-positive bacteria. On agar media form small colonies.

M. b. do not have cytochrome-containing respiratory systems, are immobile, do not form catalase, do not reduce nitrates to nitrites, do not liquefy gelatin, do not form spores and pigment; strict anaerobes or optional. They have proteolytic activity due to the action of proteases and peptidases, but do not have lipolytic activity. A source of energy for M. b. is lactic acid fermentation (see). M. b. divided into homofermentative, forming as a result of the fermentation of carbohydrates up to 90% lactic acid, as well as negligible amounts volatile to-t, ethyl alcohol and carbon dioxide, and heterofermentative, forming approx. 50% lactic acid, 25% CO 2 , 25% acetic acid and ethyl alcohol.

Systematics M. b. not fully developed. Bergey's Manual of Determinative Bacteriology (1974) includes 25 species in the genus Lactobacillus. The difficulty of classification lies in the variability of many properties of these microorganisms during cultivation on different media and in different conditions. A study of the nucleotide composition of DNA showed that the content of guanine and cytosine in the DNA of various types of M. b. is different and lies in the range from 34.2 to 53.4 mol. %.

Antigenic properties are not well understood; preliminary data were obtained on the presence of antigens common to many species of M. b.

M. b. demanding on food sources, do not grow on simple media; grow on media containing vegetable decoctions, meat and yeast extracts, protein hydrolysates, since M. b. need amino acids, vitamins and a number of inorganic compounds; The pH of the media is in the range of 5.0-6.5, the optimum pH is 5.5. M. b. can grow at pH 3.8 and below. For M.'s cultivation. Rogosa medium or its modifications are widely used. Temperature range from 15 to 45 ° depending on the species.

M. b. meet in the soil, concentrating around root system, on cultivated and wild-growing plants, in went. - kish. path of warm-blooded animals and birds, insects. At the person are found all over went. - kish. tract - from the oral cavity to the rectum. M.'s representatives. (with few exceptions) are not pathogenic to humans. The most characteristic are L. acidophilus, L. plantarum, L. casei, L. salivarius, L. fermenti and L. brevis. L. bifidus in Bergey's Key to Bacteria (1974) is separated into a separate genus Bifidobacterium (see Bifidobacteria).

M. b. apply in bakery, in the dairy industry, in biol. conservation of many products (fermentation of vegetables and fruits), preparation of kvass, ensiling. For prevention and treatment went. - kish. diseases, vitamin deficiencies and alimentary anemia in animals, drugs are used, which also include M. to-rykh.

I. I. Mechnikov pointed to M. b. as antagonists of putrefactive and pathogenic microbes living in the human intestinal tract, and proposed their use in the fight against intestinal dysfunctions and premature aging. Many peoples use fermented milk products for the treatment of burns and wounds, for the prevention and treatment of went. - kish. diseases.

The development of microbiology has expanded the scope of these microorganisms: with M.'s help. in the industry receive dairy to - that, use for synthesis of the dextran applied in medicine as a partial blood substitute; a number of antibiotics produced by these microbes have been identified; use M. b. when creating products baby food, including those used to lay down. - prof., with a goal in newborns. Acidophilic paste is used in obstetrics and gynecology. practice, dermatology and surgery. L. acidophilus, along with B. bifidum and E. coli, is part of the complex preparation "omniflora" used abroad for the treatment of intestinal disorders. Lactobacterin is produced in our country (see), the active principle of which is lyophilized bacteria of strains L. fermenti 90T-C4 and L. plantarum 8P-AZ, which have high antagonistic activity against pathogens of dysentery, enteropathogenic Escherichia coli, staphylococcus, Proteus, and bifidumbacterin (see).

Bibliography: Erzinkyan L. A. Biological features of some lactic acid bacteria, Yerevan, 1971; Kvasnikov E, I. and Nesterenko OA Lactic acid bacteria and ways of their use, M., 1975, bibliogr.; Krasilnikov N. A. Determinant of bacteria and actinomycetes, p. 208, M.-L., 1949; M e h N and to about in I. I. Academic collected works, v. 15, p. 247, M., 1962; Guide to the vaccine and serum business, ed. P. N. Burgasov, p. 94, Moscow, 1978; Bergey's manual of determinative bacteriology, ed. by R. E. Buchanan a. N. E. Gibbons, Baltimore, 1975; L e r with h e M. u. R e u t e r G. Das Yorkommen aerob wachsender grampositiver Stabchen des Genus Lactobacillus Beijerinck im Darminhalterwachsener Menschen, Zbl. Bakt., I. Abt. Orig., Bd 185, S. 446, 1962; R o g o s a M., Mitchell J. A. a. Wiseman R. F. A selective medium for the isolation and enumeration of oral lactobacilli, J. dent. Res., v. 30, p. 682, 1951.

G. I. Goncharova.

As a rule, we associate the word "bacteria" with various diseases and other troubles. However, this is not quite true. After all, our body is a habitat for a wide variety of microorganisms. Among them there are even such bacteria, without which normal life activity is impossible. This group includes lactic acid bacteria that live in the intestines of a healthy person. In general, they are a group of gram-positive microaerophilic microorganisms that promote the fermentation of carbohydrates, forming lactic acid. This fermentation is often used as industrial production products for the preservation and processing of beverages and food, and at home.

Bacteria perform many beneficial functions in the body. First of all, lactic acid bacteria maintain an optimal balance of acidity in the intestines due to their ability to produce acetic and lactic acid.

In addition, they contribute to the normalization of the protective function of the intestine, which helps a person to cope with various and other microorganisms. Lactic acid bacteria have a beneficial effect on the liver by suppressing the increased activity of metabolites.

In addition to acetic acid, these beneficial microorganisms are also capable of producing volatile compounds such as hydrogen sulfide and hydrogen peroxide, which effectively suppress various intestinal infections.

Many studies have shown that acid-resistant bacteria, which include lactic acid microorganisms, produce many trace elements and vitamins that contribute to the improvement of the body as a whole. When interacting with other substances and among themselves, they secrete enzymes necessary for a normal metabolic process and digestion, as well as better absorption of nutrients.

Of particular interest among the diversity of lactic acid bacteria are microorganisms of the Lactobacillaccae family and the Slreptocuccaccae family. The latter are widely used in the manufacture of various fermented milk products: sour cream, yogurt with fruit fillings, and cottage cheese. Such lactic acid bacteria as acidophilus bacillus easily take root on the walls of the intestine and prevent the division of putrefactive ones for human health.

In order for your body to independently maintain the necessary conditions for the reproduction of these microorganisms, special efforts are not required. Enough to follow a healthy diet. Unfortunately, modern world designed in such a way that it is not easy to fulfill this condition. The whole problem is that, despite good nutrition, not all products from the daily diet meet quality standards.

In addition to malnutrition, factors such as constant stress, alcohol abuse and smoking, as well as long-term antibiotic treatment, adversely affect the intestinal microflora.

You can restore healthy microflora in the intestines by eating homemade milk, curdled milk, sour cream, cottage cheese or kefir. You can use store-bought dairy products, but the benefits from them will be much less.

Depending on the type, lactic acid bacteria can affect the state of the immune system in different ways. For example, bifidobacteria, unlike lactobacilli, inhibit the immune response. Therefore, before buying, pay attention to what kind of lactic acid bacteria they contain in their composition.

With the use of lactic acid microorganisms, many medicines are made that are prescribed for such disorders of the digestive system as dysbacteriosis, diarrhea, and others.

Characterization of probiotic microorganisms and their

Biological role

The term "probiosis" means symbiosis, a community of two organisms that contribute to the life of both partners. "Probiotic" - an organism that participates in symbiosis and favors life.

The first assumption about the relationship of microbes that inhabit the intestines with the spiritual and physical health of a person was first put forward in 1907 in the works of the famous Russian scientist I.I. Mechnikov.

For the first time the term "probiotic" as an antonym of "antibiotic" was proposed by D.M.Lilly and P.H.Stilwell in 1965 to refer to microbial metabolites that have the ability to stimulate the development of any microorganisms. A similar interpretation of the term "probiotic" was given in 1971 by A.Sperti to refer to various tissue extracts that have a stimulating effect on microorganisms.

Subsequent advances in the study of human microbial ecology have made it possible to refine the original definition of probiotics. So, in 1974, R.B. Parker used this term to refer to microbial preparations that have the ability to regulate the microbial ecology of the intestine. According to his definition, probiotics are microorganisms or their components capable of maintaining the balance of intestinal microflora.

Later, R.Filler called probiotics any preparations from living microorganisms that, when introduced into the host's body, give a beneficial effect due to the correction of intestinal microflora. Only a limited number of intestinal microorganisms can be considered probiotics, since the addition of these bacteria to food improves the digestive functions of the gastrointestinal tract. Moreover, both monocultures and mixtures of microorganisms can act as regulators of microecology.

Subsequent advances in microbial ecology have allowed R.Filler to refine his original definition of prebiotics: they are preparations made from live microorganisms or growth promoters of microbial origin that have a beneficial effect on endogenous microflora. An attempt to bring even greater clarity to the interpretation of this term was made by G.R. Gibson and M.B. Roberfroid, who proposed to call probiotics only nutritional supplements microbial origin, showing their positive effects on the host organism through the regulation of intestinal microflora.

In accordance with GOST R 52349-2005 “Food products. Functional food products. Terms and Definitions", probiotic - functional food ingredient in the form of non-pathogenic and non-toxic live microorganisms useful for humans, which, when systematically consumed by humans directly in the form of preparations or biologically active food supplements, or as part of food products, has a beneficial effect on the human body as a result of normalizing the composition and / or increasing biological activity of normal intestinal microflora.

Probiotic microorganisms can enter the body in the following ways:

with drugs containing strains of living microorganisms, with a clear indication for use;

with biologically active food supplements (complex preparations based on living microorganisms, manufactured at pharmaceutical enterprises, which are used as biologically active additive to food, and, as a rule, are distributed through the pharmacy network);

· With food products that are enriched with them or obtained by a biotechnological method using probiotics as starter cultures.

Probiotics can contain both one type of microorganism (monoprobiotics) and an association of strains of several types of microorganisms, from 2 to 30 (associated probiotics). In this case, they are symbiotics.

Symbiotics are complex preparations that combine probiotic microorganisms of one or different taxonomic groups, selected according to the principle of the greatest survival in adverse conditions. In terms of their effects, these microorganisms complement each other.

Probiotics can be administered to a wide range of living organisms (humans, animals, birds, fish) regardless of the species of the host from which the strains of probiotic bacteria (heteroprobiotics) were originally isolated. However, most often, probiotics are prescribed for the above purpose to representatives of that animal species or to a person from whose biomaterial the corresponding strains (homoprobiotics) were isolated.

In recent years, autoprobiotics have begun to be introduced into practice, the active principle of which is strains of normal microflora taken from a particular individual and intended to correct his microecology.

Preparations - probiotics are produced in various dosage forms: dry in vials and ampoules, in the form of powders, tablets and medical suppositories. They contain a high number of viable microorganisms in a single dose, have a long shelf life and can be delivered to the most remote regions of our country. These funds are classified as medical pharmacopoeial preparations, which leads to their use mainly for therapeutic purposes (see below).

To improve the health of the general population, it is more expedient to use fermented milk products, which are both suppliers of nutrients and have a probiotic effect.

Traditional fermented milk products, obtained by fermenting milk using various types of lactic acid bacteria, have been used by people for thousands of years. Considering fermented milk products from modern positions, they can undoubtedly be attributed to products that have a probiotic effect on the human body.

The great Russian scientist I.I. Mechnikov for the first time expressed and scientifically substantiated the idea of ​​the possibility of using lactic acid bacteria to combat unwanted microflora of the human gastrointestinal tract. I.I. Mechnikov suggested using lactic acid bacteria that can take root in the intestines. In the literature, there are numerous data on the positive effect of fermented milk products on the human body.

Research carried out in the direction of obtaining fermented milk products with probiotic properties and studying their effect on the human body is opening up new ones. There are numerous data in the literature on the positive effect of fermented milk products on the human body. Dairy products contribute to a higher absorption of calcium; increase the secretion of digestive juices and bile secretion; increase gastric secretion and secretion of pancreatic juice; increase the excretion of urea and other products of nitrogen metabolism; inhibit the growth of unwanted microflora due to the bactericidal action of lactic acid and antibiotic substances produced by certain types of lactic acid bacteria and bifidobacteria; favorably affect intestinal motility; contribute to the reduction of serum cholesterol; tone the nervous system. In recent years, it has been established that fermented milk products with probiotic properties have a stimulating effect on immunity, the mechanism of which obviously includes the activation of the production of certain immune response regulators, in particular, interleukins and interferon gamma, in combination with an increase in the local immune response of enterocytes, phagocytosis and lymphocyte proliferation. The immune effect is associated with several mechanisms - it is a stimulating effect on the immune response (in particular, on the activity of microphages and killer cells); decrease under the influence of low intestinal pH due to lactic acid, the activity of 7-alpha- | hydroxylase, an enzyme of microorganisms involved in the metabolism of bile acids, which have a pro-carcinogenic effect; a decrease in the activity of enzymes of intestinal microorganisms (glucuronidase, nitroreductase and azoreductase), which are involved in the transformation of pro-carcinogenic compounds into carcinogenic ones in the intestine. There are also reports of the ability of fermented milk products with probiotic properties to reduce the risk of malignant neoplasms, in particular cancer | clean intestines and breasts, remove toxic substances from the body.

Dairy products contribute to a higher absorption of calcium; increase the secretion of digestive juices and bile secretion; increase gastric secretion and secretion of pancreatic juice; increase the excretion of urea and other products of nitrogen metabolism; inhibit the growth of unwanted microflora due to the bactericidal action of lactic acid and antibiotic substances produced by certain types of lactic acid bacteria and bifidobacteria; favorably affect intestinal motility; contribute to the reduction of serum cholesterol; tone the nervous system. In recent years, it has been established that fermented milk products with probiotic properties have a stimulating effect on the immune system.

There are also reports on the ability of fermented milk products with probiotic properties to reduce the risk of malignant neoplasms, in particular colon and breast cancer, and remove toxic substances from the body.

Main purpose fermented milk products and preparations with probiotic properties is the maintenance of good health in people of various age groups or animals.

There is a close relationship between the state of human health, the functioning of his immune system and the composition of the microflora of his gastrointestinal tract. Violation of the composition of the microflora in the body (dysbacteriosis) can have serious consequences. Strong and long-acting adverse effects can disrupt homeostasis and lead to illness or even death of the body.

According to the latest data from the Russian Academy of Medical Sciences, the spread of various forms of dysbacteriosis (violation of the composition of beneficial microflora) in Russia has reached the scale of a national catastrophe, affecting more than 90% of the population. The emergence of dysbacteriosis contribute to various external factors and diseases, including the digestive system. It is believed that intestinal normobiocenosis is the most complex ecological system, which is a kind of organ of the human immune system.

The macroorganism and intestinal microflora are a relatively stable ecological system, the balance of which, on the one hand, is determined by the physiological and immunological characteristics of the macroorganism, and, on the other hand, by the species and quantitative composition of microbial associations and the diversity of their biochemical activity. In a normal physiological state, the relationship between the macroorganism and microflora is symbiotic in nature, and the flora at the same time has a significant impact on the general immunity and natural resistance of the host to infections, takes an active part in the processes of digestion, the synthesis of various biologically active substances. For its part, the macroorganism has a regulatory effect on the composition of the intestinal microflora through the acidity of gastric juice, intestinal peristalsis, bile salts and other factors. The stability of microbial associations in the body is extremely important for the life of the host and is one of the indicators of his health.

All this leads to the widespread use of agents that contribute to the restoration and maintenance of immunobiological homeostasis. It should be noted that the human body has huge reserves of health and often these reserves are not fully utilized and therefore there is the possibility of their mobilization. One of the factors contributing to the activation of the body's own forces is the symbiotic microflora and the biologically active compounds that it synthesizes. The systematic use of fermented milk products and preparations with probiotic properties that have a regulatory effect on the body or certain organs and It should be noted that the human body has huge health reserves and often these reserves are not fully utilized and therefore there is the possibility of their mobilization. One of the factors contributing to the activation of the body's own forces is the symbiotic microflora and the biologically active compounds that it synthesizes.

It should be noted that the human body has huge reserves of health and often these reserves are not fully utilized and therefore there is the possibility of their mobilization. One of the factors contributing to the activation of the body's own forces is the symbiotic microflora and the biologically active compounds that it synthesizes.

The systematic use of fermented milk products and preparations with probiotic properties, which have a regulatory effect on the body or certain organs and systems, provides a healing effect without the use of drugs. The Benefits of Probiotics is their harmlessness to the body, the complete absence of side effects and addiction to them with prolonged use.

Most often, the following types of living microorganisms are used for the manufacture of drugs:

− genus Bifidobacterium: B.bifidum, B.adolescentis, B.breve, B.infantis, B.longum;

- genus Lactococcus: Lac. lactis, Lac. creamoris;

− genus Lactobaccilus: L.plantarum, L.acidophilus, L.casei, L.delbrueckii; L. reuteri; L. bulgaricus;

− genus Propionibacterium: P.acnes; P. freudenreichii ;

- some types of yeast: Saccharomyces cerevisiae.

bifidobacteria

Bifidoflora in children is 98%, and in adults up to 40-60% of the intestinal microflora. Morphologically, bifidobacteria are Gram-positive rods. Sticks have thickenings at one end (maces) or two ends (dumbbells). The microscopic picture of each type of bifidobacteria has features in size, shape and arrangement of cells.

The physiological property of bifidobacteria is their ability to grow and develop at a temperature of 20-40 ºС, pH 5.5-8.0. The optimal growth zone is a temperature of 37-40 ºС and a pH of 6.0-7.0. At a pH below 4.5 and above 8.5, the growth of microorganisms stops.

All types of bifidobacteria in the primary isolation are strict anaerobes. In the presence of carbon dioxide, they can be tolerant of oxygen. Under laboratory cultivation, these microorganisms acquire the ability to develop in the presence of a certain amount of oxygen, and in highly nutritious media - to grow under completely aerobic conditions.

In milk, bifidobacteria develop slowly, since cow's milk is not their natural habitat. One of the reasons for the poor growth of bifidobacteria in milk is the oxygen dissolved in it. They did not show caseolytic activity; they can absorb casein only after partial hydrolysis. As a result of the splitting of casein, polypeptides, glycopeptides, amino sugars are formed that stimulate the growth of bifidobacteria. Another reason for the inhibited growth of bifidobacteria may be their low phosphatase activity.

For the normal growth and development of bifidobacteria, the presence of growth substances is of great importance. The growth of bifidobacteria in cow's milk stimulated by yeast extracts, hydrolyzed milk, and an increase in the protein:lactose ratio. A strong stimulating effect on the growth of bifidobacteria is obtained by using casein hydrolysates.

Vegetable growth stimulators of bifidobacteria in milk are defatted soy, potato extract, cane sugar, corn extract, carrot juice. Iron salts, sorbitol, trace elements in the form of copper sulphate and iron lactate are also used as growth stimulants. In addition, vitamins (pantothenic acid, biotin, riboflavin) are used.

One way to activate the growth of bifidobacteria in milk is to obtain mutants of these microorganisms that can grow without any protection from oxygen.

Biological role bifidobacteria lies in their beneficial effect on the human body through a number of mechanisms:

1. Bifidobacteria show high antagonistic activity against pathogenic and opportunistic microorganisms. Organic acids, antimicrobial substances, bacteriocins produced by microorganisms have an antagonistic effect on pathogenic microorganisms. Production organic acids(lactic and acetic in a molar ratio of 2:3) leads to an increase in acidity and, as a result, inhibition of unwanted microflora. Among antimicrobial substances, hydrogen peroxide, which is produced by probiotic microorganisms, is of great importance.

2. Bifidobacteria regulate the body's metabolic processes by producing vitamins, in particular group B, biotin (vitamin H), PP (niacin), which are involved in the metabolism of proteins, carbohydrates, and amino acid synthesis.

3. Bifidobacteria contribute to a more complete hydrolysis of proteins, both plant and animal. This increases the digestibility of food and reduces the likelihood of developing food intolerance due to the accumulation of undigested proteins in the large intestine.

4. It has been established that the effectiveness of bifidobacteria is due to the ability to modulate various parts of the immune system (activate the production of IgA (Immunoglobulin A) in the intestine, stimulate phagocytosis ( Phagocytosis (Phago - to devour and cytos - cell) - a process in which special cells of the blood and tissues of the body ( phagocytes) capture and digest pathogens of infectious diseases and dead cells) and the formation of interleukins (Interleukins are biologically active substances secreted by hematopoietic stem cells and macrophages; they have immunoregulatory properties), increase the production of g-interferon and the synthesis of immunoglobulin). It has been established that bifidobacteria ensure the supply of essential amino acids to the body (for example, tryptophan), and are capable of anticarcinogenic and antimutagenic activity. Bifidobacteria reduce the formation of nitrites, cresol, indole, ammonia, which have carcinogenic properties.

Research on the use of bifidobacteria for dairy products goes in different ways: new strains of bifidobacteria are isolated; receive oxygen-resistant strains of bifidobacteria, select and develop special growth stimulators of bifidobacteria in milk; make the enzyme β-galactosidase, which breaks down lactose; create bacterial concentrates that can be enriched with ready-made fermented milk products. The use of bifidobacteria in combination with lactic acid bacteria has become widespread.

Lactic acid microorganisms

Bacteria of the genus Lactobacillus (streptobacteria) are rods of different lengths. A feature of streptobacteria is their high resistance to table salt (6-10%). Lactobacilli are mostly able to grow at 1 ºС and develop well at 15 ºС. The main properties are acid and aroma-forming ability, the latter is manifested in the ability to produce acetoin. Streptobacteria have a pronounced proteolytic activity, due to the developed complex of proteinases and peptidases, in relation not only to milk, but also to muscle and connective tissue proteins.

Biological role lactic acid microorganisms lies in the fact that they have a pronounced antagonistic activity, that is, they inhibit the growth and reproduction of pathogenic microorganisms.

The main metabolic products of homo- and heterofermentative lactobacilli are lactic and acetic acids, hydrogen peroxide and carbon dioxide. The formation of milk and acetic acid reduces pH, forming an acidic reaction in the gastrointestinal tract, which prevents the reproduction of gas-forming, pathogenic microflora. Lactobacilli provide a bactericidal and bacteriostatic effect due to the production of bacteriocins. With their help, the growth of clostridia, listeria, salmonella, shigella, Pseudomonas aeruginosa, staphylococci, vibrios is inhibited.

In the human body, they contribute to the activation of the immune system, are involved in the metabolism of proteins, carbohydrates, lipids, nucleic acids, metal salts, bile acids, in the synthesis of vitamins, hormones, antibiotics and other substances. Lactobacilli enhance the physiological activity of the gastrointestinal tract. Actively involved in metabolism dietary fiber, in the destruction of excess digestive enzymes, as well as in the neutralization of toxic substances that come from outside or are formed as a result of a distorted metabolism. They are a source of various biologically active substances, namely B vitamins, folic, nicotinic acids, amino acids, organic acids.

Bacteria of the genus Lactococcus are not typical representatives of microorganisms of the human gastrointestinal tract, however, probiotics based on them are tolerant to the action of bile and can inhibit the development of pathogenic and opportunistic microorganisms.

propionic acid bacteria(PCB) - small sticks 0.5-0.8x1.0-1.5 microns in size, often swollen at one end and narrowed at the other, some cells are coccoid or V-shaped; located singly, in pairs or in clusters. They do not form spores and grow under both aerobic and anaerobic conditions. Non-pathogenic, live in the rumen and intestines of ruminants. According to a number of properties, they are close to lactococci and bifidobacteria. PKB is grown on various nutrient media containing cobalt.

PCBs, developing in milk, ferment milk sugar to propionic and acetic acids, and the enzymes they secrete decompose proteins to form peptides and amino acids. The accumulation of volatile fatty acids and free forms of nitrogen in the product is associated with the formation of a specific aroma and taste of cheeses and fermented milk products.

It has been proven that liquid cultures of propionic acid bacteria are able to exhibit an antioxidant effect. PKB produce antioxidant enzymes: catalase , peroxidase and superoxide dismutase. From the sulfur-containing amino acids of milk peptides, PCBs form dimethyl sulfide, which has an antimutagenic effect (ANTIMUTAGENS are chemical and physical factors that reduce the frequency of hereditary changes in the body - mutations).

Distinctive feature PKB is synthesis cobalamins (vitamin B 12).

PCB stimulate the growth of fecal bifidobacteria and help in the treatment of bacterial dysbiosis. PCBs produce exopolysaccharides (EPS) - high molecular weight carbohydrates that form viscous clots in milk. EPS strains have increased resistance to the aggressive environment of the gastrointestinal tract due to the presence of an EPS capsule, which serves as a link during their settlement and adhesion in the intestine. There is evidence that the amount of EPS synthesized depends on the type of culture and the properties of a particular strain, as well as on the cultivation conditions.

Antimicrobial properties are associated with the production of propionic and acetic acids, diacetyl, propionicins (antibacterial substances). PKB- inhibition of the growth of various bacilli and microscopic fungi; due to the action of these substances, PCBs act as natural biopreservatives of milk protein, which allows the use of this microflora in the food industry in order to prolong the shelf life of food products.

Probiotic properties of PCBare characterized by the fact that theyare not digested in the gastrointestinal tract of humans, are resistant to the action of bile acids, withstand low (pH 2.0– 4.5) stomach acidity,inhibit the activity of β-glucuronidase, azoreductase and nitroreductase– enzymes formed by the intestinal microflora and involved in the formationmutagens, carcinogensandtumor growth promoters. PCBs have powerful immunomodulatory properties and are able to reduce the genotoxic effect of a number of chemical compounds and UV rays.