Characteristics of pathogens that spoil meat, dairy and egg products. Homofermentative lactic acid fermentation. Changes in the microflora of milk during storage

Milk is an amazing invention of nature. Man has long appreciated the nutritional and medicinal properties of milk and not only learned to use this product, but also significantly improved it.

Various food products began to be produced from milk. For example: yogurt, kefir, yogurt, sour cream, cottage cheese, butter. Over time, many questions have arisen about the qualitative composition of milk and its effect on the body.

Milk contains more than 200 substances that are easily accessible to microorganisms, so they multiply intensively in it. Milk contains proteins, peptones, polypeptides, globulins, albumins, casein, and amino acids. Milk contains fatty acids, lipids, milk sugar (lactose), vitamins, hormones, enzymes and mineral salts. And there are always microorganisms in natural milk, since the udder is an open organ.

Milk, even when received under good sanitary conditions, is not a sterile product. In practice, it is sterile only in the udder of the animal. Already at the moment of milking, milk is subject to bacterial contamination, since saprophytic bacteria are constantly present in the nipple canal and mammary gland. The first streams of milk are especially contaminated, and the last portions are mostly sterile.

The first person to see the microflora of fermented milk products was the Frenchman Louis Pasteur. These studies have generated great interest in this topic. Through the efforts of microbiological scientists, both the physiology of the microorganisms themselves and the biochemical processes of fermentation and putrefaction caused by bacteria were studied. And this is exactly what will be discussed further.

Causes of pathogenic microflora in milk

The number of bacteria in milk obtained from healthy cows is insignificant - from 1000 to 10,000 per ml. These are mainly saprophytes - non-pathogenic micrococci, coryne bacteria, penetrating from the outside through the nipple. If the sanitary rules of milking are violated, many microorganisms from the environment get into the milk: from dirty hands, from water, dust, etc. In addition to ordinary E. coli, pathogenic microorganisms (dysentery microbes, salmonella, cholera vibrios, etc.) may be present.

Putrefactive bacteria, butyric acid bacteria, proteus and many others are accidentally found in milk. Sources of milk microflora, in addition to the udder parenchyma, are: milk containers, pipelines, udder skin, milker's hands, feed, air in livestock buildings. The largest number of microbial bodies is located in the teat canal of the udder. This is facilitated by the presence of milk, the openness of the channel for microorganisms and positive temperature. Microbes in the nipple canal form a so-called bacterial plug. Before milking with the first streams of milk, the bacterial plug is removed into a separate vessel and disinfected.

Lactating animals with infectious diseases excrete pathogens in their milk (anthrax, tuberculosis, brucellosis, Q fever, etc.). In milk at a certain temperature, normal, abnormal and pathogenic microflora can multiply. Therefore, to preserve the quality of milk immediately after receiving it, it is immediately cooled to a temperature of +10-12oC.

During long-term storage of raw milk (at temperatures above 10°C), not only their quantitative growth occurs, but also a change in the phases of the microflora of fresh milk. The bacterial phase is a period of time during which the microbes present in it do not multiply due to milk substances (lysozyme, immunoglobulins, lactoferrin) that have a depressing effect on microbial bodies. The duration of the bacterial phase depends on the urgency of cooling the milk and is inversely related to the number of microbes in the milk, its temperature and can last up to 24 – 48 hours.

Phases of change in the microflora of fresh milk

The first phase is bactericidal, when the vital activity of microorganisms in milk is suppressed. Microbes in this phase, as a rule, do not multiply, sometimes their number even decreases as a result of the bactericidal effect of lactein I and II, lysozyme and leukocytes. The duration of the bactericidal phase depends on the number of bacteria present in the milk, storage temperature and the individual properties of the animal’s body. The duration of the bactericidal phase is of great importance, since milk is considered more reliable only during this phase, and after it ends, microorganisms begin to develop and the milk spoils faster.

The temperature of milk storage has a great influence on the duration of the bactericidal phase. So, at a temperature of 37°C it is only 2 hours; at 10°C - up to 36 hours, at 5°C - up to 48 hours, and at 0°C - up to 72 hours. With an increase in the number of microbes in milk by several thousand per ml at the same storage temperature, the duration of the bactericidal phase is reduced by approximately 2 times. According to GOST, the cooling temperature for prepared milk should not be higher than 10°C. However, at this temperature, milk is stored only for 24-36 hours. The most effective temperature is 3-4°C. The duration of the bactericidal phase is also influenced by the sanitary conditions of milk production. Milk obtained in strict compliance with sanitary and anti-epidemic rules retains its bactericidal properties longer.

The second phase - the phase of mixed microflora - is characterized by the most active proliferation of microorganisms. In 1-2 days, the number of bacteria in 1 ml of milk can increase from several thousand to hundreds of millions. The rate of development of microbes depends on their initial quantity and the storage temperature of the milk. In this phase, cryoflora (or flora of low temperatures), mesoflora (medium temperatures), thermoflora (high temperatures) are distinguished.

At low temperatures, milk can remain in the phase of mixed microflora (cryoflora) for a long time. However, at a temperature of about 0°C during long-term storage, the number of bacteria increases noticeably and after a few days can reach tens and hundreds of millions per 1 ml.

Mesoflora in milk develops during its storage without pre-cooling. It is characterized by the rapid development of microorganisms and an increase in the number of lactic acid bacteria. Therefore, milk should be stored and transported only in the cryoflora phase. Thermoflora is present at a milk temperature of 40-45°C, for example, during the production of cheeses with a high second heating temperature. In this case, thermophilic lactic acid bacilli and thermophilic streptococci develop.

The third phase is the phase of lactic acid bacteria. During this period, the increasing concentration of lactic acid (65-70°T) leads to the gradual death of lactic acid streptococci, which are replaced by lactic acid rods.

The fourth phase is the yeast and mold phase. These microorganisms are resistant to acid reaction and use lactic acid for metabolism. As a result of a decrease in acidity, favorable conditions are created for the development of putrefactive bacteria, which decompose the protein substances of milk into volatile and gaseous products. At a milk storage temperature of 10-12°C, the number of bacteria increases 10 times during the day, at 18-20°C - hundreds of times, at 30-35°C - tens and hundreds of thousands of times. Because of them, milk stored at low temperatures goes rancid and becomes unsuitable for food, as well as for feeding to young animals. To disinfect and preserve milk, pasteurization, boiling, drying, ultrasound and the phenomenon of cavitation are used. The sanitary quality of milk is assessed by its acidity, expressed in degrees, the number of microorganisms in 1 ml of milk, coli titer and the presence of infectious agents.

Thus, in order to maintain the quality of milk, the following conditions must be observed: immediately cool the milk on the farm to the recommended temperatures, send it as soon as possible in isothermal tanks for processing to dairy plants, create appropriate conditions for storing milk at the plant, carry out heat treatment of the milk followed by cooling and immediate shipment for sale or production of dairy products.

Brief information about fermented milk products

There are many mysteries associated with kefir, a widespread drink. For example, there is no consensus on the origin of kefir grains.

Kefir grains are a complex symbiosis (coexistence) of microorganisms formed during a long process of development. Aged microorganisms behave like a whole organism. They grow together, reproduce and pass on their structure and properties to subsequent generations.

White or slightly yellowish kefir grains have a specific sour taste. Their main microflora consists 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 grain, the microorganisms that make up its composition cause changes in the milk. Under the influence of lactic acid streptococci and rods, lactic fermentation occurs, yeast causes alcoholic fermentation.

Thanks to these processes, the constituent elements of milk undergo changes, especially milk sugar. The resulting carbon dioxide and alcohol activate the activity of the stomach, accelerate the digestion process, and stimulate the appetite. Lactic acid has a beneficial effect on the intestinal microflora and delays the development of putrefactive bacteria.

To make sour cream you need cream. In this case, pure bacterial cultures are used, which include lactic acid and creamy streptococci and aroma-forming bacteria.

Cottage cheese is a favorable environment for the development of microorganisms that can cause its spoilage. Cottage cheese is fermented with pure cultures of lactic acid streptococci and flavor-forming bacteria. Sourdough usually has a sour milk taste, without any odors, gas formation, or protruding whey.

In yogurt, a variety of lactic acid bacteria, Bulgarian bacillus, discovered by I.I. Mechnikov, is used as a starter. When preparing yogurt, the starter consists of pure cultures of thermophilic streptococcus and Bulgarian bacillus, contained in equal proportions. If this ratio is violated, the product may acquire a sharply sour taste, a grainy structure, or quickly release whey.

Like any fermented milk product, yogurt is certainly healthy (especially with dietary supplements), but live bacteria remain in it, as a rule, for no more than one to two weeks. Yogurts with a long shelf life are most often a sterile dairy dessert, with or without fruit.

Yogurt is characterized positively if it has a pleasant fermented milk taste and aroma, a homogeneous structure and a fairly dense consistency.

Yogurt quickly relieves hunger, like most fermented milk products, it is useful for people of all ages.

Human use of lactic acid products

It has been proven that the use of lactic acid products accelerates the elimination of various radionuclides. A real fermented milk product necessarily contains live microorganisms (lactic acid bacteria), which make up the bulk of the microflora of the human digestive tract. An imbalance of microflora, called dysbiosis, can lead to all sorts of diseases: gastric and duodenal ulcers, allergies, gastritis. One of the most unpleasant consequences of dysbacteriosis is a decrease in the body’s immune functions; it entails protracted treatment of diseases and the development of complications. Due to impaired digestive functions, fatigue increases, fatigue and lethargy appear.

Dysbacteriosis is common in both adults and children. The cause of their occurrence may be stress, unfavorable environmental conditions, poor-quality drinking water and food. The intestinal microflora is also disrupted after taking antibiotics, which kill bacteria necessary for the body.

Dysbiosis has to be treated with medications, but fermented milk products, primarily kefir and biokefir and bifidok prepared on its basis, help prevent it. These drinks, equivalent in composition, are improved kefir with the addition of bifidobacteria - microorganisms characteristic of humans that help the digestion process (they account for, for example, about 90% of the microflora of the large intestine).

The Japanese use kefir to prevent the treatment of ancogynesis of the stomach and intestines. Lactic acid products “healthy” the intestinal microflora and treat gastritis. To treat gastritis with high acidity, fresh (one-day old) kefir (contains traces of alcohol) is used, and with low acidity - three-day old kefir.

Also, lactic acid bacteria suppress the development of putrefactive bacteria that cause colitis: Shigella, which causes dysentery, and Salmanella, which causes typhoid fever. Fermented milk products are included in the diet of any person. Depending on the combination of genera and species of lactic acid bacteria, various fermented milk products are obtained from them.

Milk has damaging properties. With the first drops of breast milk, a mother (sow, cow, etc.) gives everything to her child (pig, calf). The composition of milk is staggering with a long list of beneficial microorganisms, but if anti-epidemic and sanitary standards are not observed, milk can not only provide many useful substances, but also seriously undermine the health of its consumer. To prevent this from happening, you need to be extremely careful and treat the process of milking and further processing of dairy products with trepidation.

Characteristics 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” is an organism that participates in symbiosis and promotes life.

The first assumption about the connection between microbes inhabiting the intestines and the spiritual and physical health of a person was first put forward back in 1907 in the works of the famous Russian scientist I.I. Mechnikov.

The term “probiotic” as an antonym of “antibiotic” was first proposed by D.M. Lilly and P.H. Stilwell in 1965 to designate 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 designate 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. Thus, in 1974, R.B.Parker used this term to refer to microbial drugs that have the ability to regulate the microbial ecology of the intestine. According to its definition, probiotics are microorganisms or their components that can maintain the balance of intestinal microflora.

Later, R. Filler called probiotics any preparations made from living microorganisms that, when introduced into the host’s body, produce 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 the field of microbial ecology allowed R. Filler to clarify his original definition of pribiotics: these are preparations from living microorganisms or growth stimulants 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 calling probiotics only food additives of microbial origin that exhibit 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-toxicogenic living microorganisms useful for humans, which, when systematically consumed by humans directly in the form of drugs or biologically active food additives, or as part of food products, provides a beneficial effect on the human body as a result of normalization of the composition and/or increase biological activity of normal intestinal microflora.

Probiotic microorganisms can enter the body in the following ways:

· with medicinal products containing strains of living microorganisms with clear indications for use;

· with biologically active food additives (complex preparations based on living microorganisms, manufactured at pharmaceutical plants, which are used as biologically active food additives and, as a rule, distributed through the pharmacy chain);

· with food products that are enriched with them or obtained biotechnologically using probiotics as starter cultures.

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

Symbiotics are complex preparations that combine probiotic microorganisms of one or different taxonomic groups, selected on the basis of the greatest survival rate under unfavorable conditions. These microorganisms complement each other in their effects.

Probiotics can be prescribed 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 the species of animal or person from whose biomaterial the corresponding strains (homoprobiotics) were isolated.

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

Probiotic preparations are produced in various dosage forms: dry in vials and ampoules, in the form of powders, tablets and medicinal suppositories. They contain a high number of viable microorganisms per dose, have a long shelf life and can be delivered to the most remote areas of our country. These drugs belong to medical pharmacopoeial drugs, which determines their use mainly for therapeutic purposes (see below).

To improve the health of the general population, it is more advisable 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 a modern perspective, they can undoubtedly be classified as products that have a probiotic effect on the human body.

The great Russian scientist I.I. Mechnikov was the first to express and scientifically substantiate the idea of ​​​​the possibility of using lactic acid bacteria to combat unwanted microflora of the human gastrointestinal tract. I.I. Mechnikov proposed using lactic acid bacteria that can take root in the intestines. The literature contains numerous data on the positive effects of fermented milk products on the human body.

Fermented milk products promote 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; suppress the growth of unwanted microflora due to the bactericidal effect of lactic acid and antibiotic substances produced by certain types of lactic acid bacteria and bifidobacteria; have a beneficial effect on intestinal motility; help reduce serum cholesterol; tone the nervous system. In recent years, it has been found that fermented milk products with probiotic properties have a stimulating effect on the immune system.

There are also reports about 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 are aimed at maintaining 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. Disruption of the microflora in the body (dysbacteriosis) can have serious consequences. Severe and long-lasting 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 dysbiosis (disturbance in the composition of beneficial microflora) in Russia has reached the scale of a national catastrophe, affecting more than 90% of the population. The occurrence of dysbiosis is facilitated by various external factors and diseases, including those of the digestive system. It is believed that intestinal normobiocenosis is a complex ecological system, which is a unique 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, 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 the microflora is symbiotic in nature, and the flora 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 and the synthesis of various biologically active substances. For its part, the macroorganism has a regulating effect on the composition of the intestinal microflora through the acidity of gastric juice, intestinal motility, 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 its health.

Systematic consumption of fermented milk products and preparations with probiotic properties, which have a regulatory effect on the body or certain organs and It should be noted that the human body has enormous 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 symbiont microflora and the biological active compounds that it synthesizes.

Systematic consumption of fermented milk products and preparations with probiotic properties, which have a regulating 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 long-term consumption.

The following types of living microorganisms are most often used for the manufacture of drugs:

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

− genus Lactococcus: Lac. lactis, Lac. сremoris;

− 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 makes up 98% of the intestinal microflora in children, and up to 40-60% of the intestinal microflora in adults. Morphologically, bifidobacteria are gram-positive rods. The sticks have thickenings at one end (clubs) 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 upon initial isolation are strict anaerobes. In the presence of carbon dioxide they can be oxygen tolerant. When cultivated in the laboratory, these microorganisms acquire the ability to develop in the presence of a certain amount of oxygen, and in highly nutritious environments - to grow in completely aerobic conditions.

Bifidobacteria develop slowly in milk, 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. No caseolytic activity was detected in them, i.e. they can only digest casein after partial hydrolysis. As a result of the breakdown of casein, polypeptides, glycopeptides, and amino sugars are formed, which 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 is 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 using casein hydrolysates.

Plant stimulators for the growth of bifidobacteria in milk are low-fat soybeans, potato extract, cane sugar, corn extract, and carrot juice. Iron salts, sorbitol, microelements in the form of copper sulfate and iron lactate are also used as growth stimulants. In addition, vitamins are used (pantothenic acid, biotin, riboflavin).

One of the ways 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 exhibit high antagonistic activity against pathogenic and opportunistic microorganisms. Organic acids, antimicrobial substances, and bacteriocins produced by microorganisms have an antagonistic effect on pathogenic microorganisms. The production of organic acids (lactic and acetic acids in a molar ratio of 2:3) leads to increased acidity and, as a consequence, 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 the synthesis of amino acids.

3. Bifidobacteria contribute to 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 - 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; have immunoregulatory properties), increase the production of g-interferon and the synthesis of immunoglobulin). It has been established that bifidobacteria provide essential amino acids into the body (for example, tryptophan) and are capable of anticarcinogenic and antimutagenic activity. Bifidobacteria reduce the formation of nitrites, cresol, indole, and ammonia, which have carcinogenic properties.

Research on the use of bifidobacteria for dairy products follows different paths: new strains of bifidobacteria are isolated; obtain oxygen-resistant strains of bifidobacteria, select and develop special stimulators for the growth of bifidobacteria in milk; the enzyme β-galactosidase is added, which breaks down lactose; create bacterial concentrates that can be used to enrich 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%). Most lactobacilli are able to grow at a temperature of 1 ºС and develop well at 15 ºС. The main properties are acid- and aroma-forming ability, the latter manifested in the ability to produce acetoin. Streptobacteria have pronounced proteolytic activity, thanks to a developed complex of proteinases and peptidases, in relation to not only milk, but also muscle and connective tissue proteins.

Biological role lactic acid microorganisms is that they have pronounced antagonistic activity, that is, they suppress 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 lactic and acetic acids lowers the pH, forming an acidic reaction in the gastrointestinal tract, which prevents the proliferation of gas-forming, pathogenic microflora. Lactobacilli provide bactericidal and bacteriostatic effects due to the production of bacteriocins. With their help, the growth of clostridia, listeria, salmonella, shigella, Pseudomonas aeruginosa, staphylococcus, and vibrio is inhibited.

In the human body, they contribute to the activation of the immune system, participate 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. They actively participate in the metabolism of dietary fiber, in the destruction of excess digestive enzymes, as well as in the neutralization of toxic substances coming from outside or resulting from distorted metabolism. They are a source of various biologically active substances, namely B vitamins, folic, nicotinic acids, amino acids, and 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 are able to inhibit the development of pathogenic and opportunistic microorganisms.

Propionic acid bacteria(PCB) - small rods measuring 0.5-0.8x1.0-1.5 microns, 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 in both aerobic and anaerobic conditions. Non-pathogenic, live in the rumen and intestines of ruminants. In a number of properties they are close to lactococci and bifidobacteria. PCB is grown on various nutrient media containing cobalt.

PCB, developing in milk, ferment milk sugar to propionic and acetic acids, and the enzymes they secrete degrade 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 can 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 incidence of hereditary changes in the body - mutations).

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

PCBs stimulate the growth of fecal bifidobacteria and help in the treatment of bacterial dysbiosis. PCBs produce exopolysaccharides (EPS), high-molecular carbohydrates that form viscous curds 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 connecting link during their colonization and adhesion in the intestine. There is evidence that the amount of synthesized EPS depends on the type of culture and the properties of a particular strain, as well as on cultivation conditions.

Antimicrobial properties are associated with the production of propionic and acetic acids, diacetyl, propionicins (antibacterial substances) PKB– suppression of the growth of various bacilli and microscopic fungi; Thanks to the action of these substances, PCB act as natural biopreservatives of milk protein, which allows the use of this microflora in the food industry 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 people, are resistant to the action of bile acids, withstand low (pH 2.0– 4.5) stomach acidity,inhibit the activity of β-glucuronidase, azareductase and nitroreductase– enzymes formed by 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.

Scientists have long established that all complexly organized multicellular organisms are in a symbiotic relationship with bacteria. Moreover, symbiont bacteria not only do not have any harmful effects on the body of their multicellular hosts, but also actively help it survive.

The place of greatest accumulation of symbiont bacteria in the human body is the digestive system.

If you think about exactly how many bacteria constantly live in our intestines, this figure will seem incredible - the intestinal microflora consists of 100 trillion bacterial cells. The number of microorganisms in the human intestine significantly exceeds the number of its own cells.

However, such a large number of bacteria in the intestinal tract seems implausibly large only at first glance. Suffice it to remember that the area of ​​the intestinal mucosa is 400 sq.m., which corresponds to the surface of two tennis courts. Just think how many bacteria live on real tennis courts!

The first bacteria enter the child’s body with the mother’s first milk in his life. As you grow older, your intestinal microflora changes its composition.

The composition of intestinal microflora is heterogeneous throughout the gastrointestinal tract. In the upper parts of the digestive tube (in the stomach), the number of microorganisms is small. Mainly aerobic streptococci, lactobacilli and yeast fungi live here.

Actually, they live mainly in the intestine itself , known as Escherichia coli, and spore-bearing bacilli. But one of the most important components of the healthy intestinal microflora is lactic acid bacteria.

What are lactic acid bacteria?

Lactic acid bacteria, which are part of the intestinal microflora, represent a large group of anaerobic gram-positive microorganisms.

Today, the meaning of the term “anaerobic” is no secret even for people who are infinitely far from biology. Most people know very well that anaerobic are those living organisms for which oxygen is contraindicated for life and reproduction.

The division of bacteria into gram-positive and gram-negative often remains unclear. A person ignorant of microbiology may even get the impression that gram-negative bacteria are some incredible organisms with negative body mass that arrived on Earth from the black hole itself.

In fact, everything is much simpler and more prosaic. The origin of these terms is due to the fact that different types of bacteria stain different colors when using the Gram method, popular in microbiology: Gram-positive bacteria show a blue color, Gram-negative bacteria show a red color. The difference in color is due to the different structure of the cell wall.

So, these are anaerobic microorganisms. They absolutely do not need oxygen for life and are even contraindicated, but the presence of carbohydrates is absolutely necessary. All lactic acid bacteria ferment carbohydrates to produce lactic acid.

Lactic acid bacteria are divided according to the shape of their cells: spherical ( Streptococcus lactis), rod-shaped ( Lactobacillus). And also according to the substrate, that is, the carbohydrate that these bacteria convert into lactic acid: Lactobacillus- glucose and lactose, Betabacterium- glucose and maltose.

Functions of lactic acid bacteria in the human body

These bacteria have several main functions.

1. By producing lactic and acetic acid, they are responsible for maintaining a normal level of acidity in the intestines.
2. They are able to normalize the barrier function in the intestines, thanks to which the human body effectively resists various pathogenic agents. In other words, these symbiotic organisms are absolutely necessary for the proper functioning of the immune system.
3. Protect the liver by suppressing the activity of toxic metabolites.

In addition to lactic and acetic acids, lactic acid bacteria produce a number of compounds useful for the human body:

• synthesis of volatile compounds (hydrogen peroxide, hydrogen sulfide), toxic to many foreign microorganisms, helps fight intestinal infections;
• the formation of short chains of fatty acids activates intestinal motility;
• Vitamins and microelements produced by lactic acid bacteria have a beneficial effect on the entire body as a whole.

The impact of lactic acid bacteria on the emotional state of a person

The functions of intestinal microflora listed above have been known to scientists for quite a long time. Recently, it has become clear that lactic acid bacteria have another extremely important task - they help maintain mental health.

Recent studies have found that

When the intestines are in poor condition (primarily the deplorable state of the microflora), a person develops depression, anxiety, and chronic stress.

It was found that for a normal mental state, certain microorganisms that regulate a person’s mood and other mental processes are absolutely necessary.

In experiments with bacteria Bifidobacterium longum NCC3001 This microorganism has been shown to be a potent anti-anxiety agent. In another bacterium - Lactobacillus rhamnosus– the possibility of influencing GABA (gamma-aminobutyric acid), which is an extremely important inhibitory neurotransmitter, was shown. Lactobacillus rhamnosus is able to regulate the level of GABA in some parts of the brain, which leads to a decrease in the release of the stress hormone cortisol and, consequently, to a decrease in anxiety.

How can bacteria living in the intestines affect brain function?

To answer this question, you just need to remember that the human body has not two (spinal and brain), but three brains.

In addition to the central nervous system, the body also has the abdominal nervous system (abdominal brain), which develops from the same embryonic anlages as the central nervous system.

The abdominal and brain work in very close connection with each other. Therefore, what happens in the intestines has the most direct impact on what happens in the head. The connection between the brain and the abdominal brain is provided by the vagus nerve, which leaves the skull and ends in the abdominal cavity.

Maintaining a normal ratio of various intestinal bacteria in the body is quite simple: all that is required is a nutritious healthy diet. Unfortunately, most of us are currently deprived of just such nutrition, even if we eat a lot of fermented milk products, fruits, vegetables and lean meat. The fact is that many modern products are not entirely benign. That is, of course, you can’t get poisoned by them, but they don’t bring much benefit either. As a result, maintaining the intestinal microflora in a normal working state becomes very difficult.

In addition to poor nutrition, factors such as smoking, alcohol abuse, nervous stress, and taking many medications (antibiotics, anti-inflammatory spheroids, laxatives) lead to suppression of intestinal microflora.

About how to help our smaller brothers, lactic acid bacteria, using modern naturopathy methods.

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"...lactic acid bacteria utilize vitamins produced by propionic acid and bifidobacteria, as a result of which the medicinal and biological value of the products decreases."

As you know, all traditional starter cultures contain lactic acid bacteria, i.e. Fermentation of milk occurs with the obligatory use of...

The main disadvantage of common probiotic starter cultures of bifidobacteria (propionic acid bacteria) is that they require complex nutrient media for their activation, and they do not ferment milk to form a clot (gel), but only enrich the product with bifidobacteria (propionic acid bacteria), and are used to obtain fermented milk product additionally lactic acid bacteria (thermophilic streptococcus or kefir starter). Co-cultivation of these microorganisms reduces the probiotic properties of fermented milk products.

The uniqueness of the probiotic starter cultures offered by our company (both industrial and home use) lies in the ability of probiotic microorganisms ( bifidobacteria And propionic acid bacteria) ferment milk and food media without the use of traditional starter cultures - lactic acid bacteria, which, as is known, include bacteria of the genera Lactobacillus and Streptococcus. All this became possible thanks to an innovative method of activating probiotic cultures in milk to obtain high enzymatic activity of microorganisms, which under normal conditions cannot be achieved due to low growth energy and acid formation.

In milk propionic acid bacteriadevelop slowly and usually clot after 5-7 days (if we talk about the so-called acid coagulation). However, the maximum acidity formed in milk by propionic acid bacteria is quite high - 160-170° T, i.e., significantly higher than the acidity formed by lactic acid streptococci. But we are talking specifically about energy (dynamics)...Bifidobacteria, for example, also develop very slowly in milk. The developed method made it possible to increase the specified energy characteristics of probiotic cultures during milk fermentation, as a result of which the dynamics of bacterial biomass growth (i.e. bacterial growth and their reproduction) and acid formation increased. This is the main innovation of the proposed bacterial starters, which gives an advantage over all known probiotic starters.

The essence of the advantage of the presented bacterial concentrates is that when fermenting milk(or other food medium) by ourprobiotics ensure its maximum enrichment with vitamins, amino acids, enzymes and other useful substances, which would be impossible to achieve with the usual enrichment of milk with probiotic microorganisms (i.e. without a developed method for their activation in milk), as well as in co-cultivation with lactic acid bacteria, for which these metabolic products (useful substances) are food for active growth. Thus, lactic acid bacteria would simply interfere with the high-quality saturation of food products fermented by probiotic microorganisms (bifido- and (or) propionic acid bacteria) with beneficial nutrients.

In other words, when used together in production, lactic acid bacteria do not allow probiotic bacteria (bifido- and propionic acid) to qualitatively enrich fermented milk products with useful substances, because they consume these same substances (vitamins, amino acids, enzymes) for their own growth.

Of course, bifido- and propionic acid bacteria also require certain nutrients necessary for their development and growth, but to a much lesser extent than the so-called. homofermentative lactic acid bacteria, which will be discussed below... The declared advantages of our starter cultures stem from the characteristics of lactic acid fermentation:

FERMENTATION (FERMENTATION)

Fermentation(fermentation) , the process of anaerobic (without access to molecular oxygen) breakdown of organic substances, mainly carbohydrates, occurring under the influence of microorganisms or enzymes isolated from them. During Fermentation, as a result of coupled redox reactions, the energy necessary for the life of microorganisms is released, and chemical compounds are formed that microorganisms use for the biosynthesis of amino acids, proteins, organic acids, fats, and so on... At the same time, they accumulate end products of fermentation: organic acids (lactic, acetic, succinic, etc.), alcohols (ethyl, butyl, etc.), acetone, CO 2, H 2.

Types of Fermentation are classified according to the main (final) products formed and distinguish between alcoholic, lactic, butyric acid fermentation, propionic acid, acetone-butyl, acetone-ethyl and other types.

LACTIC FERMENTATION

NEED FOR GROWTH FACTORS

As is known, lactic acid fermentation is caused by bacteria of the genera Lactobacillus and Streptococcus (lactobacillus and streptococcus). That is, in the traditional production of fermented milk bioproducts, for the processes of fermentation of raw materials, various lactobacilli, thermophilic streptococci are necessarily used... (note: including, in relation to this topic, kefir starter and other acid-forming microorganisms are used)...Lactic acid bacteria are gram-positive and do not form spores (except Sporolactobacillus inulinus) and are overwhelmingly immobile. They all use carbohydrates as an energy source and release lactic acid.

MOST LACTIC ACID BACTERIA FORM ALMOST ONLY ONE LACTIC ACID, WHICH COMPOSES AT LEAST 90% OF ALL FERMENTATION PRODUCTS... SUCH BACTERIA ARE HOMOFERMENTATIVE.

TO homofermentative bacteria include: Milk Streptococcus Streptococcus lactis, Creamy Streptococcus Streptococcus cremoris, Bulgarian bacillus Lactobacterium bulgaricum, Acidophilus bacillus Lactobacterium acidophilum, etc.The main beneficial property of lactic acid bacteria is the suppression of putrefactive microflora.

To be fair, we note that the so-called heterofermentative lactic acid bacteria , for which, unlike homofermentative ones, lactic acid is not the main fermentation product. For example, bifidobacteria Bifidobacterium bifidum are considered to be pronounced probioticmicroorganismsand also need certain growth factors (such bifidus factors, For example, include oligosaccharides). For growth factors, see below...

Lactic acid bacteria are only capable of fermentation; they do not contain hemoproteins, such as cytochromes and catalase (note: catalase -, which in particular can be produced propionic acid bacteria).

As is known, according to the type of nutrition, bacteria are divided into autotrophic, capable of synthesizing organic substances from inorganic ones, and heterotrophic feeding on ready-made organic matter. In other words, in addition to mineral nutrition elements and sources of carbon and energy, many bacteria also need some additional substances called GROWTH FACTORS. These substances are part of the basic composition of the cell, but some microorganisms are not able to synthesize them themselves.

THAT IS, ANOTHER DISTINGUISHING FEATURE OF LACTIC ACID BACTERIA IS THEIR GREAT NEED FOR GROWTH SUBSTANCES.

Not a single representative of this group can grow on a medium with glucose and ammonium salts. Most people need a number of vitamins, mainly Group B: (lactoflavin (riboflavin, vitamin B2), thiamine(vitamin B1), pantothenic (vitamin B5), nicotinic (niacin, vitamin PP, vitamin B3) and folic acids (vitamin B9) , biotin (vitamin H, vitamin B7, coenzyme R)) and amino acids , as well as in purines and pyrimidines. These bacteria are cultivated mainly on complex media containing relatively large amounts of yeast extract, tomato juice, whey and even blood.

CONCLUSIONS ABOUT THE ADVANTAGES OF MILK FERMENTATION WITHOUT THE USE OF LACTIC ACID BACTERIA

Thus, LACTIC ACID BACTERIA- it's kind of "METABOLIC DISABLED", which, probably as a result of their specialization (growth in milk and other media rich in nutrients and growth substances), have lost the ability to synthesize many metabolites. It should also be noted that due to the formation of large quantities of lactic acid, to which they themselves are largely tolerant, lactic acid bacteria, under suitable conditions, can multiply quite quickly, displacing other microorganisms.

That is why, TO OBTAIN QUALITY PROBIOTIC FERMENTED MILK PRODUCT sharingbifidobacteria(or propionic acid bacteria ) and homofermentative lactic acid bacteria (as acid-forming bacteria) is no longer relevant today, because The developed method for activating these probiotic microorganisms in milk without additional growth stimulants makes it possible to obtain high-quality fermented milk bioproducts, maximally enriched with useful substances, which in turn are no longer consumed for the growth of starter lactic acid bacteria.

Proposed bacterial concentrates (and), according to the functional qualities of those obtained on their basis , today have no analogues and are able to compete with any global brands in this biotechnology industry.

on a note...

More information about lactic acid bacteria

HOMOFERMENTATIVE LACTIC ACID BACTERIA PRODUCING ALMOST LACTIC ACID ONLY

Homofermentative lactic acid bacteria include the following species:

Streptococcus milky Streptococcus lactis. Its cells are oval in shape, connected in pairs or in short chains. The optimal temperature is 30-35° C. It causes milk to sour, in which about 0.8-1.0% lactic acid accumulates.

Creamy streptococcus Streptococcus cremoris are spherical cells connected in chains. The optimal growth temperature is 25-30° C. In terms of acid-forming activity, it is similar to lactic acid streptococcus.

Bulgarian stick Lactobacterium bulgaricum, isolated by I. I. Mechnikov from Bulgarian curdled milk, is a long rod that grows at a temperature of 40-48 ° C. It forms up to 3-3.5% lactic acid in milk.

Acidophilus bacillus Lactobacterium acidophilum, isolated from the excrement of infants and young animals. Its shape and action are similar to the Bulgarian stick. The optimal growth temperature is 40° C.

Grain thermophilic stick Thermobacterium cereal (Lactobacterium delbreckii) - long cells with a temperature optimum of 48-52°C, accumulate up to 2.2% lactic acid. It ferments plant materials and does not develop in milk. Lactobacterium plantarum is a small rod capable of elongation (sometimes forming chains). This species accumulates about 0.9-1.2% lactic acid. Ferments plant materials. It develops when fermenting vegetables, preserving them, and is a pest in sugar, alcohol and other industries.

cucumber stick Lactobacterium cucumeris fermentati is a short rod, often connected in pairs or in the form of a chain, accumulates about 1% lactic acid at a temperature of 35 ° C.

HETEROFERMENTATIVE LACTIC ACID BACTERIA

Representatives of heterofermentative lactic acid bacteria are bifidobacteria of the genus Bifidobacterium (B. bifidum) and coccaceae of the genus LeAndconostoc (L. mesenteroides) , Lactobacillus brevis, Bacterium coli etc. Some heterofermentative lactic acid bacteria (for example, Lactobacteriumpentoaceticum) can ferment pentoses to form lactic and acetic acids, which occurs when ensiling feed. The acids that accumulate during this process protect the silage from spoilage.

An analysis of the studied probiotic strains of lactic acid bacteria was carried out: Streptococcus thermophilus, Lactobacterium delbrucku subsp. lactis, Lactobacterium delbrucku subsp. bulgaricus (yogurt crops). Specialty crops such as Lactobacterium acidophilus, Lactobacterium casie subsp. are playing an increasingly important role. rhamnosus, as well as bifidobacteria Bifldobactirium lactis, Bifidobactirium longum, which are used in the bioindustry both independently and in combination with other lactic acid bacteria. For example, not only special yogurt cultures are added to yoghurts, but also bifidobacteria, flavor-forming bacteria or acidophilus bacilli. Many strains of cultures that are used in the dairy industry have a stimulating and regulating effect on the body and have antagonistic properties that affect pathogenic and opportunistic microorganisms of the gastrointestinal tract. It is proposed to use probiotic strains obtained from milk fungus - a symbiotic group of bacteria and microorganisms of the genus Zoogloea, used to produce a dairy product known as kefir. The kefir under study has a strong juice-containing effect, which is explained by its content of lactic acid, casein, alcohol and carbon dioxide. During the fermentation process, it accumulates antibacterial substances, free amino acids, enzymes, organic acids, vitamins and contains a huge number of living cells.

probiotics

antimicrobial substances

lactic acid bacteria

biochemical properties

probiotic strains

microorganisms

1. Digestibility of feed nutrients by broiler chickens when feeding “Laktovit-N” / V.I. Trukhachev, E.E. Epimakhova, N.V. Samokish, L.A. Pashkova // Bulletin of the AIC of Stavropol. - 2013. - No. 2 (10). - pp. 81–83.

2. Zlydnev N.Z., Svetlakova E.V., Pashkova L.A. Mechanism of action of the probiotic “Laktovit-N” // Improving the technology of production and processing of agricultural products: collection of articles. scientific articles of the 76th Regional Scientific and Practical Conference “Agricultural Science - North Caucasus Federal District”. - 2012. - pp. 21-26.

3. The influence of “Laktovit-N” on the formation of intestinal microbiocenosis of broiler chickens / V.I. Trukhachev, N.Z. Zlydnev, E.V. Svetlakova, L.A. Pashkova // Chief livestock specialist. - 2012. - No. 8. - P. 22-24.

4. “Laktovit-N” for broiler chickens / V.I. Trukhachev, N.Z. Zlydnev, V.V. Rodin, V.V. Mikhailenko, L.A. Pashkova // Chief livestock specialist. - 2012. - No. 7. - P. 31-36.

5. Lapina T.I., Shpygova V.M. Morphometric characteristics of lamb hepatocytes // Diagnosis, treatment and prevention of diseases of farm animals: collection of articles. scientific tr. - Stavropol, 2001. - pp. 67–73.

6. The effectiveness of a domestic probiotic preparation when raising lambs during the suckling period / N.A. Ostroukhov [and others] // Sheep, goats, wool business. - 2014. - No. 1. – P. 41–42.

Microbes are constant companions of the human body. Some representatives of the microcosm often coexist with humans within a stable and mutually beneficial ecosystem, developing certain of its territories. Saprophytes, commensals, and symbionts provide valuable services to the animal and human body - they help synthesize vitamins, digest and assimilate food, and effectively protect against oncogenic influences and the destructive consequences of the invasion of other, completely pathogenic representatives of the microcosm. The macroorganism does not always treat its own microbes favorably - saprophytes and opportunistic microorganisms, and therefore they can become a source of infectious disease. But in general, their role in the biology of animals and humans should be assessed as positive.

Lactic acid bacteria are widespread and often used in everyday life. They are used when eating kefirs, yoghurts, lactic acid products purchased in the store, and at the pharmacy you can buy drugs to restore intestinal microflora after taking antibiotics.

People who are overweight remember the miraculous microorganisms contained in kefir, and some women save on cosmetics by resorting to the healing effects of lactic acid microorganisms.

Lactic acid bacteria are a group of microorganisms that ferment carbohydrates, producing mainly lactic acid. However, among lactic acid bacteria there are also pathogenic and conditionally pathogenic. There is foreign data on the unsafety of spore-forming lactic acid bacteria (B. cereus and B. anthracis) for humans. Some lactic acid bacteria determine the aroma and taste of fermented milk products, for example, flavor-forming streptococci (Streptococcus diacetilactis, Streptococcus citrovorus, etc.), and also produce carbon dioxide, acids and aromatic substances. The microflora of fermented milk products, such as koumiss, synthesizes vitamins C, Bl, B2. Some important features of the Lactobacterium acidophilus strain, according to Brassort (USA), include its ability to survive while passing through the human gastrointestinal tract and to produce antimicrobial components. This strain has been found to improve symptoms associated with small intestinal bacterial overgrowth in patients with chronic kidney disease and massive diarrhea. In addition, it reduces the level of enzymes in humans associated with the conversion of procarcinogens into carcinogens. Propionic acid bacteria (genus Propionibacterium) are used in the production of rennet cheeses. As a result of their vital activity, propionic acid and its salts are formed, which are mold inhibitors. Some species (Propionibacterium shermanu) are used to obtain vitamin B2. Intestinal bacteria of the genus Bifidobacterium are of greatest importance for human health. They maintain the normal balance of intestinal microflora, being inhibitors of pathogenic microorganisms; have immunomodulating activity; reduce cholesterol levels and the concentration of potentially dangerous ammonia and amines in the blood; have antitumor activity associated with a decrease in the quantitative content of procarcinogens, and are also able to absorb carcinogens formed during frying meat; participate in the synthesis of vitamins and other biologically active substances (thiamine, riboflavin, group K), amino acids and enzymes (lysozyme and casein phosphatase). It has been established that Bifidobacterium lactis reaches a high number of cells that improve the taste of products and are resistant to the acidic reaction of the environment, as a result of which they have high adhesive properties, i.e. survival in the gastrointestinal tract during the process of microbial transformation. Acidophilus bacteria can produce their own antibiotics that suppress E. coli, dysentery bacteria, salmonella, coagulase-positive staphylococci, etc. ; have a targeted effect on certain metabolic processes that are important for accelerating recovery and increasing the body’s performance. These microorganisms, taking root in the human intestine, help reduce the growth of pathogenic microorganisms, which prevents the development of putrefactive and fermentation processes. In addition, acidophilus helps the body absorb milk protein, which is characterized by an increase in acidity and favors the absorption and assimilation of calcium salts by the human body. Thermophilic streptococci give products a dense consistency and pure fermented milk taste. Strengthening certain immune indicators corresponds to the immune status of the animal and human body. Fermented milk drinks have high dietary and medicinal properties. These properties have been known since ancient times. The great Russian physiologist I.I. Mechnikov attributed the longevity of the Bulgarians to the high consumption of yoghurt. Consumption of fermented milk drinks improves human health and increases resistance to infections and tumor formation. Acidophilus drinks are used in the treatment of gastrointestinal diseases, colitis, cholecystitis, tuberculosis, furunculosis, and childhood chest asthma. Kumis and kuranga are used in the treatment of non-healing ulcers, gastrointestinal diseases and asthma. They not only heal the gastrointestinal tract, but also have a beneficial effect on the nervous system and metabolism. Products made from lactic acid fermentation agents are recommended for use in the treatment of dyspepsia, constipation, anemia, malignant tumors, exhaustion, loss of appetite, and the prevention of other diseases. So, we see that due to their chemical composition, as well as the starter cultures used in their production, dairy products have high physiological value and are therefore recommended for daily human nutrition.

Today, such classical cultures of lactic acid bacteria are known as Streptococcus thermophilus, Lactobacterium delbrucku subsp. lactis, Lactobacterium delbrucku subsp. bulgaricus (yogurt crops), special crops such as Lactobacterium acidophilus, Lactobacterium casie subsp. are playing an increasingly important role. rhamnosus, as well as bifidobacteria Bifldobactirium lactis, Bifidobactirium longum. They are used in the bioindustry both independently and in combination with other lactic acid bacteria. For example, not only special yogurt cultures are added to yoghurts, but also bifidobacteria, flavor-forming bacteria or acidophilus bacilli. Many culture strains used in the dairy industry are probiotics. They have a stimulating and regulating effect on the body and have antagonistic properties that affect pathogenic and opportunistic microorganisms of the gastrointestinal tract.

The most studied antimicrobial substances secreted by probiotics are a group of antibacterial peptides - bacteriocins, varied in their level of activity, spectrum and mechanism of action (Cascales et al., 2007). They are easily broken down by enzymes in the digestive tract and are therefore considered to replace traditional chemical preservatives (Nes et al., 2007). Lactococcus lactis produces a bacteriocin, nisin, which has been successfully used to increase the shelf life of food products in the food industry in many countries for more than 50 years (Cleveland et al., 2001). But its use is limited by a relatively narrow spectrum of antimicrobial action, directed only against gram-positive bacteria, and the emergence of resistant forms among food pathogens (Kaur et al., 2011).

It has been established that probiotic strains of microorganisms provide a multifaceted effect. For example, probiotics are beneficial for diarrhea caused by clostridia or rotavirus, as well as associated with antibiotics or chemotherapy. There is no doubt that probiotics are capable of influencing certain immunological parameters, such as enhancing the activity of phagocytes (macrophages) and lymphocytes.

It has been proven that the action of probiotics reduces the concentration of toxic substances in the human body, the activity of carcinogenic enzymes, and improves the digestibility of lactose (especially important for people who are intolerant to it).

Probiotics have other scientifically proven healing properties: prevention of infectious diseases, osteoporosis, improvement of allergic and autoimmune diseases, lowering cholesterol levels, regulating gastrointestinal motility.

An interesting product to study is the product (kefir) obtained from the milk fungus - this is a symbiotic group of bacteria and microorganisms of the genus Zoogloea, used to produce the dairy product known as kefir. It is also known under the names “Tibetan mushroom”, “milk mushroom”, “Indian yogi mushroom” (in Belarus).

Milk mushroom appears as a result of the symbiosis of about ten different microbes growing and reproducing together. The mushroom contains:

• acetic acid bacteria,
• lactobacilli,
• milk yeast.

The kefir product, which appears as a result of the vital activity of the milk fungus, is a product of both lactic acid and alcohol fermentation. Kefir contains not only lactic acid, but also alcohol and carbon dioxide.

The resulting product has a strong juice-containing effect because it contains lactic acid, alcohol, carbon dioxide and casein. Lactic acid gives the drink not only certain taste qualities, but also determines its dietary and preventive properties. The result of its work is the activation of the release of digestive enzymes into the intestinal tract and stimulation of their action. Thanks to lactic acid, the absorption of phosphorus and calcium in the body increases.

The beneficial effect of kefir is due to its suppressive effect against a number of microorganisms, including pathogens. This effect of kefirs is due to the ability to produce lactic acid and substances (hydrogen peroxide, acetic, benzoic acids, etc.) that stop the development of harmful bacteria in the intestines, which, as a rule, leads to the inhibition of putrefactive processes and the cessation of the formation of toxic decomposition products.

As a result of lactic and alcoholic fermentation, the content of most vitamins in fermented milk products increases, with the exception of niacin. Curdled milk is easier to digest than natural milk due to changes in the main components of milk, so people suffering from lactose intolerance can consume fermented dairy products without the risk of intestinal disorders, since the amount of lactose in such products is reduced to a minimum due to the action of the microflora of the starter culture.

Kefir accumulates antibacterial substances, organic acids, enzymes, free amino acids, and vitamins. The nutritional value of kefirs is determined by their content of carbohydrates, proteins, mineral salts and vitamins, which are in a form easily digestible by the human body. Kefir contains about 250 different substances, 25 vitamins, 4 types of milk sugar, pigments and a large number of enzymes. The nutrients in kefir are not only well absorbed themselves, but also stimulate the absorption of nutrients from other foods.

The bacteria in kefir encourage the immune system to mobilize all the body's forces to fight cancer cells. Microorganisms in fermented milk products play a large role in the precise proportional accumulation of nutrients.

Scientists have paid close attention to the polysaccharides contained in kefir. Research results indicate that the milk mushroom culture neutralizes toxins in the body and reduces cholesterol levels in the blood. Thus, kefir is an excellent preventative against the prolonged effects of toxic substances on the body and diseases of the cardiovascular system. For this reason, smokers, diabetics, and those who are overweight should definitely include kefir in their diet.

Laboratory experiments have shown that lactic acid bacteria, contained in large quantities in kefir, neutralize the action of so-called enzymes, which are the main culprits in the proliferation of cancer cells in the intestines. It has been proven that lactic acid bacteria prevent the development of breast cancer and colon cancer, and also contribute to the treatment of these diseases. Scientists believe that daily consumption of kefir in the amount of 500 grams is an effective cancer prevention measure.

Based on the research results obtained by many authors, it can be argued that the cultures of microorganisms included in the kefir milk fungus product can be used in biotechnology in the production of probiotic preparations used to prevent diseases of the gastrointestinal tract of animals and even humans.