People have known about the benefits of dairy products for a long time. The scientific justification and isolation of bacteria that are responsible for their formation belongs to the Russian microbiologist Ilya Mechnikov. A group of lactic acid bacteria (lactobacilli and lactic streptococci) are microorganisms that organize the fermentation of carbohydrates with the formation of lactic acid. Today, their abilities are widely used in the food industry, in agriculture, and even in the formation of gas. We will talk about the benefits and harms of lactic streptococci and lactobacilli, their structure and microbiology below.
Bacterial cooperation
Since the earliest times, lactic streptococci and lactobacilli have helped people prepare healthy foods. In addition, many of them are part of the normal microflora of our body. But this does not exhaust the benefits of lactic streptococci and all bacteria that provide fermentation processes.
Milk streptococci and coli are quite large, stain well and are easily detectable.
Lactobacillus plantarum - lactic acid heterozyme bacillus - is responsible for the ripening of cabbage and cucumbers. In addition, it is normally present in the microflora of saliva.
Raw smoked sausages are treated with lactic acid. However, they do not lose their taste, are safe for humans and do not deteriorate for a long time.
Not only in the food industry
In the leather industry, lactic streptococci and sticks are also used, and in agriculture they help in the preparation of animal feed (silage).
Everyone knows about the use of lactobacilli in pharmaceuticals. Biological additives and preparations with live cultures of these organisms are used for a variety of diseases. Today, lactic acid bacteria are called the hope of world medicine. It is likely that in the coming decades it is thanks to them that humanity will be able to defeat many serious diseases.
Thermophilic lactic streptococci are widely used in the processing of organic substances, during which methane gas is formed. Moreover, it is quite clean and suitable for heating various rooms.
Varieties of lactobacilli
For all its diversity, these microorganisms are divided into two groups:
- Homoenzymatic - the main product of their life is lactic acid (up to 90%), as well as ethyl alcohol, fumaric and succinic acids, carbon dioxide.
- Heterofermentative - the vital products are acetic and lactic acid, ethyl alcohol and carbon dioxide.
Friendly families
All lactic acid bacteria are representatives of the family Lactobacillaceae (lactobacilli) and the family Streptococcaceae (lactococci or lactic streptococci). The most common representatives that are found in sour milk are:
- Lactobacillus acidophilus is an acidophilus bacillus that is used not only in the food industry, but also in the manufacture of medicines. Its high viability makes it possible to form colonies in the human intestines, and its ability to produce natural antibiotics creates an unfavorable environment for the life of pathogenic microorganisms.
- Lactobacillus bulgaricus - Bulgarian stick. Besides lactic acid, it also produces vitamins, amino acids and polysaccharides. Bulgarian bacillus and lactic streptococci are the basis of the quality of yoghurts. These bacteria stabilize the intestinal microflora, contribute to the normal functioning of the stomach and pancreas, have a beneficial effect on the immune system.
- Lactobacillus casei - these lactobacilli are part of the normal microflora of the oral cavity, intestines and genitals. They displace Helicobacter pylori from the medium, a pathogenic bacillus that is responsible for the occurrence of gastrointestinal ulcers and gastritis.
- Streptococcus lactic acid - thermophilic and mesophilic. We will tell you more about them below.
- Acetobacter aceti - acetic bacteria, which in the process of life form nicotinic acid, vitamins B 6 and B 12 .
Lactococcus family
In relation to the optimal temperature for life, lactic streptococci are:
- Heat-loving or thermophilic are bacteria whose optimum temperatures are 40-42 ° C.
- Mesophilic lactic streptococci develop most well at a temperature of 30-35 ° C.
All of them belong to gram-positive bacteria (stained according to the Gram method), in the culture they form short or long chains. The shape of the cells of lactic streptococci has an oval shape, without flagella. These are motionless bacteria that do not form spores or capsules and multiply mainly by simple division. All of them are facultative anaerobic organisms, can exist in an environment without oxygen.
Mesophilic streptococci
This is a heterogeneous group of bacteria, which consists of acidifiers (Streptococcus lactis, Streptococcus. Cremoris) and aroma-forming cocci (Leuconostoc citrovorum and Leuconostoc dextranicum).
Streptococcus lactis is the main milk streptococcus. Forms diplococci (paired cells) or short chains in milk. Oval bacteria up to 1 micrometer in size. When the culture is added to 10 ml of milk at a temperature of 25-30 ° C, coagulation occurs within 10-12 hours with the formation of an even and dense clot. This is the main component of starter cultures in the preparation of cottage cheese, yogurt and sour cream. Lactic acid streptococcus causes harm when it gets into pasteurized milk, which leads to a decrease in its resistance.
Creamy streptococcus (Streptococcus. Cremoris) often forms long chains in culture. It is this bacterium that forms clots of creamy consistency in milk.
Aroma-forming lactococci give a specific taste and aroma to fermented milk products. And with excessive amounts can lead to gas formation.
Thermophilic Lactococci
The benefits and harms of thermophilic lactic streptococci have been proven by I.I. Mechnikov. It was he who isolated them in clots, which are formed during the fermentation of milk at a temperature of about 50 ° C. And he introduced the first sourdough containing these microorganisms.
The cells of these bacteria are oval, slightly larger than the mesophilic cocci, form chains of different lengths in the culture. It is these bacteria that are able to process lactose and are effectively used in the treatment of lactase deficiency in children, helps to improve the digestion of milk mixtures and normalizes the intestinal microflora.
Thermophilic streptococci respond to penicillin antibiotics. This property of them is used to determine the presence of antibiotics in milk.
These bacteria are used to treat and prevent diseases of the gastrointestinal tract (enterocolitis, dysbacteriosis, diarrhea), and are included in most dietary supplements. Medical cosmetology uses these lactococci as one of the components of the mask to restore and rejuvenate the skin.
What is going on in our body
Once in our intestines, lactobacilli are collected in colonies and attached to the mucous membranes, creating conditions that inhibit the vital activity of pathogenic microflora. But their action is temporary. That is why it is necessary to use products with their content regularly. This is the only way to maintain the right amount and extend their effectiveness.
Milk contains lactose, and in fermented milk products it turns into lactic acid. The latter activates the gastrointestinal tract, increasing the production of gastric juice, promotes intestinal motility and improves metabolism.
The action of lactobacilli is based on the production of enzymes by them, which are able to accelerate various processes. Today, doctors can choose the special composition of bacteria, depending on which process in the body needs to be activated. Such drugs are called eubiotics and may contain bifidobacteria (the inhabitants of our intestines), lactobacilli (correctors of the digestive system) and colibacteria (safe strains of E. coli).
They are beneficial for the body.
Modern research has shown that the use of these bacteria by children significantly reduces the risk of dental caries and significantly increases the overall immune status of the body.
The systematic use of dairy products has a beneficial effect on the prevention of cancer pathologies. And the daily use of natural yoghurts increases the level of lipoproteins in the blood, which leads to a decrease in the risk of atherosclerosis and pathologies of the cardiovascular system.
However, you should consider the possible harm to the body. Sour-milk products are contraindicated in case of intolerance to living components and food additives.
A variety of milk products
The modern food industry offers many products, the preparation of which occurs with the participation of lactic acid bacteria:
- Yogurt is the simplest fermented milk product that has many variations. Bulgarian bacillus and mesophilic streptococci participate in its formation.
- Fermented baked milk - using the same lactobacilli, fermented milk is fermented with the addition of cream. Color and taste are given to this product by melanoids - colored substances that are formed as a result of the interaction of proteins and sugars as a result of the most “tasty” Maillard reaction (sugar amine condensation, or enzymatic browning).
- Sour cream is an original Russian product, which is obtained by fermentation of cream.
- Cottage cheese is a protein mass obtained by squeezing whey. It contains important amino acids: lysine, methionine, choline.
- Acidophilus milk - pasteurized milk saturated with mesophilic bacteria. It is widely used for feeding infants, with poisoning and diseases of the gastrointestinal tract.
The most favorite - yogurt and kefir
Yogurt is the favorite product of children. For its preparation, fermentation with the correct proportions of various lactobacilli is required. If various additives and thickeners are added to yoghurts, then thermalization is necessary for its storage. Such a product has a shelf life of up to a month, but there are no live cultures of bacteria in it.
Kefir is a product of mixed lactic acid and alcoholic fermentation. Sticks and cocci, fungi and yeast take part in its preparation. All of them are contained in the finished product, which is indispensable for pathologies of the stomach and intestines, disorders of the nervous system, chronic fatigue, and infectious diseases.
Kvass - saved from a hundred diseases
Sour-milk bacteria are also used in the preparation of this old Russian drink. In its preparation, yeast is used, which triggers alcoholic fermentation, and lactic acid bacteria, which are responsible for fermentation. This sour drink is made from flour and malt, rye bread, beets, fruits, berries. Sometimes with the addition of wax, aromatic herbs, honey.
Vegetable fermentation is the organization of spontaneous lactic acid fermentation while restricting oxygen availability. The same principle is used for silage of pet foods , which significantly increases their nutritional properties.
The preparation of various cheeses and butter is also not without the participation of lactobacilli. After all, the first stage in the preparation of these products is the fermentation of milk.
Two sides of the same coin
Lactic acid bacteria are common where there is a substrate for their vital functions - carbohydrates. There are many of them in milk, on the surface of plants, fruits and vegetables, in places of rotting organics, in the digestive tract and on the mucous membranes of animals and people. Despite all the positive aspects that are associated with their activities, they can lead to spoilage of products and even harm to human health.
Some of the lactic acid bacteria may not be safe for humans. This applies mainly to spore-forming lactobacilli, which cause an upset of the intestinal tract. The pathogenicity of strains of lactobacilli is determined only by laboratory methods.
Stains on the surface of cheeses, the bitter taste of milk and the rancid taste of butter - all these phenomena are also associated with the activity of these microorganisms. Acetic acid bacteria lead to souring of wine, and cocci, breaking down proteins, lead to rotting of products. Lactic acid bacteria spoil flour and ready-made bread, breaking down starch and making bread sticky and unpleasantly smelling.