People have known about the benefits of fermented milk products for a long time. The scientific justification and isolation of the bacteria that are responsible for their formation belongs to the Russian microbiologist Ilya Mechnikov. A group of lactic acid bacteria (lactobacilli and lactic acid streptococci) are microorganisms that organize the processes of fermentation of carbohydrates with the formation of lactic acid. Today, their abilities are widely used in the food industry, in agriculture and even in gas generation. Let's talk about the benefits and harms of lactic streptococci and lactobacilli, their structure and microbiology below.
Bacterial cooperation
Since the earliest times, lactic acid streptococci and lactobacilli have helped people prepare he althy food. In addition, many of them are part of the normal microflora of ourorganism. But this does not exhaust the benefits of lactic acid streptococci and all bacteria that provide fermentation processes.
Milky streptococci and coli are quite large, stain well and are easy to detect.
Lactobacillus plantarum - lactic acid heteroenzyme bacillus - is responsible for the fermentation of cabbage and cucumbers. In addition, it is normally present in the microflora of saliva.
Raw smoked sausages are treated with lactic acid. At the same time, they do not lose their taste, are safe for humans and do not deteriorate for a long time.
Not only in the food industry
The leather industry also uses lactic acid streptococci and bacillus, 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 wide 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 mankind will be able to defeat many serious diseases.
Thermophilic lactic streptococci are widely used in the processing of organic matter, during which methane gas is produced. At the same time, it is quite clean and suitable for heating various rooms.
Varieties of lactobacilli
For all their diversity, these microorganisms are divided into two groups:
- Homofermentative is the main producttheir vital activity is lactic acid (up to 90%), as well as ethyl alcohol, fumaric and succinic acids, carbon dioxide.
- Heteroenzymatic - the waste products are acetic and lactic acid, ethyl alcohol and carbon dioxide.
Friendly families
All lactic acid bacteria are members of the Lactobacillaceae family (lactobacilli) and the Streptococcaceae family (lactococci or lactic acid streptococci). The most common representatives found in sour milk are:
- Lactobacillus acidophilus is an acidophilus bacillus that is used not only in the food industry, but also in the production of medicines. Its high viability allows it to form colonies in the human intestine, and its ability to produce natural antibiotics creates an unfavorable environment for the vital activity of pathogenic microorganisms.
- Lactobacillus bulgaricus - Bulgarian stick. In addition to lactic acid, it also produces vitamins, amino acids and polysaccharides. Bulgarian stick 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, and have a beneficial effect on the immune system.
- Lactobacillus casei - these lactobacilli are part of the normal microflora of the oral cavity, intestines and genital organs. They displace Helicobacter pylori, a pathogenic bacillus that is responsible forthe occurrence of ulcers of the gastrointestinal tract and gastritis.
- Lactic acid streptococci are thermophilic and mesophilic. Below we will tell you more about them.
- Acetobacter aceti - acetic acid bacteria that in the process of life form nicotinic acid, vitamins B6 and B12.
Lactococcus family
In relation to the optimal temperature for life, lactic streptococci are:
- Heat-loving or thermophilic - these are bacteria, the optimal temperatures for which are 40-42 ° С.
- Mesophilic lactic streptococci develop best at 30-35°C.
They are all gram-positive bacteria (stained by the Gram method), in culture they form short or long chains. The shape of the cells of lactic acid streptococci has an oval outline, without flagella. These are non-motile bacteria that do not form spores or capsules and multiply primarily by simple division. All of them are facultative anaerobic organisms, they can exist in an environment without oxygen.
Mesophilic streptococci
This is a heterogeneous group of bacteria that consists of acid-producing (Streptococcus lactis, Streptococcus. cremoris) and flavor-forming cocci (Leuconostoc citrovorum and Leuconostoc dextranicum).
Streptococcus lactis is the main dairy streptococcus. In milk, it forms diplococci (paired cells) or short chains. Oval bacteria up to 1 micrometer in size. When makingcultures in 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, curdled milk and sour cream. Lactic streptococcus causes harm when it enters 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 creamy clots in milk.
Aroma-forming lactococci give a specific taste and aroma to fermented milk products. And in excess, they can lead to gas formation.
Thermophilic lactococci
The benefits and harms of thermophilic lactic streptococci were proven by II 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 marketed the first starter containing these microorganisms.
The cells of these bacteria are oval, slightly larger than mesophilic cocci, and form chains of various lengths in culture. It is these bacteria that are able to process lactose and are effectively used in the treatment of lactase deficiency in children, improves the digestion of milk mixtures and normalizes the intestinal microflora.
Thermophilic streptococci react to penicillin antibiotics. This property is used to determine the presence of antibiotics in milk.
These bacteria are used to treat and prevent diseases of the gastrointestinalintestinal tract (enterocolitis, dysbacteriosis, diarrhea), is 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 happens in our body
Once in our intestines, lactic acid bacteria gather in colonies and attach to the mucous membranes, creating conditions that suppress the vital activity of pathogenic microflora. But their effect is temporary. That is why it is necessary to consume products with their content regularly. This is the only way to maintain the right amount of them and prolong their effectiveness.
Milk contains lactose, which is converted into lactic acid in fermented milk products. The latter activates the work of the gastrointestinal tract, increasing the production of gastric juice, promotes intestinal peristalsis and improves metabolism.
The action of lactobacilli is based on the production of enzymes that can accelerate various processes. Today, doctors can choose a special composition of bacteria, depending on which process in the body needs to be activated. Such preparations are called eubiotics and may contain bifidobacteria (inhabitants of our intestines), lactobacilli (digestive system correctors) and colibacilli (safe strains of E. coli).
They are good for the body
Modern studies have proven that the consumption of these bacteria by children significantly reduces the risk of dental caries and significantly increasesoverall immune status of the organism.
The systematic use of fermented milk products has a beneficial effect on the prevention of oncological pathologies. And daily consumption 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, the possible harm to the body should also be taken into account. Dairy products are contraindicated in case of intolerance to live ingredients and food additives.
Variety of milk products
Modern food industry offers many products that are cooked with lactic acid bacteria:
- Curdled milk is the simplest fermented milk product that has many variations. Its formation involves the Bulgarian stick and mesophilic streptococci.
- Ryazhenka - with the help of the same lactobacilli, baked milk is fermented with the addition of cream. The color and taste of this product is given by melanoids - colored substances that are formed as a result of the interaction of proteins and sugars as a result of the most “delicious” Maillard reaction (saccharoamine condensation, or enzymatic browning).
- Sour cream is an original Russian product that is obtained by fermenting cream.
- Cottage cheese is a protein mass obtained by squeezing whey. It contains important amino acids: lysine, methionine, choline.
- Acidophilus milk is pasteurized milk saturated with mesophilic bacteria. It is widely used for feeding infants, withpoisoning and diseases of the gastrointestinal tract.
Most favorite - yogurt and kefir
Yogurt is the favorite food of children. For its preparation, a starter culture with the correct proportions of various lactobacilli is required. If various additives and thickeners are added to yoghurts, then thermization 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 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, infectious diseases.
Kvass - saved from a hundred diseases
Lactic acid 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 m alt, rye bread, beets, fruits, berries. Sometimes with the addition of foundation, aromatic herbs, honey.
Sourage of vegetables is the organization of spontaneous lactic acid fermentation with limited oxygen access. The same principle is used in the ensiling of pet food, which significantly improves its nutritional properties.
Cooking various cheeses and butter is also not complete without the participation of lactobacilli. After all, the first stage of preparation of these products– fermentation of milk.
Two sides of the same coin
Lactic acid bacteria are common where there is a substrate for their vital activity - carbohydrates. There are many of them in milk, on the surface of plants, fruits and vegetables, in places of decay of organic matter, 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 he alth.
Some of the lactic acid bacteria may not be safe for humans. This applies mainly to spore-forming lactobacilli, which cause disruption 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 sourness of wine, and cocci, breaking down proteins, lead to rotting of products. Lactic acid bacteria spoil flour and baked bread by breaking down starch and making bread sticky and smelly.
