What Are the Different Uses for Lactobacillus Bacteria?
Lactic acid bacteria (LAB) is a collective name for a group of bacteria that can produce large amounts of lactic acid using fermentable carbohydrates. This kind of bacteria is extremely widespread in nature and has rich species diversity, including at least 18 genera and a total of more than 200 species. [1] With the exception of very few, most of them are essential bacteria in the human body and have important physiological functions, and they are widely present in the human intestine. [2]
- Chinese scientific name
- Lactobacillus
- boundary
- Bacterial kingdom
- door
- Firmicutes
- Tsuna
- Bacillus
- Head
- Lactobacillales
- Branch
- Lactobacillaceae
- Genus
- Lactobacillus, Pediococcus, Streptococcus, etc.
- Metabolic type
- Heterotrophic anaerobic
- Lactic acid bacteria (LAB) is a collective name for a group of bacteria that can produce large amounts of lactic acid using fermentable carbohydrates. This kind of bacteria is extremely widespread in nature and has rich species diversity, including at least 18 genera and a total of more than 200 species. [1] With the exception of very few, most of them are essential bacteria in the human body and have important physiological functions, and they are widely present in the human intestine. [2]
- Lactic acid bacteria are not only ideal materials for studying classification, biochemistry, genetics, molecular biology and genetic engineering (theoretical value is important in theory), but also in important fields closely related to human life, such as industry, agriculture and animal husbandry, food and medicine Has extremely high application value. [3]
Lactobacillus
- Lactic acid bacteria are probiotics that ferment carbohydrates into lactic acid.
- Figure 1 Lactic acid bacteria
Classification of Lactic Acid Bacteria
- Lactic acid bacteria are a kind of spore-free, Gram-staining positive bacteria whose main product is lactic acid, which contains many species. [6] Most lactic acid bacteria do not move, a few move around the hairs, and the bacteria are often arranged in chains. Streptococcus lactis, spheroids, usually in pairs or chains. Lactobacillus, rod-shaped, single or chain-shaped, sometimes filamentous, producing pseudo-branches. [4] Ordinary lactic acid bacteria are extremely weak. They can only survive in relatively restricted environments. Once detached from these environments, they will perish. [7]
- In terms of classification, lactic acid bacteria, as a family of lactic acid bacteria in the Eubacteria, can be divided into cocci and bacilli. Among them, spherical lactic acid bacteria include Streptococcus, Leuconostoc, Pediococcus; bacillus includes Lactococcus, Lactobacillus, Bifidobacterium, etc .; from the perspective of growth temperature, can be divided into high temperature type, medium temperature type; In other words, it can be divided into homo-fermentation and hetero-fermentation. [8] From the source, it can be roughly divided into animal-derived lactic acid bacteria and plant-derived lactic acid bacteria. [7]
- According to the biochemical classification in the Berry Bacteriology Handbook, lactic acid bacteria can be divided into 5 genera, including Lactobacillus, Streptococcus, Leuconostoc, Bifidobacterium, and Pediococcus.
Lactobacillus
- Lactobacillus cells have various morphologies, (0.5 ~ 1.2) m × (1.0 ~ 10.0) m. Long or slender rod-shaped curved short rod-shaped and stick-shaped club-shaped, usually into a short chain. Gram-positive and non-spore-forming. Cells rarely move with pericyate flagella. The colonies on the nutrient agar are convex, colorless on the whole, and the diameter is 2mm ~ 5mm. [9]
Lactobacillus
- The cells of Pediococcus are spheroidal and never extend, with a diameter of 12 m to 20 m. Under suitable conditions, the division forms a quadruplet in two straight directions, although sometimes it can also appear in pairs. Single cells are seen without forming a chain. Does not move and does not produce spores. [9]
Streptococcus
- Streptococcus spheroids form an oval shape with a diameter of no more than 2 m and are arranged in chains. No spores, most without flagella, juvenile bacteria (2-3 hours culture) often have capsules. In liquid medium, it often grows as a precipitate, but some grow uniformly and turbidly (such as Streptococcus pneumoniae); on the solid medium, small, smooth, round off-white, translucent or opaque colonies are formed. Colonies growing on blood plates may have hemolytic circles with different properties. [9]
Lactobacillus bifidobacterium
- Bifidobacterium is a bacterium with very inconsistent morphology, (0.5 ~ 1.3) m × (1.5 ~ 8) m, often curved, stick-shaped and branched. Solitary, paired, V-shaped, sometimes chained, cells parallel to a fence, or rosette-shaped. Occasionally swollen clubs. [9]
Leuconostoc
- Leuconostoc cells are spherical or bean-shaped, arranged in pairs or chains. In natural growth environments, Leuconostoc cells are arranged in pairs or short chains; in some competitive growth environments, the cells are arranged in longer chains. [9]
Lactic acid bacteria reproduction and development
- Lactic acid bacteria have small colonies on solid media and grow slowly. It can grow quickly in the liquid fermentation medium. After centrifugal washing, high purity bacteria can be obtained, and it has both aerobic and anaerobic properties. [6]
- Studies have shown that oligosaccharides can promote the proliferation of lactic acid bacteria. There are multiple ways to promote the proliferation of beneficial bacteria and inhibit the function of pathogenic microorganisms: one is the barrier effect, which is described as competitive inhibition of the intestinal mucosa epithelium; the other is metabolites On pathogenic bacteria and inhibition. [10] Stewart et al. (1993) and Tomilka et al. (1992) confirmed that isomalto-oligosaccharides (IMO) can promote the proliferation of bifidobacteria and lactic acid bacteria. The low-energy fatty acids produced by the metabolism of these bacteria can lower the pH value, so E. coli, salmonella, etc. Bacterial growth that is sensitive to acidic conditions is inhibited by low pH. The lectin activity of intestinal lactic acid bacteria (such as Bifidobacterium) is significantly higher than that of pathogenic bacteria (such as E. coli and Salmonella), which may be the reason why the normal intestinal flora has a competitive advantage in competitive rejection. one. [10-11]
Physiological functions of lactic acid bacteria
- Organic acids, special enzymes, and bacteriocins produced by lactic acid bacteria through fermentation have special physiological functions. A large amount of research data shows that lactic acid bacteria can promote animal growth, regulate the normal flora of the gastrointestinal tract, and maintain a micro-ecological balance, thereby improving gastrointestinal function, improving food digestibility and bioavailability, reducing serum cholesterol, controlling endotoxin, and inhibiting intestines Growth of spoilage bacteria in the tract, improving the body's immunity, etc. [2]
Lactic acid bacteria promote body growth
- Lactic acid bacteria can normally exert their metabolic activities in the body, and break down proteins, sugars, synthetic vitamins, and fats in food. Under the action of lactic protease, the macromolecular protein in food is partially degraded into small molecular peptides and essential amino acids that can be directly used by the host, which significantly improves the digestibility and biovalence of food, and promotes gastrointestinal absorption. After fermentation by lactic acid bacteria, lactose in food can be converted into glucose and galactose by lactic acid bacteria, and then into small molecular compounds such as lactic acid, which is easy to digest. Part of the fat can be degraded by lactic acid bacteria, which is easy to digest and increase the content of free fatty acids and volatile fatty acids. Lactic acid bacteria consume part of vitamins in the metabolic process, and simultaneously synthesize B vitamins such as folic acid to improve the biological activity of mineral elements, thereby achieving the role of providing essential nutrients to the host, enhancing nutrient metabolism, and promoting its growth. In addition, acidic metabolites produced by lactic acid bacteria can make the intestinal environment appear acidic, which is consistent with the optimal pH of general digestive enzymes (amylase 6.5, saccharifying enzyme 4.4), which is beneficial to the digestion and absorption of nutrients. [12] [13]
Lactic acid bacteria maintain intestinal flora balance
- Under normal circumstances, the entire digestive tract of animals is parasitized with a large number of microorganisms, which can be divided into three types according to their functions: symbiotic type, mainly facultative anaerobic bacteria. In ecological balance, their physiological functions are beneficial to the host. Pathogenic type, the number is small under normal circumstances, parasitic in the normal part, and will not cause the host to get sick; when it is out of control, it can cause host adverse reactions. Intersexual type has both physiological and pathogenic effects.
- The balance of the intestinal microflora is very important to the health of the body, and lactic acid bacteria can regulate this microecological balance, ensuring the normal physiological state of the host. Lactic acid bacteria are intestinal bacteria (ordinary bacteria), which can change the environment of the intestine, inhibit the reproduction of harmful bacteria, and adjust and maintain the balance of the gastrointestinal flora. Lactic acid bacteria can tightly bind to intestinal mucosal cells through adhesin, colonize and occupy the intestinal mucosal surface, and become the main component of the physiological barrier, so as to restore the host's resistance, repair the intestinal flora barrier, and cure intestinal diseases. If this barrier is damaged by antibiotics or other factors, the soil loses its resistance to foreign bacteria, which will cause the resistant intestinal bacteria to proliferate abnormally and replace the dominant bacteria, causing an imbalance in the intestinal microecological balance ( Placeholders and barriers ). [12] [13]
Lactic acid bacteria improve immunity
- Lactobacillus preparations can enhance immunity in two ways: one is to affect non-specific immune responses, enhance the viability of monocyte phagocytic cells and polymorphonuclear leukocytes, and stimulate the secretion of reactive oxygen species, lysosomal enzymes and mononuclear factors; Specific immune response, such as strengthening the levels of IgA, IgM, IgG and other immunoglobulins in the mucosal surface and serum, strengthening humoral immunity, promoting the proliferation of T and B lymphocytes, and strengthening cellular immunity. [13]
- Lactobacillus and bifidobacteria can obviously activate the phagocytosis of macrophages on the one hand, and because they can colonize the intestine, they are equivalent to natural autoimmunity. They can also stimulate peritoneal macrophages, induce interferon production, promote cell division, produce antibodies, and promote cellular immunity, etc., so they can enhance the body's non-specific and specific immune response and improve the body's ability to resist disease. When foreign bodies invade the body, immune cells are activated by lactic acid bacteria, which enhances the body's role in producing antibodies to foreign bodies. Chndra (1984) believes that the reason why lactic acid bacteria can stimulate the body to produce antibodies is because the bacteria stimulate lymphocytes through lymph nodes and mucous membranes to stimulate lymphocytes and then circulate into the bloodstream through the mesenteric lymph nodes (MIN) and distribute them throughout the body. Thus regulating the body's immune response. [13]
Lactic acid bacteria inhibit the growth of harmful flora
- Lactic acid bacteria have a good inhibitory effect on some spoilage bacteria and low-temperature bacteria, and can be used to prevent and treat diarrhea, diarrhea, enteritis, constipation, and various diseases caused by intestinal dysfunction and skin inflammation. Its antibacterial mechanism is mainly reflected in the following aspects:
- Organic acids such as lactic acid can significantly reduce the environmental pH and Eh (redox potential) value, and make the intestine in an acidic environment. For pathogenic bacteria such as dysentery bacillus, typhoid, paratyphoid, campylobacter, staphylococcus Etc. have antagonistic effects;
- The generated hydrogen peroxide can activate the "catalase-thiocyanate" system in milk and inhibit and kill Gram-negative bacteria and catalase-positive bacteria such as Pseudomonas, E. coli, and Salmonella, etc .;
- Produce small proteins or peptides (antibacterial peptides) similar to bacteriocins, such as various lactobacillins and bifidobacteria, which have antagonistic effects on staphylococci, clostridium spp. And salmonella and shigella. In addition, bifidobacteria and the like can also break down the combined bile acid into free creatine, which has a stronger inhibitory effect on bacteria than the former. [13]
Main applications of lactic acid bacteria
Lactic acid bacteria food industry
- 1. Fermented dairy products processing
- Yogurt is a fermented dairy product made from animal milk such as cow's milk and goat's milk fermented by lactic acid bacteria.
- Figure 2 Dairy products
- Active lactic acid bacteria beverage is a fermented milk beverage made by fermenting milk with lactic acid bacteria. It is popular with consumers for its refreshing taste, unique flavor and high nutrition and health functions. The biggest advantage is that the lactic acid bacteria in the beverage are in the form of live bacteria in the product, which helps to exert the physiological functions of lactic acid bacteria in the human intestine. [14]
- Cream and cheese . Lactobacillus fermentation can be used to produce cream. The lactic acid produced in fermentation can inhibit the spoilage bacteria to a certain extent and improve the stability of the cream. The other role is to produce aroma, so the sour cream produced by the fermentation method has more than sweet cream. Stronger aroma. Cheese is a product made by adding an appropriate amount of a lactic acid bacteria starter to milk to coagulate the protein in the milk, excluding whey, and pressing the clot. The added lactic acid bacteria starter ferments to produce acid, which can make the cheese mature and produce flavor. [14]
- 2. Fruit, vegetable and cereal products processing
- Kimchi processing: During the production and processing of kimchi, lactic acid bacteria use the nutrients of vegetables to ferment, which can improve the nutritional value of vegetable products, improve the flavor of vegetable products, and prevent spoilage. [14]
- Fermented soybean milk products : Soymilk made from soybeans, inoculated with fermenting agents such as Streptococcus thermophilus, Lactobacillus bulgaricus or Lactobacillus plantarum, and cultured at 38-42 ° C for 6-10 hours, can be made without beany smell, good solidification state, sweet-sour Suitable sour milk products. [14]
- 3. Fermented meat products processing
- Lactic acid bacteria reproduce and produce acid in meat products, which can reduce NO -2 to NO. NO can give meat products a bright red color by combining with myoglobin in meat. The acid-producing effect of lactic acid bacteria can also inhibit the growth and reproduction of miscellaneous bacteria, thereby preventing the flesh color from turning green and fat oxidation. Using lactic acid bacteria to ferment meat products can also extend the shelf life of fermented meat products, reduce the nitrite content in fermented meat products, and improve the food safety of such foods. [14]
- 4. Natural food preservatives
- Lactobacillus is a type of antibacterial polypeptide or protein that is synthesized by lactic acid bacteria during metabolism and secreted outside the cell, and has bacteriolytic effect. Because lactic acid bacteria are considered to be safe food-grade microorganisms in the world, the antibacterial substances they produce can be used directly in the food industry as natural food preservatives. [14]
- 5.Condiment production
- Appropriate artificial inoculation of lactic acid bacteria in the process of brewing fermented soy sauce can make the soy sauce rich in aroma, good flavor and good texture. Adding lactic acid bacteria to the soybean paste fermentation produces organic acid, which can produce a variety of flavor substances, and the soybean paste fermentation is stable, which can prevent the soybean paste from rancidity. When liquid deep fermentation is used to make vinegar, the added lactic acid bacteria can metabolize and produce the main flavor substances in vinegar such as organic acids, diacetyl and its derivatives. In addition, lactic acid bacteria can also be used with yeast to produce beer, wine, and milk. [14]
- 6. Production of lactic acid
- Lactic acid is not only an excellent raw material for the food industry, but also an important organic acid that has a wide range of uses in the chemical industry. Large-scale production of lactic acid through microbial fermentation such as lactic acid bacteria through renewable resources such as starch, grain, cellulose, industrial and agricultural, and civilian waste. An important method for the production of lactic acid. [14]
Lactic acid bacteria
- 1. Make quality silage
- The production of silage is completed by the fermentation of lactic acid bacteria. As an anaerobic bacteria, lactic acid bacteria rely on the sugar in the plant to survive, and the two are interdependent. The application of lactic acid bacteria in animal husbandry generally inoculates the same type of lactic acid bacteria, so that the pH value of the silage is appropriately reduced, the lactic acid content is increased, and the quality of the silage is improved. During the silage process, lactic acid bacteria continuously grow and multiply the sugar in the plant into lactic acid, and the growth of a large number of lactic acid bacteria makes the reproduction of other fungi, maintaining the integrity and safety of plant nutrients. In addition, grass plants can increase the appetite of livestock through the fermentation of lactic acid bacteria. At the same time, the silage produced by lactic acid bacteria fermentation can also provide livestock with high-quality forage with good taste and high nutrients in the dry season such as winter, which is warmly welcomed by all kinds of livestock and breeding animal husbandry. [15]
- 2.Improve poultry production performance
- In the production of poultry and livestock, the use of lactic acid bacteria can improve its production performance. For example, adding 0.50% concentration, 0.10% concentration, and 0.05% concentration of lactic acid bacteria, it can be found that the use of lactic acid bacteria can significantly improve the survival rate of chicks; preventing piglets from diarrhea is the key to raising pigs. [16] When diarrhea occurs, lactic acid bacteria can convert lactose to lactic acid, thereby lowering the intestinal pH value and inhibiting the growth of E. coli. Studies have confirmed that lactic acid bacteria preparation can significantly improve the performance of weaned piglets. [17]
- The application of lactic acid bacteria instead of antibiotics in aquaculture is mainly reflected in water quality improvement, treatment of diseases and immunity to aquatic animals. Some of the lactic acid bacteria fed in the form of feed can be colonized in the intestine, and most of them are excreted into the water through feces, thereby increasing the number of lactic acid bacteria in the water body to become the dominant bacteria. In this way, not only can Vibrio intestinal and water bodies be significantly inhibited through competitive inhibition, but also nitrite in water can be eliminated through direct chemical action and indirect promotion of microbial denitrification, which has the effect of purifying water quality. [17]
- Lactic acid bacteria micro-ecological preparations provide a new efficient, harmless and pollution-free option for the feed and animal husbandry aquaculture industry. As more and more new strains and specific strains are used in production, we must fully consider the characteristics of the animal flora and the relationship between parasites and the environment, and use them scientifically and reasonably to achieve the greatest ecological effects and Economic benefits. [17-18]