Bacteriocin is considered to be molecularly inherited, genetically efficient, non-toxic, acid-tolerant, heat-resistant, residue-free, drug-resistant, most genes located on plasmids, small molecular weight, modified amino acids, and complex structures. Engineering, Protein Engineering and Food Additives, Cosmetics, Skin Care, Good Materials for Suppressing Pathogens and Regulating the Intestinal Flora. In 1988, Nisin (Nisin) was first approved as a food additive by the FDA. Nisin has been used as a food preservative in 52 countries and regions, which has promoted the study of other types of bacteriocins and bacteriocins in other fields. As a "green preservative", bacteriocins are getting people's attention. With the widespread promotion of probiotics in feed and people's attention to feed hygiene, bacteriocin has a broad application prospect in feed. 1 The discovery and definition of bacteriocins The bacteriocins were discovered by Gratia (1946) during the mid-20th century when the strains in the Escherichia coli v strain were studied. Gratia and Fredericq later isolated the inhibitors produced by the v strain and found that Similar to phage, but not autonomously replicating, Fredericq (1957) called it colicin. Because many bacteria can produce similar substances, Jacob (1953) called these substances bacteriocins. A bacteriocin is generally defined as a protein-based antibacterial substance produced by bacteria that normally acts only on other strains of the same species as the producing bacteria or closely related species. It is a complex of polypeptides or peptides with sugars and lipids, but the discovery of many broad-spectrum bacteriocins has expanded the concept of bacteriocins. 2 Types of bacteriocins Klaenhammer classifies bacteriocins into two categories, one is a bacteriocin with a narrow antibacterial spectrum that only inhibits related bacteria; the second is bacteriocins with broad-spectrum antibacterial activity, and they are pathogenic. Bacteria, such as Clostridium botulinum and Listeria, have inhibitory effects. A broad spectrum of protein bacteriocins produced by Lactobacillus acidophilus has bacteriostatic action against Salmonella, Shigella and pseudomonas. At present, research on bacteriocins is deeper at home and abroad. Dozens of bacteriocins have been discovered. The bacteriocins that have been identified include Nisin, Lactacin, Lactocin, Helveticin, FerITienticin, Sakecin, Lacticin, Plantacin, and Subiicin (Yang Jiebin et al., 1996. Etc. Among them, Nisin, also known as Nisin, has been widely used. 3 Types of Producing Bacteria and Antibacterial Spectrum The research on bacteriocin-producing bacteria is currently focused on lactic acid bacteria, lactic acid bacteria in almost every genus of each genus, and even each bacterium can produce several bacteriocins. Nisin produced by Lactococcus lactis inhibits streptococci, Staphylococcus, some species of Bacillus, Clostridium and other lactic acid bacteria; bacteriocins produced by Lactobacillus acidophilus and Lactobacillus fermentum against Lactobacillus, Pediococcus, and Beads Bacteria, Lactococcus, and Streptococcus thermophilus have inhibitory effects; Honso (1977) reported that bacteriocins produced by Lactobacillus acidophilus can inhibit DNA synthesis in E. coli; subticin is extracted from Bacillus subtilis, It is a cyclic polypeptide that inhibits fungi but has little effect on bacteria; bacteriocins produced by Tori et al. (Efaecalis) and Efaecium isolated from Tori can inhibit Listeria monocytogenes (L. Pathogens and contaminants such as monocytOgenes) and Clostridium tyroburicum also have certain application prospects in feed. Bacteriocins contain some antagonistic substances, but also contain some beneficial substances. However, these are not very clear at present, and the bacteriocin production mechanism and influencing factors should be further studied. Both bacteriocins and antibiotics are produced by microorganisms. The amounts used are very small. They all have a certain antibacterial spectrum and can strongly inhibit or even kill other microorganisms. Adding 100,000 to 10,000 parts of Nisin in foods is enough to inhibit the growth and reproduction of many gram-positive bacteria. Because bacteriocins have some properties and effects similar to those of antibiotics, bacteriocins were originally even considered to be antibiotics. But bacteriocins and antibiotics are different. Antibiotics are the transformation of primary metabolites into structural secondary metabolites by enzymatic reactions by certain microorganisms, such as Gramicidin S and the like, which convert amino acids into structurally complex compounds through enzymatic reactions. Nisin and other bacteriocins need to be synthesized by ribosomes, and thus are truly proteinaceous substances. The fundamental difference between bacteriocins and antibiotics is that most bacteriocins only harm the bacteria in close relationship, and have the advantages of being non-toxic, having no side effects, no residue, no drug resistance, and no environmental pollution. Therefore, the use of bacteriocins can in some cases reduce or even replace the use of antibiotics. Bacteriocins are currently widely used in foods and are used less in feeds. Bacteriocins are widely used in feeds and must be safe and effective. Bhunia et al. (1991) demonstrated that Pe-diocinAcH did not produce any adverse effects and lethal effects when humans were injected subcutaneously, intravenously and intraperitoneally with bacteriocin Pe-diocinAcH. The direct use of bacteriocins in food also shows that bacteriocins are safe for animals and humans. Bacteriocin as a feed additive has two functions: The first is to prevent the feed itself from being contaminated by pathogenic bacteria such as Salmonella. With the rapid development of China's feed industry, livestock and poultry production is increasingly dependent on feed, so it effectively prevents the contamination of feed by pathogenic bacteria, to a large extent, cut off the harm of pathogenic bacteria to animals; Is the prevention of pathogenic bacteria on the intestinal tract of animals. Since most bacteriocins have a relatively narrow spectrum of antimicrobial activity, selecting appropriate bacteriocins can effectively prevent and control the effects of certain pathogenic bacteria in the intestine, without affecting other beneficial microorganisms in the intestinal tract of animals. However, because many bacteriocins are easily degraded by some proteases (such as trypsin) in the digestive tract, this is the advantage of bacteriocins. The direct effect of bacteriocins in the intestine remains to be further explored. Lactic acid bacteria producing Lactobacillus, especially Lactobacillus is the dominant bacteria in the intestinal tract of animals, so they can be used to develop probiotics for the gastrointestinal ecological regulation of the host animal. With the deep research of probiotics in the prevention and treatment of gastrointestinal diseases in animals such as pigs, dogs and cattle, the role of probiotics has been accepted by more and more people. The sales of probiotics in the US have exceeded US$30 million. The species is Lactobacillus acidophilus and Bifidobacterium. However, the effect of probiotics is not as ideal as expected. This is mainly due to the fact that the mechanism of action of probiotics is not clear, and there is a certain degree of blindness in the selection of bacteria. Because the factors that determine the dominant bacteria in the intestine depend not only on the acid production ability of the strains, but also on the factors such as whether the strains produce bacteriocins, especially because of the host specificity of the strains. The study of the relationship between gut microbiota and bacteriocins will allow better selection of probiotic strains so that they can be better colonized in the gut system and produce better results. There are 6 kinds of probiotics approved by China in 1994: Bacillus, Lactobacillus, Streptococcus faecalis, Yeast, Aspergillus niger and Aspergillus oryzae. Among them, Lactobacillus and Streptococcus faecalis are normal microorganisms in the intestine. Bacillus has high protease, lipase and amylase activities, and significantly increases the growth rate and feed utilization rate of animals. Therefore, many manufacturers combine these bacteria together. It was used, but it was not studied further if the activity of the bacteria was affected. According to reports (Rogers, 1928), the antibacterial spectrum of the bacteriocin Nisin produced by Lactococcus lactis includes some species of streptococci and Bacillus, in particular it inhibits the formation of spores, therefore, in Lactobacillus and some Streptococcus When Bacillus is used in combination, it is very likely to produce antagonism. Therefore, studying bacteriocins is also helpful for studying the relationship between probiotics. Because bacteriocin has many excellent properties: it has a good selective bactericidal effect, so it is not only suitable for general feed, but also suitable for biological feed, etc. It is easily degraded by some proteases (such as trypsin) in the human digestive tract. It does not cause adverse reactions due to accumulation in the animal body, no side effects, no residue, no drug resistance, and no environmental pollution; it has thermal stability, and is resistant to acid and low temperature storage; it has no adverse effects on the taste, taste, etc. of the feed; At the same time, its use can reduce the sterilization temperature of the feed and reduce the heat treatment time, so as to maintain the original nutritional value and flavor of the feed. In short, bacteriocins not only have beneficial effects similar to those of antibiotic feed additives, but also have no toxicity, no side effects, no residues, no drug resistance and good diffusion, and do not pollute the environment. Therefore, bacteriocins are bound to develop gradually and Feed is widely used.
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