# The Role of Microorganisms and Their Antibacterial Compounds in Food Biopreservation
## 3 Antimicrobial Compounds Produced by Bacteria
### Bacteriocins
In 1983, nisin was registered in the European Union for application in food products. In 1988, the FDA accepted nisin as an antimicrobial agent on the list of Direct Food Substances Affirmed As Generally Recognized as Safe [64,65]. Nisin is a bacteriocin of class I. It is thermally stable and does not lose activity in processes like pasteurization and sterilization. At pH 2, it remains active even at 121 \({}^{\circ}\)C. As the pH increases, it becomes less heat-stable [43,66]. Now, nisin still meets the criteria for safety and is approved in more than 80 countries. There are two variants, namely Nisin A and Z of the similar, broad range of Gram-positive antibacterial spectrum from species responsible for foodborne illnesses such as _Listeria monocytogenes_, _Staphylococcus aureus_, _Clostridium_ spp. and _Bacillus cereus_ to beneficial species strains, such as _Lactobacillus acidophilus_ and _Lactobacillus plantarum_[59]. Nisin was found to inhibit the growth of _C. botulinum_ spores in cheese [67]. In combination with natamycin, nisin inhibits the growth of yeasts and molds [68]. As a biopreservative, nisin is used in various food products, including dairy, meat, seafood, vegetables, and fruits. The spoilage of dairy products is efficiently prevented by using nisin in the purified form or by using live bacteria that produce nisin [69,70]. Nisin-synthesizing bacterial strains, i.e., Lactococci, are used to preserve cheddar cheese [59,71]. On the EFSA food additives/preservatives list, nisin has the number E234 (Table 2) [14]. Pedicons are a group of bacteriocin synthesized by _Pedicoccus_ strains that act against Gram-positive bacteria including _Listeria monocytogenes_, _Staphylococcus aureus_, _Clostridium_ spp., _Bacillus cereus_, _E. faecalis_, and _Clostridium perfringens_. They are thermostable bacteriocisions belonging to class II. They are heat-stable at 100 \({}^{\circ}\)C for 10 min. The highest stability is achieved at pH 4-6. The heat stability decreases with more alkaline pH. Freezing (\(-25\)\({}^{\circ}\)C) does not reduce pedicocin activity [72]. Pedicons showed applications in food biopreservation (dairy, meat, vegetables, and seafood) and the medical sector for the prevention of infection. The commercial name of Pediccin PA-1 in the market is ALTA(tm) 2341 (Table 2) [1,59,60]. Enterocin is a circular peptide synthesized by _Enterococcus_ spp. Its bacteriostatic antimicrobial activity is available even in extreme temperatures (activity present after 15 min at 121 \({}^{\circ}\)C), pH (at pH range from 3 to 12), and high salt concentrations, and it is effective on bacterial spores in food products [47,73]. Enterocins' antimicrobial effects cover bacteria such as _Clostridium perfringens_, _Clostridium botulinum_, _Listeria monocytogenes_, _Staphylococcus aureus_, _Klebsiella pneumoniae_, _Escherichia coli_, _Pseudomonas_ spp., and _Shigella sonnei_[74,75]. The applications as food biopreservative include fruits, vegetables, rice, seafood, cakes, and creams [59]. Epsilon-poly-L-lysine is approved by FDA and in Japan, South Africa, and many Asian countries as a preservative [76]. Natamycin peptide secreted by _Streptomyces natalensis_ and _Streptomyces chattanogenesis_ has antifungal activity and acts against yeasts and molds. Natamycin, known as pimaricin, was discovered in 1955 [77]. It remains heat-stable even after continuous heating at 100 \({}^{\circ}\)C [61]. As a biopreservative, it prevents fungal growth and can be applied for dairy, meat, olives, wines, bakery, and fruit related products. Natamycin is approved by WHO, FDA, and EFSA and has GRAS status [59,61]. On the EFSA food additives/preservatives list, natamycin has the number E235 (Table 2) [14]. Plantaricins are produced by _Lactobacillus_ plantarum, which is present in abundance in starter-free cheese synthesized from raw milk. It is heat-stable at 121 \({}^{\circ}\)C for 20 min [78]. Plantaricins are effective against _Listeria monocytogenes_[79]. Reuterin are peptides produced by _Lactobacillus_ reuteri.