Bacteriocins: Properties and potential use as antimicrobials

Abstract A variety of bacteriocins originate from lactic acid bacteria, which have recently been modified by scientists. Many strains of lactic acid bacteria related to food groups could produce bacteriocins or antibacterial proteins highly effective against foodborne pathogens such as Staphylococcus aureus, Pseudomonas fluorescens, P. aeruginosa, Salmonella typhi, Shigella flexneri, Listeria monocytogenes, Escherichia coli O157:H7, and Clostridium botulinum. A wide range of bacteria belonging primarily to the genera Bifidobacterium and Lactobacillus have been characterized with different health‐promoting attributes. Extensive studies and in‐depth understanding of these antimicrobials mechanisms of action could enable scientists to determine their production in specific probiotic lactic acid bacteria, as they are potentially crucial for the final preservation of functional foods or for medicinal applications. In this review study, the structure, classification, mode of operation, safety, and antibacterial properties of bacteriocins as well as their effect on foodborne pathogens and antibiotic‐resistant bacteria were extensively studied.

against closely related and non-related species. 7,8 Bacteriocins may be secreted by both Gram-positive and Gram-negative bacteria. In particular, among Gram-positive bacteria, bacteriocins derived from lactic acid bacteria are of great interest (LAB). 9 Lactic acid bacteria are a miscellaneous group of acid-tolerant, facultative anaerobes, and fermentative organisms that possess generally regarded as safe (GRAS) and qualified presumption of safety (QPS) status.
Therefore, their bacteriocins are regarded as safe by the USFDA (the U.S. Food and Drug Administration). 2,5,10 LAB-secreted bacteriocins are heat-stable, proteases-sensitive, ribosomally synthesized, and antimicrobial peptides, which either undergo or do not undergo enzymatic post-translational modification process. 2,4,6,9,11 They are very diverse in terms of length, genetic origin, biochemical features, molecular weight (MW), cellular receptors, and interaction with the immune system. 5,9,12 So far, many bacteriocins have been widely identified with various modes of action as follows: inducing cytoplasmic membrane permeability (by pore formation), inhibiting cell wall biosynthesis, and interfering with metabolic pathways. 1,6 Membrane pore formation as a common inhibitory mechanism, high inhibitory activity with low concentrations in the nanomolar range, and relatively narrow-spectrum antimicrobial activity are the characteristics of many LAB-derived bacteriocins. 1 During the last decade, LAB bacteriocins have received a great deal of attention due to their high potential, especially as natural food preservatives and novel therapeutic antibiotics, which have made them attractive for various applications. 13 In particular, numerous studies have been published in recent years, suggesting that bacteriocins may be used as an alternative to antibacterial agents in the prevention or treatment of bacterial infections. 10 Despite the long history of bacteriocins usage, there is no report about the development of bacterial resistance to bacteriocins. Some possible reasons may be as follows: having a fast pore-formation mechanism, being easily degraded by proteolytic enzymes, and having a shorter biological half-life in the human body or in natural environments; these factors minimize the possibility of interaction between bacteriocins and bacteria, as a starting point in the development of antibiotic resistance. 13 The most significant property that further enhances bacteriocins functional potential compared with conventional antibiotics is stability in a wide range of physicochemical conditions. In addition, due to their primary metabolite nature, bacteriocins also have other features such as genetic amenability through bioengineering to increase their activity/specificity against target bacterial pathogens and antibiotic-resistant strains. 13 Lastly, bacteriocins modulate the host immune responses (as signaling peptides), and they have no destructive effect on commensal bacteria and low/no cytotoxicity against eukaryotic cells (more specifically to target cells). 3,14 Comparison of bacteriocins and antibiotics in terms of mode of action and physicochemical properties, especially the mechanism of resistance development (used by bacteria), provides evidence of the need for alternative antimicrobial compounds to combat bacterial infections. Bacteriocins have the potential to be used as ideal candidates. 10 In recent years, several studies have shown the protective effects of LAB bacteriocins on the gastrointestinal tract via eliminating pathogens or supporting the gut from bacterial colonization. 2 They have also demonstrated the inhibitory ability of bacteriocins against intestinal pathogens such as Listeria monocytogenes, Salmonella enteritidis, Clostridium difficile, Staphylococcus aureus, and vancomycinresistant enterococci (VRE). 14 Moreover, in clinical applications, some bacteriocins have been shown to be highly effective in treating infections, especially those caused by multidrug-resistant (MDR) strains. 13 Given the harmful effect of antibiotics on intestinal microbiota and the importance of gastrointestinal infections in human health, it seems that LAB-derived bacteriocins could be considered as a promising antibiotic in the treatment of intestinal infections. 2

| B I OSYNTHE S IS AND P OTENTIAL APPLI C ATI ON OF L AB BAC TERI O CIN S
There are some factors affecting the production of bacteriocins, such as culture conditions and the type of microbial strain.
Bacteriocins are post-translationally modified and ribosomally synthesized peptides that are initially produced as inactive pre-peptides and then converted into an active form. 5,46 After transport and cleavage of produced pre-peptides, they are converted into mature (active) bacteriocins. Depending on the type of bacteriocins, genes responsible for pre-peptides transport and modification are located close to the bacteriocin biosynthesis gene, and genes responsible for the immunity and active bacteriocin production are broadly located in operon clusters and might be harbored in plasmid, genome, or other mobile genetic factors. 47 In addition to inducible expression, these operons require auto-inducer peptides to induce bacteriocin production. The regulation of expression is generally fulfilled by a two-part regulatory system, but in some cases, this process is done by three-element ones. The production of bacteriocins is fulfilled in the exponential growth phase by retaining a line-to-line connection to the biomass production. 44

| AC TIVIT Y OF L AB AG AIN S T FOODBORNE PATHOG ENS
According to the FDA, the most prevalent foodborne pathogenic bacteria are as follows: L. monocytogenes, S. enteritidis, Shigella, S. typhimurium, pathogenic Escherichia coli, Campylobacter jejuni, C.
perfringes, and S. aureus. 41 Due to some restrictions on the use of therapeutic antibiotics in food production and processing as well as nontoxicity of treatment with LAB-derived antimicrobial peptides, most research in recent years has been devoted to investigating these bacteriocins. Given the cleavage of bacteriocins by gastrointestinal proteases, reducing their activity level, they are generally safe and show a considerable capacity to constrain foodborne pathogens growth. 41,48 Also, considering bacteriocins ability to form pores in the cell membrane of sensitive bacteria, they are naturally bactericidal or bacteriostatic. For instance, BMP11 as a new bacteriocin produced by L. crustorum against L. monocytogenes, has been shown to destroy cell membrane integrity and increase membrane permeability. 49 Moreover, it has been well documented that P. acidilactici QC38 is able to inhibit L. monocytogenes, L. innocua, S. typhimurium, E. coli, V. cholerae NO 01, and V. cholerae O1 Ogawa. 50 The inhibitory activity of Pediococcus spp. (isolated from cheese) against Listeria species was reported by Cavicchioli et al. 51 They indicated that bacteriocins produced by E. hirae ST57ACC and P. pentosaceus ST65ACC inhibited 100% of L. monocytogenes strains and two L. innocua strains. Nisin, produced by L. lactis subsp. Lactis, has been reported to inhibit the growth of Gram-positive bacteria as well as Clostridium and Bacillus spores. Considering its antimicrobial activity against Listeria spp., pediocin (P. acidilactici) has been shown to mitigate the growth of spoilage microorganisms during storage in the meat industry as well as to be efficient against L. monocytogenes in beef, turkey, and sliced jambon. 44 Similar to pediocin, the semipurified bacteriocin BacTN635 (produced by L. plantarum sp. TN635) has also been shown to be strongly active against spoilage microorganisms in chicken breast and beef. 52 Furthermore, the potency of combined application of various bacteriocins, including subclass IIa bacteriocins, L. fermentum ACA-DC179, and bioprotective cultures of E. faecium PCD71, in inhibiting L. monocytogenes in various meat products has been documented. In addition to enterocins as broad-spectrum antimicrobial bacteriocins against foodborne pathogens (Clostridium spp. and Listeria spp.), 45 purified bifidocin A has also been indicated to display a broad range of antimicrobial activity against spoilage and foodborne pathogenic bacteria, such as S. aureus, L. monocytogenes, E. coli, and some types of yeasts. 53

| ARE BAC TERI O CIN S THE B E S T SUBS TITUTE FOR ANTIB I OTI C THER APY ?
To the best of our knowledge, antibiotics play an important role in the disease prevention and treatment in animals and humans.
In addition to adverse effects of some antibiotics, the emergence of antibiotic-resistant, MDR (multidrug-resistant), and XDR (extensively drug-resistant) strains has recently become a major concern. 54,55 It is estimated that by 2060, at least 20 new antibiotics are needed to overcome the problem of antibiotic resistance, while the design of new antibiotics is a time-consuming and slow procedure. 56 Therefore, it is necessary to develop new treatment strategies that could eliminate antibiotic-resistant microorganisms. 57 One of the strategies is to use antimicrobial peptides to achieve this goal.
Bacteriocin is considered as a suitable antimicrobial peptide due to its thermal stability and high efficacy with nano-molecular size. 58,59 In addition to the immune system, bacteriocins are able to affect other bacteria through competition in colonization. 21,33 Researchers are looking for anti-pathogenic bacteriocins that are as effective as antibiotic therapy. 60 Bacteriocins have been shown to possess advantages over antibiotics. 61 These antimicrobial peptides are considered to provide more protection with no side effects compared to antibiotics. A study examining the differences between bacteriocins and antibiotics found that oral administration of pediocin PA-1 had no side effects on the gastrointestinal tract, while under the same conditions, the use of antibiotics such as penicillin and tetracycline exhibited different results. 62 Bacteriocins are synthesized ribosomally and considered as primary metabolites, while antibiotics are a type of secondary metabolites. This feature allows researchers to design novel bacteriocins with more effective capabilities using bioengineering techniques based on bacteriocins synthesis ways. 63 Unlike antibiotic-producing bacteria, bacteriocins are not inhibited by antimicrobial agents. The activity of bacteriocins on drug-resistant strains, hospital-acquired infections, respiratory tract infections, skin diseases, dental infections, vaginosis, and tuberculosis has been proved. 62 Several antibiotics are not active against infections caused by S. aureus, enterococci, and pneumococci strains.
Studies have shown that MRSA (methicillin-resistant S. aureus) and VRE (vancomycin-resistant enterococci) are affected by bacteriocins such as nisin A and lacticin 3147. 64 Nisin F and mersacidin were shown in a study to inhibit S. aureus growth as a respiratory pathogen without damaging the lungs and other respiratory organs such as bronchi and trachea in animal model. 65 Proteolytic digestion of bacteriocins in the gastrointestinal tract may affect bacteriocins activity; however, it is possible to overcome the problem by their encapsulation and insertion into liposomes. 63 Also, the use of synergistic function of bacteriocins is economically more cost effective than producing expensive antibiotics. 63 The inherent resistance of certain bacteria to these peptides with very strong antimicrobial activity at nanomolar concentrations is one of the most challenging aspects of bacteriocins usage. Although few studies have examined resistance to bacteriocins, some studies have shown a nearly 10-fold increase in nisin MIC against L. monocytogenes, indicating a 10-fold increase in resistance to nisin. Degradation of nisin by B.
cereus-synthesized nisinase leads to inactivation of this bacteriocin, while bacitracin, polymyxin, and gramicidin are resistant to these enzymes. 66,67 Unlike widespread studies on enzymes mediating extensive resistance to β-lactam antibiotics, such as β-lactamases and carbapenemases, resistance of bacteriocin-degrading enzymes has not been properly investigated. 68 Therefore, there is controversy over whether bacteriocins could be considered as alternatives to antibiotics or not. Studies results describe bacteriocins as supplements for antibiotics due to their high stability, no side effects, and potential to induce a synergistic effect. 69 In combination with antibiotics, bacteriocins act synergistically; they not only increase the efficiency of antibiotics and prevent the emergence of antibiotic-resistant species but also reduce the side effects of antibiotics by lowering the concentration of antibiotics needed to eliminate bacteria. 61,63,70,71 Nowadays, the therapeutic efficacy of bacteriocins could be enhanced by designing engineered bacteriocins; this requires biological and chemical modification methods and further investigations. 57

| IMPAC T OF BAC TERI O CIN S ON ANTIB I OTI C RE S IS TAN CE PROFILE OF DRUG -RE S IS TANT BAC TERIA
The incidence of antibiotic resistance is attributed to several factors, including overuse of antibiotics, self-medication at home, and improper antibiotic administration. When people consume contaminated food with such drug-resistant bacteria, they lose sensitivity to the relevant antibiotics. 72 According to available information, many patients die due to antibiotic resistance with an annual rate of at least 700,000 cases, and this number is likely to increase by 2050.
Some bacteriocins such as nisins A and F, mersacidin, mutacin 1140, lactacin 3147, and pediocin AcH/PA-1 are active against MRSA and VRE strains. 65,73,74 Brand et al. 75 indicated that nisin F could inhibit S. aureus infection in mice and reported that the growth-inhibition time lasted only 15 minutes. Another study by Fernández et al. (2008) demonstrated the antibacterial activity of nisin A in mastitis. They also described bacteriocins as efficient alternatives to antibiotics and showed that after two weeks, the number of bacteria in the milk of mothers with mastitis was significantly reduced and then followed by relief of symptoms. 76 It has been shown that Bacillus spp. are able to reduce MRSA infection in animal model by producing mersacidin. 73 Bacteriocin LipA is active against Pseudomonas aeruginosa and could eliminate resistant strains. Drug-resistant S. aureus strains in goat milk are also affected by AS-48 and nisin. These bacteriocins both individually and synergistically are able to eliminate S. aureus. 77 Researchers have shown that B. subtilis KIBGE IB-17 produces a heat-resistant bacteriocin called BAC-IB-17 which is very effective against MRSA strains. 78 Also, the effect of another bacteriocin called sonorensinon has been proven against various Gram-positive bacteria, such as antibiotic-resistant S. aureus biofilms and Gramnegative bacteria. 79 In an animal study in the field of bacteriocin design, bacteriocin peptide Ω76 was introduced as an active substance against carbapenem-and tigecycline-resistant Acinetobacter baumannii. However, in this study, the relevant bacteriocin showed toxic effects such as nephrotoxicity, which was resolved in combination with antibiotics. 80

| IS IT P OSS IB LE TO CONTROL FOODBORNE BAC TERIA BY BAC TERI O CIN S?
Food pathogenic bacteria are present in both planktonic and biofilm forms as foodborne pathogens. In addition to being able to counteract with drug-resistant bacteria, bacteriocins may also be used as food and dairy products preservatives. 81 According to studies, LAB-derived bacteriocins such as nisin, pediocin PA-1, pediocin, mersacidin, mutacin, and lacticin are mostly used in the food processing industry as preservatives that are capable of preventing the

| CL A SS IFI C ATI ON OF BAC TERI O CIN S
Up to now, four classes of LAB bacteriocins have been identified: Class I, known as lantibiotics, is composed of modified bacteriocins; Class II includes heat-stable, minimally modified bacteriocins; Class III includes larger, heat-labile bacteriocins; and Class IV is composed of complex bacteriocins with carbohydrate or lipid moieties.
Classes I and II bacteriocins have been the focus of most probiotic research. 92 Lantibiotics are divided into three groups based on their structure and mode of action. Type A lantibiotics, such as nisin, are small (2-5 kDa) proteins with positively charged molecules, which kill bacteria via the formation of membrane pores, causing dissipation of membrane integrity and efflux of small metabolites from the sensitive cells. Mersacidin is a member of Type B lantibiotics that kill bacteria by interfering with cellular enzymatic reactions, such as cell wall synthesis. 93 Another subgroup, such as lacticin 3147, is two-component lantibiotics that synergistically display antimicrobial activity. It has been shown that dual activities could be distributed across two peptides: While one resembles Type B lantibiotic mersacidin that depolarizes the membrane, the other one is more similar to Type A lantibiotic nisin that acts through pore formation. Class II LAB bacteriocins are also small non-lanthionine-containing peptides that kill bacteria by inducing membrane permeability and the subse-

| Bacteriocins of Gram-positive bacteria
Bacteriocins of Gram-positive bacteria are as abundant as and even more diverse than those found in Gram-negative bacteria.
Bacteriocins of Gram-positive bacteria, in general, and lantibiotics, in particular, require more genes for their production than those of Gram-negative bacteria. The nisin gene cluster, for example, includes genes for encoding the pre-peptide (nisA), modifying amino acids (nisB, nisC), cleavage of the leader peptide (nisP), secretion   104 Also, plantaricin C-11, 105 plantaricin NA, 106 and bacteriocin AMA-K have been shown to have a strong anti-Listeria activity and therefore may be used in food preservation in the future. 107,108 Amortegui et al. 109  The highest anti-Listeria activity was recorded for ET05, ET30, and nisin derived from L. lactis subsp. lactis ATCC 11454. 112 In another study in 2015, bacteriocins produced by L. curvatus MBSa2 (sakacin P) and L. curvatus MBSa3 (sakacin X) were shown to have inhibitory activity against L. monocytogenes strains. Bacteriocin produced by L.
curvatus MBSa2 caused a 2 and 1.5 log reduction in the count of L. monocytogenes in the salami after 10 and 20 days, respectively, suggesting that application of these bacteriocins could be an additional measure to improve the safety of these ready-to-eat products with regards to L. monocytogenes. 113 In a study by Mokoena (2017), bacteriocins ST22Ch, ST153Ch, and ST154Ch, produced by L. sakei strains (ST22Ch, ST153Ch, and ST154Ch) isolated from Salpicao, were shown to have inhibitory activity against Listeria spp., Enterococcus spp., Klebsiella spp., E. coli, Pseudomonas spp., Staphylococcus spp., and Streptococcus spp. Maximum activity of these bacteriocins was recorded during the early stationary phase. All sakacins belonged to the Class IIa bacteriocins and possessed strong antilisterial activity.
Bacteriocins ST22Ch, ST153Ch, and ST154Ch were produced at high levels during all phases of (fermented) meat processing. The spectrum of antibacterial activity of these strains (ST22Ch, ST153Ch, and ST154Ch) indicates their potential application in a mixed starter culture for the fermentation of meat products. 5

| Bacteriocin of Enterococcus
Enterococcus is the third main genus of lactic acid bacteria (LAB) after Lactobacillus and Streptococcus. 126 (Table 2). Since some of these bacteriocins could not be grouped with typical LAB-derived bacteriocins according to traditional classification, enterocins classification into four new classes has been proposed. 129 Cytolysin produced by E.
faecalis is a two-linear peptide lantibiotic with cytolytic (hemolytic) activity, and its encoding genes are found in both hospital and food isolates. It differs structurally from other linear lantibiotics including nisins A and Z. 130,131 Class II enterocins are two-peptide bacteriocins of the pediocin family. 132 The most common antimicrobial peptides are pediocin-like enterocins, also known as Class II-1 bacteriocins, which are classified into two subgroups based on sequence similarity. 133 All of them have a conserved YGNGVXC "pediocin box" motif and a β-sheet domain supported by a conserved disulfide bridge at the N-terminus. 134 Enterocin A, mundticins, and enterocin CRL5 are among the first subgroup. 129 The second subgroup is represented by bacteriocin 31, bacteriocin T8, bacteriocin RC714, enterocin SEK4, enterocin P, and enterocin M. 129 Class II-2 bacteriocins lack the YGNGVXC motif and are not synthesized with a leader peptide; however, they must have complementary actions of both peptides to be completely active. 13   is used as an industrial dairy starter culture, especially for yogurt manufacturing. 155 It could improve the quality of fermented dairy products through various probiotic effects and the production of bacteriocins, flavor substances, and extracellular polysaccharides. 156 Renye et al. 157  as vegetables, meat, sausage products, and cheddar cheese. 163 Bacteriocins of Pediococcus species are designated as pediocins and produced by three species that play an important role in food biopreservation, including P. acidilactici, P. cerevisiae, and P. pentosaceus.
They generally belong to the Class IIa bacteriocin family with a small  Table 4.
Various species are stable in a broad span of pH and temperature, which makes them suitable for biopreservation of various food products. 164  In a study, pediocin PA-1 was derived from P. acidilactici PAC1 and shown to lyse a strain of L. monocytogenes. 166 165 A new proteinaceous compound with a molecular mass of 23 kDa has been derived from P. pentosaceus for the first time, which is active against S. dysenteriae; this bacteriocin could be supplemented into any food to make it safe against S. dysenteriae as a foodborne pathogen causing alarm in many developing countries. 170 A pediocin-producing strain of P.
acidilactici able to survive in the GI tract has been recently isolated and found to be an effectual inhibitor of various Gram-positive bacterial pathogens, such as Enterococcus spp. and L. monocytogenes. It

| Bacteriocins of Leuconostoc
Leuconostoc spp. are lactic acid bacteria that are most commonly associated with fermented food products, such as fermented sausages, fermented vegetables, cereal products, and a wide variety of fermented milk products. 185,186 They are environmental organisms that are generally found in fresh plants, raw milk, or chilled food products. 185 Leuconostoc spp. have the ability to produce aroma compounds (diacetyl and acetoin) in dairy products by metabolizing citrate. 187 Antimicrobial activity of these organisms has long been recognized. 188 Several studies have identified bacteriocin-producing strains of leuconostocs (Table 6). [189][190][191] Most Leuconostoc bacteriocins are classified as Class II, which are small (less than 10) and heat stable. They

TA B L E 3 (Continued)
are non-lanthionine-containing bacteriocins without post-translational modification. 16 Several strains of Leuconostoc spp. could produce bacteriocin (Table 6). According to Table 6, L. mesenteroides is the most common bacteriocin-producing species. They mainly prevent the growth of Gram-negative and Gram-positive bacteria, including E. coli, Salmonella, Listeria spp, and S. aureus, which are foodborne pathogens.
Therefore, this species is considered as a good candidate for the use in fermented food products in the food industry.  (Table 7). Bifidocin A is produced in the exponential growth phase with the maximal production in the midi-stationary phase. This suggests that bifidocin A production depends on the cell number, and bifidocin A is a secondary metabolite. 203 The reduction in the activity of bifidocin A at the end of the stationary phase may be because of the activity of endogenous extracellular proteases, which peak pending this growth phase. 204  is curbed to Gram-negative pathogenic bacteria. 206 Yildirim et al. (1999) showed that their application could be beneficial in the food commercial enterprise in modelling HACCP plans to effectively delete Gram-negative pathogenic bacteria in meat products, especially E. coli 0157:H7 xx. Bifidocin B was made in a study in the ex-  (Table 8). Nisin has been used extensively in cheese and pasteurized cheese spreads as an alternative to nitrate in order to hinder the outgrowth of clostridia spores. 211

| Colicin
Colicins produced by E. coli are present in 30-50% of strains isolated from human hosts. E. coli colicins have been the most widely studied Gram-negative bacteriocins since their discovery; they are now used as a model system for studying bacteriocin structure/ function, genetic organization, ecology, and evolution. 235

| Microcin
In addition to colicins, E. coli strains could produce microcins, which are smaller than colicins and have more properties in common with bacteriocins produced by Gram-positive bacteria, such as thermostability, protease resistance, relative hydrophobicity, and resistance to extreme pH. 239 So far, 14 microcins have been discovered, but only seven have been isolated and thoroughly characterized.

| New bacteriocin
Bacteriocins are ribosomally synthesized peptides produced by lactic acid bacteria (LAB), which have the potential to be used as food preservatives as well as antibiotics against multidrug-resistant pathogens. 60 The discovery of new bacteriocins with different properties indicates that there is still a lot of information to be understood about these peptide antibiotics. In this review, articles entitled with new bacteriocins from 2014 to 2020 were investigated (Table 9). Newly identified bacteriocins may differ in many respects, including the type of classes and subgroups to which they belong, biosynthetic mechanisms, structural characteristics, modes of antimicrobial action, and sources of isolation. Ahmad et al. 243

| Thuricin CD
Thuricin CD is a recently identified bacteriocin with effective narrow-spectrum inhibitory activity against C. difficile. The primary advantage of thuricin CD is that its antimicrobial activity is mostly

| FOOD TECHNOLOGY
In food technology, nisin as the first antibacterial peptide found in LAB is produced by L. lactis. It is also a commercial bacteriocin marketed as Nisaplin ® , which is used as a food preservative against contamination with microorganisms. It is the only bacteriocin approved by USFDA for use as a preservative in many food products and licensed as a food additive in over 45 countries. Another commercially available bacteriocin is pediocin PA-1 marketed as Alta ® 2341, which inhibits the growth of L. monocytogenes in meat products. Enterocin AS-48 is used in cider, fruit and vegetable juices, and canned vegetables for contamination inhibition. Enterocins CCM4231 and EJ97 are used in soy milk and zucchini purée to suppress contamination, respectively. 280 The use of bacteriocins as food preservatives may be beneficial in several aspects: (i) to decrease the risk of food poisoning, (ii) to decrease cross-contamination in the food chain, (iii) to improve the shelf life of food products, (iv) to protect food during temperature-abuse episodes, (v) to decrease economic losses due to food spoilage, (vi) to reduce the level of chemical preservatives added, (vii) to reduce the intensity of physical treatments in order to better preserve food nutritional value and decrease processing costs, and (viii) to provide alternative preservation methods for "novel food" in order to meet the demands of consumers for freshtasting, lightly preserved, ready-to-eat food products. 281

| CON CLUS ION
Given their broad-spectrum and potent inhibitory activity, this study results indicated that lactic acid bacteria are able to exert antago-

CO N FLI C T O F I NTE R E S T
The authors declare that there is no conflict of interest.

AUTH O R CO NTR I B UTI O N S
RG and MK conceived, designed, and supervised the study. AD and AA contributed to data collection, interpretation, and final approval of data for the work. AD and MM developed the first and final draft of the manuscript. EO and MT developed the second draft of the manuscript.
ADE and MH designed and checked all figures and tables. All authors reviewed, contributed to the revisions, and finalized the drafts.

DATA AVA I L A B I L I T Y S TAT E M E N T
All relevant data are included in the manuscript.