The objective of this study was to reveal the antibacterial mode of action of garviecin LG34 against S. aureus CICC 21600 and L. monocytogenes CICC 21633 and measure the inhibitions on these two foodborne pathogenic bacteria in milk. Antibacterial mechanism of garviecin LG34 was ascertained by its effect on the efflux of Potassium (K+) ions, extracellular electrical conductivity, UV-absorbing substances, potential across the membrane (ΔΨ) and cell permeability. The inhibition of garviecin LG34 against S. aureus CICC 21600 and L. monocytogenes CICC 21600 in milk was studied by viable counting method. Supplementation with 160 AU/ml of garviecin LG34 had a bactericidal effect on S. aureus CICC 21600 and L. monocytogenes CICC 21633. 80, 160 and 320 AU/ml of garviecin LG34 resulted in the effusion of potassium ion and UV-absorbing substances, the leakage of cellular electrolytes and the dissipation of electrical potential across the membrane of these two food-borne bacteria and showed a dose dependent. Moreover, the increase in cell permeability of both strains were observed by flow cytometer after cells treated with 160 AU/ml of garviecin LG34. Garviecin LG34 significantly inhibited the growth of these two food-borne bacteria in milk, especially in skimmed milk. Garviecin LG34 could cause pore formation, intracellular materials release and permeability increase of S. aureus CICC 21600 and L. monocytogenes CICC 21633, and could be applied to milk as bio-preservative.

Cancer poses a severe threat to human health. Although conventional chemotherapy remains a cornerstone of cancer treatment, its significant side effects and the growing issue of drug resistance necessitate the urgent search for more efficient and less toxic anticancer drugs. In recent years, bacteriocins, antimicrobial peptides of microbial origin, have garnered significant attention due to their targeted antitumor activity. This unique activity is mainly attributed to their cationic and amphiphilic nature, which enables bacteriocins to specifically kill tumor cells without harming normal cells. When involving non-membrane-disrupting mechanisms, such as apoptosis induction, cell cycle blockade, and metastasis inhibition, the core mechanism of action is achieved by disrupting cell membranes, which endows bacteriocins with low drug resistance and high selectivity. However, the susceptibility of bacteriocins to hydrolysis and hemolysis in vivo limits their clinical application. To overcome these challenges, structural optimization of bacteriocins or their combination with nanotechnology is proposed for future development. This review aims to study the mechanism of action and current research status of bacteriocins as anticancer treatments, thus providing new insights for their clinical development and application.

Inflammatory bowel disease (IBD) is one of the most challenging diseases in the 21st century, and more than 10 million people around the world suffer from IBD. Because of the limitations and adverse effects associated with conventional IBD therapies, there has been increased scientific interest in microbial-derived biomolecules, known as postbiotics. Postbiotics are defined as the preparation of inanimate microorganisms and/or their components that confer a health benefit on the host, comprising inactivated microbial cells, cell fractions, metabolites, etc. Postbiotics have shown potential in enhancing IBD treatment by reducing inflammation, modulating the immune system, stabilizing intestinal flora and maintaining the integrity of intestinal barriers. Consequently, they are considered promising adjunctive therapies for IBD. Recent studies indicate that postbiotics offer distinctive advantages, including spanning clinical (safe origin), technological (easy for storage and transportation) and economic (reduced production costs) dimensions, rendering them suitable for widespread applications in functional food/pharmaceutical. This review offers a comprehensive overview of the definition, classification and applications of postbiotics, with an emphasis on their biological activity in both the prevention and treatment of IBD. © 2024 Society of Chemical Industry.

In the postantibiotic era, the pathogenicity and resistance of pathogens have increased, leading to an increase in intestinal inflammatory disease. Bacterial infections remain the leading cause of animal mortality. With increasing resistance to antibiotics, there has been a significant decrease in resistance to both inflammation and disease in animals, thus decreasing production efficiency and increasing production costs. These side effects have serious consequences and have detracted from the development of China\'s pig industry. Microcin C7 (McC7) demonstrates potent antibacterial activity against a broad spectrum of pathogens, stable physicochemical properties, and low toxicity, reducing the likelihood of resistance development. Thus, McC7 has received increasing attention as a potential clinical antibacterial and immunomodulatory agent. McC7 has the potential to serve as a new generation of antibiotic substitutes; however, its commercial applications in the livestock and poultry industry have been limited. In this review, we summarize and discuss the biosynthesis, biochemical properties, structural characteristics, mechanism of action, and immune strategies of McC7. We also describe the ability of McC7 to improve intestinal health. Our aim in this study was to provide a theoretical basis for the application of McC7 as a new feed additive or new veterinary drug in the livestock and poultry breeding industry, thus providing a new strategy for alleviating resistance through feed and mitigating drug resistance. Furthermore, this review provides insight into the new functions and anti-infection mechanisms of bacteriocin peptides and proposes crucial ideas for the research, product development, and application of bacteriocin peptides in different fields, such as the food and medical industries.

MccY is a novel, structurally stable microcin with antibacterial activity against Enterobacteriaceae. However, the bioavailability of orally administrated MccY is unknown. This study evaluated the effects of MccY as a antimicrobial on pre-digestion in vitro and its intake, digestion and gut metabolism in vivo. The result of pre-digestion results that MccY maintained its biological activity and was resistant to decomposition. The study established a safe threshold of 4.46-9.92 mg/kg for the MccY dosage-body weight relationship in BALB/c mice. Mice fed with MccY demonstrated improved body weight and intestinal barrier function, accompanied with increased IgM immunogenicity and decreased levels of TNF-α, IL-6, and IL-10 in the intestine. MccY significantly facilitates the growth and activity of probiotics including Lactobacillus, Prevotella, and Bacteroides, and leading to the production of SCFAs and MCFAs during bacterial interactions. Furthermore, MccY effectively protects against the inflammatory response caused by Salmonella Typhimurium infection and effectively clears the Salmonella bacteria from the gut. In conclusion, MccY is seen as a promising new therapeutic target drug for enhancing the intestinal microbe-barrier axis and preventing enteritis.

Bacteriocins have the potential to effectively improve food-borne infections or gastrointestinal diseases and hold promise as viable alternatives to antibiotics. This study aimed to explore the antibacterial activity of three bacteriocins (nisin, enterocin Gr17, and plantaricin RX-8) and their ability to attenuate intestinal barrier dysfunction and inflammatory responses induced by Listeria monocytogenes, respectively. Bacteriocins have shown excellent antibacterial activity against L. monocytogenes without causing any cytotoxicity. Bacteriocins inhibited the adhesion and invasion of L. monocytogenes on Caco-2 cells, lactate dehydrogenase (LDH), trans-epithelial electrical resistance (TEER), and cell migration showed that bacteriocin improved the permeability of Caco-2 cells. These results were attributed to the promotion of tight junction proteins (TJP) assembly, specifically zonula occludens-1 (ZO-1), occludin, and claudin-1. Furthermore, bacteriocins could alleviate inflammation by inhibiting the mitogen-activated protein kinase (MAPK) and nuclear factor kappa B (NF-κB) pathways and reducing the secretion of interleukin-6 (IL-6), interleukin-1 β (IL-1β) and tumor necrosis factor α (TNF-α). Among three bacteriocins, plantaricin RX-8 showed the best antibacterial activity against L. monocytogenes and the most pronounced protective effect on the intestinal barrier due to its unique structure. Based on our findings, we hypothesized that bacteriocins may inhibit the adhesion and invasion of L. monocytogenes by competing adhesion sites. Moreover, they may further enhance intestinal barrier function by inhibiting the expression of L. monocytogenes virulence factors, increasing the expression of TJP and decreasing the secretion of inflammatory factors. Therefore, bacteriocins will hopefully be an effective alternative to antibiotics, and this study provides valuable insights into food safety concerns. KEY POINTS: • Bacteriocins show excellent antibacterial activity against L. monocytogenes • Bacteriocins improve intestinal barrier damage and inflammatory response • Plantaricin RX-8 has the best protective effect on Caco-2 cells damage.

Class IIa bacteriocins produced in lactic acid bacteria are short cationic peptides with antimicrobial activity. In the search for new biopreservation agents, class IIa bacteriocins are considered to be the best potential candidates, not only due to their large abundance but also because of their high biological activity and excellent thermal stability. However, regulated by the biosynthetic regulatory system, the natural class IIa bacteriocin yield is low, and the extraction process is complicated. The biotechnological production of class IIa bacteriocins in various cell factories has been attempted to improve this situation. In this review, we focus on the application of biotechnological routes for class IIa bacteriocin production. The drawbacks and improvements in the production of class IIa bacteriocins in various cell factories are discussed. Furthermore, we present the main challenge of class IIa bacteriocins, focusing on increasing their production by constructing suitable cell factories. Recombinant bacteriocins have made considerable progress from inclusion body formation, dissolved form and low antibacterial activity to yield recovery. The development of prospective cell factories for the biotechnological production of bacteriocins is still required, which may facilitate the application of bacteriocins in the food industry.

Bacterial cellulose (BC) has been found extensive applications in diverse domains for its exceptional attributes. However, the lack of antibacterial properties hampers its utilization in food and biomedical sectors. Leucocin, a bacteriocin belonging to class IIa, is synthesized by Leuconostoc that demonstrates potent efficacy against the foodborne pathogen, Listeria monocytogenes. In the current study, co-culturing strategy involving Kosakonia oryzendophytica FY-07 and Leuconostoc carnosum 4010 was used to confer anti-listerial activity to BC, which resulted in the generation of leucocin-containing BC (BC-L). The physical characteristics of BC-L, as determined by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA), were similar to the physical characteristics of BC. Notably, the experimental results of disc diffusion and growth curve indicated that the BC-L film exhibited a potent inhibitory effect against L. monocytogenes. Scanning electron microscopy (SEM) showed that BC-L exerts its bactericidal activity by forming pores on the bacterial cell wall. Despite the BC-L antibacterial mechanism, which involves pore formation, the mammalian cell viability remained unaffected by the BC-L film. The measurement results of zeta potential indicated that the properties of BC changed after being loaded with leucocin. Based on these findings, the anti-listerial BC-L generated through this co-culture system holds promise as a novel effective antimicrobial agent for applications in meat product preservation and packaging.

Broad-spectrum antibiotics are frequently used to treat bacteria-induced infections, but the overuse of antibiotics may induce the gut microbiota dysbiosis and disrupt gastrointestinal tract function. Probiotics can be applied to restore disturbed gut microbiota and repair abnormal intestinal metabolism. In the present study, two strains of Enterococcus faecium (named DC-K7 and DC-K9) were isolated and characterized from the fecal samples of infant dogs. The genomic features of E. faecium DC-K7 and DC-K9 were analyzed, the carbohydrate-active enzyme (CAZyme)-encoding genes were predicted, and their abilities to produce short-chain fatty acids (SCFAs) were investigated. The bacteriocin-encoding genes in the genome sequences of E. faecium DC-K7 and DC-K9 were analyzed, and the gene cluster of Enterolysin-A, which encoded a 401-amino-acid peptide, was predicted. Moreover, the modulating effects of E. faecium DC-K7 and DC-K9 on the gut microbiota dysbiosis induced by antibiotics were analyzed. The current results demonstrated that oral administrations of E. faecium DC-K7 and DC-K9 could enhance the relative abundances of beneficial microbes and decrease the relative abundances of harmful microbes. Therefore, the isolated E. faecium DC-K7 and DC-K9 were proven to be able to alter the gut microbiota dysbiosis induced by antibiotic treatment.

A variety of bacteria, including beneficial probiotic lactobacilli, produce antibacterials to kill competing bacteria. Lactobacilli secrete antimicrobial peptides (AMPs) called bacteriocins and organic acids. In the food industry, bacteriocins, but even whole cell-free supernatants, are becoming more and more important as bio-preservatives, while, in orthopedics, bacteriocins are introducing new perspectives in biomaterials technologies for anti-infective surfaces. Studies are focusing on Lactiplantibacillus plantarum (previously known as Lactobacillus plantarum). L. plantarum exhibits great phenotypic versatility, which enhances the chances for its industrial exploitation. Importantly, more than other lactobacilli, it relies on AMPs for its antibacterial activity. In this study, Response Surface Methodology (RSM) through a Box-Behnken experimental design was used to estimate the optimal conditions for the production of antibacterials by L. plantarum. A temperature of 35 °C, pH 6.5, and an incubation time of 48 h provided the highest concentration of antibacterials. The initial pH was the main factor influencing the production of antibacterials, at 95% confidence level. Thanks to RSM, the titer of antibacterials increased more than 10-fold, this result being markedly higher than those obtained in the very few studies that have so far used similar statistical methodologies. The Box-Behnken design turned out to be a valid model to satisfactorily plan a large-scale production of antibacterials from L. plantarum.