The potential of the endolysin Lysdb from Lactobacillus delbrueckii phage for combating Staphylococcus aureus during cheese manufacture from raw milk

Application of phage-derived enzymes for enhancing food safety

Foodborne pathogens such as Salmonella, Escherichia coli, Listeria monocytogenes, and Staphylococcus aureus present significant public health threats, causing widespread illness and economic loss. Contaminated food is responsible for an estimated 600 million illnesses and 420,000 deaths annually, with low- and middle-income countries facing losses of approximately $110 billion each year. Traditional methods to ensure food safety, including antimicrobials and preservatives, can contribute to the development of antimicrobial-resistant bacteria, highlighting the need for alternative strategies. Bacteriophages are gaining renewed attention as promising alternatives to conventional antibiotics due to their specifically target bacteria and their lower potential for causing adverse effects. However, their practical application is limited by challenges such as narrow host ranges, the emergence of phage-resistant bacteria, and stability issues. Recent research has shifted focus towards phage-derived enzymes, including endolysins, depolymerases, holins, and spanins, which are involved in the phage lytic cycle. These enzymes, as potential approaches to food safety, have demonstrated significant efficacy in targeting and lysing bacterial pathogens, making them suitable for controlling foodborne pathogens and preventing foodborne illnesses. Phage-derived enzymes also show promise in controlling biofilms and enhancing antimicrobial activity when combined with other antimicrobials. Therefore, this review emphasizes recent advancements in the use of the phage-derived enzymes for food safety, addresses their limitations, and suggests strategies to enhance their effectiveness in food processing and storage environments.

Phage Endolysins as an Alternative Biocontrol Strategy for Pathogenic and Spoilage Microorganisms in the Food Industry

Food contamination by pathogenic and spoilage bacteria causes approximately 47 million cases of foodborne diseases in the United States and leads to tons of food spoilage, worsening the food loss situation worldwide. In addition, conventional preservation treatments implemented in the food industry decrease food's nutritional and organoleptic quality. Therefore, there is a need for new alternatives to counteract food contamination without altering its characteristics. Endolysins are a promising strategy due to their unique properties, such as host specificity, synergism with other antibacterial agents, mode of action, and low probability of resistance development. These characteristics differentiate them from other antibacterial agents used in the food industry. Endolysins are enzymes produced by bacteriophages during the process of bacterial infection and lysis. This review describes the advances related to endolysin application systems in food, considering their potential for food safety and an overview of the application conditions according to the type of food and bacteria to be controlled. We also highlight the need for new studies on endolysin encapsulation and prolongation of the action time in cases of outbreaks that allow obtaining key information to improve the application of endolysins in different food matrices during food processing and storage.

Characterization of a phage endolysin LysLFP01 and its antibacterial activity

Lyase, a peptidoglycan hydrolase derived from phage, has been considered as a promising alternative antimicrobial agent. To date, adequate information regarding the characteristics of the Lactobacillus phage lyase is lacking. In this study, a lyase from Lactobacillus phage LFP01 was cloned and heterologously expressed in Escherichia coli (E. coli) for subsequent characterization of the antibacterial activity. The removal efficacy of bacterial biofilm and antimicrobial activity in raw milk were also evaluated. The results showed that LysLFP01 demonstrated broad-spectrum antibacterial activity, surpassing its phage counterpart, with particular efficacy against gram-positive bacteria. It exhibited strong thermostability (4-72 °C) and retained activity across a pH range of 3.0-9.0, although its activity decreased with higher NaCl concentrations. LysLFP01 effectively inhibited and removed Staphylococcus aureus (S. aureus) biofilms, as observed through scanning electron microscopy. Additionally, it exhibited significant antibacterial activity in raw milk at 4 °C, reducing bacterial counts effectively over time. Taken together, these findings indicated the potential of LysLFP01 as a novel and robust antimicrobial agent for food safety applications, particularly in combating S. aureus contamination in low-salt, non-acidic environments.

A comparative guide to expression systems for phage lysin production

Phage lysins, bacteriophage-encoded enzymes tasked with degrading their host's cell wall, are increasingly investigated and engineered as novel antibacterials across diverse applications. Their rapid action, tuneable specificity, and low likelihood of resistance development make them particularly interesting. Despite numerous application-focused lysin studies, the art of their recombinant production remains relatively undiscussed. Here, we provide an overview of the available expression systems for phage lysin production and discuss key considerations guiding the choice of a suitable recombinant host. We systematically surveyed recent literature to evaluate the hosts used in the lysin field and cover various recombinant systems, including the well-known bacterial host Escherichia coli or yeast Saccharomyces cerevisiae, as well as plant, mammalian, and cell-free systems. Careful analysis of the limited studies expressing lysins in various hosts suggests a host-dependent effect on activity. Nonetheless, the multitude of available expression systems should be further leveraged to accommodate the growing interest in phage lysins and their expanding range of applications.

A comprehensive review of the applications of bacteriophage-derived endolysins for foodborne bacterial pathogens and food safety: recent advances, challenges, and future perspective

Foodborne diseases are caused by food contaminated by pathogenic bacteria such as Escherichia coli, Salmonella, Staphylococcus aureus, Listeria monocytogenes, Campylobacter, and Clostridium, a critical threat to human health. As a novel antibacterial agent against foodborne pathogens, endolysins are peptidoglycan hydrolases encoded by bacteriophages that lyse bacterial cells by targeting their cell wall, notably in Gram-positive bacteria due to their naturally exposed peptidoglycan layer. These lytic enzymes have gained scientists' interest in recent years due to their selectivity, mode of action, engineering potential, and lack of resistance mechanisms. The use of endolysins for food safety has undergone significant improvements, which are summarized and discussed in this review. Endolysins can remove bacterial biofilms of foodborne pathogens and their cell wall-binding domain can be employed as a tool for quick detection of foodborne pathogens. We explained the applications of endolysin for eliminating pathogenic bacteria in livestock and various food matrices, as well as the limitations and challenges in use as a dietary supplement. We also highlight the novel techniques of the development of engineering endolysin for targeting Gram-negative bacterial pathogens. In conclusion, endolysin is safe and effective against foodborne pathogens and has no adverse effect on human cells and beneficial microbiota. As a result, endolysin could be employed as a functional bio-preservative agent to improve food stability and safety and maintain the natural taste of food quality.

Characterization of Lactobacilli Phage Endolysins and Their Functional Domains-Potential Live Biotherapeutic Testing Reagents

Phage endolysin-specific binding characteristics and killing activity support their potential use in biotechnological applications, including potency and purity testing of live biotherapeutic products (LBPs). LBPs contain live organisms, such as lactic acid bacteria (LAB), and are intended for use as drugs. Our approach uses the endolysin cell wall binding domains (CBD) for LBP potency assays and the endolysin killing activity for purity assays. CBDs of the following five lactobacilli phage lysins were characterized: CL1, Jlb1, Lj965, LL-H, and ΦJB. They exhibited different bindings to 27 LAB strains and were found to bind peptidoglycan or surface polymers. Flow cytometry based on CBD binding was used to enumerate viable counts of two strains in the mixture. CL1-lys, jlb1-lys, and ΦJB-lys and their enzymatic domains (EADs) exhibited cell wall digestive activity and lytic activity against LAB. Jlb1-EAD and ΦJB-EAD were more sensitive than their respective hololysins to buffer pH and NaCl changes. The ΦJB-EAD exhibited stronger lytic activity than ΦJB-lys, possibly due to ΦJB-CBD-mediated sequestration of ΦJB-lys by cell debris. CBD multiplex assays indicate that these proteins may be useful LBP potency reagents, and the lytic activity suggests that CL1-lys, jlb1-lys, and ΦJB-lys and their EADs are good candidates for LBP purity reagent development.

Biopreservative technologies of food: an alternative to chemical preservation and recent developments

Despite centuries of developing strategies to prevent food-associated illnesses, food safety remains a significant concern, even with multiple technological advancements. Consumers increasingly seek less processed and naturally preserved food options. One promising approach is food biopreservation, which uses natural antimicrobials found in food with a long history of safe consumption and can help reduce the reliance on chemically synthesized food preservatives. The hurdle technology method that combines multiple antimicrobial strategies is often used to improve the effectiveness of food biopreservation. This review attempts to provide a research summary on the utilization of lactic acid bacteria, bacteriocins, endolysins, bacteriophages, and biopolymers helps in the improvement of the shelf-life of food and lower the risk of food-borne pathogens throughout the food supply chain. This review also aims to evaluate current technologies that successfully employ the aforementioned preservatives to address obstacles in food biopreservation.

A Genomic Analysis of the Bacillus Bacteriophage Kirovirus kirovense Kirov and Its Ability to Preserve Milk

Bacteriophages are widely recognized as alternatives to traditional antibiotics commonly used in the treatment of bacterial infection diseases and in the food industry, as phages offer a potential solution in combating multidrug-resistant bacterial pathogens. In this study, we describe a novel bacteriophage, Kirovirus kirovense Kirov, which infects members of the Bacillus cereus group. Kirovirus kirovense Kirov is a broad-host-range phage belonging to the Caudoviricetes class. Its chromosome is a linear 165,667 bp double-stranded DNA molecule that contains two short, direct terminal repeats, each 284 bp long. According to bioinformatics predictions, the genomic DNA contains 275 protein-coding genes and 5 tRNA genes. A comparative genomic analysis suggests that Kirovirus kirovense Kirov is a novel species within the Kirovirus genus, belonging to the Andregratiavirinae subfamily. Kirovirus kirovense Kirov demonstrates the ability to preserve and decontaminate B. cereus from cow milk when present in milk at a concentration of 104 PFU/mL. After 4 h of incubation with the phage, the bacterial titer drops from 105 to less than 102 CFU/mL.

Lactococcus lactis secreting phage lysins as a potential antimicrobial against multi-drug resistant Staphylococcus aureus

BACKGROUND

Staphylococcus aureus is an opportunistic Gram-positive bacterium that can form biofilm and become resistant to many types of antibiotics. The treatment of multi-drug resistant Staphylococcus aureus (MDRSA) infection is difficult since it possesses multiple antibiotic-resistant mechanisms. Endolysin and virion-associated peptidoglycan hydrolases (VAPGH) enzymes from bacteriophage have been identified as potential alternative antimicrobial agents. This study aimed to assess the ability of Lactococcus lactis NZ9000 secreting endolysin and VAPGH from S. aureus bacteriophage 88 to inhibit the growth of S. aureus PS 88, a MDRSA.

METHOD

Endolysin and VAPGH genes were cloned and expressed in L. lactis NZ9000 after fusion with the SPK1 signal peptide for secretion. The recombinant proteins were expressed and purified, then analyzed for antimicrobial activity using plate assay and turbidity reduction assay. In addition, the spent media of the recombinant lactococcal culture was analyzed for its ability to inhibit the growth of the S. aureus PS 88.

RESULTS

Extracellular recombinant endolysin (Endo88) and VAPGH (VAH88) was successfully expressed and secreted from L. lactis which was able to inhibit S. aureus PS 88, as shown by halozone formation on plate assays as well as inhibition of growth in the turbidity reduction assay. Moreover, it was observed that the spent media from L. lactis NZ9000 expressing Endo88 and VAH88 reduced the viability of PS 88 by up to 3.5-log reduction with Endo88 being more efficacious than VAH88. In addition, Endo88 was able to lyse all MRSA strains tested and Staphylococcus epidermidis but not the other bacteria while VAH88 could only lyse S. aureus PS 88.

CONCLUSION

Recombinant L. lactisNZ9000 expressing phage 88 endolysin may be potentially developed into a new antimicrobial agent for the treatment of MDRSA infection.

Bacteriophage endolysins against gram-positive bacteria, an overview on the clinical development and recent advances on the delivery and formulation strategies

Facing the increasing threat of multi-drug antimicrobial resistance (AMR), humans strive to search for antibiotic drug candidates and antibacterial alternatives from all possible places, from soils in remote areas to deep in the sea. In this "gold rush for antibacterials," researchers turn to the natural enemy of bacterial cells, bacteriophage (phages), and find them a rich source of weapons for AMR bacteria. Endolysins (lysins), the enzymes phages use to break the bacterial cells from within, have been shown to be highly selective and efficient in killing their target bacteria from outside while maintaining a low occurrence of bacterial resistance. In this review, we start with the structures and mechanisms of action of lysins against Gram-positive (GM+) bacteria. The developmental history of lysins is also outlined. Then, we detail the latest preclinical and clinical research on their safety and efficacy against GM+ bacteria, focusing on the formulation strategies of these enzymes. Finally, the challenges and potential hurdles are discussed. Notwithstanding these limitations, the trends in development indicate that the first, approved lysin drugs will be available soon in the near future. Overall, this review presents a timely summary of the current progress on lysins as antibacterial enzymes for AMR GM+ bacteria, and provides a guidebook for biomaterial researchers who are dedicating themselves to the battle against bacterial infections.

Bacteriophage-encoded enzymes destroying bacterial cell membranes and walls, and their potential use as antimicrobial agents

Appearance of pathogenic bacteria resistant to most, if not all, known antibiotics is currently one of the most significant medical problems. Therefore, development of novel antibacterial therapies is crucial for efficient treatment of bacterial infections in the near future. One possible option is to employ enzymes, encoded by bacteriophages, which cause destruction of bacterial cell membranes and walls. Bacteriophages use such enzymes to destroy bacterial host cells at the final stage of their lytic development, in order to ensure effective liberation of progeny virions. Nevertheless, to use such bacteriophage-encoded proteins in medicine and/or biotechnology, it is crucial to understand details of their biological functions and biochemical properties. Therefore, in this review article, we will present and discuss our current knowledge on the processes of bacteriophage-mediated bacterial cell lysis, with special emphasis on enzymes involved in them. Regulation of timing of the lysis is also discussed. Finally, possibilities of the practical use of these enzymes as antibacterial agents will be underlined and perspectives of this aspect will be presented.

Bacillus-infecting bacteriophage Izhevsk harbors thermostable endolysin with broad range specificity

Several bacterial species belonging to the Bacillus cereus group are known to be causative agents of food poisoning and severe human diseases. Bacteriophages and their lytic enzymes called endolysins have been widely shown to provide for a supplemental or primary means of treating bacterial infections. In this work we present a new broad-host-range phage Izhevsk, which infects the members of the Bacillus cereus group. Transmission electron microscopy, genome sequencing and comparative analyses revealed that Izhevsk is a temperate phage with Siphoviridae morphology and belongs to the same genus as the previously described but taxonomically unclassified bacteriophages Tsamsa and Diildio. The Ply57 endolysin of Izhevsk phage has broad-spectrum activity against B. cereus sensu lato. The thermolability of Ply57 is higher than that of the PlyG of Wβ phage. This work contributes to our current understanding of phage biodiversity and may be useful for further development of efficient antimicrobials aimed at diagnosing and treating infectious diseases and food contaminations caused by the Bacillus cereus group of bacteria.

Bacteriophage-Derived Endolysins Applied as Potent Biocontrol Agents to Enhance Food Safety

Endolysins, bacteriophage-encoded enzymes, have emerged as antibacterial agents that can be actively applied in food processing systems as food preservatives to control pathogens and ultimately enhance food safety. Endolysins break down bacterial peptidoglycan structures at the terminal step of the phage reproduction cycle to enable phage progeny release. In particular, endolysin treatment is a novel strategy for controlling antibiotic-resistant bacteria, which are a severe and increasingly frequent problem in the food industry. In addition, endolysins can eliminate biofilms on the surfaces of utensils. Furthermore, the cell wall-binding domain of endolysins can be used as a tool for rapidly detecting pathogens. Research to extend the use of endolysins toward Gram-negative bacteria is now being extensively conducted. This review summarizes the trends in endolysin research to date and discusses the future applications of these enzymes as novel food preservation tools in the field of food safety.

Role of Bacteriophages in the Implementation of a Sustainable Dairy Chain

The growing human population is currently facing an unprecedented challenge regarding global food sustainability. Thus, it is of paramount to maintain food production and quality while avoiding a negative impact on climate change and the environment at large. Along the food chain, several practices could compromise future food safety and human health. One example is the widespread use of antibiotics and disinfectants in dairy production, which has contributed to the current antibiotic resistance crisis. Moreover, the uncontrolled release of antimicrobials to the environment poses a significant threat to natural ecosystems. For these reasons, research has recently focused on exploiting natural antimicrobials with the goal of achieving a safer and more sustainable dairy production chain. In this context, bacteriophages, viruses that infect bacteria, may become good allies to prevent and treat diseases in cattle, or be used as disinfectants in dairy facilities and as preservatives in dairy products. This review provides an overview of the current research regarding the use of phages as a global approach to reduce economic losses and food waste, while increasing food safety and reducing the environmental impact of food production. Our current understanding of progress, solutions, and future challenges in dairy production, processing, safety, waste processing, and quality assurance is also discussed.

Strategies to Encapsulate the Staphylococcus aureus Bacteriophage phiIPLA-RODI

The antimicrobial properties of bacteriophages make them suitable food biopreservatives. However, such applications require the development of strategies that ensure stability of the phage particles during food processing. In this study, we assess the protective effect of encapsulation of the Staphylococcus aureus bacteriophage phiIPLA-RODI in three kinds of nanovesicles (niosomes, liposomes, and transfersomes). All these systems allowed the successful encapsulation of phage phiIPLA-RODI with an efficiency ranged between 62% and 98%, regardless of the concentration of components (like phospholipids and surfactants) used for vesicle formation. Only niosomes containing 30 mg/mL of surfactants exhibited a slightly lower percentage of encapsulation. Regarding particle size distribution, the values determined for niosomes, liposomes, and transfersomes were 0.82 ± 0.09 µm, 1.66 ± 0.21 µm, and 0.55 ± 0.06 µm, respectively. Importantly, bacteriophage infectivity was maintained during storage for 6 months at 4 °C for all three types of nanovesicles, with the exception of liposomes containing a low concentration of components. In addition, we observed that niosomes partially protected the phage particles from low pH. Thus, while free phiIPLA-RODI was not detectable after 60 min of incubation at pH 4.5, titer of phage encapsulated in niosomes decreased only 2 log units. Overall, our results show that encapsulation represents an appropriate procedure to improve stability and, consequently, antimicrobial efficacy of phages for application in the food processing industry.

Swapping the roles of bacteriocins and bacteriophages in food biotechnology

To move towards a safer and more sustainable food production chain, natural antimicrobials have been traditionally applied to enhance safety. This is well exemplified by the use of bacteriocins, antimicrobial peptides synthesized by bacteria, as food biopreservatives. However, as knowledge on bacteriocin biology develops, novel functions beyond food preservation emerge and a shift towards health applications is positioning bacteriocins as anti-infectives and modulators of gut microbiota. On the other hand, bacteriophages, viruses infecting bacteria, have been long regarded as a threat for dairy fermentations. However, they may also become allies when specific phages infecting pathogenic or spoilage bacteria are intentionally used. This review summarizes the `dark side' and rather unexplored roles of bacteriocins and phages that, certainly, have much to learn from each other.

Are Phage Lytic Proteins the Secret Weapon To Kill Staphylococcus aureus?

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most threatening microorganisms for global human health. The current strategies to reduce the impact of S. aureus include a restrictive control of worldwide antibiotic use, prophylactic measures to hinder contamination, and the search for novel antimicrobials to treat human and animal infections caused by this bacterium. The last strategy is currently the focus of considerable research. In this regard, phage lytic proteins (endolysins and virion-associated peptidoglycan hydrolases [VAPGHs]) have been proposed as suitable candidates. Indeed, these proteins display narrow-spectrum antimicrobial activity and a virtual lack of bacterial-resistance development. Additionally, the therapeutic use of phage lytic proteins in S. aureus animal infection models is yielding promising results, showing good efficacy without apparent side effects. Nonetheless, human clinical trials are still in progress, and data are not available yet. This minireview also analyzes the main obstacles for introducing phage lytic proteins as human therapeutics against S. aureus infections. Besides the common technological problems derived from large-scale production of therapeutic proteins, a major setback is the lack of a proper legal framework regulating their use. In that sense, the relevant health authorities should urgently have a timely discussion about these new antimicrobials. On the other hand, the research community should provide data to dispel any doubts regarding their efficacy and safety. Overall, the appropriate scientific data and regulatory framework will encourage pharmaceutical companies to invest in these promising antimicrobials.

Synergistic antibacterial mechanism of the Lactobacillus crispatus surface layer protein and nisin on Staphylococcus saprophyticus

SlpB, a surface layer protein isolated from Lactobacillus crispatus, has the potential to enhance the antimicrobial activity of nisin. Previous research indicated that, when combined with nisin, SlpB acted synergistically to inhibit Staphylococcus saprophyticus growth, thus extending the shelf life of chicken meat. In order to understand how SlpB enhances the antibacterial activity of nisin, electron microscopy, confocal laser scanning microscopy, flow cytometry and transmembrane electrical potential analysis were used to study cell wall organization and cell membrane integrity. No remarkable bacteriolytic effects were observed, indicating that cell death could not be attributed to cell lysis, although SlpB caused dramatic modifications of cell wall, thereby altering cell shape. The combination of SlpB and nisin also induced the release of ATP or UV-absorbing materials, as well as sudden dissipation of the transmembrane electrical potential by compromising membrane integrity. Considering that SlpB led to structural disorganization of the cell wall, and nisin access is enhanced to form a stable pore, cell death is a predictable outcome. SlpB significantly enhanced the effect of nisin at half of the minimum inhibitory concentration, which resulted in cell death by destroying the cell wall and cell membrane, therefore providing a new, feasible approach in food preservation.