Inhibitory effect of four novel synthetic peptides on food spoilage yeasts

Revolutionizing agroindustry: Towards the industrial application of antimicrobial peptides against pathogens and pests

Antibiotics are essential chemicals for medicine and agritech. However, all antibiotics are small molecules that pathogens evolve antimicrobial resistance (AMR). Alternatively, antimicrobial peptides (AMPs) offer potential to overcome or evade AMR. AMPs provide broad-spectrum activity, favourable biosafety profiles, and a rapid and efficient mechanism of action with low resistance incidence. These properties have driven innovative applications, positioning AMPs as promising contributors to advancements in various industrial sectors. This review evaluates the multifaceted nature of AMPs and their biotechnological applications in underexplored sectors. In the food industry, the application of AMPs helps to suppress the growth of microorganisms, thereby decreasing foodborne illnesses, minimizing food waste, and prolonging the shelf life of products. In animal husbandry and aquaculture, incorporating AMPs into the diet reduces the load of pathogenic microorganisms and enhances growth performance and survival rates. In agriculture, AMPs provide an alternative to decrease the use of chemical pesticides and antibiotics. We also review current methods for obtaining AMPs, including chemical synthesis, recombinant DNA technology, cell-free protein synthesis, and molecular farming, are also reviewed. Finally, we look to the peptide market to assess its status, progress, and transition from the discovery stage to benefits for society and high-quality products. Overall, our review exemplifies the other side of the coin of AMPs and how these molecules provide similar benefits to conventional antibiotics and pesticides in the agritech sector.

Membrane Selectivity Mechanisms of the Antimicrobial Peptide Snakin-Z Against Prokaryotic and Eukaryotic Membrane Models

Snakin-Z, a novel cationic antimicrobial peptide (AMP) derived from Zizyphus jujuba fruits, exhibits broad-spectrum antimicrobial activity against bacteria and fungi. Importantly, it displays minimal hemolytic activity toward human red blood cells (RBCs). Elucidating the molecular basis of membrane selectivity of Snakin-Z is essential for its development as a novel antimicrobial agent. In this study, all-atom molecular dynamics (MD) simulations were employed to provide detailed molecular insights into the interactions between Snakin-Z and bacterial, fungal, and RBC membrane models. The simulations revealed a helical-coil conformation for Snakin-Z, with its amphipathic structure, polarity, and residues such as Arg, Lys, Ser, and Tyr playing crucial roles in mediating selective interactions with the microbial membrane models. Specifically, Arg28, Lys29, and Arg3 were identified as playing a crucial role in mediating membrane binding and stability. Snakin-Z was observed to be deeply embedded in the Candida albicans and Bacillus subtilis membrane models, followed by Escherichia coli and RBC membrane models. A considerable thinning and strong disordering of Candida albicans, Bacillus subtilis and Escherichia coli membranes acyl chains were observed. The presence of cholesterol in the RBC membrane contributes to its resistance to Snakin-Z-mediated disruption. This study presents the first comprehensive investigation of the selective mechanism underlying the antimicrobial activity of Snakin-Z against bacterial membrane models. Our findings provide insights into the antimicrobial properties of Snakin-Z at the molecular level, highlighting its significant potential for use in the food and biotechnology industries as a promising alternative to conventional antibiotics and preservatives.

Evaluating the Role of Nutrient Competition in Debaryomyces hansenii Biocontrol Activity Against Spoilage Molds in the Meat Industry

The rejection of chemical preservatives reflects the growing demand for natural and safe products. This concern has spurred scientific interest in yeasts as biocontrol agents, given their antagonistic activity against undesired fungi, which is one of the main problems associated with preservative reduction. Debaryomyces hansenii is a non-conventional yeast that has shown great potential for inhibiting filamentous fungi in the food industry. This study investigated the role of nutrient competition in the biocontrol activity of D. hansenii against unwanted molds. Potentially pathogenic molds from spoiled food were isolated using different media and identified using Sanger sequencing. The inhibitory effects of different autochthonous D. hansenii strains under varying nutrient conditions were assessed against isolated molds using semipermeable membranes. Inhibition activity was measured by assessing mycelial expansion and spore production using image software analysis and classical cell counting using a Neubauer chamber. The results indicated that D. hansenii effectively inhibited mold growth and sporulation, with the autochthonous strains LR2 and SRF1 showing higher inhibitory activity than the control strain CBS767. The effectiveness of inhibition varied with the yeast-mold combination, highlighting the need for a species-specific analysis. Nutrient competition plays a complementary role in D. hansenii biocontrol but does not directly impact overall inhibition. This suggests that other mechanisms, such as direct cell interactions or metabolite production, may be crucial. These findings enhance our understanding of the potential of D. hansenii as a natural preservative and advance biocontrol methods for food safety.

Adaptation and Validation of a Modified Broth Microdilution Method for Screening the Anti-Yeast Activity of Plant Phenolics in Apple and Orange Juice Models

Yeasts are the usual contaminants in fruit juices and other beverages, responsible for the decrease in the quality and shelf-life of such products. Preservatives are principally added to these beverages to enhance their shelf-life. With the increasing consumer concern towards chemical food additives, plant-derived antimicrobials have attracted the attention of researchers as efficient and safer anti-yeast agents. However, the methods currently used for determining their anti-yeast activity are time- and material-consuming. In this study, the anti-yeast effect of plant phenolic compounds in apple and orange juice food models using microtiter plates has been evaluated in order to validate the modified broth microdilution method for screening the antimicrobial activity of juice preservative agents. Among the twelve compounds tested, four showed a significant in vitro growth-inhibitory effect against all tested yeasts (Saccharomyces cerevisiae, Zygosaccharomyces bailii, and Zygosaccharomyces rouxii) in both orange and apple juices. The best results were obtained for pterostilbene in both juices with minimum inhibitory concentrations (MICs) ranging from 32 to 128 μg/mL. Other compounds, namely oxyresveratrol, piceatannol, and ferulic acid, exhibited moderate inhibitory effects with MICs of 256-512 μg/mL. Furthermore, the results indicated that differences in the chemical structures of the compounds tested significantly affected the level of yeast inhibition, whereas stilbenes with methoxy and hydroxy groups produced the strongest effect. Furthermore, the innovative assay developed in this study can be used for screening the anti-yeast activity of juice preservative agents because it saves preparatory and analysis time, laboratory supplies, and manpower in comparison to the methods commonly used.

Conventional and advanced detection techniques of foodborne pathogens: A comprehensive review

Foodborne pathogens are a major public health concern and have a significant economic impact globally. From harvesting to consumption stages, food is generally contaminated by viruses, parasites, and bacteria, which causes foodborne diseases such as hemorrhagic colitis, hemolytic uremic syndrome (HUS), typhoid, acute, gastroenteritis, diarrhea, and thrombotic thrombocytopenic purpura (TTP). Hence, early detection of foodborne pathogenic microbes is essential to ensure a safe food supply and to prevent foodborne diseases. The identification of foodborne pathogens is associated with conventional (e.g., culture-based, biochemical test-based, immunological-based, and nucleic acid-based methods) and advances (e.g., hybridization-based, array-based, spectroscopy-based, and biosensor-based process) techniques. For industrial food applications, detection methods could meet parameters such as accuracy level, efficiency, quickness, specificity, sensitivity, and non-labor intensive. This review provides an overview of conventional and advanced techniques used to detect foodborne pathogens over the years. Therefore, the scientific community, policymakers, and food and agriculture industries can choose an appropriate method for better results.

Immunomodulatory and Allergenic Properties of Antimicrobial Peptides

With the growing problem of the emergence of antibiotic-resistant bacteria, the search for alternative ways to combat bacterial infections is extremely urgent. While analyzing the effect of antimicrobial peptides (AMPs) on immunocompetent cells, their effect on all parts of the immune system, and on humoral and cellular immunity, is revealed. AMPs have direct effects on neutrophils, monocytes, dendritic cells, T-lymphocytes, and mast cells, participating in innate immunity. They act on B-lymphocytes indirectly, enhancing the induction of antigen-specific immunity, which ultimately leads to the activation of adaptive immunity. The adjuvant activity of AMPs in relation to bacterial and viral antigens was the reason for their inclusion in vaccines and made it possible to formulate the concept of a “defensin vaccine” as an innovative basis for constructing vaccines. The immunomodulatory function of AMPs involves their influence on cells in the nearest microenvironment, recruitment and activation of other cells, supporting the response to pathogenic microorganisms and completing the inflammatory process, thus exhibiting a systemic effect. For the successful use of AMPs in medical practice, it is necessary to study their immunomodulatory activity in detail, taking into account their pleiotropy. The degree of maturity of the immune system and microenvironment can contribute to the prevention of complications and increase the effectiveness of therapy, since AMPs can suppress inflammation in some circumstances, but aggravate the response and damage of organism in others. It should also be taken into account that the real functions of one or another AMP depend on the types of total regulatory effects on the target cell, and not only on properties of an individual peptide. A wide spectrum of biological activity, including direct effects on pathogens, inactivation of bacterial toxins and influence on immunocompetent cells, has attracted the attention of researchers, however, the cytostatic activity of AMPs against normal cells, as well as their allergenic properties and low stability to host proteases, are serious limitations for the medical use of AMPs. In this connection, the tasks of searching for compounds that selectively affect the target and development of an appropriate method of application become critically important. The scope of this review is to summarize the current concepts and newest advances in research of the immunomodulatory activity of natural and synthetic AMPs, and to examine the prospects and limitations of their medical use.

Determination of the Relationships between the Chemical Structure and Antimicrobial Activity of a GAPDH-Related Fish Antimicrobial Peptide and Analogs Thereof

The structure–activity relationships and mode of action of synthesized glyceraldehyde-3-phosphate dehydrogenase (GAPDH)-related antimicrobial peptides were investigated. Including the native skipjack tuna GAPDH-related peptide (SJGAP) of 32 amino acid residues (model for the study), 8 different peptide analogs were designed and synthesized to study the impact of net charge, hydrophobicity, amphipathicity, and secondary structure on both antibacterial and antifungal activities. A net positive charge increase, by the substitution of anionic residues or C-terminal amidation, improved the antimicrobial activity of the SJGAP analogs (minimal inhibitory concentrations of 16–64 μg/mL), whereas the alpha helix content, as determined by circular dichroism, did not have a very definite impact. The hydrophobicity of the peptides was also found to be important, especially for the improvement of antifungal activity. Membrane permeabilization assays showed that the active peptides induced significant cytoplasmic membrane permeabilization in the bacteria and yeast tested, but that this permeabilization did not cause leakage of 260 nm-absorbing intracellular material. This points to a mixed mode of action involving both membrane pore formation and targeting of intracellular components. This study is the first to highlight the links between the physicochemical properties, secondary structure, antimicrobial activity, and mechanism of action of antimicrobial peptides from scombrids or homologous to GAPDH.

Bioactive Peptides: A Promising Alternative to Chemical Preservatives for Food Preservation

Bioactive peptides used for food preservation can prolong the shelf life through bacteriostasis and antioxidation. On the one hand, bioactive peptides can inhibit lipid oxidation by scavenging free radicals, interacting with metal ions, and inhibiting lipid peroxidation. On the other hand, bioactive peptides can fundamentally inhibit the growth and reproduction of microorganisms by destroying their cell membranes or targeting intracellular components. Besides, bioactive peptides are biocompatible and biodegradable in vivo. Therefore, they are regarded as a promising alternative to chemical preservatives. However, bioactive peptides are easily affected by the external environment in practical application, which hinders their commercialization. Currently, the studies to overcome the weakness focus on encapsulation and chemical synthesis. Bioactive peptides have been applied to the preservation of various foods in experimental research, with good results. In the future, with the deepening understanding of their safety and structure-activity relationship, there may be more bioactive peptides as food preservatives.

In Vitro Activity of Selected Phenolic Compounds against Planktonic and Biofilm Cells of Food-Contaminating Yeasts

Phenolic compounds are natural substances that can be obtained from plants. Many of them are potent growth inhibitors of foodborne pathogenic microorganisms, however, phenolic activities against spoilage yeasts are rarely studied. In this study, planktonic and biofilm growth, and the adhesion capacity of Pichia anomala, Saccharomyces cerevisiae, Schizosaccharomyces pombe and Debaryomyces hansenii spoilage yeasts were investigated in the presence of hydroxybenzoic acid, hydroxycinnamic acid, stilbene, flavonoid and phenolic aldehyde compounds. The results showed significant anti-yeast properties for many phenolics. Among the tested molecules, cinnamic acid and vanillin exhibited the highest antimicrobial activity with minimum inhibitory concentration (MIC) values from 500 µg/mL to 2 mg/mL. Quercetin, (-)-epicatechin, resveratrol, 4-hydroxybenzaldehyde, p-coumaric acid and ferulic acid were also efficient growth inhibitors for certain yeasts with a MIC of 2 mg/mL. The D. hansenii, P. anomala and S. pombe biofilms were the most sensitive to the phenolics, while the S. cerevisiae biofilm was quite resistant against the activity of the compounds. Fluorescence microscopy revealed disrupted biofilm matrix on glass surfaces in the presence of certain phenolics. Highest antiadhesion activity was registered for cinnamic acid with inhibition effects between 48% and 91%. The active phenolics can be natural interventions against food-contaminating yeasts in future preservative developments.

An ornithine-rich dodecapeptide with improved proteolytic stability selectively kills gram-negative food-borne pathogens and its action mode on Escherichia coli O157:H7

Food-borne pathogenic bacteria are dispersed throughout the entire chain of the food industry. However, many food preservatives are limited by poor biocompatibility such as cumulative poisoning. The antimicrobial peptide is increasingly regarded as a promising preservative in food research due to its high bioactivity and low cytotoxicity. In this study, thirteen peptides were designed, synthesized, and screened for application as food preservatives. One of them, termed zp65, whose sequence is GIOAOIIIOIOO-NH₂, demonstrated potent bactericidal effect against common Gram-negative strains including enterohemorrhagic Escherichia coli, Salmonella, and Citrobacter freundii. Encouragingly, zp65 showed negligible cytotoxicity to both mammalian cells and Galleria mellonella larvae. Peptide zp65 was prone to form α-helix structure in amphiphilic environments, facilitating its affinity with bacterial membrane. Furthermore, the proteolytic stability of zp65 was much higher than its derivatives consisting of totally natural amino acids. Isothermal titration calorimetry indicated that zp65 has a strong binding affinity to lipopolysaccharide with K_d = 1.3 μM, suggesting its possible action target on the bacterial envelope. Mechanistic studies revealed that this peptide also influenced the membrane potential of E.coli O157:H7 (O157) in a dose-dependent manner. Surprisingly, peptide zp65 did not induce disruption of membrane permeability even at a higher concentration of 4-fold minimal inhibitory concentration. By employing confocal microscopy, peptide zp65 labeled by fluorescein isothiocyanate mainly aggregated on the bacterial membrane. These results suggested that the bactericidal mode of action of zp65 is likely attributed to depolarization of the cell membrane. The minced lean beef experiment indicated that the maximum reduction of O157 reached 1.46 log colony-forming unit (CFU) per gram on day 1 after zp65 treatment at the dosage of 40 μg/g. Compared with the untreated cooked beef sample, the CFU of the zp65-treated group remained at a much lower level after 10-day storage. Subsequently, treatment with zp65 at concentrations above 32 μM also significantly reduced O157 viable counts in fresh tomato juice. And the zp65 treatment could rescue about 40% of Galleria mellonella larvae injected with O157-contaminated tomato juice. The peptide zp65 exhibits great potential and deserves further study as a candidate for food preservative.

Growth Inhibitory Effect of Garlic Powder and Cinnamon Extract on White Colony-Forming Yeast in Kimchi

White colony-forming yeast (WCFY), also referred to as film forming yeast or spoilage yeast, that appear on the surface of kimchi can deteriorate the sensory properties of kimchi, such as odor and texture. Thus, the aim of this study was to develop a method to inhibit the formation of the white colony in kimchi. First, alterations in kimchi manufacturing and storage conditions, including temperatures, pH, salinity, and anaerobic condition, were investigated to determine if they could inhibit the growth of WCFY (i.e., Kazachstania servazzii, Candida sake, Debaryomyces hansenii, Pichia kudriavzevii, and Hanseniaspora uvarum). Thereafter, the anti yeast activity of freeze-dried garlic powder (FGP) and cinnamon ethanol extract (CEE) was evaluated against WCFY using the agar-well diffusion assay. Following the direct application of FGP and CEE to the surface of the kimchi, the inhibitory effects on white colony were determined. The results showed that WCFY can grow under various manufacturing and storage conditions of kimchi. Regarding the growth inhibitory effect on WCFY, FGP exhibited anti yeast activity against four WCFYs. It did not show anti yeast activity against K. servazzii. However, CEE showed anti yeast activity against K. servazzii. In particular, the mixture of 10% FGP and 1.75% CEE, which was manufactured considering the influence of sensory properties in kimchi, exhibited anti yeast activity against all WCFY. Furthermore, the application of the FGP and CEE mixture supplemented with 0.02% xanthan gum to kimchi to enhance adhesion to the kimchi surface, led to a delay in the formation of a white colony on the surface of the kimchi by an average of 17 d at 10 °C compared to the control group. Collectively, the use of a FGP, CEE, and xanthan gum mixture could be an effective method for the inhibition of white colony formation on the surface of kimchi, extending its shelf life.

Plant compounds for the potential reduction of food waste - a focus on antimicrobial peptides

A large portion of global food waste is caused by microbial spoilage. The modern approach to preserve food is to apply different hurdles for microbial pathogens to overcome. These vary from thermal processes and chemical additives, to the application of irradiation and modified atmosphere packaging. Even though such preservative techniques exist, loss of food to spoilage still prevails. Plant compounds and peptides represent an untapped source of potential novel natural food preservatives. Of these, antimicrobial peptides (AMPs) are very promising for exploitation. AMPs are a significant component of a plant's innate defense system. Numerous studies have demonstrated the potential application of these AMPs; however, more studies, particularly in the area of food preservation are warranted. This review examines the literature on the application of AMPs and other plant compounds for the purpose of reducing food losses and waste (including crop protection). A focus is placed on the plant defensins, their natural extraction and synthetic production, and their safety and application in food preservation. In addition, current challenges and impediments to their full exploitation are discussed.

Current Trends of Bioactive Peptides-New Sources and Therapeutic Effect

Generally, bioactive peptides are natural compounds of food or part of protein that are inactive in the precursor molecule. However, they may be active after hydrolysis and can be transported to the active site. Biologically active peptides can also be synthesized chemically and characterized. Peptides have many properties, including antihypertensive, antioxidant, antimicrobial, anticoagulant, and chelating effects. They are also responsible for the taste of food or for the inhibition of enzymes involved in the development of diseases. The scientific literature has described many peptides with bioactive properties obtained from different sources. Information about the structure, origin, and properties of peptides can also be found in many databases. This review will describe peptides inhibiting the development of current diseases, peptides with antimicrobial properties, and new alternative sources of peptides based on the current knowledge and documentation of their bioactivity. All these issues are part of modern research on peptides and their use in current health or technological problems in food production.