Antimicrobial efficacy of pepsin-digested bovine lactoferrin on spoilage bacteria contaminating traditional Mozzarella cheese

Recent Advances on Antimicrobial Peptides from Milk: Molecular Properties, Mechanisms, and Applications

Traditional antibiotics are facing a tremendous challenge due to increased antimicrobial resistance; hence, there is an urgent need to find novel antibiotic alternatives. Milk protein-derived antimicrobial peptides (AMPs) are currently attracting substantial attention considering that they showcase an extensive spectrum of antimicrobial activities, with slower development of antimicrobial resistance and safety of raw materials. This review summarizes the molecular properties, and activity mechanisms and highlights the applications and limitations of AMPs derived from milk proteins comprehensively. Also the analytical technologies, especially bioinformatics methodologies, applied in the process of screening, identification, and mechanism illustration of AMPs were underlined. This review will give some ideas for further research and broadening of the applications of milk protein-derived AMPs in the food field.

Lactoferricin, an antimicrobial motif derived from lactoferrin with food preservation potential

The growth of bacteria and fungi may cause disease inf human or spoilage of food. New antimicrobial substances need to be discovered. Lactoferricin (LFcin) is a group of antimicrobial peptides derived from the N-terminal region of the milk protein lactoferrin (LF). LFcin has antimicrobial ability against a variety of microorganisms, which is significantly better than that of its parent version. Here, we review the sequences, structures, and antimicrobial activities of this family and elucidated the motifs of structural and functional significance, as well as its application in food. Using sequence and structural similarity searches, we identified 43 new LFcins from the mammalian LFs deposited in the protein databases, which are grouped into six families according to their origins (Primates, Rodentia, Artiodactyla, Perissodactyla, Pholidota, and Carnivora). This work expands the LFcin family and will facilitate further characterization of novel peptides with antimicrobial potential. Considering the antimicrobial effect of LFcin on foodborne pathogens, we describe the application of these peptides from the prospective of food preservation.

Alternative Protein Sources and Novel Foods: Benefits, Food Applications and Safety Issues

The increasing size of the human population and the shortage of highly valuable proteinaceous ingredients has prompted the international community to scout for new, sustainable, and natural protein resources from invertebrates (e.g., insects) and underutilized legume crops, unexploited terrestrial and aquatic weeds, and fungi. Insect proteins are known for their nutritional value, being rich in proteins with a good balance of essential amino acids and being a valuable source of essential fatty acids and trace elements. Unconventional legume crops were found rich in nutritional, phytochemical, and therapeutic properties, showing excellent abilities to survive extreme environmental conditions. This review evaluates the recent state of underutilized legume crops, aquatic weeds, fungi, and insects intended as alternative protein sources, from ingredient production to their incorporation in food products, including their food formulations and the functional characteristics of alternative plant-based proteins and edible insect proteins as novel foods. Emphasis is also placed on safety issues due to the presence of anti-nutritional factors and allergenic proteins in insects and/or underutilized legumes. The functional and biological activities of protein hydrolysates from different protein sources are reviewed, along with bioactive peptides displaying antihypertensive, antioxidant, antidiabetic, and/or antimicrobial activity. Due to the healthy properties of these foods for the high abundance of bioactive peptides and phytochemicals, more consumers are expected to turn to vegetarianism or veganism in the future, and the increasing demand for such products will be a challenge for the future.

Pseudomonas fluorescens and Escherichia coli in Fresh Mozzarella Cheese: Effect of Cellobiose Oxidase on Microbiological Stability during Refrigerated Shelf Life

Background: Mozzarella cheese possesses a high moisture content (50−60%) and a relatively high pH (around 5.5) and is therefore considered a perishable food product characterized by high quality deterioration and the potential risk of microbial contamination. Moreover, it can be spoiled by Pseudomonas spp. and coliform bacteria, which may be involved in different negative phenomena, such as proteolysis, discolorations, pigmentation, and off-flavors. To prevent these, different methods were investigated. In this context, the present study aims to assess the antimicrobial effect of cellobiose oxidase on Pseudomonas fluorescens (5026) and Escherichia coli (k88, k99) in mozzarella cheese during refrigerated shelf life. Methods: microbiological challenge tests were designed by contaminating the mozzarella covering liquid containing different cellobiose oxidase concentrations with P. fluorescens (5026) and E. coli (k88, k99). The behavior of these microorganisms and the variation of hydrogen peroxide concentrations were then tested under refrigerated conditions for 20 days to simulate the mozzarella cheese shelf life. Results and Conclusions: The data obtained demonstrated the effect of cellobiose oxidase on microbial growth. In particular, E. coli (k88, k99) was inhibited over the entire shelf life, while P. fluorescens (5026) was only partially affected after a few days of refrigerated storage.

Molecular modeling of lactoferrin for food and nutraceutical applications: insights from in silico techniques

Lactoferrin is a protein, primarily found in milk that has attracted the interest of the food industries due to its health properties. Nevertheless, the instability of lactoferrin has limited its commercial application. Recent studies have focused on encapsulation to enhance the stability of lactoferrin. However, the molecular insights underlying the changes of structural properties of lactoferrin and the interaction with protectants remain poorly understood. Computational approaches have proven useful in understanding the structural properties of molecules and the key binding with other constituents. In this review, comprehensive information on the structure and function of lactoferrin and the binding with various molecules for food purposes are reviewed, with a special emphasis on the use of molecular dynamics simulations. The results demonstrate the application of modeling and simulations to determine key residues of lactoferrin responsible for its stability and interactions with other biomolecular components under various conditions, which are also associated with its functional benefits. These have also been extended into the potential creation of enhanced lactoferrin for commercial purposes. This review provides valuable strategies in designing novel nutraceuticals for food science practitioners and those who have interests in acquiring familiarity with the application of computational modeling for food and health purposes.

Synthesis, characterization and application of antibacterial lactoferrin nanoparticles

Lactoferrin (L) and gellan gum (G) nanoparticles were produced in different biopolymer proportions through electrostatic complexation to enhance the antimicrobial properties of lactoferrin. The nanoparticles were characterized according to size, charge density, morphology and antimicrobial activity against S. aureus and E. coli, in two different broths to show the effect of the broth composition on the nanoparticle activity. The 9L:1G particles showed the highest positive zeta potential (+21.20 mV) and reduced diameter (92.03 nm) which resulted in a minimum inhibitory concentration six times smaller (0.3 mg/ml) than pure lactoferrin (2 mg/ml). However, the bacteriostatic action of nanoparticles was inhibited in the presence of divalent cations. When applied to strawberries as a coating, lactoferrin nanoparticles extended fruit shelf-life up to 6 days in the presence of carboxymethylcellulose (CMC). Therefore, lactoferrin-gellan gum complexation was proved to be a promising tool to enhance lactoferrin antimicrobial action and broaden its application as a food preserver.

Lactoferrin and Its Derived Peptides: An Alternative for Combating Virulence Mechanisms Developed by Pathogens

Due to the emergence of multidrug-resistant pathogens, it is necessary to develop options to fight infections caused by these agents. Lactoferrin (Lf) is a cationic nonheme multifunctional glycoprotein of the innate immune system of mammals that provides numerous benefits. Lf is bacteriostatic and/or bactericidal, can stimulate cell proliferation and differentiation, facilitate iron absorption, improve neural development and cognition, promote bone growth, prevent cancer and exert anti-inflammatory and immunoregulatory effects. Lactoferrin is present in colostrum and milk and is also produced by the secondary granules of polymorphonuclear leukocytes, which store this glycoprotein and release it at sites of infection. Lf is also present in many fluids and exocrine secretions, on the surfaces of the digestive, respiratory and reproductive systems that are commonly exposed to pathogens. Apo-Lf (an iron-free molecule) can be microbiostatic due to its ability to capture ferric iron, blocking the availability of host iron to pathogens. However, apo-Lf is mostly microbicidal via its interaction with the microbial surface, causing membrane damage and altering its permeability function. Lf can inhibit viral entry by binding to cell receptors or viral particles. Lf is also able to counter different important mechanisms evolved by microbial pathogens to infect and invade the host, such as adherence, colonization, invasion, production of biofilms and production of virulence factors such as proteases and toxins. Lf can also cause mitochondrial and caspase-dependent regulated cell death and apoptosis-like in pathogenic yeasts. All of these mechanisms are important targets for treatment with Lf. Holo-Lf (the iron-saturated molecule) can contain up to two ferric ions and can also be microbicidal against some pathogens. On the other hand, lactoferricins (Lfcins) are peptides derived from the N-terminus of Lf that are produced by proteolysis with pepsin under acidic conditions, and they cause similar effects on pathogens to those caused by the parental Lf. Synthetic analog peptides comprising the N-terminus Lf region similarly exhibit potent antimicrobial properties. Importantly, there are no reported pathogens that are resistant to Lf and Lfcins; in addition, Lf and Lfcins have shown a synergistic effect with antimicrobial and antiviral drugs. Due to the Lf properties being microbiostatic, microbicidal, anti-inflammatory and an immune modulator, it represents an excellent natural alternative either alone or as adjuvant in the combat to antibiotic multidrug-resistant bacteria and other pathogens. This review aimed to evaluate the data that appeared in the literature about the effects of Lf and its derived peptides on pathogenic bacteria, protozoa, fungi and viruses and how Lf and Lfcins inhibit the mechanisms developed by these pathogens to cause disease.

Natural bioactive substances for the control of food-borne viruses and contaminants in food

Abstract

Food-borne viruses and contaminants, as an important global food safety problem, are caused by chemical, microbiological, zoonotic, and other risk factors that represent a health hazard. Natural bioactive substances, originating from plants, animals, or microorganisms, might offer the possibility of preventing and controlling food-borne diseases. In this contribution, the common bioactive substances such as polyphenols, essential oils, proteins, and polysaccharides which are effective in the prevention and treatment of food-borne viruses and contaminants are discussed. Meanwhile, the preventive effects of natural bioactive substances and the possible mechanisms involved in food protection are discussed and detailed. The application and potential effects of natural bioactive substances in the adjuvant treatment for food-borne diseases is also described.

Graphical abstract

Lactoferrin-Derived Peptides as a Control Strategy against Skinborne Staphylococcal Biofilms

Coagulase-negative staphylococci (CoNS) widely colonize the human skin and play an active role in host defense. However, these bacteria may cause malodours and increase infection incidence rate in immune-compromised patients and individuals with catheters and implants. CoNS spreading is favored by biofilm formation that also promotes the release of virulence factors and drug resistance. Biofilm control or eradication by antimicrobial peptides (AMPs) represents an attractive strategy which is worth investigating. In this work, bovine lactoferrin (BLF) hydrolysate (HLF) was in vitro evaluated for its antimicrobial and antibiofilm activities against skin-related coagulase negative and positive staphylococci. Despite a minimal inhibitory concentration (MIC) recorded for HLF ranging from 10 to more than 20 mg/mL, a minimal biofilm inhibitory concentration (MIBC) equal to 2.5 mg/mL was found for most target strains. Conversely, MIBC values referred to the individual peptides, LFcinB or LFmpin (herein purified and identified) were significantly lower. Finally, the application of 2.5 mg/mL HLF solution by dipping and spraying on biofilm-attached glass surfaces also caused a high biofilm eradication rate depending on the incubation time, thus attracting interest for future applications in cosmetic formulation for skin care.

Biofilm and Pathogenesis-Related Proteins in the Foodborne P. fluorescens ITEM 17298 With Distinctive Phenotypes During Cold Storage

In food chain, Pseudomonas spp. cause spoilage by reducing shelf life of fresh products, especially during cold storage, with a high economic burden for industries. However, recent studies have shed new light on health risks occurring when they colonize immunocompromised patient tissues. Likewise to P. aeruginosa, they exhibit antibiotic resistance and biofilm formation, responsible for their spread and persistence in the environment. Biofilm formation might be induced by environmental stresses, such as temperature fluctuations causing physiological and metabolic changes exacerbating food spoilage (by protease and pigment synthesis), and the production of adhesion molecules, chemotactic or underestimated virulence factors. In order to provide a new insight into phenotypic biodiversity of Pseudomonas spoilers isolated from cold stored cheese, in this work 19 Pseudomonas spp. were investigated for biofilm, pigments, exopolysaccharide production and motility at low temperature. Only nine strains showed these phenotypic traits and the blue pigmenting cheese strain P. fluorescens ITEM 17298 was the most distinctive. In addition, this strain decreased the survival probability of infected Galleria mellonella larvae, showing, for the first time, a pathogenic potential. Genomic and proteomic analyses performed on the ITEM 17298 planktonic cells treated or not with lactoferrin derived antibiofilm peptides allowed to reveal specific biofilm related-pathways as well as proteins involved in pathogenesis. Indeed, several genes were found related to signaling system by cGMP-dependent protein kinases, cellulose, rhamnolipid and alginate synthesis, antibiotic resistance, adhesion and virulence factors. The proteome of the untreated ITEM 17298, growing at low temperature, showed that most of the proteins associated with biofilm regulation, pigmentation motility, antibiotic resistance and pathogenecity were repressed, or decreased their levels in comparison to that of the untreated cultures. Thus, the results of this work shed light on the complex pathways network allowing psychrotrophic pseudomonads to adapt themselves to food-refrigerated conditions and enhance their spoilage. In addition, the discovery of virulence factors and antibiotic resistance determinants raises some questions about the need to deeper investigate these underestimated bacteria in order to increase awareness and provide input to update legislation on their detection limits in foods.

The Effect of Lactoferrin and Pepsin-Treated Lactoferrin on IEC-6 Cell Damage Induced by Clostridium Difficile Toxin B

Clostridium difficile infections (CDI) have recently increased worldwide. Some CDI progress to fulminant and recurrent CDI and are associated with high mortality and morbidity. CD produces toxins A and B, which cause intestinal mucosal damage, although toxin B exhibits greater cytotoxicity. Pepsin-treated lactoferrin (PLF) is the decomposed product of lactoferrin (LF), a multifunctional glycoprotein with anti-inflammatory properties. Here, we investigate the effects of LF and PLF in toxin B-stimulated rat intestinal epithelial (IEC-6) cells. Different toxin B concentrations were added to IEC-6 cells with or without LF or PLF. Mitochondrial function and cell cytotoxicity were assessed by measuring WST-1 and LDH levels, respectively. WST-1 levels were higher in IEC-6 cells treated with toxin B and LF or PLF than in the toxin B-only control (P < 0.05). Compared with the toxin B-only control, LDH levels significantly decreased after toxin B and LF or PLF addition (P < 0.05). Wound restitution measurement using microscopy demonstrated significantly greater levels of wound restitution in cells treated with toxin B and LF or PLF than in those treated with toxin B alone after 12 h (P < 0.001). Furthermore, changes in IEC-6 cell tight junctions (TJs) were evaluated by immunofluorescence microscopy and zonula occludens-1 (ZO-1) protein expression. When LF or PLF were added to IEC-6 cells, TJ structures were maintained, and ZO-1 and occludin expression was upregulated. Taken together, these results demonstrate that LF and PLF prevent the cytotoxicity of toxin B and might have the potential to control CDI.

Antibiotic Resistant Pseudomonas Spp. Spoilers in Fresh Dairy Products: An Underestimated Risk and the Control Strategies

Microbial multidrug resistance (MDR) is a growing threat to public health mostly because it makes the fight against microorganisms that cause lethal infections ever less effective. Thus, the surveillance on MDR microorganisms has recently been strengthened, taking into account the control of antibiotic abuse as well as the mechanisms underlying the transfer of antibiotic genes (ARGs) among microbiota naturally occurring in the environment. Indeed, ARGs are not only confined to pathogenic bacteria, whose diffusion in the clinical field has aroused serious concerns, but are widespread in saprophytic bacterial communities such as those dominating the food industry. In particular, fresh dairy products can be considered a reservoir of Pseudomonas spp. resistome, potentially transmittable to consumers. Milk and fresh dairy cheeses products represent one of a few "hubs" where commensal or opportunistic pseudomonads frequently cohabit together with food microbiota and hazard pathogens even across their manufacturing processes. Pseudomonas spp., widely studied for food spoilage effects, are instead underestimated for their possible impact on human health. Recent evidences have highlighted that non-pathogenic pseudomonads strains (P. fluorescens, P. putida) are associated with some human diseases, but are still poorly considered in comparison to the pathogen P. aeruginosa. In addition, the presence of ARGs, that can be acquired and transmitted by horizontal genetic transfer, further increases their risk and the need to be deeper investigated. Therefore, this review, starting from the general aspects related to the physiological traits of these spoilage microorganisms from fresh dairy products, aims to shed light on the resistome of cheese-related pseudomonads and their genomic background, current methods and advances in the prediction tools for MDR detection based on genomic sequences, possible implications for human health, and the affordable strategies to counteract MDR spread.

A review of the design and modification of lactoferricins and their derivatives

Lactoferricin (Lfcin), a multifunction short peptide with a length of 25 residues, is derived from the whey protein lactoferrin by acidic pepsin hydrolysis. It has potent nutritional enhancement, antimicrobial, anticancer, antiviral, antiparasitic, and anti-inflammatory activities. This review describes the research advantages of the above biological functions, with attention to the molecular design and modification of Lfcin. In this examination of design and modification studies, research on the identification of Lfcin active derivatives and crucial amino acid residues is also reviewed. Many strategies for Lfcin optimization have been studied in recent decades, but we mainly introduce chemical modification, cyclization, chimera and polymerization of this peptide. Modifications such as incorporation of D-amino acids, acetylation and/or amidation could effectively improve the activity and stability of these compounds. Due to their wide array of bio-functions and applications, Lfcins have great potential to be developed as biological agents with multiple functions involved with nutritional enhancement, as well as disease preventive and therapeutic effects.

Reduction of whey protein concentrate antigenicity by using a combined enzymatic digestion and ultrafiltration approach

The global interest in saving food resources is leading to recycle wasted-food materials to extract useful nutrients. In dairy industry, the recycling of whey proteins determines their utilization in the healthy-addressed foods, which, however, can cause immunological responses in allergic subjects. In this work, a whey protein concentrate (WPC) was alternatively hydrolyzed with pepsin, papain, trypsin and rennin in order to attenuate or abolish the β-lactoglobulin (BLG) antigenicity. The electrophoretic profiles of both pepsin and papain WPC hydrolysates proved the disappearance of the BLG band, even though a slight antigenicity was still found by ELISA. Pepsin hydrolysates, filtered through a 10-kDa cut-off membrane, did not produce immunological response. A deeper investigation carried out on pepsin digested and ultrafiltered samples by LC-MS/MS showed the disappearance of the immunoreactive BLG-fragment IVTQMKGLDIQKVAGTW. The remaining peptides, partially overlapped to major IgE binding epitopes, were not able to give immunoreactivity response. The combined WPC pepsin digestion with ultrafiltration confirmed to be a user-friendly strategy to reduce markedly the WPC antigenicity. The improvement of this two-steps process could be used to produce novel hypoallergenic infant food formulas.

Development of a Synbiotic Beverage Enriched with Bifidobacteria Strains and Fortified with Whey Proteins

The objective of this study was to develop a new synbiotic beverage evaluating the ability of some bifidobacteria strains to grow in this beverage which was fortified with whey proteins up to 20 g L^-1, and enriched with 10 g L^-1 of prebiotic inulin or resistant starch. The ability of Bifidobacterium strains to survive for 30 days at 4°C was evaluated in two synbiotic whey protein fortified beverages formulated with 2% of whey proteins and 1% of inulin or resistant starch. Microbial growth was significantly affected by the whey protein amount as well as by the kind of prebiotic fiber. Resistant starch promoted the growth of the Bifidobacterium pseudocatenulatum strain and its viability under cold storage, also conferring higher sensory scores. The development of this new functional beverage will allow to carry out in vivo trials in order to validate its pre- and probiotic effects.

Antimicrobial Activity of Lactoferrin-Related Peptides and Applications in Human and Veterinary Medicine

Antimicrobial peptides (AMPs) represent a vast array of molecules produced by virtually all living organisms as natural barriers against infection. Among AMP sources, an interesting class regards the food-derived bioactive agents. The whey protein lactoferrin (Lf) is an iron-binding glycoprotein that plays a significant role in the innate immune system, and is considered as an important host defense molecule. In search for novel antimicrobial agents, Lf offers a new source with potential pharmaceutical applications. The Lf-derived peptides Lf(1-11), lactoferricin (Lfcin) and lactoferrampin exhibit interesting and more potent antimicrobial actions than intact protein. Particularly, Lfcin has demonstrated strong antibacterial, anti-fungal and antiparasitic activity with promising applications both in human and veterinary diseases (from ocular infections to osteo-articular, gastrointestinal and dermatological diseases).

Efficacy of lactoferricin B in controlling ready-to-eat vegetable spoilage caused by Pseudomonas spp

The microbial content of plant tissues has been reported to cause the spoilage of ca. 30% of chlorine-disinfected fresh vegetables during cold storage. The aim of this work was to evaluate the efficacy of antimicrobial peptides in controlling microbial vegetable spoilage under cold storage conditions. A total of 48 bacterial isolates were collected from ready-to-eat (RTE) vegetables and identified as belonging to Acinetobacter calcoaceticus, Aeromonas media, Pseudomonas cichorii, Pseudomonas fluorescens, Pseudomonas jessenii, Pseudomonas koreensis, Pseudomonas putida, Pseudomonas simiae and Pseudomonas viridiflava species. Reddish or brownish pigmentation was found when Pseudomonas strains were inoculated in wounds on leaves of Iceberg and Trocadero lettuce and escarole chicory throughout cold storage. Bovine lactoferrin (BLF) and its hydrolysates (LFHs) produced by pepsin, papain and rennin, were assayed in vitro against four Pseudomonas spp. strains selected for their heavy spoiling ability. As the pepsin-LFH showed the strongest antimicrobial effect, subsequent experiments were carried out using the peptide lactoferricin B (LfcinB), well known to be responsible for its antimicrobial activity. LfcinB significantly reduced (P ≤ 0.05) spoilage by a mean of 36% caused by three out of four inoculated spoiler pseudomonads on RTE lettuce leaves after six days of cold storage. The reduction in the extent of spoilage was unrelated to viable cell density in the inoculated wounds. This is the first paper providing direct evidence regarding the application of an antimicrobial peptide to control microbial spoilage affecting RTE leafy vegetables during cold storage.

Pepsin-digested bovine lactoferrin prevents Mozzarella cheese blue discoloration caused by Pseudomonas fluorescens

The aim of this work was to check the efficacy of bovine lactoferrin hydrolyzed by pepsin (LFH) to prevent blue discoloration of Mozzarella cheese delaying the growth of the related spoilage bacteria. Among 64 Pseudomonas fluorescens strains, isolated from 105 Mozzarella samples, only ten developed blue discoloration in cold-stored Mozzarella cheese slices. When Mozzarella cheese samples from dairy were treated with LFH and inoculated with a selected P. fluorescens strain, no pigmentation and changes in casein profiles were found up to 14 days of cold storage. In addition, starting from day 5, the count of P. fluorescens spoiling strain was steadily ca. one log cycle lower than that of LFH-free samples. ESI-Orbitrap-based mass spectrometry analyses allowed to reveal the pigment leucoindigoidine only in the blue LFH-free cheese samples indicating that this compound could be considered a chemical marker of this alteration. For the first time, an innovative mild approach, based on the antimicrobial activity of milk protein hydrolysates, for counteracting blue Mozzarella event and controlling psychrotrophic pigmenting pseudomonads, is here reported.