Influence of Bovine Lactoferrin on the Growth of Listeria monocytogenes

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.

Bovine Lactoferrin can Decrease the In Vitro Biofilm Production and Show Synergy with Antibiotics Against Listeria and Escherichia coli Isolates

BACKGROUND

Bovine Lactoferrin (bLf) has been reported as antimicrobial, antiviral, immunomodulatory and anticancer protein. Escherichia coli and Listeria spp. are food-borne bacteria that can produce illness in human being and mammals, the emergent antimicrobial drug resistance has been reported in these pathogens.

OBJECTIVE

The aim for this study was to evaluate the bLf effect on in vitro biofilm production and the synergic effect of antibiotics on E. coli and Listeria isolates.

METHODS

E. coli and Listeria specimens were isolated from bovine carcasses and slaughterhouses surfaces, respectively. Biofilm formation was analyzed with or without bLf, incubated for 48 h and spectrophotometry, cell viability was analyzed by colony-forming unit (CFU) and the synergistic effect of bLf with ampicillin, oxytetracycline, and streptomycin was evaluated through the fractional concentration index (FCI).

RESULTS

Our results show that a low bLf concentration (0.8 μM) can diminish the in vitro biofilm production in Listeria isolates; also improves the in vitro oxytetracycline and streptomycin activity against E. coli, and ampicillin activity against Listeria isolates.

CONCLUSION

bLf can affect the biofilm production in Listeria isolates from slaughterhouses surfaces and shown synergic effect with ampicillin. Also has a synergic effect with oxytetracycline and streptomycin against E. coli isolates from bovine carcasses.

Short communication: Antimicrobial effect of lactoferrin and its amidated and pepsin-digested derivatives against Salmonella Enteritidis and Pseudomonas fluorescens

The antimicrobial effect of bovine lactoferrin (LF) and its amidated and pepsin-digested derivatives, at concentrations varying from 0.25 to 20 mg/mL, against 3 Salmonella Enteritidis strains and 3 Pseudomonas fluorescens strains was investigated. Lactoferrin showed its maximum antimicrobial effect at 10 mg/mL against the 3 Salmonella strains, with reductions ranging from 1.3 to 2.0 log units, and the 3 Pseudomonas strains, with reductions ranging from 1.8 to 5.4 log units. In the case of amidated LF, the maximum effect on the 3 Salmonella strains was recorded at 0.25 mg/mL, with reductions in the range of 0.8 to 1.2 log units, whereas it was recorded at 1 mg/mL for the 3 Pseudomonas strains, with reductions in the range of 4.4 to 6.0 log units. Pepsin-digested LF showed its maximum antimicrobial effect at 1 mg/mL against the 3 Salmonella strains, with reductions ranging from 2.6 to 3.4 log units, and at 20 mg/mL against the 3 Pseudomonas strains, with reductions ranging from 4.5 to 5.4 log units. It is worth noting the pronounced effect (reductions exceeding 2.5 log units) of a low (1 mg/mL) concentration of pepsin-digested LF, which is naturally formed in the gastrointestinal tract, on Salmonella and Pseudomonas strains. A highly significant inverse correlation was found between capsule polysaccharide levels of bacterial strains and their lethality in the presence of different concentrations of amidated lactoferrin.

Influence of desiccation on the sensitivity of Cronobacter spp. to lactoferrin or nisin in broth and powdered infant formula

Although outbreaks caused by Cronobacter spp. (Enterobacter sakazakii) are rare, infections by this organism have a case-fatality rate which may reach 80%. Powdered infant milk formula (PIMF) is considered a major source for human infection with Cronobacter spp. The organism has the capability to survive in dry environments for long periods (approximately 2 years). Current interest in the use of natural antimicrobials including lactoferrin (LF) and nisin has developed because of the desire for preservative-free food products. The objective of the present study was to evaluate the antimicrobial activity of bovine LF or nisin against undesiccated and desiccated Cronobacter spp. cells in 0.2% peptone water (PW) and reconstituted PIMF at different temperatures. In 0.2% PW, 2.5 mg/ml LF was able to inactivate 4 log(10) CFU/ml of undesiccated cells of Cronobacter spp. in 4 h at 37 degrees C but at lower temperatures, higher concentrations of LF as well as longer exposure were needed to achieve the same effect as at 37 degrees C. Similarly, the effect of nisin against undesiccated cells of Cronobacter spp. was concentration and temperature dependent in 0.2% PW. It was found that 1500 IU/ml caused a 4 log(10) CFU/ml reduction of undesiccated cells of Cronobacter spp. at 21 degrees C and 37 degrees C. Desiccated Cronobacter spp. cells in 0.2% PW were more sensitive to LF action than were undesiccated cells. A 4 log(10) CFU/ml reduction was obtained with 2.5 mg/ml LF after 1 h at 21 and 37 degrees C or 8 h at 10 degrees C. In contrast, desiccated cells of Cronobacter spp. were more resistant to nisin. Furthermore, neither LF nor nisin had detectable antimicrobial activity against desiccated or undesiccated Cronobacter spp. in reconstituted PIFM. Heating at 55 degrees C for 5 min with nisin in reconstituted PIFM did not enhance the antimicrobial activity of nisin. Unexpectedly, nisin appeared to protect Cronobacter spp. from the damaging effects of heat treatment. The reduced antimicrobial activity of LF and nisin in reconstituted PIMF was potentially explained by the higher concentration of Ca(2+), Mg(2+) and Fe(3+) in the latter.

Antibacterial activity of recombinant human lactoferrin from rice: effect of heat treatment

The antibacterial activity of recombinant human lactoferrin from rice (rhLF) compared with that of human milk lactoferrin (hLF) was evaluated against Escherichia coli O157:H7, Salmonella Enteritidis and Listeria monocytogenes. The hydrolysates of rhLF and hLF were found to be more active than native proteins against E. coli O157:H7, and their activity was independent of their iron saturation. The effect of different heat treatments on the antibacterial activity of apo-rhLF was studied and compared with hLF. We observed that an HTST pasteurization treatment did not affect the antimicrobial activity of lactoferrin against the pathogens studied. Furthermore, the activity of apo-rhLF and hLF against E. coli O157:H7 and L. monocytogenes in UHT milk and whey was assayed, finding a decrease in the number of bacteria, although lower than that observed in a broth medium. This study shows the similar antibacterial activity of rhLF and hLF which is important in order to consider the addition of rhLF as a supplement in special products.

Bactericidal activity of lactoferrin and its amidated and pepsin-digested derivatives against Pseudomonas fluorescens in ground beef and meat fractions

The antibacterial activity of lactoferrin (LF) and its amidated and pepsin-digested derivatives (AMILF and PDLF, respectively) against Pseudomonas fluorescens ATCC 948 in ground beef was investigated. LF, AMILF, and PDLF at 1 mg/ml decreased bacterial counts by 1.9, 6.4, and 3.5 log units, respectively, after 1 h at 30 degrees C when the assays were performed in distilled water, but their bactericidal activity disappeared when added at 1 mg/g to ground beef held for 24 h at 5 degrees C. To identify meat components responsible for the loss of bactericidal activity, ground beef was homogenized and separated into fractions of different molecular weights. When cations were removed (fraction > 1 kDa), the bactericidal activity of AMILF was completely restored, whereas the effectiveness of LF and PDLF remained 1.0 and 0.4 log units lower, respectively, than the results obtained in distilled water. EDTA at 5 mM greatly enhanced the bactericidal activity of the three antimicrobials at 1 mg/ml in meat homogenate and in the presence of 5 mM sodium bicarbonate completely restored the bactericidal activity. However, when 1 mg/g AMILF, 5 mM sodium bicarbonate, and increasing EDTA concentrations were added to inoculated ground beef, bacterial counts declined by only 0.2, 0.4, and1.2 log units in the presence of 8, 32, and 128 mM EDTA, respectively, after 24 h at 5 degrees C.

In vitro inhibition of food spoilage and foodborne pathogenic bacteria by essential oil and leaf extracts of Magnolia liliflora Desr

The aim of this study was to examine the chemical composition of the essential oil isolated from the floral parts of Magnolia liliflora Desr. by hydrodistillation, and to test the efficacy of essential oil and various leaf extracts against a diverse range of microorganisms comprising food spoilage and foodborne pathogenic bacteria. The chemical composition of essential oil was analyzed by GC-MS. It was determined that 52 compounds, which represented 78.07% of total oil, were present in the oil. The oil contained mainly levoxine (15.59%), methylcyclopropane (24.26%), 2-beta-pinene (5.3%), caryophyllene oxide (4.01%), and beta-caryophyllene (1.7%). The oil (1000 ppm/disc) and leaf extracts (1500 ppm/disc) exhibited promising antibacterial effects against the tested pathogens as a diameter of zones of inhibition (9 to 18 and 7 to 12 mm) and MIC values (125 to 1000 and 500 to 3000 microg/mL), respectively. Also, the oil had a potent detrimental effect on the viable count of the tested bacteria. The results obtained in this study support the role of essential oil and the leaf extracts derived from M. liliflora as a remarkable approach to inhibit the growth of food spoilage and foodborne pathogens.

Antimicrobial activity of lactoferrin against foodborne pathogenic bacteria incorporated into edible chitosan film

The objectives of this research were to develop and characterize edible chitosan film containing lactoferrin as a natural antimicrobial agent, and to investigate the combination effects of lactoferrin with lysozyme in chitosan film against the growth of Escherichia coli O157:H7 and Listeria monocytogenes. Chitosan films containing lactoferrin, lysozyme, or nisin were fabricated, and the antimicrobial concentrations were 0.5, 1, or 2 mg in a circular disc of chitosan film. Three concentrations of lactoferrin or EDTA (0.28, 0.56, or 1.12 mg per disc) were also incorporated into the chitosan film containing lysozyme to investigate the combination effects of lactoferrin. The water barrier properties of the chitosan films containing lactoferrin were characterized. The antimicrobial activities against E. coli O157:H7 and L. monocytogenes were determined using the agar diffusion assay and cell count assay. The chitosan films containing lactoferrin less than 1 mg per disc did not alter the water vapor permeability of the chitosan film. Although the film containing lysozyme exhibited significant antimicrobial activity, the incorporation of lactoferrin alone into chitosan film did not exhibit significant antimicrobial activity against both E. coli O157:H7 and L. monocytogenes. However, the combination of lactoferrin with lysozyme-containing chitosan film significantly decreased the growth of E. coli O157:H7, exhibiting a comparable effect to that of the combination of EDTA with lysozyme (P < 0.05). Furthermore, the combination of lactoferrin with lysozyme in chitosan film exhibited greater reduction in the growth of L. monocytogenes than did the combination EDTA with lysozyme, resulting in an approximate 3-log reduction.

On the role of breastfeeding in health promotion and the prevention of allergic diseases

Based on animal models, we specify the major role of different bioactive milk components known to participate significantly in neonatal health promotion and in protection against a large number of infectious diseases and the development of allergies and asthma.

Bovine whey proteins – Overview on their main biological properties

Whey, a liquid by-product, is widely accepted to contain many valuable constituents. These include especially proteins that possess important nutritional and biological properties – particularly with regard to promotion of health, as well as prevention of diseases and health conditions. Antimicrobial and antiviral actions, immune system stimulation, anticarcinogenic activity and other metabolic features have indeed been associated with such whey proteins, as α-lactalbumin, β-lactoglobulin, lactoferrin, lactoperoxidase, and bovine serum albumin. The most important advances reported to date pertaining to biological properties of whey proteins are reviewed in this communication.

The synergistic effect of nisin and lactoferrin on the inhibition of Listeria monocytogenes and Escherichia coli O157:H7

AIMS

The goal of this study was to determine whether nisin and lactoferrin would act synergistically to inhibit the growth of Listeria monocytogenes and Escherichia coli O157:H7.

METHODS AND RESULTS

Lactoferrin and nisin separately or in combination were suspended in peptone yeast glucose broth and following inoculation with L. monocytogenes or E. coli O157:H7 growth inhibition of each pathogen was determined. At 1000 microg ml(-1) lactoferrin L. monocytogenes was effectively inhibited. However, E. coli O157:H7 initially was inhibited and then grew to cell density similar to the control. A combination of 500 microg ml(-1) of lactoferrin and 250 IU ml(-1) of nisin effectively inhibited the growth of E. coli O157:H7, whereas, 250 microg ml(-1) of lactoferrin and 10 IU ml(-1) of nisin were inhibitory to L. monocytogenes.

CONCLUSIONS

The results suggest that lactoferrin and nisin act synergistically to inhibit the growth of L. monocytogenes and E. coli O157:H7.

SIGNIFICANCE AND IMPACT OF THE STUDY

Natural preservatives that are active against gram-positive and gram-negative pathogens are desirable to the food industry and consumers. This study demonstrates that lactoferrin and nisin work synergistically reducing the levels required independently inhibiting growth of two major foodborne pathogens. Previous reported results indicated a low level of antimicrobial activity; however, this work was not performed in low divalent cation concentration media. It has been suggested that nondivalent cation-limiting medium such as trypticase soy broth (TSB), can reduce or completely eliminate the inhibitory activity. Further knowledge of these interactions can increase the understanding of the antimicrobial activity of lactoferrin. This should make the use of these compounds by industry more attractive.

Milk biologically active components as nutraceuticals: review

Milk contains components that provide critical nutritive elements, immunological protection, and biologically active substances to both neonates and adults. Milk proteins are currently the main source of a range of biologically active peptides. Concentrates of these peptides are potential health-enhancing nutraceuticals for food and pharmaceutical applications. Several bioactive peptides may be used as nutraceuticals, for example, in the treatment of diarrhea, hypertension, thrombosis, dental diseases, as well as mineral malabsorption, and immunodeficiency. Minor whey proteins, such as lactoferrin, lactoperoxidase, lysozyme, and immunoglobulins, are considered antimicrobial proteins. Milk also contains some natural bioactive substances. These include oligosaccharides, fucosylated oligosaccharides, hormones, growth factors, mucin, gangliosides, and endogenous peptides, which are present in milk at secretion. Most of the claimed physiological properties of milk bioactive components have been carried out in vitro or in animal model systems, and these hypothesized properties remain to be proven in humans. Whether these milk bioactive components will replace drugs entirely in the immediate future is still unclear, but the increasing appreciation of "drug foods" or nutraceuticals plays a complementary rather than a substitutional role to the synthetic pharmacological drugs.

Apoptotic death of Listeria monocytogenes-infected human macrophages induced by lactoferricin B, a bovine lactoferrin-derived peptide

Listeria monocytogenes, an intracellular facultative food-borne pathogen, was reported to induce apoptosis in vitro and in vivo in a variety of cell types with the exception of murine macrophages. These cells represent the predominant compartment of bacterial multiplication and die as a result of necrosis. In this study we showed that human non-activated and IFN-gamma-activated macrophagic-like (THP-1) cells infected with L. monocytogenes, mainly die by necrosis rather than by an apoptotic process. Two natural products derived from bovine milk, lactoferrin and its derivative peptide lactoferricin B, are capable of regulating the fate of infected human macrophages. Bovine lactoferrin treatment of macrophages protects them from L. monocytogenes-induced death whereas lactoferricin B, its derivative peptide, determines a shifting of the equilibrium from necrosis to apoptosis.

Antimicrobial edible films and coatings

Increasing consumer demand for microbiologically safer foods, greater convenience, smaller packages, and longer product shelf life is forcing the industry to develop new food-processing, cooking, handling, and packaging strategies. Nonfluid ready-to-eat foods are frequently exposed to postprocess surface contamination, leading to a reduction in shelf life. The food industry has at its disposal a wide range of nonedible polypropylene- and polyethylene-based packaging materials and various biodegradable protein- and polysaccharide-based edible films that can potentially serve as packaging materials. Research on the use of edible films as packaging materials continues because of the potential for these films to enhance food quality, food safety, and product shelf life. Besides acting as a barrier against mass diffusion (moisture, gases, and volatiles), edible films can serve as carriers for a wide range of food additives, including flavoring agents, antioxidants, vitamins, and colorants. When antimicrobial agents such as benzoic acid, sorbic acid, propionic acid, lactic acid, nisin, and lysozyme have been incorporated into edible films, such films retarded surface growth of bacteria, yeasts, and molds on a wide range of products, including meats and cheeses. Various antimicrobial edible films have been developed to minimize growth of spoilage and pathogenic microorganisms, including Listeria monocytogenes, which may contaminate the surface of cooked ready-to-eat foods after processing. Here, we review the various types of protein-based (wheat gluten, collagen, corn zein, soy, casein, and whey protein), polysaccharide-based (cellulose, chitosan, alginate, starch, pectin, and dextrin), and lipid-based (waxes, acylglycerols, and fatty acids) edible films and a wide range of antimicrobial agents that have been or could potentially be incorporated into such films during manufacture to enhance the safety and shelf life of ready-to-eat foods.

Lactoferricin influences early events of Listeria monocytogenes infection in THP-1 human macrophages

Bovine lactoferrin (BLf) and its derivative peptide lactoferricin B (LfcinB) are known for their antimicrobial activity towards several pathogens, includingListeria monocytogenes, a food-borne Gram-positive invasive bacterium that infects a wide variety of host cells, including professional phagocytes. To add further information on the antibacterial effects of these compounds, the influence of BLf, LfcinB and the antimicrobial centre of LfcinB, the hexapeptide LfcinB4–9, on the invasive behaviour ofL. monocytogeneswas analysed in IFN-γ-activated human macrophagic cells (THP-1). Significant inhibition of bacterial entry in THP-1 cells was observed at LfcinB concentrations that were unable to produce any bacteriostatic or bactericidal effect, compared with BLf and LfcinB4–9peptide. This inhibition occurred when LfcinB was incubated during the bacterial infection step and was not due only to competition for common glycosaminoglycan receptors. Assays performed through a temperature shift from 4 to 37 °C showed that inhibition of invasion took place at an early post-adsorption step, although an effect on a different step of intracellular infection could not be ruled out.

Enhancement of nisin, lysozyme, and monolaurin antimicrobial activities by ethylenediaminetetraacetic acid and lactoferrin

A microtiter plate assay was employed to systematically assess the interaction between ethylenediaminetetraacetic acid (EDTA) or lactoferrin and nisin, lysozyme, or monolaurin against strains of Listeria monocytogenes, Escherichia coli, Salmonella enteritidis, and Pseudomonas fluorescens. Low levels of EDTA acted synergistically with nisin and lysozyme against L. monocytogenes but EDTA and monolaurin interacted additively against this microorganism. EDTA synergistically enhanced the activity of nisin, monolaurin, and lysozyme in tryptic soy broth (TSB) against two enterohemorrhagic E. coli strains. In addition, various combinations of nisin, lysozyme, and monolaurin with EDTA were bactericidal to some gram-negative bacteria whereas none of the antimicrobials alone were bactericidal. Lactoferrin alone (2000 microg ml(-1)) did not inhibit any of the bacterial strains, but did enhance nisin activity against both L. monocytogenes strains. Lactoferrin in combination with monolaurin inhibited growth of E. coli O157:H7 but not E. coli O104:H21. While lactoferrin combined with nisin or monolaurin did not completely inhibit growth of the gram-negative bacteria, there was some growth inhibition. All combinations of EDTA or lactoferrin with antimicrobials were less effective in 2% fat UHT milk than in TSB. S. enteritidis and P. fluorescens strains were consistently more resistant to antimicrobial combinations. Resistance may be due to differences in the outer membrane and/or LPS structure.

Antibacterial activity of pepsin-digested lactoferrin on foodborne pathogens in buffered broth systems and ultra-high temperature milk with EDTA

AIMS

To evaluate the antimicrobial activity in peptone yeast extract glucose (PYG) broth and ultra-high temperature (UHT) milk of bovine lactoferrin hydrolysate (LFH) with pepsin against the foodborne pathogens Salmonella Stanley, Escherichia coli, Listeria monocytogenes and Staphylococcus aureus.

METHODS AND RESULTS

The LFH was suspended in PYG and the minimum inhibitory concentration for each pathogen determined. The LFH was also suspended in UHT milk adjusted to pH 4 or 7, samples incubated at 4 or 35 degrees C and the change in bacterial cell population determined. Experiments in UHT milk were conducted using L. monocytogenes and E. coli O157:H7. At pH 4 LFH reduced the population of E. coli O157:H7 and L. monocytogenes by approx. 2 log; however, only E. coli O157:H7 was inhibited in samples adjusted to pH 7. The addition of EDTA (10 mg ml(-1)) to UHT milk supplemented with LFH did not markedly influence the growth of E. coli O157:H7 or L. monocytogenes.

CONCLUSIONS

The results suggest that, under low pH and refrigeration conditions, LFH can limit the growth or reduce the population of pathogenic bacteria in a dairy product.

SIGNIFICANCE AND IMPACT OF THE STUDY

Natural preservatives that are active against Gram-negative and Gram-positive bacteria are desirable to the food industry. This study demonstrates that LFH is effective in a complex food system. Moreover, the LFH used was not purified, making its use by industry more attractive.

Effects of milk-derived bioactives: an overview

Milk contains various components with physiological functionality. Peptides derived from caseins and whey proteins including opioid peptides, antihypertensive peptides, casein phosphopeptides, alpha- and beta-lactorphins and albutensin have been shown to possess various bioactive properties. This review considers an overview of the bioactive components in milk proteins and whey and their physiological function.

Preparation of apolactoferrin with a very low iron saturation

Iron(III) removal from lactoferrin by an iron(III)-chelating resin with immobilized 3-hydroxy-2-methyl-4(1H)-pyridinone ligands was studied at physiological pH in the presence of citrate. The resin had a marked effect on the extent of iron removal. By using the iron(III)-chelating resin, removal of iron from lactoferrin was nearly complete in < 24 h. Apolactoferrin with 4% iron saturation could be prepared conveniently from 100% or from 18% iron-saturated lactoferrin under mild conditions without affecting the iron-binding capacity of the protein. The iron saturation of the obtained apolactoferrin was much lower than that of the apolactoferrin prepared by reported methods.

Iron removal from milk and other nutrient media with a chelating resin

A water-insoluble iron(III)-chelating resin was used to study iron removal from milk and other nutrient media. Seventy to 85% of the iron could be removed from wine and beer with the resin, which was a crosslinked copolymer of 1-(beta-acrylamidoethyl)-3-hydroxy-2-methyl-4(1H)- pyridinone and N,N-dimethylacrylamide. Iron removal from milk was dependent on the pH of milk and on the concentration of soluble chelators added. Under the same conditions as used for the removal of iron from wine and beer, only 11 to 19% of the iron could be removed from milk. However, in combination with water-soluble chelators, the resin removed 60 to 75% of the iron from the milk. Preliminary results showed that the growth of spores of Clostridium tyrobutyricum in the treated milk was reduced. Moreover, addition of the resin and sodium bicarbonate to the milk completely inhibited the growth of the spores.

Psychrotrophs in dairy products: their effects and their control

Health concerns and technological effects of psychrotrophic bacteria in dairy products are reviewed, as well as methods to control their presence and development. The various Gram-negative and Gram-positive psychrotrophic species are listed and, with respect to pathogenic psychrotrophs, emphasis is given on Listeria monocytogenes, Yersinia enterocolitica, and Bacillus cereus. The influence of psychrotrophic bacteria on the quality of raw milk, pasteurized and UHT milks, butter, ice cream, cheese, and powders is examined. Public health considerations of Listeria monocytogenes, Yersinia enterocolitica, and Bacillus cereus of these various dairy products are also presented. Methods that can be used to eliminate or control the development of psychrotropic bacteria include low or high temperatures, chemicals, gases, the lactoperoxidase system, lactic acid bacteria, microfiltration, bactofugation, lactoferrin-related proteins, sanitation, flavors, and naturally occurring spore germinants.