Biocontrol of Listeria monocytogenes in a meat model using a combination of a bacteriocinogenic strain with curing additives

Genomic Characterization of Piscicolin CM22 Produced by Carnobacterium maltaromaticum CM22 Strain Isolated from Salmon (Salmo salar)

Carnobacterium maltaromaticum is a species of lactic acid bacteria (LAB) that has been isolated from various natural environments. It is well-known for producing a diverse spectrum of bacteriocins with potential biotechnological applications. In the present study, a new psychrotolerant strain of C. maltaromaticum CM22 is reported, isolated from a salmon gut sample and producing a variant of the bacteriocin piscicolin 126 that has been named piscicolin CM22. After identification by 16S rRNA gene, this strain has been genomically characterized by sequencing and assembling its complete genome. Moreover, its bacteriocin was purified and characterized. In vitro tests demonstrated that both the strain and its bacteriocin possess antimicrobial activity against several Gram-positive bacteria of interest in human and animal health, such as Listeria monocytogenes, Clostridium perfringens, or Enterococcus faecalis. However, this bacteriocin did not produce any antimicrobial effect on Gram-negative species. The study of its genome showed the genetic structure of the gene cluster that encodes the bacteriocin, showing a high degree of homology to the gene cluster of piscicolin 126 described in other C. maltaromaticum. Although more studies are necessary concerning its functional properties, this new psychrotolerant strain C. maltaromaticum CM22 and its bacteriocin could be considered an interesting candidate with potential application in agri-food industry.

Beyond Conventional Meat Preservation: Saddling the Control of Bacteriocin and Lactic Acid Bacteria for Clean Label and Functional Meat Products

Advancements in food science and technology have paved the way for the development of natural antimicrobial compounds to ensure the safety and quality of meat and meat products. Among these compounds, bacteriocin produced by lactic acid bacteria has gained considerable scientific attention for its ability to preserve the healthy properties of meat while preventing spoilage. This natural preservative is seen as a pioneering tool and a potent alternative to chemical preservatives and heat treatment, which can have harmful effects on the nutritional and sensory qualities of meat. Bacteriocin produced by lactic acid bacteria can be used in various forms, including as starter/protective cultures for fermented meats, purified or partially purified forms, loaded in active films/coatings, or established in encapsulate systems. This review delves into the downstream purification schemes of LAB bacteriocin, the elucidation of their characteristics, and their modes of action. Additionally, the application of LAB bacteriocins in meat and meat products is examined in detail. Overall, the use of LAB bacteriocins holds immense potential to inspire innovation in the meat industry, reducing the dependence on harmful chemical additives and minimizing the adverse effects of heat treatment on nutritional and sensory qualities. This review provides a comprehensive understanding of the potential of bacteriocin produced by lactic acid bacteria as a natural and effective meat preservative.

Inactivation of Foodborne Pathogens by Lactiplantibacillus Strains during Meat Fermentation: Kinetics and Mathematical Modelling

This study examined the effect of beef fermentation with Lactiplantibacillus paraplantarum (L) PTCC 1965, Lactiplantibacillus (L) plantarum subsp. plantarum PTCC 1745, and Lactiplantibacillus (L) pentosus PTCC 1872 bacteria on the growth of pathogenic bacteria, including Salmonella (S) Typhi PTCC 1609 and Staphylococcus (S) aureus PTCC 1826. The growth of lactic acid bacteria (LAB) and the effect of fermentation on pathogenic bacteria were studied using Weibull: biphasic linear and competitive models. The results showed that the rate of pH reduction was lower in the early stages and increased as the microbial population grew. The α parameter was lower for L. plantarum subsp. plantarum compared to L. paraplantarum and L. pentosus. The comparison of the α parameter for bacterial growth and pH data showed that the time interval required to initiate the rapid growth phase of the bacteria was much shorter than that for the rapid pH reduction phase. The pH value had a 50% greater effect on the inactivation of S. Typhi when compared to the samples containing L. plantarum subsp. plantarum and L. pentosus. The same parameter was reported to be 72% for the inactivation of St. aureus. In general, during the fermentation process, LAB strains caused a decrease in pH, and as a result, reduced the growth of pathogens, which improves consumer health and increases the food safety of fermented meat.

Research Progress of Nitrite Metabolism in Fermented Meat Products

Nitrite is a common color and flavor enhancer in fermented meat products, but its secondary amines may transfer to the carcinogen N-nitrosamines. This review focuses on the sources, degradation, limitations, and alteration techniques of nitrite. The transition among NO3− and NO2−, NH4+, and N2 constitutes the balance of nitrogen. Exogenous addition is the most common source of nitrite in fermented meat products, but it can also be produced by contamination and endogenous microbial synthesis. While nitrite is degraded by acids, enzymes, and other metabolites produced by lactic acid bacteria (LAB), four nitrite reductase enzymes play a leading role. At a deeper level, nitrite metabolism is primarily regulated by the genes found in these bacteria. By incorporating antioxidants, chromogenic agents, bacteriostats, LAB, or non-thermal plasma sterilization, the amount of nitrite supplied can be decreased, or even eliminated. Finally, the aim of producing low-nitrite fermented meat products is expected to be achieved.

Bioprotective Lactic Acid Bacteria and Lactic Acid as a Sustainable Strategy to Combat Escherichia coli O157:H7 in Meat

Human infection by Enterohemorrhagic Escherichia coli (EHEC) constitutes a serious threat to public health and a major concern for the meat industry. Presently, consumers require safer/healthier foods with minimal chemical additives, highlighting the need for sustainable solutions to limit and prevent risks. This work evaluated the ability of two antagonistic lactic acid bacteria (LAB) strains, Lactiplantibacillus plantarum CRL681 and Enterococcus mundtii CRL35, and their combination in order to inhibit EHEC in beef (ground and vacuum sealed meat discs) at 8 °C during 72 h. The effect of lower lactic acid (LA) concentrations was evaluated. Meat color was studied along with how LAB strains interfere with the adhesion of Escherichia coli to meat. The results indicated a bacteriostatic effect on EHEC cells when mixed LAB strains were inoculated. However, a bactericidal action due to a synergism between 0.6% LA and LAB occurred, producing undetectable pathogenic cells at 72 h. Color parameters (a*, b* and L*) did not vary in bioprotected meat discs, but they were significantly modified in ground meat after 24 h. In addition, LAB strains hindered EHEC adhesion to meat. The use of both LAB strains plus 0.6% LA, represents a novel, effective and ecofriendly strategy to inactivate EHEC in meat.

Lactic Acid Bacteria and Bacteriocins: Novel Biotechnological Approach for Biopreservation of Meat and Meat Products

Meat and meat products are perishable in nature, and easily susceptible to microbial contamination and chemical deterioration. This not only results in an increased risk to health of consumers, but also causes economic loss to the meat industry. Some microorganisms of the lactic acid bacteria (LAB) group and their ribosomal-synthesized antimicrobial peptides-especially bacteriocins-can be used as a natural preservative, and an alternative to chemical preservatives in meat industry. Purified or partially purified bacteriocins can be used as a food additive or incorporated in active packaging, while bacteriocin-producing cells could be added as starter or protective cultures for fermented meats. Large-scale applications of bacteriocins are limited, however, mainly due to the narrow antimicrobial spectrum and varying stability in different food matrixes. To overcome these limitations, bioengineering and biotechnological techniques are being employed to combine two or more classes of bacteriocins and develop novel bacteriocins with high efficacy. These approaches, in combination with hurdle concepts (active packaging), provide adequate safety by reducing the pathogenicity of spoilage microorganisms, improving sensory characteristics (e.g., desirable flavor, texture, aroma) and enhancing the shelf life of meat-based products. In this review, the biosynthesis of different classes of LAB bacteriocins, their mechanism of action and their role in the preservation of meats and meat products are reviewed.

Novel Approaches to Environmental Monitoring and Control of Listeria monocytogenes in Food Production Facilities

Listeria monocytogenes is a serious public health hazard responsible for the foodborne illness listeriosis. L. monocytogenes is ubiquitous in nature and can become established in food production facilities, resulting in the contamination of a variety of food products, especially ready-to-eat foods. Effective and risk-based environmental monitoring programs and control strategies are essential to eliminate L. monocytogenes in food production environments. Key elements of the environmental monitoring program include (i) identifying the sources and prevalence of L. monocytogenes in the production environment, (ii) verifying the effectiveness of control measures to eliminate L. monocytogenes, and (iii) identifying the areas and activities to improve control. The design and implementation of the environmental monitoring program are complex, and several different approaches have emerged for sampling and detecting Listeria monocytogenes in food facilities. Traditional detection methods involve culture methods, followed by confirmation methods based on phenotypic, biochemical, and immunological characterization. These methods are laborious and time-consuming as they require at least 2 to 3 days to obtain results. Consequently, several novel detection approaches are gaining importance due to their rapidness, sensitivity, specificity, and high throughput. This paper comprehensively reviews environmental monitoring programs and novel approaches for detection based on molecular methods, immunological methods, biosensors, spectroscopic methods, microfluidic systems, and phage-based methods. Consumers have now become more interested in buying food products that are minimally processed, free of additives, shelf-stable, and have a better nutritional and sensory value. As a result, several novel control strategies have received much attention for their less adverse impact on the organoleptic properties of food and improved consumer acceptability. This paper reviews recent developments in control strategies by categorizing them into thermal, non-thermal, biocontrol, natural, and chemical methods, emphasizing the hurdle concept that involves a combination of different strategies to show synergistic impact to control L. monocytogenes in food production environments.

Strategies for Biocontrol of Listeria monocytogenes Using Lactic Acid Bacteria and Their Metabolites in Ready-to-Eat Meat- and Dairy-Ripened Products

Listeria monocytogenes is one of the most important foodborne pathogens. This microorganism is a serious concern in the ready-to-eat (RTE) meat and dairy-ripened products industries. The use of lactic acid bacteria (LAB)-producing anti-L. monocytogenes peptides (bacteriocins) and/or lactic acid and/or other antimicrobial system could be a promising tool to control this pathogen in RTE meat and dairy products. This review provides an up to date about the strategies of use of LAB and their metabolites in RTE meat products and dairy foods by selecting the most appropriate strains, by analysing the mechanism by which they inhibit L. monocytogenes and methods of effective application of LAB, and their metabolites in these kinds of products to control this pathogen throughout the processing and storage. The selection of LAB with anti-L. monocytogenes activity allows to dispose of effective strains in meat and dairy-ripened products, achieving reductions form 2–5 logarithmic cycles of this pathogen throughout the ripening process. The combination of selected LAB strains with antimicrobial compounds, such as acid/sodium lactate and other strategies, as the active packaging could be the next future innovation for eliminating risk of L. monocytogenes in meat and dairy-ripened products.

Application of lactic acid bacteria for the biopreservation of meat products: A systematic review

The increasing concern of consumers about food quality and safety and their rejection of chemical additives has promoted the breakthrough of the biopreservation field and the development of studies on the use of beneficial bacteria and their metabolites as potential natural antimicrobials for shelf life extension and enhanced food safety. Control of foodborne pathogens in meat and meat products represents a serious challenge for the food industry which can be addressed through the intelligent use of bio-compounds or biopreservatives. This article aims to systematically review the available knowledge about biological strategies based on the use of lactic acid bacteria to control the proliferation of undesirable microorganisms in different meat products. The outcome of the literature search evidenced the potential of several strains of lactic acid bacteria and their purified or semi-purified antimicrobial metabolites as biopreservatives in meat products for achieving longer shelf life or inhibiting spoilage and pathogenic bacteria, especially when combined with other technologies to achieve a synergistic effect.

Use of Starter Cultures in Foods from Animal Origin to Improve Their Safety

Starter cultures can be defined as preparations with a large number of cells that include a single type or a mixture of two or more microorganisms that are added to foods in order to take advantage of the compounds or products derived from their metabolism or enzymatic activity. In foods from animal origin, starter cultures are widely used in the dairy industry for cheese, yogurt and other fermented dairy products, in the meat industry, mainly for sausage manufacture, and in the fishery industry for fermented fish products. Usually, microorganisms selected as starter culture are isolated from the native microbiota of traditional products since they are well adapted to the environmental conditions of food processing and are responsible to confer specific appearance, texture, aroma and flavour characteristics. The main function of starter cultures used in food from animal origin, mainly represented by lactic acid bacteria, consists in the rapid production of lactic acid, which causes a reduction in pH, inhibiting the growth of pathogenic and spoilage microorganisms, increasing the shelf-life of fermented foods. Also, production of other metabolites (e.g., lactic acid, acetic acid, propionic acid, benzoic acid, hydrogen peroxide or bacteriocins) improves the safety of foods. Since starter cultures have become the predominant microbiota, it allows food processors to control the fermentation processes, excluding the undesirable flora and decreasing hygienic and manufacturing risks due to deficiencies of microbial origin. Also, stater cultures play an important role in the chemical safety of fermented foods by reduction of biogenic amine and polycyclic aromatic hydrocarbons contents. The present review discusses how starter cultures contribute to improve the microbiological and chemical safety in products of animal origin, namely meat, dairy and fishery products.

Antimicrobial Potential of Food Lactic Acid Bacteria: Bioactive Peptide Decrypting from Caseins and Bacteriocin Production

Lactic acid bacteria (LAB) potential in the food industry and in the biotechnological sector is a well-established interest. LAB potential in counteracting especially food-borne infections has received growing attention, but despite being a road full of promises is yet poorly explored. Furthermore, the ability of LAB to produce antimicrobial compounds, both by ribosomal synthesis and by decrypting them from proteins, is of high value when considering the growing impact of multidrug resistant strains. The antimicrobial potential of 14 food-derived lactic acid bacteria strains has been investigated in this study. Among them, four strains were able to counteract Listeria monocytogenes growth: Lactococcus lactis SN12 and L. lactis SN17 by high lactic acid production, whereas L. lactis 41FLL3 and Lactobacillus sakei I151 by Nisin Z and Sakacin P production, respectively. Strains Lactococcus lactis MG1363, Lactobacillus rhamnosus 17D10 and Lactobacillus helveticus 4D5 were tested and selected for their potential attitude to hydrolyze caseins. All the strains were able to release bioactive peptides with already known antimicrobial, antihypertensive and opioid activities. These features render these strains or their bioactive molecules suitable for use in food as biocontrol agents, or as nutraceutical supplements to treat mild disorders such as moderate hypertension and children insomnia. These results highlight once again that LAB potential in ensuring food safety, food nutraceutical value and ultimately in favoring human health is still underexplored and underexploited.

Bacillus amyloliquefaciens ALB65 Inhibits the Growth of Listeria monocytogenes on Cantaloupe Melons

Listeria monocytogenes is a foodborne pathogen that causes high rates of hospitalization and mortality in people infected. Contamination of fresh, ready to eat produce by this pathogen is especially troubling because of the ability of this bacterium to grow on produce under refrigeration temperatures. In this study, we created a library of over 8,000 plant phyllosphere-associated bacteria and screened them for the ability to inhibit the growth of L. monocytogenes in an in vitro fluorescence-based assay. One isolate, later identified as Bacillus amyloliquefaciens ALB65, was able to inhibit the fluorescence of L. monocytogenes by >30-fold in vitro. B. amyloliquefaciens ALB65 was also able to grow, persist, and reduce the growth of L. monocytogenes by >1.5 log CFU on cantaloupe melon rinds inoculated with 5 × 10³ CFU at 30°C and was able to completely inhibit its growth at temperatures below 8°C. DNA sequence analysis of the B. amyloliquefaciens ALB65 genome revealed six gene clusters that are predicted to encode genes for antibiotic production; however, no plant or human virulence factors were identified. These data suggest that B. amyloliquefaciens ALB65 is an effective and safe biological control agent for the reduction of L. monocytogenes growth on intact cantaloupe melons and possibly other types of produce.IMPORTANCE Listeria monocytogenes is estimated by the Centers for Disease Control and Prevention and the U.S. Food and Drug Administration to cause disease in approximately 1,600 to 2,500 people in the United States every year. The largest known outbreak of listeriosis in the United States was associated with intact cantaloupe melons in 2011, resulting in 147 hospitalizations and 33 deaths. In this study, we demonstrated that Bacillus amyloliquefaciens ALB65 is an effective biological control agent for the reduction of L. monocytogenes growth on intact cantaloupe melons under both pre- and postharvest conditions. Furthermore, we demonstrated that B. amyloliquefaciens ALB65 can completely inhibit the growth of L. monocytogenes during cold storage (<8°C).

Antimicrobials for food and feed; a bacteriocin perspective

Bacteriocins are natural antimicrobials that have been consumed via fermented foods for millennia and have been the focus of renewed efforts to identify novel bacteriocins, and their producing microorganisms, for use as food biopreservatives and other applications. Bioengineering bacteriocins or combining bacteriocins with multiple modes of action (hurdle approach) can enhance their preservative effect and reduces the incidence of antimicrobial resistance. In addition to their role as food biopreservatives, bacteriocins are gaining credibility as health modulators, due to their ability to regulate the gut microbiota, which is strongly associated with human wellbeing. Indeed the strengthening link between the gut microbiota and obesity make bacteriocins ideal alternatives to Animal Growth Promoters (AGP) in animal feed also. Here we review recent advances in bacteriocin research that will contribute to the development of functional foods and feeds as a consequence of roles in food biopreservation and human/animal health.

Carnobacterium maltaromaticum as bioprotective culture in vitro and in cooked ham

The bioprotective effects of Carnobacterium maltaromaticum (CM) strains were assessed in vitro and in sliced cooked ham. CM strains were tested in vitro against Listeria monocytogenes (LM), Escherichia coli O157:H7 (EC) and Salmonella Typhimurium (ST). In vitro effect was evaluated using co-culture (with and without EDTA) and cell-free supernatant (CFS). CFS was tested by agar well diffusion and minimum inhibitory concentration. In cooked ham, the inhibitory effect of CM on L. innocua (LI) and on the physicochemical parameters were evaluated for 7 days at 4 °C. In co-cultures at -1 °C and 4 °C, all CM isolates inhibited LM. A slight inhibition was observed against the Gram-negative bacteria with the addition of EDTA. CFS did not show inhibitory effect under the studied conditions. In cooked ham, CM inhibited LI growth and did not affect the physicochemical parameters of the product during storage. CM strains show potential to be used as bioprotective cultures in cold-stored cooked ham and improve its safety.

Physiological and proteomic response of Escherichia coli O157:H7 to a bioprotective lactic acid bacterium in a meat environment

The enterohemorrhagic Escherichia (E.) coli (EHEC) is a pathogen of great concern for public health and the meat industry all over the world. The high economic losses in meat industry and the high costs of the illness highlight the necessity of additional efforts to control this pathogen. Previous studies have demonstrated the inhibitory activity of Enterococcus mundtii CRL35 towards EHEC, showing a specific proteomic response during the co-culture. In the present work, additional studies of the EHEC-Ent. mundtii interaction were carried out: i) differential protein expression of E. coli O157:H7 NCTC12900 growing in co-culture with Ent. mundtii in a meat environment, ii) the reciprocal influence between these two microorganisms in the adhesion to extracellular matrix (ECM) proteins and iii) the possible induction of the phage W933, coding for Shiga toxin (Stx1), by Ent. mundtii CRL35. Proteomic analysis showed a significant repression of a number of E. coli NCTC12900 proteins in co-culture respect to its single culture, these mostly related to the metabolism and transport of amino acids and nucleotides. On the other hand, statistically significant overexpression of EHEC proteins involved in stress, energy production, amino acid metabolism and transcription was observed at 30 h respect to 6 h when EHEC grew in co-culture. Data are available via ProteomeXchange with identifier PXD014588. Besides, EHEC showed a decreased adhesion capacity to ECM proteins in the presence of the bioprotective strain. Finally, Ent. mundtii CRL35 did not induce the lytic cycle of W933 bacteriophage, thus indicating its potential safe use for eliminating this pathogen. Overall, this study expands the knowledge of EHEC- Ent. mundtii CRL35 interaction in a meat environment, which will certainly contribute to find out effective biological strategies to eliminate this pathogen.

A peptidomic approach of meat protein degradation in a low-sodium fermented sausage model using autochthonous starter cultures

Fermented sausage technology is currently compromised in decreasing the addition of NaCl. Use of starter cultures with peptidogenic potential could be a valuable strategy that can mask or hide off flavors produced by the use of NaCl substituents. In the present work, the peptidogenic potential of four lactic acid bacteria species was evaluated in a low-sodium beaker sausage (BS) model. Using a peptidomic approach, a total of 86 low molecular weight (LMW) peptides were accurately identified, mostly derived from myofibrillar proteins, especially actin, which generated 53 peptides. The BS inoculated with L. curvatus CRL705 generated 56 LMW peptides, followed by Enterococcus (E.) mundtii CRL35 with 43 peptides. In addition, BS inoculated with Lactobacillus (L.) plantarum and with L. sakei produced higher amino acid amounts over time as compared to the rest of BS models, highlighting the importance of both, time and sample effect on the overall free amino acid generation. The presence of each LAB strain in BS models generated a unique profile of small peptides and amino acids that could serve as a distinctive biochemical trait to differentiate specific fermented products. According to these results, E. mundtii and L. sakei, which are compatible between them, are proposed as the most efficiently adapted to low-sodium conditions. The use of selected strains during the processing of low-sodium fermented sausages could have a positive effect on the production of small peptides and free amino acids.