Antimicrobial effect of nisin in processed cheese - Quantification of residual nisin by LC-MS/MS and development of new growth and growth boundary model for Listeria monocytogenes

The effect of antimicrobial peptide-added adhesive resins on shear bond strength and the adhesive remnant index of orthodontic brackets

OBJECTIVES

The aim of this study was to evaluate the effect of in-vivo produced Nisin which is an antimicrobial peptide (AMP) added to adhesive resin on shear bond strength (SBS) and the adhesive remnant index (ARI) of orthodontic brackets.

METHODS

Bacterial AMP was produced by fermentation and the ideal AMP/Bond concentration and antimicrobial efficacy of the mixture were tested. To evaluate the SBS and ARI scores of AMP-added adhesive resins, 80 maxillary premolar teeth extracted for orthodontic purposes were used and randomly assigned into 2 groups (n = 40). Group 1: Control Group (teeth bonded with standard adhesive resin); Group 2: Experimental Group (teeth bonded with AMP-added adhesive resin). Statistical analysis was performed using the SPSS package program and applying the Mann-Whitney U and Fisher's exact tests. P < 0.05 was considered as statistically significant.

RESULTS

Nisin synthesized in-vivo from Lactococcus lactis (L. lactis) (ATCC 7962) bacteria was provided to form a homogenous solution at an ideal concentration To find the minimum AMP/Bond mixture ratio that showed maximum antimicrobial activity, AMP and Bond mixtures were tested at various concentration levels between 1/160 and 1/2 (AMP/Bond). As a result, the optimum ratio was determined as 1/40. The antimicrobial efficacy of Nisin-added adhesive resin was tested against Streptococcus mutans (S. mutans) (ATCC 35,688) and Lactobacillus strains (cariogenic microorganisms). AMP formed a 2.7 cm diameter zone alone, while 1/40 AMP-bond mixture formed a 1.2 cm diameter zone. SBS values of the teeth bonded with Nisin added adhesive (17.49 ± 5.31) were significantly higher than the control group (14.54 ± 4.96) (P = 0.004). According to the four point scale, Nisin added adhesive provided a higher ARI score in favour of the adhesive and tooth compared to the control group (ARI = 3, n = 20).

CONCLUSIONS

Nisin produced from L. lactis (ATCC 7962) had greater antimicrobial effects after mixing with adhesive bond against cariogenic microorganisms S. mutans (ATCC 35,688) and Lactobacillus strains. Nisin added adhesive increased shear bond strength (SBS) of orthodontic brackets and ARI scores in favor of adhesive & teeth.

CLINICAL RELEVANCE

Clinicians should take into account that using Nisin-added adhesive resin in orthodontic treatments can provide prophylaxis against tooth decay, especially in patients with poor oral hygiene.

Recent advances and potentiality of postbiotics in the food industry: Composition, inactivation methods, current applications in metabolic syndrome, and future trends

Postbiotics are defined as "preparation of inanimate microorganisms and/or their components that confers a health benefit on the host". Postbiotics have unique advantages over probiotics, such as stability, safety, and wide application. Although postbiotics are research hotspots, the research on them is still very limited. This review provides comprehensive information on the scope of postbiotics, the preparation methods of inanimate microorganisms, and the application and mechanisms of postbiotics in metabolic syndrome (MetS). Furthermore, the application trends of postbiotics in the food industry are reviewed. It was found that postbiotics mainly include inactivated microorganisms, microbial lysates, cell components, and metabolites. Thermal treatments are the main methods to prepare inanimate microorganisms as postbiotics, while non-thermal treatments, such as ionizing radiation, ultraviolet light, ultrasound, and supercritical CO2, show great potential in postbiotic preparation. Postbiotics could ameliorate MetS through multiple pathways including the modulation of gut microbiota, the enhancement of intestinal barrier, the regulation of inflammation and immunity, and the modulation of hormone homeostasis. Additionally, postbiotics have great potential in the food industry as functional food supplements, food quality improvers, and food preservatives. In addition, the SWOT analyses showed that the development of postbiotics in the food industry exists both opportunities and challenges.

Antimicrobial Active Packaging Containing Nisin for Preservation of Products of Animal Origin: An Overview

The preservation of food represents one of the greatest challenges in the food industry. Active packaging materials are obtained through the incorporation of antimicrobial and/or antioxidant compounds in order to improve their functionality. Further, these materials are used for food packaging applications for shelf-life extension and fulfilling consumer demands for minimal processed foods with great quality and safety. The incorporation of antimicrobial peptides, such as nisin, has been studied lately, with a great interest applied to the food industry. Antimicrobials can be incorporated in various matrices such as nanofibers, nanoemulsions, nanoliposomes, or nanoparticles, which are further used for packaging. Despite the widespread application of nisin as an antimicrobial by directly incorporating it into various foods, the use of nisin by incorporating it into food packaging materials is researched at a much smaller scale. The researchers in this field are still in full development, being specific to the type of product studied. The purpose of this study was to present recent results obtained as a result of using nisin as an antimicrobial agent in food packaging materials, with a focus on applications on products of animal origin. The findings showed that nisin incorporated in packaging materials led to a significant reduction in the bacterial load (the total viable count or inoculated strains), maintained product attributes (physical, chemical, and sensorial), and prolonged their shelf-life.

Novel electrochemical and electrochemiluminescence dual-modality sensing platform for sensitive determination of antimicrobial peptides based on probe encapsulated liposome and nanochannel array electrode

With the increasing application of antimicrobial peptides (AMPs) to replace antibiotics in medicine, food and agriculture, it is highly desired to develop a fast, reliable, and convenient strategy for sensitive detection of AMPs. Herein, a novel electrochemical (EC) and electrochemiluminescence (ECL) dual-modality sensing platform was developed based on probe encapsulated liposomes and nanochannel array modified electrodes, which enables sensitive determination of nisin in food samples. The bifunctional probe with both EC and ECL signals, tris(2,2-bipyridyl) dichlororuthenium (II) (Ru(bpy)₃²⁺), was chosen to be easily encapsulated in liposomes (Ru(bpy)₃²⁺@liposome). Based on the unique sterilization mechanism that AMPs can disrupt cell membranes, Ru(bpy)₃²⁺@liposome can be destroyed by nisin and release a large number of Ru(bpy)₃²⁺ probes. Vertically-ordered mesoporous silica-nanochannel film (VMSF) modified ITO electrodes (VMSF/ITO) prepared by electrochemically assisted self-assembly (EASA) method were applied as the sensing electrode. Due to the efficient enrichment of Ru(bpy)₃²⁺ by the negatively charged nanochannel arrays, VMSF/ITO enables detection of the EC/ECL signals of the released Ru(bpy)₃²⁺ probes with ultrahigh sensitivity. In consequence, sensitive dual-modality detection of nisin was achieved by the combination of Ru(bpy)₃²⁺@liposome and VMSF/ITO. The developed sensing system can realize sensitive determination of nisin in ECL mode in the concentration range of 10 ng/ml to 50 μg/ml with a limit of detection (LOD) of 9.3 ng/ml, or in EC mode from 800 ng/ml to 100 μg/ml with a LOD of 70 ng/ml. Combined with the excellent anti-fouling and anti-interference performance of VMSF, rapid and sensitive detection of nisin in milk or egg white was also achieved by the sensor.

Advances in Rational Protein Engineering toward Functional Architectures and Their Applications in Food Science

Protein biomolecules including enzymes, cagelike proteins, and specific peptides have been continuously exploited as functional biomaterials applied in catalysis, nutrient delivery, and food preservation in food-related areas. However, natural proteins usually function well in physiological conditions, not industrial conditions, or may possess undesirable physical and chemical properties. Currently, rational protein design as a valuable technology has attracted extensive attention for the rational engineering or fabrication of ideal protein biomaterials with novel properties and functionality. This article starts with the underlying knowledge of protein folding and assembly and is followed by the introduction of the principles and strategies for rational protein design. Basic strategies for rational protein engineering involving experienced protein tailoring, computational prediction, computation redesign, and de novo protein design are summarized. Then, we focus on the recent progress of rational protein engineering or design in the application of food science, and a comprehensive summary ranging from enzyme manufacturing to cagelike protein nanocarriers engineering and antimicrobial peptides preparation is given. Overall, this review highlights the importance of rational protein engineering in food biomaterial preparation which could be beneficial for food science.

Postbiotics as the new frontier in food and pharmaceutical research

Food is the essential need of human life and has nutrients that support growth and health. Gastrointestinal tract microbiota involves valuable microorganisms that develop therapeutic effects and are characterized as probiotics. The investigations on appropriate probiotic strains have led to the characterization of specific metabolic byproducts of probiotics named postbiotics. The probiotics must maintain their survival against inappropriate lethal conditions of the processing, storage, distribution, preparation, and digestion system so that they can exhibit their most health effects. Conversely, probiotic metabolites (postbiotics) have successfully overcome these unfavorable conditions and may be an appropriate alternative to probiotics. Due to their specific chemical structure, safe profile, long shelf-life, and the fact that they contain various signaling molecules, postbiotics may have anti-inflammatory, immunomodulatory, antihypertensive properties, inhibiting abnormal cell proliferation and antioxidative activities. Consequently, present scientific literature approves that postbiotics can mimic the fundamental and clinical role of probiotics, and due to their unique characteristics, they can be applied in an oral delivery system (pharmaceutical/functional foods), as a preharvest food safety hurdle, to promote the shelf-life of food products and develop novel functional foods or/and for developing health benefits, and therapeutic aims. This review addresses the latest postbiotic applications with regard to pharmaceutical formulations and commercial food-based products. Potential postbiotic applications in the promotion of host health status, prevention of disease, and complementary treatment are also reviewed.

Cold Shock Proteins Promote Nisin Tolerance in Listeria monocytogenes Through Modulation of Cell Envelope Modification Responses

Listeria monocytogenes continues to be a food safety challenge owing to its stress tolerance and virulence traits. Several listeriosis outbreaks have been linked to the consumption of contaminated ready-to-eat food products. Numerous interventions, including nisin application, are presently employed to mitigate against L. monocytogenes risk in food products. In response, L. monocytogenes deploys several defense mechanisms, reducing nisin efficacy, that are not yet fully understood. Cold shock proteins (Csps) are small, highly conserved nucleic acid-binding proteins involved in several gene regulatory processes to mediate various stress responses in bacteria. L. monocytogenes possesses three csp gene paralogs; cspA, cspB, and cspD. Using a panel of single, double, and triple csp gene deletion mutants, the role of Csps in L. monocytogenes nisin tolerance was examined, demonstrating their importance in nisin stress responses of this bacterium. Without csp genes, a L. monocytogenes ΔcspABD mutant displayed severely compromised growth under nisin stress. Characterizing single (ΔcspA, ΔcspB, and ΔcspD) and double (ΔcspBD, ΔcspAD, and ΔcspAB) csp gene deletion mutants revealed a hierarchy (cspD > cspB > cspA) of importance in csp gene contributions toward the L. monocytogenes nisin tolerance phenotype. Individual eliminations of either cspA or cspB improved the nisin stress tolerance phenotype, suggesting that their expression has a curbing effect on the expression of nisin resistance functions through CspD. Gene expression analysis revealed that Csp deficiency altered the expression of DltA, MprF, and penicillin-binding protein-encoding genes. Furthermore, the ΔcspABD mutation induced an overall more electronegative cell surface, enhancing sensitivity to nisin and other cationic antimicrobials as well as the quaternary ammonium compound disinfectant benzalkonium chloride. These observations demonstrate that the molecular functions of Csps regulate systems important for enabling the constitution and maintenance of an optimal composed cell envelope that protects against cell-envelope-targeting stressors, including nisin. Overall, our data show an important contribution of Csps for L. monocytogenes stress protection in food environments where antimicrobial peptides are used. Such knowledge can be harnessed in the development of better L. monocytogenes control strategies. Furthermore, the potential that Csps have in inducing cross-protection must be considered when combining hurdle techniques or using them in a series.

Novel Bovine Plasma Protein Film Reinforced with Nanofibrillated Cellulose Fiber as Edible Food Packaging Material

Proteins, such as those in blood from slaughterhouses, are a good option for developing edible films. However, films made exclusively from proteins have low strength and high water solubility, which makes them difficult to use in the food industry. The use of cellulosic material, such as nanofibrillated cellulose (NFC), can improve the properties of these films. In the present work, bovine plasma was acidified and treated with ethanol to precipitate its proteins, and these proteins were used to prepare films reinforced with several concentrations of NFC. In addition, control films prepared with untreated bovine plasma and reinforced with NFC were prepared as well. These new edible films were characterized according to their mechanical properties, water vapor permeability, light transmittance, and microstructure. Furthermore, the film with the best properties was selected to be additivated with nisin to test its antimicrobial properties by wrapping meat previously contaminated with Staphylococcus aureus. In this sense, films prepared with the extracted proteins showed better properties than the films prepared with untreated plasma. In addition, the results showed that the reinforcement of the films with a 10% (w/w) of NFC decreased their water solubility and improved their puncture strength and water vapor barrier properties. Finally, the addition of nisin to the films prepared with extracted protein from bovine plasma and NFC gave them antimicrobial properties against S. aureus.

From Cheese-Making to Consumption: Exploring the Microbial Safety of Cheeses through Predictive Microbiology Models

Cheeses are traditional products widely consumed throughout the world that have been frequently implicated in foodborne outbreaks. Predictive microbiology models are relevant tools to estimate microbial behavior in these products. The objective of this study was to conduct a review on the available modeling approaches developed in cheeses, and to identify the main microbial targets of concern and the factors affecting microbial behavior in these products. Listeria monocytogenes has been identified as the main hazard evaluated in modelling studies. The pH, a_w, lactic acid concentration and temperature have been the main factors contemplated as independent variables in models. Other aspects such as the use of raw or pasteurized milk, starter cultures, and factors inherent to the contaminating pathogen have also been evaluated. In general, depending on the production process, storage conditions, and physicochemical characteristics, microorganisms can grow or die-off in cheeses. The classical two-step modeling has been the most common approach performed to develop predictive models. Other modeling approaches, including microbial interaction, growth boundary, response surface methodology, and neural networks, have also been performed. Validated models have been integrated into user-friendly software tools to be used to obtain estimates of microbial behavior in a quick and easy manner. Future studies should investigate the fate of other target bacterial pathogens, such as spore-forming bacteria, and the dynamic character of the production process of cheeses, among other aspects. The information compiled in this study helps to deepen the knowledge on the predictive microbiology field in the context of cheese production and storage.