Application Of Nisin Research Articles

Nisin—A Promising Antimicrobial Compound from Lactic Acid Bacteria

Nisin is a classical bacteriocin consisting of thirty-four amino acid residues and undergoing a high degree of post-translational modification to form a unique pentacyclic structure. Nisin is mainly synthesised by lactic acid bacteria. Under natural conditions, it exhibits strong antibacterial activity against Gram-positive organisms and, when combined with chelating agents, is effective against Gram-negative organisms. An excellent safety profile, low cytotoxicity and slow development of resistance are additional benefits. Currently, the application of nisin is focused on food preservation. This is due to the fact that nisin is naturally present in a wide range of historical fermented foods and its safety is fully guaranteed. With the continuous development of bacterial drug resistance and the consequent demand for new anti-infective drugs, its biomedical applications are being actively explored. However, due to the problems of drug stability, safety, and in vivo activity, there is still a certain distance from clinical application. In this paper, the author summarized the structure, biosynthetic mechanism, applications, and possible research directions of nisin.

Effects of nisin on bacterial community and fermentation profiles, in vitro rumen fermentation, microbiota, and methane emission of alfalfa silage.

Alfalfa (Medicago sativa L.) has been used widely in preparing silage. However, forage legumes are prone to contamination by spoilage bacteria during fermentation. Nisin has broad-spectrum antibacterial properties and has been applied as an inhibitor of rumen methane emissions. However, little research has been carried out on the application of nisin in silage. This study therefore aimed to investigate the impacts of different nisin concentrations on the bacterial community and fermentation dynamics, in vitro ruminal fermentation characteristics, microbiota, and methane emissions of alfalfa silage. The detection limits of organic acid in nisin-treated silages were not reached in 0.09 g kg-1 nisin (0.09 level) from days 1 to 7 of ensiling. With increasing nisin concentrations, the silage dry matter increased linearly (P < 0.05), and dry matter loss decreased linearly (P < 0.05). Moreover, both the 0.06 g kg-1 nisin (0.06 level) and 0.09 level treatments increased the relative abundance of Pediococcus acidilactici during ensiling. Concurrently, as the nisin concentrations increased, ruminal methane production decreased linearly (P < 0.05), while the relative abundances of ruminal Succinivibrio, Fibrobacter succinogenes and Ruminobacter amylophilus increased linearly (P < 0.05). The populations of ruminal total bacteria, methanogens, protozoa, and fungi decreased linearly with increasing nisin concentrations (P < 0.05). The addition of nisin delayed the fermentation process, preserved more nutrients in alfalfa silage, and promoted fermentation dominated by P. acidilactici in the late phase of ensiling. Moreover, nisin reduced in vitro rumen methane emissions without adverse effects on dry matter digestibility. © 2023 Society of Chemical Industry.

Synergistic antimicrobial effect of nisin−octanoic acid nanoemulsions against E. coli and S. aureus

Food safety is a major public health concern all over the world. Therefore, the prevention of food contamination is becoming extremely crucial. In this study, an antimicrobial nanoemulsion composed of water-soluble nisin and fat-soluble octanoic acid was successfully prepared. The results showed that the average particle size and the polymer dispersity index of the nisin-octanoic acid (NOA) nanoemulsion were around 52.21nm and 0.253, respectively. The NOA nanoemulsion required less amounts of nisin and octanoic acid to achieve the effective antimicrobial effect against Escherichia coli and Staphylococcus aureus. In addition, the growth curves of E. coli and S. aureus were determined. The OD600 of NOA nanoemulsion was significantly lower than free nisin after being incubated for 24h (p < 0.001), indicating that the antimicrobial effect of NOA nanoemulsion was outstanding. Meanwhile, the synergistic antimicrobial property of NOA nanoemulsion against E. coli and S. aureus was significantly better than free nisin under nonacid conditions (p < 0.05). Overall, the results of this study may provide guidance for the further application of nisin in more forms.

Synthesis, high yield strategy and application of nisin: A review

SummaryNisin is a peptide with antibacterial activity against a variety of pathogens. It was originally obtained from a Lactococcus lactis. It is classified as a class I bacteriocin, as it is synthesised by ribosomes and post‐translationally modified. It has been studied extensively and has a wide range of applications in the food industry, biomedicine, veterinary, and research fields. It is approved as a food preservative by the Food and Agriculture Organization (FAO). What's more, nisin, the only antimicrobial peptide that has generally considered as safe (GRAS) status from both World Health Organization (WHO) and Food and Drug Administration (FDA), has the potential to become an important natural antibiotic as bacteria become more resistant to traditional antibiotics. However, nisin purified from biological sources usually results in low yields and high production costs, limiting industrial‐scale manufacturing and application in other fields. Hence, more methods need to be used to optimise the production of nisin. Therefore, this paper aimed to understand the structure and biosynthesis mechanism of nisin and to summarise the innovative methods for increasing the production of nisin using biosynthesis regulation.

In Vivo Evaluation of the Efficacy of a Nisin-Biogel as a New Approach for Canine Periodontal Disease Control.

Periodontal disease (PD) is a common oral disease in dogs. Recent in vitro research revealed that nisin−biogel is a promising compound for canine PD control. In this work, a clinical trial was developed to assess the in vivo efficacy of nisin−biogel in dogs by determining the dental plaque index (DPI), gingivitis index (GI), and periodontal pocket depth (PPD) after dental administration. The biogel’s influence on aerobic bacteria counts was also evaluated, as well as its acceptance/adverse effects in dogs. Twenty animals were allocated to one of two groups: a treatment group (TG) subjected to a dental topical application of nisin−biogel for 90 days and a control group (CG) with no treatment. Besides daily monitoring, on day 1 (T0) and at the end of the assay (T90), animals were subjected to blood analysis, periodontal evaluation, dental plaque sampling, scaling, and polishing. Statistical analysis with mixed models showed a significant reduction in mean PPD (estimate = −0.371, p-value < 0.001) and DPI (estimate = −0.146, p-value < 0.05) in the TG animals at T90. A reduction in the GI (estimate = −0.056, p-value > 0.05) was also observed but with no statistical significance. No influence on total bacterial counts was observed, and no adverse effects were detected. The nisin−biogel was revealed to be a promising compound for canine PD control.

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.

Nisin Mutant Prevention Concentration and the Role of Subinhibitory Concentrations on Resistance Development by Diabetic Foot Staphylococci.

The most prevalent microorganism in diabetic foot infections (DFI) is Staphylococcus aureus, an important multidrug-resistant pathogen. The antimicrobial peptide nisin is a promising compound for DFI treatment, being effective against S. aureus. However, to avoid the selection of resistant mutants, correct drug therapeutic doses must be established, being also important to understand if nisin subinhibitory concentrations (subMIC) can potentiate resistant genes transfer between clinical isolates or mutations in genes associated with nisin resistance. The mutant selection window (MSW) of nisin was determined for 23 DFI S. aureus isolates; a protocol aiming to prompt vanA horizontal transfer between enterococci to clinical S. aureus was performed; and nisin subMIC effect on resistance evolution was assessed through whole-genome sequencing (WGS) applied to isolates subjected to a MEGA-plate assay. MSW ranged from 5–360 μg/mL for two isolates, from 5–540 μg/mL for three isolates, and from 5–720 μg/mL for one isolate. In the presence of nisin subMIC values, no transconjugants were obtained, indicating that nisin does not seem to promote vanA transfer. Finally, WGS analysis showed that incubation in the presence of nisin subMIC did not promote the occurrence of significant mutations in genes related to nisin resistance, supporting nisin application to DFI treatment.

Breeding of a High-Nisin-Yielding Bacterial Strain and Multiomics Analysis

Nisin is a green, safe and natural food preservative. With the expansion of nisin application, the demand for nisin has gradually increased, which equates to increased requirements for nisin production. In this study, Lactococcus lactis subsp. lactis lxl was used as the original strain, and the compound mutation method was applied to induce mutations. A high-yielding and genetically stable strain (Lactobacillus lactis A32) was identified, with the nisin titre raised by 332.2% up to 5089.29 IU/mL. Genome and transcriptome sequencing was used to analyse A32 and compare it with the original lxl strain. The comparative genomics results show that 107 genes in the A32 genome had mutations and most base mutations were not located in the four well-researched nisin-related operons, nisABTCIPRK, nisI, nisRK and nisFEG: 39 single-nucleotide polymorphisms (SNPs), 34 insertion mutations and 34 deletion mutations. The transcription results show that the expression of 92 genes changed significantly, with 27 of these differentially expressed genes upregulated, while 65 were downregulated. Our findings suggest that the output of nisin increased in L. lactis strain A32, which was accompanied by changes in the DNA replication-related gene dnaG, the ABC-ATPase transport-related genes patM and tcyC, the cysteine thiometabolism-related gene cysS, and the purine metabolism-related gene purL. Our study provides new insights into the traditional genetic mechanisms involved nisin production in L. lactis, which could provide clues for a more efficient metabolic engineering process.

The combined bactericidal effect of nisin and thymoquinone against Listeria monocytogenes in Tryptone Soy Broth and sterilized milk

In this study, the combined bactericidal effect of nisin and thymoquinone (TQ) on Listeria monocytogenes was investigated in Tryptone Soy Broth (TSB) and sterilized milk. The combined treatment resulted in a greater reduction in bacterial number than either nisin or TQ treatment alone. Nisin and TQ respectively caused depolarization and hyperpolarization of the cell membrane of L. monocytogenes , which indicated early injury to the bacteria. Confocal laser scanning microscopy and N -phenyl-l-naphthylamine uptake assay showed disruption of the cell membrane on treatment. Field emission scanning electron microscopy revealed depression and collapse of the cell surface following treatment with nisin and TQ. Growth curves showed that nisin and TQ acted on the bacteria in different growth phases. Fourier-transform infrared spectroscopy demonstrated a reversible hydrogen-bonding interaction between nisin and TQ. Our results suggest that nisin combined with TQ is a more effective antibacterial effect against L. monocytogenes in both TSB and in sterilized milk than either agent alone. Our study sheds light on the inhibitory mechanisms of nisin, TQ, and their combination, and provides a theoretical basis for the synergistic antibacterial application of nisin and TQ in the food industry. • The anti bacterial effect of combined nisin and thymoquinone (TQ) treatment exceeded that of either treatment alone. • Nisin and TQ damaged the bacterial membrane and morphology by different mechanisms. • The inhibitory effects of nisin and TQ on the growth phases of L. monocytogenes were different. • Nisin and TQ interact via intermolecular hydrogen bonding.

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.

Applications of Nisin and EDTA in Food Packaging for Improving Fabricated Chitosan-Polylactate Plastic Film Performance and Fish Fillet Preservation

This study aimed to increase the antibacterial activity of chitosan-polylactic acid (PLA) composite film by adding nisin and ethylenediaminetetraacetic acid (EDTA). We evaluated the mechanical, physicochemical, and antibacterial properties of various PLA composite films, as well as the enhancement effect of PLA composite films with EDTA + nisin on the preservation of grouper fillets. Films of PLA alone, PLA plus chitosan (C5), PLA plus nisin + EDTA (EN2), and PLA plus chitosan plus nisin + EDTA (C5EN1 and C5EN2) were prepared. The addition of EDTA + nisin to the chitosan-PLA matrix significantly improved the antibacterial activity of the PLA composite film, with C5EN1 and C5EN2 films showing the highest antibacterial activity among the five films. Compared with the fish samples covered by C5, the counts of several microbial categories (i.e., mesophilic bacteria, psychrotrophic bacteria, coliforms, Aeromonas, Pseudomonas, and Vibrio) and total volatile basic nitrogen content in fish were significantly reduced in the samples covered by C5EN1. In addition, the counts of samples covered by C5EN1 or C5 were significantly lower compared to the uncovered and PLA film-covered samples.

The effects of nisin on the growth of foodborne pathogens and biogenic amine formation: in vivo and in vitro studies

The effects of different concentrations of nisin on the biogenic amine formation in seabass (Dicentrarchus labrax) fillets stored at 4 ± 2 °C (in vivo) and also on foodborne pathogens (in vitro) in amino acid decarboxylase broth were investigated. The in vitro impact of nisin on microbial growth and biogenic amine production was observed in histidine and tyrosine decarboxylase broth (TDB). The results showed that Gram-positive foodborne pathogens were more sensitive (especially 1ml/100 ml nisin) than Gram-negative groups. Bacterial loads in histidine decarboxylase broth (HDB) and TDB were not always correlated with biogenic amine formation. The impact of nisin on biogenic amine production varied with specific microbial strains and broth used. The results demonstrated that nisin inhibited the microbial growth, resulting in reduced biogenic amine production in seabass fillets. The application of nisin (especially 0.8 %) as in vivo preserved the microbiologic quality and thus reduced biogenic amine production. Consequently, nisin has the potential to be used as a novel antimicrobial agent against foodborne pathogen and food spoilage bacteria that produce biogenic amines in foods.

The impact of different levels of nisin as a biopreservative agent on the chemical, sensory and microbiological quality of vacuum-packed sea bass (Dicentrarchus labrax) fillets stored at 4 ± 2 °C

Nisin is produced by Lactococcus lactis subsp. lactis and is also known as an antimicrobial agent especially effective against gram-positive bacteria. It has long been used as a preservative in foods and beverages and is generally regarded as safe (GRAS). In the present work, the effects of different concentrations of nisin (0.2, 0.4 and 0.8%) on the sensory, chemical and microbiological quality and shelf-life of vacuum-packed sea bass (Dicentrarchus labrax) fillets were investigated during chilled (4 ± 2 °C) storage. The sensory points for raw and cooked fillets increased with time during the storage period (p &lt; 0.05). The control group, with scores of 9.08, was rejected by panelists on day 12; whereas nisin-treated groups were rejected on day 14 with scores ranging from 9.00-9.17 score. As a result of chemical analyses, lower values (p &lt; 0.05) were obtained from the nisin groups with low oxidative rancidity. Moreover, nisin inhibited microbial growth, which shows antimicrobial activity. Consequently, it was concluded that the application of nisin (especially 0.8%) preserved the organoleptic quality and extended the shelf-life of sea bass fillets.

Effects of Nisin Treatment on the Shelf Life of Ready-to-Eat Roasted Shrimp (&amp;lt;i&amp;gt;Penaeus vannamei&amp;lt;/i&amp;gt;)

The microbiological, biochemical, and physicochemical changes of ready-to-eat shrimps (Penaeus vannamei) with high water content, subjected to nisin treatment in combination of hurdle technology, were investigated. The ready-to-eat shrimps were processed by boiling, drying, treatment with nisin solution, seasoning, and roasting, followed by vacuum packaging, sterilization, and storage at room temperature (25°C). The results showed that the samples treated with nisin in combination with other hurdles resulted in a significant decrease in bacterial counts (Bacillus cereus and native microflora) compared to the control samples. Additionally, the nisin-treated samples possessed better biochemical and physicochemical properties, as well as better sensory patterns. According to the safety guidelines for roasted shrimp (SC/T 3305-2003), the shelf life of ready-to-eat shrimp with 48–53% moisture content was extended by nisin application at concentrations of 60 and 100 mg/kg of nisin; specifically, ready-to-eat shrimp maintained good quality from 4–6 days up to 6–12 and 8–14 days corresponding to 60 and 100 mg/kg of nisin treatments, respectively. Nisin treatment combined with hurdle technology in the production of ready-to-eat shrimp provides a highly valued product in China.

Chemical and biological protection of food grade nisin through their partial intercalation in laminar hydroxide salts

The use of antimicrobial agents within a matrix, specifically layered compounds, is of growing interest for reducing contamination due to food borne pathogens and deteriorative microorganisms, one of the main health problems worldwide. In this study, zinc layered hydroxide nanoparticles were synthesized as a matrix for nisin immobilization. Layered materials were characterized by X-ray diffraction, Fourier-Transform Infrared and Ultra Violet-Visible spectra, Scanning Electron Microscopy, and by Thermogravimetric Analysis. Thermal, chemical, enzymatic, and biological stabilities were assessed against Lactobacillus brevis as control strain. Free and immobilized nisin in solution were previously subjected to 25 and 121°C, pH (7, 9) and inactivation with protease before antimicrobial tests that lasted 21days. Immobilized nisin was found to maintain the activity levels after the protease action while the pure nisin solution lost its activity gradually. Furthermore, immobilized nisin treated at 121°C and pH 7 showed higher activity than pure nisin after 21days. These results may support that immobilizing nisin in zinc layered hydroxide salts promoted extended nisin inhibitory activity in solution after thermal, chemical or enzymatic treatments. This research provides an alternative to nisin application that could be used in processes where such operating conditions take place, as in dairy products.

Nisin as a Novel Feed Additive: The Effects on Gut Microbial Modulation and Activity, Histological Parameters, and Growth Performance of Broiler Chickens.

Simple SummaryIn an era with an increasing number of antibiotic-resistant bacteria strains, there is a need to find a novel and efficient alternative to the antibiotics commonly used in animal nutrition. As natural proteins synthesized by most known bacteria, bacteriocins are considered future candidates. To date, nisin (E234), the best-known bacteriocin, is used as a preservative against food-borne pathogens such as Listeria monocytogenes in the food industry. However, there are scarce data about the application of nisin in the diet of livestock, including poultry. In this study, we evaluated the effect of nisin in broiler chicken diets on selected microbial populations, the activities of which are related to gastrointestinal health, growth performance, and gut histomorphology. We found that nisin application positively affects the feed conversion ratio and exerts a similar effect as the ionophore coccidiostat monensin in the case of microbiota modulation. Additionally, nisin supplementation decreased microbial fermentation in the jejunum. No changes in ileal histomorphology or internal organ weights were noted. We conclude that nisin may be considered a natural and safe antimicrobial agent and growth promoter in broiler chicken nutrition.Two independent experiments were performed to evaluate the effect of nisin alone or with monensin on gut microbiota, gut microbial activities, and histomorphology (exp 1) and the effect of nisin application in a dose‒response manner on the growth performance of broiler chickens (exp 2). A total of 900 one-day-old female Ross 308 chicks (400, exp 1; 500, exp 2) were randomly distributed to four groups (exp 1; 10 replicate pens per treatment with 10 birds each), i.e., NA, no additives; MON, monensin (100 ppm); NIS, nisin (2700 IU/kg diet); and MON + NIS, a mixture of monensin (100 ppm) and nisin (2700 IU/kg diet); or 5 treatments (exp 2), NA, no additives; NIS100, nisin (100 IU/kg diet); NIS200, nisin (200 IU/kg diet); NIS400, nisin (400 IU/kg diet); and NIS800, nisin (800 IU/kg diet). Nisin supplementation positively affected the microbiota of the gut by reducing potentially pathogenic bacterial populations in the jejunum and ceca. The bacterial fermentation in the jejunum was significantly lowered by nisin addition. The addition of nisin from 100 IU to 800 IU decreased the FCR value over the entire experimental period. According to the results, nisin can be considered a natural dietary supplement for broiler chickens.

Farklı Konsantrasyonlarda Kullanılan Nisinin Soğukta ve Vakum Paketlenerek Depolanan Levrek (Dicentrarchus labrax, Linnaeus, 1758) Filetolarının Renk Değişimleri Üzerine Etkileri

Bu çalışmada farklı konsantrasyonlarda (%0,2, %0,4 ve %0,8) hazırlanan nisin solüsyonlarının levrek filetolarının soğukta ve vakum paketlenerek depolanması esnasında renk değişimleri üzerindeki etkileri incelenmiştir. Panelistler tarafından gerçekleştirilen duyusal analizlerde (çiğ ve pişmiş olarak) levreğin raf ömrü I. denemede kontrol grubunda 6 gün, nisin uygulanan gruplarda ise 8 gün olarak; II. denemede ise kontrol grubunda 12 gün, nisin uygulanan gruplarda ise 14 gün olarak belirlenmiştir. Nisin uygulanmasının balık etinin doğal kokusu ve aroması üzerine olumsuz bir etkisi gözlenmemiştir. Panelistler tarafından kontrol grubuna göre daha çok tercih edilmiş olan nisin uygulamasının levreğin raf ömrünü 2 gün uzattığı tespit edilmiştir. Elde edilen sonuçlar, filetolanmış levreğin tek başına nisin ile muamelesinde (Deneme I) ve vakum paketleme ile nisinin kombine kullanımları (Deneme II) sonucunda rengini daha iyi koruduğunu, 4±2°C‘de deneme I‘ de 12 günlük ve deneme II‘de 18 günlük depolamada daha iyi renk sonuçları ile kontrol grubundan daha iyi tüketici algısı oluşturmuştur. Sonuç olarak nisin uygulaması, filetoların renk stabilitesi üzerine pozitif etki yapmıştır. Mevcut çalışma sonucunda elde edilen bulgular, su ürünlerinin kalitesi ve kontrolü üzerine yararlı bilgiler içermektedir. İnsan sağlığı üzerinde olumlu etkilere sahip alternatif doğal bir koruyucu olarak nisinin kullanımı hakkında gıda sektörü ve tüketicilerin bilgilendirilmesinin ekonomik ve sosyal bir yaygın etki sağlayabileceği öngörülmektedir.

Nisin application delays growth of Listeria monocytogenes on fresh-cut iceberg lettuce in modified atmosphere packaging, while the bacterial community structure changes within one week of storage

Listeria monocytogenes poses a risk to minimally processed ready-to-eat foods such as lettuce due to its ability to grow under refrigeration conditions. Since many natural anti-listerial products render Iceberg lettuce unsuitable for consumption within 2 d of storage, this study investigated the efficacy of Nisin A as anti-listerial agent and its sensory impact on lettuce. In addition, the evolution of the bacterial community on fresh-cut lettuce was monitored for the duration of storage. In-vitro assays confirmed the efficacy of Nisin A to inhibit growth of a three strain mix of L. monocytogenes in model atmospheres and air. The L. monocytogenes strain mix was added to lettuce that was subsequently treated either with Nisin, L. lactis DSM20729 (a Nisin A producer) or was kept without inoculation. Incubation took place at 4 and 8 °C under various atmospheres. On days 0, 2, 5 and 7, L. monocytogenes was enumerated on selective agar and a sensory panel graded the lettuce on visual appearance. At 4 and 8 °C a 10 to 100-fold reduction of L. monocytogenes growth was achieved with 5 mg kg−1 Nisin over a seven-day period, while lettuce kept an acceptable sensory appearance over the first 5 d. Direct application of L. lactis had no detectable effect on L. monocytogenes growth in situ. The bacterial community structure changed substantially from each sampling day to the next over the seven days of incubation. However, Pseudomonadaceae with the genus Pseudomonas were most abundant at all times and increased in relative abundance to over 90% by day 7. In conclusion, the application of Nisin A to minimally processed vegetables like lettuce seems to be a viable alternative to reduce and delay growth of pathogen L. monocytogenes, while not impacting the sensory appearance for 2–5 d.

The anticlostridial effect of lactococcal and enterococcal adjunct starters in Dutch‐type low‐scalded cheese

Lactococcal and enterococcal adjuncts with verified anticlostridial activity were successfully applied in the technology process of Dutch‐type low‐scalded cheese. The microbial status of experimental cheeses, physicochemical parameters and late blowing defects were evaluated for batches inoculated with Clostridium tyrobutyricum, and compared with noninoculated controls and the application of nisin. Two strains (CCDM 731 and CCDM 71) belonging to the species Lactococcus lactis subsp. lactis had significant anticlostridial effects which were comparable to nisin. Regardless of the noneffective enterococci adjunct, both lactococcal strains effectively supported the fermentation and ripening process in combination with the commercial starter itself or in combination with nisin.

Applications of nisin for biofouling mitigation of reverse osmosis membranes

This study addresses the potential of application of nisin, a polycyclic antimicrobial peptide produced by Lactococcus lactis, as a novel biological agent for control/mitigation of biofilms formed by three different microorganisms: (i) Pseudomonas aeruginosa P60, (ii) Bacillus species, and (iii) a mixed culture of the two species. Nisin did not affect the growth rate of either strain, while the viability of Bacillus sp. was decreased, as compared to P. aeruginosa P60. Nisin was particularly effective for the dislodging of bacterial cells and extracellular polymeric substances (EPS) for P. aeruginosa P60. Water permeability of biofouled membranes was recovered by over 92% for all the bacterial strains investigated after nisin cleaning in a dead-end filtration system. Nisin has no detrimental effect on RO membrane and thus, has a potential as a biological agent for the mitigation of membrane biofouling.