New insights into the toxicological effects of dietary biogenic amines

Genotoxicity of putrescine and its effects on gene expression in HepG2 cell line

Decomposing bodies release necro-leachate, a toxic fluid containing harmful compounds such as biogenic amines. This study investigated the genotoxic effects of the different concentrations (0.5, 1.4, 2.3, 3.2 mM) of bioamine putrescine on HepG2 cells using the comet assay, the micronucleus test, and gene expression analysis. The results were compared to negative control and indicated significant DNA damage in the comet assay highlighting tail DNA intensity that exhibited significant differences across all tested concentrations (0.5 = 192 %, 1.4 = 189 %, 2.3 = 208 %, 3.2 = 132 %). The micronucleus test revealed a significant increase in micronuclei for concentrations 0.5 (193 %), 1.4 (229 %), 2.3 (206 %); nuclear buds 3.2 (173 %); chromosomal bridges 3.2 (735 %). Furthermore, genes linked to oxidative stress and DNA damage exhibited statistically significant expression alterations. These findings suggest that putrescine has genotoxic potential in human-derived HepG2 cells, raising concerns about cemetery contaminants' occupational and environmental risks. This study is the first to assess putrescine's toxicity as an environmental pollutant, as previous research has mainly focused on its role in the food sector. These insights highlight the potential threats necro-leachate poses to environmental health, emphasizing the need for further research on cemetery pollution.

Can the Contents of Biogenic Amines in Olomoucké Tvarůžky Cheeses Be Risky for Consumers?

Smear-ripened cheeses are fermented dairy products characterised by an increased content of biogenic amines (BAs). The high contents of these bioactive compounds can negatively affect consumers. The study aimed to observe the contents of BAs and po-lyamines (PAs) in Olomoucké tvarůžky cheeses depending on selected factors (year, batch, ripening/storage time, shape, weight, specific surface area, acidity, and salt content). The results showed that the variability was explained primarily by the batch (83% for the sum of BAs) and by the year (63% for the sum of PAs). The storage time significantly influenced the contents of putrescine, cadaverine, spermidine, and spermine (the explained variability was only 1-3%). The total BA contents negatively correlated with weight (r = -0.6374; p < 0.001) and positively with specific surface area (r = +0.4349; p < 0.001). A negligible positive correlation coefficient was found between the total BAs and pH (r = +0.1303). A low negative correlation was also found between the total BAs and salt content (r = -0.1328). Compared to previous studies, the total average BA contents were considerably low. In conclusion, this type of cheese does not represent a serious problem for most consumers.

Polydopamine-Mediated, Centrifugal Force-Driven Gold Nanoparticle-Deposited Microneedle SERS Sensors for Food Safety Monitoring Theoretical Study of the SERS Substrate Fabrication

Microneedle (MN) sensors have great promise for food safety detection, but the rapid preparation of MNs for surface-enhanced Raman scattering (SERS) sensors with tunable and homogeneous nanoparticles remains a great challenge. To address this, a SERS sensor of gold nanoparticles@polydopamine@poly(methyl methacrylate) MN (AuNPs@PDA@PMMA-MN) was developed. The extended-Derjaguin-Landau-Verwey-Overbeek theory was applied to calculate the interaction energy between AuNPs and PDA. It was confirmed that an appropriate centrifugal force could be utilized to overcome the electrostatic repulsion between AuNPs and PDA. Together with the adhesion force of PDA, AuNPs can therefore be uniformly and densely deposited on the MN substrate. The AuNPs@PDA@PMMA-MN had an enhancement factor of up to 1.74 × 106 for R6G. Furthermore, a MN sensor for the selective detection of putrescine and cadaverine was successfully constructed by modifying 4-mercaptobenzaldehyde (4-MBA) on AuNPs@PDA@PMMA-MN substrates. This sensor could quantitatively detect putrescine and cadaverine in meat. It has been successfully applied to the in situ detection of putrescine and cadaverine in real meat samples. The AuNPs@PDA@PMMA-MN SERS sensor has the advantages of facile fabrication, high sensitivity, high specificity, and online, in situ detection capability. It is expected to have applications in food quality testing, environmental monitoring, and disease diagnosis.

The development of a whole-cell biosensor enabled the identification of agmatine-producing Hafnia spp. in cheese

Agmatine, the decarboxylation product of arginine, is the precursor of putrescine - a harmful biogenic amine (BA) - that can accumulate in dairy products via bacterial metabolism involving the agmatine deiminase (AGDI) pathway. This first requires agmatine be produced via the decarboxylation of arginine and it remains unknown which microorganisms are responsible for this prior decarboxylation step. In addition, agmatine, as other BA, plays different physiological roles including those of co-transmitter and neuromodulator. Preclinical and clinical studies have shown agmatine to have a neuroprotective effect, rendering it of therapeutic interest being agmatine-producing bacteria proposed as psychobiotics. The identification of BA-producing microorganisms is based on the rise in pH due to the consumption of H+ during such decarboxylation reactions. However, in the detection of agmatine-producing microorganisms in cheese, this would lead to false positives since many bacteria possess arginine deiminase activity; this produces ornithine and ammonium from arginine, which also increases the pH. To overcome this problem, a whole-cell biosensor based on a previously developed agmatine-inducible transcription system was designed, and a protocol optimized for the successful identification of agmatine-producing microorganisms in cheese. The application of this protocol in cheese samples allowed for the isolation of agmatine-producing microorganisms identified as Hafnia spp. and unravels, for first time, the capacity of Hafnia paralvei to produce agmatine. This finding evidence the potential role of Hafnia spp. in putrescine accumulation in dairy products.

The Health Impact of Cocoa from Cultivation to the Formation of Biogenic Amines: An Updated Review

Cocoa and chocolate are known for their health benefits, which depend on factors like cocoa variety, post-harvest practices, and manufacturing processes, including fermentation, drying, roasting, grinding, and refining. These processing methods can influence the concentration and bioavailability of bioactive compounds, such as polyphenols that are linked to cardiovascular health and antioxidant effects. Recent scientific research has led to the development of cocoa-based products marketed as functional foods. However, despite the growing interest in the functional potential of cocoa, the literature lacks crucial information about the properties of different varieties of cocoa and their possible implications for human health. Moreover, climate change is affecting global cocoa production, potentially altering product composition and health-related characteristics. In addition to polyphenols, other compounds of interest are biogenic amines, due to their role and potential toxic effects on human health. Based on toxicological data and recent research on the complex relationship between biogenic amines and cocoa fermentation, setting limits or standards for biogenic amines in cocoa and chocolate could help ensure product safety. Finally, new trends in research on biogenic amines in chocolate suggest that these compounds might also be used as quality markers, and that product formulation and process conditions could change content and diversity of the different amines.

Tryptamine accumulates in cheese mainly via the decarboxylation of tryptophan by lactic acid bacteria

Few microorganisms are known to decarboxylate L-tryptophan, thereby producing tryptamine, a neuromodulator biogenic amine (BA) that can accumulate in cheese. Since lactic acid bacteria (LAB) are largely responsible for the production of other BA in this product, it was hypothesised that they would also be the main agents of tryptamine production. Using a rapid test based on the natural fluorescence of tryptamine, thousands of bacterial isolates from several cheese samples were screened. Only 1.4% of all isolates (43 out of 2982) were able to synthesise tryptamine and secrete it into the culture medium, highlighting the rarity of tryptophan-decarboxylating activity in this food source. Moreover, over 90% of these isolates were identified as belonging to Loigolactobacillus coryniformis, Enterococcus durans, or the Latilactobacillus sakei group (all lactic acid bacteria). No strain belonging to either of the first two species has previously been described as a tryptamine producer. Strains of the non-LAB species Staphylococcus epidermidis, Klebsiella pneumonia and Corynebacterium flavescens were also identified as tryptamine producers for the first time. Further typification of the producers based on their tryptamine yield was performed, and their potential applications as technological adjuncts for use in the dairy industry, as cell factories, or even as psychobiotics, are discussed.

A Review on Analytical Techniques for Quantitative Detection of Biogenic Amines in Aquatic Products

Aquatic products contain a large amount of protein, which can promote the production of a variety of biogenic amines through the function of microorganisms. Biogenic amines are a broad category of organic substances that contain nitrogen and have a low molecular weight. The presence of biogenic amines can cause the deterioration and excessive accumulation of aquatic products, which can cause damage to human health. Therefore, it is essential to discover a fast, convenient, and easy to operate method for the determination of biogenic amines in aquatic products. In this paper, the function and research significance of biogenic amines are analyzed from the aspects of their formation, toxicological properties, harm to the human body, and control methods. Several common direct detection techniques and indirect techniques for biogenic amines are briefly introduced especially sensors. This review provides references for efficient detection in the future.

Cyclometalated Iridium(III) Complex with Substituted Benzimidazole: pH Directed Organelle-Specific Localization Within Lysosome

We report the synthesis and pH dependent emission spectral behaviour of four emissive iridium(III) complexes (Ir1-Ir4) with two isomeric pairs of bis-trifluoromethyl appended benzimidazole ligands. The imidazolyl hydrogen(N-H) has been replaced by phenyl groups (N-Ph) in two ligands to understand the impact of hydrogen bonding on the photophysical properties of the complexes and it indeed plays interesting role in the charge-transfer dynamics. The pH dependent electronic spectral change is observed for two of the complexes. The enhancement of emission intensity is observed at different wavelength for pH<7 and pH>7 for Ir1 and Ir3. The emission sensing of biogenic amines with pka values ranging from 5.80-9.74 is reported along with cellular imaging. The complex Ir1 specifically localizes within lysosome (pH=4.5-5) and thus image this organelle with great precision. The detail electronic spectra and electrochemical behaviour were reported here along with TDDFT results.

Biogenic amines and bacterial spoilage in Plant-Based grill sausage alternatives

Vegan and vegetarian diets are increasing in popularity. Consequently, the supply and demand of plant-based meat alternatives has increased steadily over the past few years. However, scientific research on spoilage processes for such products is still inadequate as compared to research on traditional meat products. In traditional meat products, biogenic amines are prominent spoilage markers and potential sources of food toxicity, especially for people sensitive to biogenic amines. Plant-based meat alternatives are manufactured to mimic the taste, look, texture, and nutritional value of meat, and they have a protein-rich basis. It is therefore hypothesized that biogenic amines could be markers for spoilage in such products as well. Further analysis of their presence and concentrations and comparison to conventional meat products is necessary. If biogenic amines are lower in plant-based meat alternatives, these products are possibly better suited for consumption by people with biogenic amine sensitivities. A simple and rapid extraction method, followed by HILIC-MS/MS separation and detection was therefore developed as a first step and validated for nine biogenic amines in plant-based meat alternatives. This method showed a strong linear correlation between amine concentration and detector response, high accuracy, and precision (< 12 %), as well as high sensitivity, as proven by the lowest limits of quantification (i.e., the lowest concentration within the calibration model) of 1 mg/kg for all analytes, which also compares well with other methods. Subsequently, as part of a pilot spoilage study, the method was applied to one vegetarian and nine vegan grill sausage alternatives during a period of 32 days of open-package storage at refrigerator temperature. Correlations with the results of microbiological testing of the same samples, as well as with the storage time were investigated. However, the results of the correlation analysis showed that biogenic amines are not suitable as spoilage indicators for plant-based meat alternatives, as almost no increase in biogenic amines was identified during the spoilage study for all the samples investigated. Differences in the microbiota of conventional meat products versus plant-based meat alternatives, as well as possibly lower concentrations of free amino acids, are proposed as reasons for biogenic amines not being similarly prevalent, and consequently, not being suitable spoilage markers in plant-based meat alternatives. However, as spoilage of the analyzed products was evident, both via sensory assessment and appearance of mold growth, further targeted and non-targeted research on potential spoilage markers for plant-based meat alternatives is required in the future.

Identification of technological/metabolic/environmental profiles associated with cheeses accumulating the neuroactive compound tryptamine

Tryptamine is a neuromodulator of the central nervous system. It is also a biogenic amine, formed by the microbial decarboxylation of L-tryptophan. Tryptamine accumulation in cheese has been scarcely examined. No studies are available regarding the factors that could influence its accumulation. Determining the tryptamine content and identifying the factors that influence its accumulation could help in the design of functional tryptamine-enriched cheeses without potentially toxic concentrations being reached. We report the tryptamine concentration of 300 cheese samples representing 201 varieties. 16% of the samples accumulated tryptamine, at between 3.20 mg kg-1 and 3012.14 mg kg-1 (mean of 29.21 mg kg-1). 4.7% of cheeses accumulated tryptamine at higher levels than those described as potentially toxic. Moreover, three technological/metabolic/environmental profiles associated with tryptamine-containing cheese were identified, as well as the hallmark varieties reflecting each. Such knowledge could be useful for the dairy industry to control the tryptamine content of their products.

Advances in Selective Detection of Cadaverine by Electronic, Optical, and Work Function Sensors Based on Cu-Modified B12N12 and Al12N12 Nanocages: A Density Functional Theory (DFT) Study

This work explores Cu-modified B12N12 and Al12N12 nanocages for cadaverine diamine (Cad) detection using advanced density functional theory (DFT) calculations. The study found that Cu modification altered the geometry of the nanocages, increased the dipole moment, reduced the energy gap, and enhanced the reactivity. While pristine B12N12 and Al12N12 were not sensitive to Cad, the modified Cu(b64)B12N12 and Cu(b66)Al12N12 nanocages showed significantly higher electronic sensitivity (Δgap = 39.8% and 35.6%, respectively), surpassing the literature data. However, molecular dynamics (MD) revealed that the Cu(b66)Al12N12 nanocage is not stable in the long term, since the nanocage changes configuration to Cu(b64)Al12N12, which is less sensitive and has an even longer recovery time for Cad sensing. Adsorption energy analysis (Eads) showed a strong interaction of Cad/nanocages, while charge analysis suggested that the nanocages act as Lewis acids, accepting electrons from Cad. UV-vis spectra confirmed that Cu(b64)B12N12 responds optically to the presence of Cad. Furthermore, Cu(b64)B12N12 showed greater sensitivity to Cad compared to NO, H2, H2S, CO, COCl2, N2O, N2 gases, or H2O, showing high selectivity to diamine against interfering gases or water, standing out as a promising material for environmental applications in electronic, optical or work function sensors for cadaverine detection, even in humid environments.

Metabolomic profiling of Fiore Sardo cheese: Investigation of the influence of thermal treatment and ripening time using univariate and multivariate classification techniques

The effect of different sub-pasteurization heat treatments and different ripening times was investigated in this work. The metabolite profiles of 95 cheese samples were analyzed using GC-MS in order to determine the effects of thermal treatment (raw milk, 57 °C and 68 °C milk thermization) and ripening time (105 and 180 days). ANOVA test on GC-MS peaks complemented with false discovery rate correction was employed to identify the compounds whose levels significantly varied over different ripening times and thermal treatments. The univariate t-test classifier and Partial Least Square Discriminant Analysis (PLS-DA) provided acceptable classification results, with an overall accuracy in cross-validation of 76% for the univariate model and 72% from the PLS-DA. The metabolites that mostly changed with ripening time were amino acids and one endocannabinoid (i.e., arachidonoyl amide), while compounds belonging to the classes of biogenic amines and saccharides resulted in being strongly affected by the thermization process.

Do the biogenic amines ethylamine, ethanolamine and methylamine reach toxic concentrations in foods?

Ethylamine, ethanolamine and methylamine are biogenic amines (BA) - active metabolites that, despite having important biological functions, may accumulate at toxic concentrations in certain foods. Very little information exists on the toxicity of these BA in this context. This study provides new insights into their cytotoxicity with respect to a human intestinal epithelial cell line, as assessed using real-time cell analyzer technology. A preliminary evaluation of the cytotoxic mode of action was also performed. The present results show that only ethylamine was cytotoxic for these cells at food concentrations. These new data should help establish legal limits for these BA in foods.

Insights into Genomic Characteristics and Biogenic Amine Degradation Potential and Mechanisms: A Strain of Pediococcus acidilactici Sourced from Doubanjiang

The control of excess biogenic amines (BAs) is crucial for the sustainable development of fermented foods. This study aimed to screen endogenous functional strains in Doubanjiang with the capacity to degrade BAs and to elucidate their application potential. Pediococcus acidilactici L-9 (PA), which was confirmed as a safe strain by phenotypic and genotypic analyses, exhibited an efficient degradation ability on BAs, particularly regarding tyramine. Notably, the degradation of tyramine was maintained at 24.03-50.60% at different temperatures (20-40 °C), pH values (4.0-9.0), and NaCl concentrations (3-18%, w/v). Additionally, genomic data revealed the presence of the laccase-coding gene, which was demonstrated to play a pivotal role in BA degradation by heterologous expression. Further, molecular docking results indicated that the degradation of BA by laccase is closely linked to the electron transfer pathway formed by the substrate and key amino acid residues. Finally, the degradation of tyramine by PA remained within the range of 8.19-64.19% under the simulated system with 6-12% salinity. This study provided valuable insights into the safety of PA and its potential degradation capacity on BAs, particularly in mitigating tyramine accumulation, which could improve the quality of Doubanjiang and other fermented foods.

Modulation of Aromatic Amino Acid Metabolism by Indigenous Non-Saccharomyces Yeasts in Croatian Maraština Wines

This study aimed to provide novel information on the impact of indigenous non-Saccharomyces yeasts, including Metschnikowia chrysoperlae, Metschnikowia sinensis/shanxiensis, Metschnikowia pulcherrima, Lachancea thermotolerans, Hanseniaspora uvarum, Hanseniaspora guilliermondii, and Pichia kluyveri, on metabolites related to the metabolism of tryptophan, phenylalanine, and tyrosine. The experiment included two fermentation practices: monoculture and sequential fermentation with commercial Saccharomyces cerevisiae, using sterile Maraština grape juice. A targeted approach through ultrahigh-resolution liquid chromatography associated with mass spectrometry was used to quantify 38 metabolites. All the indigenous yeasts demonstrated better consumption of tryptophan in monoculture than in interaction with S. cerevisiae. M. sinensis/shanxiensis was the only producer of indole-3-carboxylic acid, while its ethyl ester was detected in monoculture fermentation with H. guilliermondii. H. guilliermondii consumed the most phenylalanine among the other isolates. 5-hydroxy-L-tryptophan was detected in fermentations with M. pulcherrima and M. sinensis/shanxiensis. M. pulcherrima significantly increased tryptophol content and utilised tyrosine in monoculture fermentations. Sequential fermentation with M. sinensis/shanxiensis and S. cerevisiae produced higher amounts of N-acetyl derivatives of tryptophan and phenylalanine, while H. guilliermondii-S. cerevisiae fermentation resulted in wines with the highest concentrations of L-kynurenine and 3-hydroxyanthranilic acid. P. kluyveri produced the highest concentration of N-acetyl-L-tyrosine in monoculture fermentations. These findings highlight the different yeast metabolic pathways.

Using bioactive compounds to mitigate the formation of typical chemical contaminants generated during the thermal processing of different food matrices

With rising consumer awareness of health and wellness, the demand for enhanced food safety is rapidly increasing. The generation of chemical contaminants during the thermal processing of food materials, including polycyclic aromatic hydrocarbons, heterocyclic aromatic amines, and acrylamide happens every day in every kitchen all around the world. Unlike extraneous chemical contaminants (e.g., pesticides, herbicides, and chemical fertilizers), these endogenic chemical contaminants occur during the cooking process and cannot be removed before consumption. Therefore, much effort has been invested in searching for ways to reduce such thermally induced chemical contaminants. Recently, the addition of bioactive compounds has been found to be effective and promising. However, no systematic review of this practical science has been made yet. This review aims to summarize the latest applications of bioactive compounds for the control of chemical contaminants during food thermal processing. The underlying generation mechanisms and the toxic effects of these chemical contaminants are discussed in depth to reveal how and why they are suppressed by the addition of certain bioactive ingredients. Examples of specific bioactive compounds, such as phenolic compounds and organic acids, as well as their application scenarios, are outlined. In the end, outlooks and expectations for future development are provided based on a comprehensive summary and reflection of references.

Multicopper Oxidase from Lactobacillus hilgardii: Mechanism of Degradation of Tyramine and Phenylethylamine in Fermented Food

Elevated levels of biogenic amines (BAs) in fermented food can have negative effects on both the flavor and health. Mining enzymes that degrade BAs is an effective strategy for controlling their content. The study screened a strain of Lactobacillus hilgardii 1614 from fermented food system that can degrade BAs. The multiple copper oxidase genes LHMCO1614 were successfully mined after the whole genome protein sequences of homologous strains were clustered and followed by homology modeling. The enzyme molecules can interact with BAs to stabilize composite structures for catalytic degradation, as shown by molecular docking results. Ingeniously, the kinetic data showed that purified LHMCO1614 was less sensitive to the substrate inhibition of tyramine and phenylethylamine. The degradation rates of tyramine and phenylethylamine in huangjiu (18% vol) after adding LHMCO1614 were 41.35 and 40.21%, respectively. Furthermore, LHMCO1614 demonstrated universality in degrading tyramine and phenylethylamine present in other fermented foods as well. HS-SPME-GC-MS analysis revealed that, except for aldehydes, the addition of enzyme treatment did not significantly alter the levels of major flavor compounds in enzymatically treated fermented foods (p > 0.05). This study presents an enzymatic approach for regulating tyramine and phenylethylamine levels in fermented foods with potential applications both targeted and universal.

Optimising the hygiene of a liquid feeding system to improve the quality of liquid feed for pigs

Poor feeding system hygiene may contribute to uncontrolled spontaneous fermentation in liquid pig feed and its associated undesirable effects. This study aimed to determine the effects of an intensive sanitisation programme in a grow-finisher liquid feeding system by monitoring microbiological and physico-chemical parameters of liquid feed and microbial colonisation of the feeding system surfaces. The sanitisation programme involved a combination of physical and chemical cleaning between batches of grow-finisher pigs, combined with nightly rinsing of the system with an organic acid blend. Improved hygiene of the internal surfaces of the mixing tank and feed pipeline, particularly until week 5 post-cleaning, was evidenced by reduced counts of lactic acid bacteria, total aerobes, Enterobacteriaceae, yeasts and moulds and decreased adenosine triphosphate concentrations. Enterobacteriaceae and moulds remained undetectable on pipeline surfaces for 10 weeks. Scanning electron microscopy of the feed pipelines confirmed these findings. Conversely, the impact on liquid feed microbiology was minimal and short-lived. However, acetic acid, ethanol and biogenic amine concentrations decreased in the feed post-cleaning and no gross energy losses were observed. Therefore, by controlling surface microbial communities on liquid feeding systems via implementation of the sanitisation programme developed in the current study, on-farm liquid feed quality should be improved.

Bacteriocins against biogenic amine-accumulating lactic acid bacteria in cheese: Nisin A shows the broadest antimicrobial spectrum and prevents the formation of biofilms

Cheese is a food in which toxic concentrations of biogenic amines (BA) may be reached, mainly as a consequence of the decarboxylation of determined amino acids by certain lactic acid bacteria (LAB). To maintain the food safety of cheese, environmentally friendly strategies are needed that specifically prevent the growth of BA-producing LAB and the accumulation of BA. The bacteriocins produced by LAB are natural compounds with great potential as food biopreservatives. This work examines the antimicrobial potential of 7 bacteriocin-containing, cell-free supernatants (CFS: coagulin A-CFS, enterocin A-CFS, enterocin P-CFS, lacticin 481-CFS, nisin A-CFS, nisin Z-CFS and plantaricin A-CFS) produced by LAB against 48 strains of the LAB species largely responsible for the accumulation of the most important BA in cheese, that is, histamine, tyramine, and putrescine. Susceptibility to the different CFS was strain-dependent. The histamine-producing species with the broadest sensitivity spectrum were Lentilactobacillus parabuchneri (the species mainly responsible for the accumulation of histamine in cheese) and Pediococcus parvulus. The tyramine-producing species with the broadest sensitivity spectrum was Enterococcus faecium, and Enterococcus faecalis and Enterococcus hirae were among the most sensitive putrescine producers. Nisin A-CFS was active against 31 of the 48 BA-producing strains (the broadest antimicrobial spectrum recorded). Moreover, commercial nisin A prevented biofilm formation by 67% of the BA-producing, biofilm-forming LAB strains. These findings underscore the potential of bacteriocins in the control of BA-producing LAB and support the use of nisin A as a food-grade biopreservative for keeping BA-producing LAB in check and reducing BA accumulation in cheese.

Assessment of the Safety and Probiotic Properties of Enterococcus faecium B13 Isolated from Fermented Chili

Enterococcus faecium B13, selected from fermentation chili, has been proven to promote animal growth by previous studies, but it belongs to opportunistic pathogens, so a comprehensive evaluation of its probiotic properties and safety is necessary. In this study, the probiotic properties and safety of B13 were evaluated at the genetic and phenotype levels in vitro and then confirmed in vivo. The genome of B13 contains one chromosome and two plasmids. The average nucleotide identity indicated that B13 was most closely related to the fermentation-plant-derived strain. The strain does not carry the major virulence genes of the clinical E. faecium strains but contains aac(6')-Ii, ant (6)-Ia, msrC genes. The strain had a higher tolerance to acid at pH 3.0, 4.0, and 0.3% bile salt and a 32.83% free radical DPPH clearance rate. It can adhere to Caco-2 cells and reduce the adhesion of E. coli to Caco-2 cells. The safety assessment revealed that the strain showed no hemolysis and did not exhibit gelatinase, ornithine decarboxylase, lysine decarboxylase, or tryptophanase activity. It was sensitive to twelve antibiotics but was resistant to erythromycin, rifampicin, tetracycline, doxycycline, and minocycline. Experiments in vivo have shown that B13 can be located in the ileum and colon and has no adverse effects on experiment animals. After 28 days of feeding, B13 did not remarkable change the α-diversity of the gut flora or increase the virulence genes. Our study demonstrated that E. faecium B13 may be used as a probiotic candidate.

Spotlight on autochthonous microbiota, morpho-textural characteristics, and volatilome of a traditional Polish cold-smoked raw sausage

The aim of the present study was to obtain information on the bacterial diversity of traditional Polish cold-smoked raw sausages (Kiełbasa polska wędzona) manufactured by two artisanal producers using different selective growth media and a metataxonomic analysis. Physico-chemical and morpho-textural characteristics were also carried out, together with Microextraction-Gas Chromatography/Mass Spectrometry (HS-SPMEGC/MS) to study the volatile organic compounds (VOCs). The results overall obtained allowed a picture of the microbiota, the morpho-textural characteristics, and the volatilome of traditional Polish cold-smoked raw sausages (Kiełbasa polska wędzona) to be drawn for the first time. In more detail, viable counting revealed active populations of presumptive lactobacilli, enterococci, coagulase-negative cocci, and a few spoilage microorganisms typically occurring in raw meat products. The metataxonomic analysis revealed the dominance of Latilactobacillus sakei occurring with a relative frequency between 77% and 89%. Pediococcus pentosaceus, Weissella hellenica, and Leuconostoc carnosum were detected among the minority taxa. In the sausages herein studied, no histamine levels of concern were detected. The Principal Component Analysis (PCA) performed on the Amplicon Sequence Variants (ASVs) did not show significant differences in the microbiota composition among producers. The HS-SPMEGC/MS analysis allowed the detection and identification of more than 90 volatile components belonging to ten main classes, namely: aldehydes, ketones, esters and acetates, acids, alcohols, phenols, furans, sulphur compounds, terpenoids, and benzene derivatives. The detected VOCs originated from spices, smoke, and microbial metabolism. The PCA of volatile compounds allowed differences between the sausage samples of the two producers to be identified.

The gene cluster associated with strong biofilm-formation capacity by histamine-producing Lentilactobacillus parabuchneri encodes a sortase-mediated pilus and is located on a plasmid

Histamine is a biogenic amine synthesized through the enzymatic decarboxylation of the amino acid histidine. It can accumulate at high concentrations in foods through the metabolism of certain bacteria, sometimes leading to adverse reactions in consumers. In cheese, histamine can accumulate at toxic levels; Lentilactobacillus parabuchneri has been identified the major cause of this problem. Previous studies have shown some L. parabuchneri strains to form biofilms on different surfaces, posing a contamination risk during cheese production, particularly for cheeses that are processed post-ripening (e.g., grating or slicing). The food contamination they cause can result in economic losses and even foodborne illness if histamine accumulates in the final product. The aim of the present work was to identify the genes of L. parabuchneri involved in biofilm formation, and to determine their function. The genomes of six strains with different biofilm-production capacities (strong, moderate and weak) were sequenced and analysed. A cluster of four genes, similar to those involved in sortase-mediated pilus formation, was identified in the strong biofilm-producers, suggesting it to have a role in surface adhesion. Cloning and heterologous expression in Lactococcus cremoris NZ9000 confirmed its functionality and involvement in adhesion and, therefore, in biofilm formation. PacBio sequencing showed this cluster to be located on a 33.4 kb plasmid, which might increase its chances of horizontal transmission. These findings provide insight into the genetic factors associated with biofilm formation in histamine-producing L. parabuchneri, and into the risks associated with this bacterium in cheese production.