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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, i.e., 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, while 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.

Cheese is a fermented food in which toxic concentrations of biogenic amines (BAs) may accumulate, mainly as a result of the metabolism of certain lactic acid bacteria (LAB); the formation of these compounds needs to be limited. This work reports the antimicrobial potential of bacteriocin AS-48 against the LAB largely responsible for the accumulation of the BA histamine, tyramine and putrescine in cheese. Most of the 50 analysed BA-producing LAB strains were sensitive to AS-48. The bacteriocin also prevented biofilm formation of 92% of the BA-producing strains tested. This result is of great technological importance since, in cheese production, biofilms are an important source of contamination by BA-producing LAB. This study supports the potential use of AS-48 as a biopreservative for controlling BA-producing LAB in fermented food.

Bacterial biofilms on the surfaces of food industry equipment act as reservoirs of spoilage and pathogenic bacteria that contaminate food matrix constituting a health threat. Lentilactobacillus parabuchneri is a heterofermentative lactic acid bacteria present in the microbiota of fermented dairy products that was identified as the main responsible for the production and accumulation of elevated concentrations of histamine -a toxic biogenic amine- in cheese [1]. Some L. parabuchneri strains have been shown to produce biofilms on the surfaces of dairy industrial equipment [2]. Such biofilms are a reservoir of histamine producers that contaminate the cheese during the elaboration processes and results in the accumulation of histamine in the final product. The ability to form biofilms in 25 L. parabuchneri strains isolated from cheese was evaluated. The strains were categorized as strong, moderate and weak biofilms formers and two representatives from each category were selected for further work. The influence of temperature and pH -relevant factors during cheese elaboration- in the capacity of the selected strains to form biofilm, was studied. The adherence to different materials -plastic, rubber, stainless steel, and wood- commonly used in the manufacture of cheese, was also evaluated. In addition, the composition of the extracellular matrix of L. parabuchneri biofilms was also investigated using different approaches, namely confocal microscopy, real-time infrared spectroscopy and enzymatic treatments. Genome sequencing and analysis of the selected strains made it possible to identify a cluster of 4 genes -present only in the strong biofilm-forming strains- which showed high similarity with genes involved in pili formation, following the sortase-mediated pilus model. Therefore, such genes could be related to the ability to adhere to surfaces, the first step of biofim formation. The heterologous expression of the cluster in Lactococcus lactis demonstrated its relevant

Lentilactobacillus parabuchneri, a lactic acid bacterium, is largely responsible for the production and accumulation of histamine, a toxic biogenic amine, in cheese. L. parabuchneri strains can form biofilms on the surface of industry equipment. Since they are resistant to cleaning and disinfection, they may act as reservoirs of histamine-producing contaminants in cheese. The aim of this study was to investigate the biofilm-producing capacity of L. parabuchneri strains. Using the crystal violet technique, the strains were first categorized as weak, moderate or strong biofilm producers. Analysis of their biofilm matrices revealed them to be mainly composed of proteins. Two strains of each category were then selected to analyze the influence on the biofilm-forming capacity of temperature, pH, carbon source, NaCl concentration and surface material (i.e., focusing on those used in the dairy industry). In general, low temperature (8 °C), high NaCl concentrations (2–3% w/v) and neutral pH (pH 6) prevented biofilm formation. All strains were found to adhere easily to beech wood. These findings increase knowledge of the biofilm-forming capacity of histamine-producing L. parabuchneri strains and how their formation may be prevented for improving food safety.

Foodborne pathogenic microorganisms form biofilms at abiotic surfaces, which is a particular challenge in food processing industries. The complexity of biofilm formation requires a fundamental understanding on the involved molecular mechanisms, which may then lead to efficient prevention strategies. In the present study, biogenic amine producing bacteria, i.e., Lentilactobacillus parabuchneri DSM 5987 strain isolated from cheese were studied in respect with biofilm formation, which is of substantial relevance given their contribution to the presence of histamine in dairy products. While scanning electron microscopy was used to investigate biofilm adhesion at stainless steel surfaces, in situ infrared attenuated total reflection spectroscopy (IR-ATR) using a custom flow-through assembly was used for real-time and non-destructive observations of biofilm formation during a period of several days. The spectral window of 1700–600 cm provides access to vibrational signatures characteristic for identifying and tracking L. parabuchneri biofilm formation and maturation. Especially, the amide I and II bands, lactic acid produced as the biofilm matures, and a pronounced increase of bands characteristic for extracellular polymeric substances (EPS) provide molecular insight into biofilm formation, maturation, and changes in biofilm architecture. Finally, multivariate data evaluation strategies were applied facilitating the unambiguous classification of the observed biofilm changes via IR spectroscopic data.

La histamina es una amina biógena que se sintetiza mediante descarboxilación enzimática del aminoácido histidina y que debido al metabolismo de algunas bacterias se puede acumular en concentraciones elevadas en los alimentos, provocando reacciones adversas en los consumidores. El queso es uno de los alimentos en los que más frecuentemente se acumula histamina a concentraciones tóxicas, siendo Lentilactobacillus parabuchneri el principal responsable. Trabajos previos revelaron la capacidad de algunas de sus cepas de formar biofilms en distintas superficies, lo que constituye un riesgo de contaminación de los quesos durante su producción, especialmente de los quesos procesados, como los rallados y cortados. Los biofilms son comunidades de microorganismos que permanecen adheridos a una superficie y embebidos en una matriz extracelular. Su presencia en la industria alimentaria es muy habitual, pudiendo adherirse a las superficies de los equipamientos utilizados, provocando la contaminación de los alimentos. Dependiendo de las especies pueden causar su deterioro, con la consecuente pérdida económica, e incluso pueden ser responsables de intoxicaciones alimentarias. El objetivo del presente trabajo fue identificar los genes de L. parabuchneri involucrados en la formación del biofilm y determinar su funcionalidad. Con este fin, se secuenció y analizó el genoma de 6 cepas con diferentes capacidades de producción de biofilm (fuertes, moderadas y débiles). En ellas, se confirmó la presencia del cluster HDC de producción de histamina. Además, se identificó un cluster de 4 genes, presente únicamente en las cepas formadoras de biofilm fuerte, que mostró similitud con genes implicados en la formación de pili, siguiendo el modelo sortase-mediated pilus, y que por tanto podría estar relacionado con la capacidad de adhesión a superficies. Se realizó la clonación de las 8kb del cluster, y su expresión heteróloga en Lactococcus lactis NZ9000 permitió comprobar su funcionalidad e impli

Se denomina biofilms o biopelículas a comunidades de microorganismos que permanecen adheridos a una superficie y embebidos en una matriz extracelular formada por polisacáridos, proteínas, ADN de las células lisadas y/o ácidos teicoicos. La formación y el desarrollo de los biofilms dependen de múltiples factores, incluyendo la especie y cepa microbiana, las propiedades de los materiales de la superficie a la que se adhieren y las condiciones ambientales (pH, temperatura¿). La presencia de biofilms es habitual en la industria alimentaria, ya que las bacterias pueden adherirse a la superficie de algunos de los materiales empleados: plástico, metal, goma y madera. Estos biofilms son muy resistentes a los métodos de lavado y desinfección de las instalaciones y actúan como un reservorio de microorganismos que contaminan los alimentos, deteriorándolos y provocando pérdidas económicas significativas. Además, dependiendo de las especies presentes en el biofilm, pueden incluso ser responsables de intoxicaciones alimentarias y de la transmisión de enfermedades. Las bacterias del ácido láctico (BAL) cumplen un papel fundamental en la industria alimentaria. Sin embargo, algunas BAL son responsables de la acumulación de aminas biógenas (AB), como la histamina, en altas concentraciones en alimentos fermentados. El consumo de alimentos con concentraciones elevadas de histamina provoca reacciones adversas en los consumidores y por este motivo, las autoridades sanitarias recomiendan evitar su presencia en los alimentos. Lentilactobacillus parabuchneri ha sido descrito como el principal responsable de la acumulación de histamina en quesos. Trabajos previos realizados en nuestro grupo de investigación revelaron la capacidad de algunas cepas de L. parabuchneri de formar biofilms, incluso sobre el acero empleado en la maquinaria industrial, lo que constituye un riesgo de contaminación de los quesos durante el proceso de elaboración que tendrá como consecuencia la posterior acumulación de

Lentilactobacillus parabuchneri is a heterofermentative lactic acid bacteria usually present in fermented dairy products that was identified as the main responsible for the production and accumulation of elevated concentrations of histamine in cheese. The consumption of cheeses with high concentration of this biogenic amine has toxicological effects in consumers and is a safe concern. Our group has found that some L. parabuchneri strains produce biofilms on the surface of dairy industry equipment. These biofilms are very resistant against cleaning and disinfection procedures, and act as reservoirs of histamine-producing bacteria. Therefore, the cheeses become contaminated during the elaboration processes and when consumed, they may have undesirable concentrations of histamine. The present work was aimed to investigate the biofilm production of 25 dairy L. parabuchneri strains. The strains were categorized as strong, moderate and weak biofilms formers and two of them were selected from each category. The influence of temperature, surface materials, and pH on their ability to form biofilms was studied. In addition, the nature of extracellular matrix was also investigated. This study highlights the importance of the industrial environment control to decrease undesired bacterial biofilms and improve cheese safety.