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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.

El sector agrícola está atrapado en las polémicas vinculadas a la transición energética y económica. ¿Cómo hacer frente a los retos de la sostenibilidad en una sociedad neoliberal repleta de desigualdades?

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.

Biogenic amines (BA) are nitrogenous compounds with biological activity that can accumulate in cheese in toxic concentrations due to the metabolism of some lactic acid bacteria (LAB). Putrescine, one of the BA most frequently found in cheese, is synthesized from arginine through the agmatine deiminase (AGDI) route. Arginine is first decarboxylated to produce agmatine, which is subsequently deaminated by the agmatine deiminase pathway (AgdI) to produce putrescine. Our group has identified Enterococcus faecalis and some strains of Lactococcus lactis as those responsible for the conversion of agmatine to putrescine in cheese. However, little is known about which microorganisms perform the decarboxylation of arginine to produce agmatine. Moreover, these microorganisms would be of additional interest since there is evidence of the usefulness of agmatine in the treatment of neuropathies and mood disorders. The identification of BA-producing microorganisms in food samples is usually based on the pH rise due to the decarboxylation of the amino-acid substrate, revealed by a pH indicator. However, for the detection of agmatine-producing microorganisms in cheese, this would lead to a large number of false positives, since many LAB possess the arginine deiminase activity which, from arginine, produces ornithine and ammonium, which causes a pH increase even greater. To solve this problem, we have designed a new biosensor for the detection of agmatine-producing microorganisms based on the agmatine-inducible transcription system (ACE) designed in our group. Here we describe the design and optimization of a protocol that has allowed us to isolate and identify agmatine-producing microorganisms from dairy samples.

The rise of antimicrobial resistant (AMR) bacteria is a major health concern, especially with regard to members of the ESKAPE group, to which vancomycin-resistant (VRE) Enterococcus faecium belongs. Phage therapy has emerged as a novel alternative for the treatment of AMR infections. This, however, relies on the isolation and characterisation of a large collection of phages. This work describes the exploration of human faeces as a source of new E. faecium-infecting phages. Phage vB_EfaH_163 was isolated and characterised at the microbiological, genomic, and functional levels. vB_EfaH_163 phage, a new member of Herelleviridae, subfamily Brockvirinae, has a dsDNA genome of 150,836 bp that does not harbour any virulence factors or antibiotic resistance genes. It infects a wide range of E. faecium strains of different origins, including VRE strains. Interestingly, it can also infect Enterococcus faecalis strains, even some that are linezolid-resistant. Its capacity to control the growth of a clinical VRE isolate was shown in broth culture and in a Galleria mellonella animal model. The discovery and characterisation of vB_EfaH_163 increases the number of phages that might be used therapeutically against AMR bacteria.

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

Enterococcus is a diverse genus of Gram-positive bacteria belonging to the lactic acid bacteria (LAB) group. It is found in many environments, including the human gut and fermented foods. This microbial genus is at a crossroad between its beneficial effects and the concerns regarding its safety. It plays an important role in the production of fermented foods, and some strains have even been proposed as probiotics. However, they have been identified as responsible for the accumulation of toxic compounds—biogenic amines—in foods, and over the last 20 years, they have emerged as important hospital-acquired pathogens through the acquisition of antimicrobial resistance (AMR). In food, there is a need for targeted measures to prevent their growth without disturbing other LAB members that participate in the fermentation process. Furthermore, the increase in AMR has resulted in the need for the development of new therapeutic options to treat AMR enterococcal infections. Bacteriophages have re-emerged in recent years as a precision tool for the control of bacterial populations, including the treatment of AMR microorganism infections, being a promising weapon as new antimicrobials. In this review, we focus on the problems caused by Enterococcus faecium and Enterococcus faecalis in food and health and on the recent advances in the discovery and applications of enterococcus-infecting bacteriophages against these bacteria, with special attention paid to applications against AMR enterococci.

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.

In recent years, there has been a growing interest in obtaining probiotic bacteria from plant origins. This is the case of Lactiplantibacillus pentosus LPG1, a lactic acid bacterial strain isolated from table olive biofilms with proven multifunctional features. In this work, we have sequenced and closed the complete genome of L. pentosus LPG1 using both Illumina and PacBio technologies. Our intention is to carry out a comprehensive bioinformatics analysis and whole-genome annotation for a further complete evaluation of the safety and functionality of this microorganism. The chromosomic genome had a size of 3,619,252 bp, with a GC (Guanine-Citosine) content of 46.34%. L. pentosus LPG1 also had two plasmids, designated as pl1LPG1 and pl2LPG1, with lengths of 72,578 and 8713 bp (base pair), respectively. Genome annotation revealed that the sequenced genome consisted of 3345 coding genes and 89 non-coding sequences (73 tRNA and 16 rRNA genes). Taxonomy was confirmed by Average Nucleotide Identity analysis, which grouped L. pentosus LPG1 with other sequenced L. pentosus genomes. Moreover, the pan-genome analysis showed that L. pentosus LPG1 was closely related to the L. pentosus strains IG8, IG9, IG11, and IG12, all of which were isolated from table olive biofilms. Resistome analysis reported the absence of antibiotic resistance genes, whilst PathogenFinder tool classified the strain as a non-human pathogen. Finally, in silico analysis of L. pentosus LPG1 showed that many of its previously reported technological and probiotic phenotypes corresponded with the presence of functional genes. In light of these results, we can conclude that L. pentosus LPG1 is a safe microorganism and a potential human probiotic with a plant origin and application as a starter culture for vegetable fermentations.

La triptamina es una amina biógena (AB) que se sintetiza en animales, plantas y microorganismos mediante la descarboxilación del aminoácido triptófano. La triptamina puede actuar como neurotransmisor o neuromodulador del sistema nervioso central, donde se encuentra en bajas concentraciones. Como otras AB, se puede acumular en los alimentos y ha sido reconocida por la Agencia Europea de Seguridad Alimentaria (EFSA) como potencial agente tóxico. Hasta el momento ningún organismo regulador ha establecido oficialmente un umbral de seguridad para su ingesta, aunque en nuestro grupo de investigación hemos demostrado su citotoxicidad in vitro [1]. Sin embargo, la triptamina se considera un SRA (agente liberador de serotonina) [2], un tipo de fármaco que induce la liberación de serotonina en la hendidura sináptica neuronal. Los SRA se han utilizado clínicamente como supresores del apetito y también se han propuesto como nuevos antidepresivos y ansiolíticos. Además, se ha propuesto que la triptamina es un potenciador de la actividad serotoninérgica [3]. También hay estudios que muestran los efectos beneficiosos de la triptamina producida por la microbiota intestinal sobre el sistema gastrointestinal, ya que aumenta la secreción de fluidos dependientes de aniones y acelera el tránsito gastrointestinal [4]. Durante la maduración del queso se produce la proteólisis de las caseínas y, al igual que sucede con otros aminoácidos, tiene lugar la liberación de triptófano a partir del cual podría sintetizarse la triptamina. Dado que los datos disponibles actualmente son muy escasos, nos propusimos como objetivo estudiar el contenido de triptófano y triptamina en distintos tipos de quesos e identificar los microorganismos productores. En este trabajo, se ha analizado mediante un método de cromatografía líquida (UHPLC) desarrollado en nuestro grupo, el contenido de triptófano y triptamina en más de 250 variedades de queso. Aplicando técnicas de análisis multivariante se han identificado

The quality and commercial value of a cheese depends on its organoleptic qualities and nutritional properties. Moreover, consumers and industry interest in a cheese may be increased if it also contains bioactive compounds with demonstrated health-promoting effects, such as gamma amino butyric acid (GABA), the main inhibitory neurotransmitter of the human central nervous system. Indeed, the ingestion of a GABA-enriched cheese has proven an anti-hypertensive effect on human [1]. In our group, we have demonstrated the presence of large quantities of GABA in several cheese samples from Europe [2]. Gy¿r-Moson-Sopron megyei Csemege is one of the most traditional cow¿s milk cheese specialities in Hungary. It has been registered as a protected geographical indication (PGI) in the European Union, based on tradition, a unique production method, the specific skills required for production, and the reputation of the cheese. To date, no published studies concerning to this cheese variety are available in the scientific literature. The aim of the present study was to initiate the chemical and microbiological characterization of Gy¿r-Moson-Sopron megyei Csemege PGI cheese. Thus, we determined the content of free proteinogenic aminoacids, and GABA by ultra-high performance liquid chromatography (UHPLC). Also, for safety considerations, we examined the content of biogenic amines. Finally, we determined the volatile organic composition of the cheese by gas chromatography coupled to mass spectrometry. The microbial diversity of Gy¿r-Moson-Sopron megyei Csemege PGI cheese was explored by means of viable counting on selective culture media. Moreover, individual colonies grown on MRS and M17 culture media whose morphology resembled that of lactic acid bacteria were cultured in acidic conditions in the presence of the precursor monosodium glutamate and screened for its potential ability to change the colour of the medium, due to the presumptive production of GABA. The confirmation of thos

Las aminas biógenas (AB) son compuestos nitrogenados derivados de aminoácidos y que tienen actividad biológica. Las AB se pueden acumular en algunos tipos de quesos a concentraciones tóxicas, debido al metabolismo de algunas bacterias del ácido láctico (BAL). La putrescina es una de las AB que se encuentra más frecuentemente en quesos y se sintetiza a partir del aminoácido arginina mediante una descarboxilación y una desaminación [1]. Dependiendo del orden de estas dos reacciones, se diferencian dos rutas diferentes, siendo la ruta de la agmatina deiminasa (AGDI) la que prevalece en alimentos fermentados, incluido el queso. En esta ruta, la arginina es descarboxilada por la arginina decarboxilasa (Adc) para dar lugar a agmatina, la cual es posteriormente desaminada por la actividad de la agmatina deiminasa (AgdI) generándose como producto final la putrescina. En nuestro grupo hemos identificado Enterococcus faecalis y algunas cepas de Lactococcus lactis como los principales microorganismos responsables de la conversión de agmatina a putrescina en quesos [2]. Sin embargo, se desconoce que microorganismos realizan el primer paso de la ruta, es decir, la descarboxilación de la arginina para producir agmatina. Nuestro objetivo es aislar e identificar los microorganismos responsables de este paso imprescindible para la acumulación de putrescina. Además, estos microorganismos tendrían un doble interés, ya que existen evidencias clínicas de la utilidad de la agmatina en el tratamiento de enfermedades relacionadas con neuropatías y con trastornos del estado de ánimo como la ansiedad y la depresión [4]. También está aprobada como suplemento alimenticio para el aumento de la masa muscular. La identificación de microorganismos productores de AB en muestras de alimentos suele basarse en el aumento de pH debido a la descarboxilación del aminoácido sustrato, revelado por un indicador de pH añadido al medio de cultivo suplementado con el aminoácido correspondiente, arginina en est

Este libro surge como una iniciativa para compilar una serie de artículos alumbrados a partir de la génesis del Grupo CURIE (Científic@s Unid@s por la Reactivación de la Investigación en España), semilla de la Asociación Española para el Avance de la Ciencia (AEAC). Durante meses sus miembros estuvieron intercambiando reflexiones y debatiendo sobre la distancia entre la ciencia y la sociedad, y la necesidad de crear una asociación que llenase ese vacío entre los científicos y los ciudadanos, que apostase por llevar la ciencia y los conocimientos generados por la misma a toda la sociedad, tal y como establecen la Declaración de Derechos Humanos y la Constitución Española, en su artículo 44.

La conciencia ambiental debe ir paralela con la conciencia humanística para que nos preocupemos de que todos los pueblos del planeta se beneficien de este movimiento ecológico, en lugar de que el bienestar de unos implique la marginación y explotación de otros.

La regeneración mundial necesita que los pactos verdes se apoyen en la inteligencia colectiva para poder evitar la catástrofe ambiental desde los valores y el bienestar común

Los autores reflexionan desde una perspectiva de análisis CTS (Ciencia, Tecnología y Sociedad) sobre los múltiples dilemas que se nos plantean para hacer frente a la gran cantidad de información, no siempre veraz, que recibimos tanto desde los medios de comunicación como desde las diferentes redes sociales

Una reflexión de Emilio Muñoz sobre los problemas de salud mental en nuestra sociedad, con mención especial al lo sucedido durante los juegos olímpicos

En este artículo nuestros socios, Emilio Muñoz, Victor Ladero y Jesús Rey exploran las posibilidades que ofrece el análisis de los datos de patrones de lecturas de artículos de divulgación científica en plataformas online y en abierto, usando para este análisis inicial los datos referentes a varios artículos publicados por ellos en la plataforma para la divulgación The Conversation. Para ello has utilizado el método científico e incluso han acercado el análisis al de sistemas biológicos y reflexionan sobre la importancia de los datos obtenidos para entender la complejidad que subyace en la comunicación científica

Currently, consumption of spontaneously fermented milks is common in Algeria, making it a feasible source of diverse lactic acid bacteria (LAB) with the potential to be used as adjunct cultures to improve quality and safety of fermented dairy products. In this context, to select eligible indigenous strains which could be applied as bioprotective and/or starter cultures, the present study aimed to characterize the genomic variability, biotechnological potential, and safety of thirty-eight LAB isolated from Algerian dairy and farm sources of western Algeria. The isolates were unequivocally identified by 16S rRNA gene and fingerprint-based methods. The following species were identified: Enterococcus faecium (n = 15), Enterococcus durans (n = 2), Enterococcus hirae (n = 2), Enterococcus lactis (n = 1), Lactiplantibacillus plantarum (n = 6), Lactococcus lactis (n = 4), Levilactobacillus brevis (n = 3), Lacticaseibacillus paracasei (n = 3), Lacticaseibacillus rhamnosus (n = 1), and Pediococcus acidilactici (n = 1). Among the strains, three of them, L. lactis LGMY8, Lb. plantarum LGMY30 and Lb. paracasei LGMY31 were safe and showed some valuable biotechnological properties, such as high acidification, proteolytic activity, EPS production, and inhibition of undesirable bacteria that made them powerful candidates to be used as starter.

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

Dispersion of transferable oxazolidinone resistance genes among enterococci poses a serious problem to human health. Prompt detection of bacteria carrying these genes is crucial to avoid their spread to multidrug-resistant bacteria. The aim of the study was to describe the presence of optrA-positive isolates among enterococci in a Spanish hospital, and to determine their genetic context and location through whole genome sequencing. All enterococci recovered in a Spanish hospital (Hospital El Bierzo; HEB) from February to December 2018 (n = 443), with minimal inhibitory concentrations (MICs) to linezolid (LZD) ≥4 mg/L, were tested by polymerase chain reaction for the presence of cfr, optrA, and poxtA transferable genes. Only four Enterococcus faecalis isolates (0.9%) had LZD MICs ≥4 mg/L and none of them was positive for cfr or poxtA genes. However, the optrA gene was detected in three isolates collected from urine samples of community patients, whose genomes were sequenced and subjected to bioinformatics analysis. These isolates belonged to different clones: ST7, ST480, and ST585. In these three isolates, the optrA gene was located on plasmids, associated with IS1216 in different arrays. In one isolate, the optrA plasmid coexists with a second plasmid, which carried multiple resistance genes for different classes of antibiotics. Detection of optrA-positive E. faecalis isolates in the community is a matter of concern. The spread of these bacteria into hospital settings, particularly in those, such as the HEB, where vancomycin-resistant enterococci are endemic, should be avoided, to preserve the efficacy of the last-resort oxazolidinones.

La depresión es una enfermedad creciente en todo el mundo, que se estima afectan a más de 300 millones de personas. En la actualidad existen evidencias de que los microorganismos en el intestino podrían estar involucrados en los trastornos mentales a través del eje cerebro-intestino. De hecho, se ha propuesto el uso de probióticos como terapia adjunta en el manejo de la depresión. Recientemente, se ha visto que los efectos beneficiosos de estos microorganismos estarían mediados por su capacidad para producir y liberar compuestos neuroactivos. Entre estos microorganismos, destacan las bacterias del ácido láctico (BAL) ya que son especies seguras, que juegan un papel fundamental en la elaboración de alimentos fermentados, como el queso, y que podrían utilizarse para la elaboración de alimentos fermentados funcionales enriquecidos en compuestos neuroactivos para ayudar en el tratamiento de la depresión. Dentro de estos compuestos destaca la ¿-feniletilamina (PEA), la cual se utiliza en la actualidad como suplemento nutricional para mejorar el estado de ánimo y el bienestar, entre otros beneficios. En este trabajo se llevó a cabo una búsqueda de BAL capaces de producir PEA y que tuviese potencial biotecnológico para ser utilizadas como cultivos, ya sea iniciadores o adjuntos, para la elaboración de alimentos lácteos fermentados funcionales. Para ello se partió de muestras de queso con alto contenido en PEA y se llevó a cabo una búsqueda, identificación y tipificación de potenciales productores de PEA. Las cepas identificadas como Enterococcus durans, fueron caracterizadas a nivel tecnológico para su inclusión en productos lácteos fermentados. Se seleccionó la cepa con mejores aptitudes tecnológicas y se realizó un estudio de la influencia de factores tecnológicos en su capacidad de producir PEA, comprobando que la temperatura y la sal afectan positiva y negativamente a su producción.

Some bacteria decarboxylate amino acids as a means of resisting acid stress. It is a mechanism commonly used by bacteria in fermented dairy products. The decarboxylation of histidine to histamine occurs frequently in some types of cheese, but high concentrations of histamine can be harmful to consumers. Not all amino acid decarboxylation products are, however, undesirable. GABA, the decarboxylation product of glutamate, has positive effects on human health. Although histamine and GABA accumulate in large quantities in many types of cheese, there is little information regarding their relationship, and that which is available is restricted to a few cheese varieties. The present work examines whether cheeses exist with high concentrations of GABA but safe concentrations of histamine. The GABA and histamine contents of 250 cheeses representing 143 European varieties were examined, and the technological, environmental and metabolic (TEM) traits governing their accumulation identified. Two TEM profiles were associated with high GABA contents and safe histamine concentrations. These findings could help the dairy industry select the best technological conditions for making GABA-rich, histamine-safe cheeses.

Research background. Consumption of spontaneously fermented camel’s milk is common in Algeria, making it a feasible source of diverse lactic acid bacteria (LAB) with the potential to be used as adjunct cultures to improve quality and safety of fermented dairy products. Experimental approach. Twelve raw camel´s milk samples were used as a source of indigenous LAB, which were further characterised by examining 39 phenotypic traits with technological relevance. Results and conclusions. Thirty-five non-starter LAB (NSLAB) were isolated from 12 Algerian raw camel's milk samples and they were microbiologically, biochemically and genetically characterised. Some isolates showed proteolytic activity, acidifying capacity, the ability to use citrate, and to produce dextran and acetoin. Ethanol, acetaldehyde, methyl acetate, acetoin and acetic acid were the major volatile compounds detected. Cluster analysis performed using the unweighted group with arithmetic average (UPGMA) method, and based on the thirty-nine phenotypic characteristics investigated, reflected the microbial diversity that can be found in raw camel´s milk. Novelty and scientific contribution. The isolated strains, from a non-typical source, showed interesting technological traits to be considered as potential adjunct cultures. Cluster analysis based on the examined phenotypic characteristics proved to be a useful tool for the typification of isolates when no genetic information is available. These findings may be of use towards an industrialised production of camel's milk dairy products

Histamine, one of the most toxic and commonly encountered biogenic amines (BA) in food, is produced by the microbial decarboxylation of histidine. It may accumulate at high concentrations in fish and fermented food. Cheese has some of the highest histamine concentrations, the result of the histidine-decarboxylase activity of certain lactic acid bacteria (LAB). The present work describes the nucleotide sequence and transcriptional organization of the gene cluster responsible for histamine biosynthesis (the HDC cluster) in Lactobacillus vaginalis IPLA 11064 isolated from cheese. The influence of histidine availability and pH on histamine production and the expression of the HDC cluster genes is also examined. As expected, the results suggest that the production of histamine under acidic conditions improves cell survival by maintaining the cytosol at an appropriate pH. However, the transcriptional regulation of the HDC cluster is quite different from that described in other dairy histamine-producing LAB, probably due to the lack of a termination-antitermination system in the histidyl-tRNA synthetase gene (hisS).

Los autores reflexionan sobre los miedos y las incertidumbres que genera el COVID-19. El miedo a lo desconocido de esta enfermedad, así como la incertidumbre sobre las herramientas de que disponemos para enfrentarnos a ella. A pesar de aplicar el método científico, aún no tenemos certezas sobre su desarrollo, incertidumbre de la que se aprovecha la infodemia para extenderse en la sociedad utilizando las redes sociales como vehículo de transmisión

El marco de la presentación de la Iniciativa Cívica por un Pacto para la Reconstrucción Social de España, los autores reivindican la necesidad de estatutos especiales para los colectivos de trabajadores que han demostrado ser esenciales durante esta pandemia y que por sus peculiaridades requieren de estatutos que faciliten reconocer la dedicación, la profesionalidad y la excelencia de estos colectivos.