The aims were to isolate, characterize and quantifylactic acid bacteria's (LAB) antimicrobial activity, and evaluate their application on fish paste. One hundred and thirty two LAB were isolated from mussels of the Argentine coast. From all, 22 LAB isolated which's cell-free supernatant (CFS) presented activity against Listeria innocua and Lactobacillus plantarum were identified as Enterococcus mundtii by biochemical tests and 16S rDNA gene phylogenetic analyses. None of selected strains presented virulence factors. All of them presented the gene that codifies either for mundticin KS, or for mundticin KS and enterocin L50A. Their CFS showed activity against Gram positive bacteria. The interaction among binary mixtures of CFS was assessed against L. innocua, and an additive response was observed. The strain E. mundtii STw38 was selected because of its high capacity to grow and produce bacteriocins at refrigeration temperatures. It was applied as a protective culture to fish paste stored at 4°C. In a first stage fish paste-systems were air-packed, and then, vacuum-packed. In both cases, E. mundtii STw38 survived storage conditions and succeeded in reducing the development of native flora of fish paste. Results suggest that E. mundtii STw38 is a promising strain to be used for fish biopreservation.

Con el objetivo de evaluar la actividad antimicrobiana frente a bacterias multi-drogo resistentes, se estudiaron 234 cepas de actinobacterias aisladas de suelo de Argentina y Perú. Se seleccionaron 13 cepas sobre la base de su actividad antagonista contra Staphylococcus aureus meticilina-resistente (SAMR) y Enterococcus resistente a vancomicina (EVR-van A y van B). La presencia de los genes NRPS, PKS-I y PKS-II fueron investigados por técnicas de PCR. Entre las 13 actinobacterias seleccionadas, la cepa AC69C mostró la mayor actividad en las pruebas de difusión en medio sólido y se evaluó posteriormente la producción de metabolitos antagonistas en medios líquidos. Los mejores resultados se lograron en caldo de fermentación con carbohidratos, al usarse en combinación almidón y glucosa. Se obtuvieron actividades antimicrobianas de 640 unidades arbitrarias (UA), 320 UA, 320 UA y 80 UA contra EVR-van A, EVR-van B, Listeria monocytogenes ATCC7644 y SAMR, respectivamente. La amplificación por PCR del gen ARNr 16S y el análisis filogenético subsecuente de la cepa AC69C exhibieron una homología del 100 % con Streptomyces antibioticus NRRL B-1701. No fue posible establecer una correlación entre los genes amplificados y la actividad antimicrobiana de las 13 cepas seleccionadas. Los resultados de este trabajo demuestran la amplia distribución de las actinobacterias en suelo y la importancia del aislamiento de cepas para la búsqueda de nuevos metabolitos activos contra bacterias multi-drogo resistentes de origen clínico.Palabras clave: Actinobacterias, Streptomyces, metabolitos antimicrobianos. ABSTRACTTwo hundred and thirty four actinobacteria strains were isolated from Argentinian and Peruvian soil in order to evaluate the antimicrobial activity against multidrug resistant bacteria On the basis of their antagonist activity against methicillin-resistant Staphylococcus aureus (MRSA) and two vancomycin-resistant Enterococcus (EVR-Van A and EVR Van B),13 strains were selected. The presence of NRPS, PKS-I and PKS-II genes were also investigated by PCR techniques. Among the 13 selected actinobacteria, strain AC69C displayed the higher activity in diffusion tests in solid medium and was further evaluated for the production of antagonist metabolites in liquid media. The best results were obtained using fermentation broth with carbohydrates, when starch and glucose were used in combination. Antimicrobial activities of 640 arbitrary units (AU), 320 AU, 320 AU and 80 AU were obtained against EVR-Van A, EVR-Van B, Listeria monocytogenes ATCC7644 and MRSA, respectively. PCR amplification of 16S rRNA gene and subsequent phylogenetic analysis of AC69C strain displayed a 100 % homology with Streptomyces antibioticus NRRL B-1701. It was not possible to establish a correlation between the amplified genes and antimicrobial activity of the 13 selected strains. The results of this work show the wide distribution of actinobacteria in soil and the importance of the isolation of strain to screen novel active metabolites against multidrug resistan...

Introduction. Brassica L. vegetables are rich in fiber, minerals, and bioactive compounds. Lactic fermentation can improve their nutritional value. The goal of this study was to evaluate phytase, calcium, phytic acid, total phenolic content, and antioxidants during spontaneous fermentation of white cabbage, red cabbage, and Chinese cabbage. Study objects and methods. The research featured samples of water extract, methanol extract, and brine. The procedure involved monitoring lactic bacteria and pH during cabbage fermentation. Diphenyl-1-picrylhydrazyl radical (DPPH) scavenging assay and cupric reducing antioxidant capacity (CUPRAC) assay were used to measure the antioxidant activity and Folin-Ciocalteau method to determine total phenolic content in the water and methanol extracts. In the brine samples, we studied calcium, phytic acid, and phytase activity. Results and discussion. The samples of white and red cabbage displayed the highest phytase activity on days 5–10 and had a maximal decrease of phytic acid and increase of calcium concentration, while in Chinese cabbage these processes occurred gradually throughout the fermentation. The total phenolic content in the brine and extracts was very similar for all the cultivars throughout the fermentation process. A continuous release from the solid phase to brine could be observed during the first ten days of fermentation. DPPH and CUPRAC assays revealed a similar phenomenon for the total phenolic content. The antioxidant capacity decreased in the water and methanol extracts and increased in the brine. At the end of fermentation, the red cabbage samples demonstrated a significant increase in the total phenolic content and total antioxidant activity, which was less prominent in the Chinese cabbage. The samples of white cabbage, on the contrary, showed a decrease in these parameters. Conclusion. Fermentation made it possible to increase the concentration of free calcium in white, red, and Chinese cabbages, as well as improve the antioxidant capacity of red and Chinese cabbages.

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En este estudio se evaluó la actividad antibacteriana de una cepa de Enterococcus mundtii tw278 productora de bacteriocina aislada del contenido intestinal de Hemiodema spectabilis (pepino de mar), recolectado en la costa patagónica de la Argentina. La cepa se identificó mediante pruebas bioquímicas y análisis filogenético del gen ARNr 16S. Además, se detectó el gen estructural que codifica para la mundticina KS mediante técnicas de PCR. La investigación de los factores de virulencia reveló que la cepa de E. mundtii tw278 no presentó actividad gelatinasa ni hemolítica y fue susceptible a todos los antibióticos analizados, excepto la cefalotina. La máxima actividad inhibitoria se logró al final de la fase logarítmica cuando se utilizó el caldo MRS como medio de cultivo a 35 °C. Luego de 12 h de incubación, el sobrenadante libre de células (SLC) alcanzó un título de 163 840 unidades arbitrarias por mililitro contra la cepa indicadora de Listeria innocua ATCC 33090. El SLC exhibió actividad contra todas las cepas de Listeria ensayadas, Enterococcus faecalis ATCC 29212, enterococos resistentes a vancomicina (Van A, Van B y Van C), Lactobacillus plantarum TwLb 5 y Vibrio anguilarum V10. Este sería el primer estudio que informa el aislamiento de una cepa bacteriocinogénica de E. mundtii aislada del contenido intestinal de Hemiodema spectabilis.