Emilio Rogelio Marguet

Sakacin Q produced by Lactobacillus curvatus ACU-1: Functionality characterization and antilisterial activity on cooked meat surface

This work was conducted to evaluate the antilisterial activity of sakacin Q produced by Lactobacillus curvatus ACU-1 on the surface of cooked pork meat. A genetic re-characterization of the producer strain and a study of the structural genes involved in bacteriocin production were carried out as complementary data. Studies indicated that the bacteriocin was not attached to the producer cells favoring pre-purifications steps. Bacteriocin effectiveness was not compromised by adsorption to meat and fat tissues. Several ways of dispensing the bacteriocin onto the meat surface, namely cell culture, cell free supernatant (CFS), a mixture of both and freeze-dried reconstituted CFS, were investigated. The use of the latter was the most effective one to control Listeria growth within studied systems. L. curvatus ACU-1 and its bacteriocin presented promising technological characteristics that made them suitable for meat biopreservation.

Biosilo de residuos de merluza y harina de cebada fermentados con bacterias ácido lácticas seleccionadas

Suitability of Lactococcus lactis Tw34 and Lactobacillus plantarum Lb7 as bio-silage inoculants was studied. Experiments were carried out with a mixture of hake (Merluccius hubbsi) by-products and barley meal fermented during 7 days. A sample acidified with lactic acid was used as control. In biological mixtures, the pH dropped below 5,0 after 2 days of fermentation and remained stable until the end of the experience. Maximum populations (> 109 CFU/g) were reached after 5 days of incubation at 18°C. Water soluble peptides concentration increased during the 7 days of incubation and no significant differences (p 0,05). After 7 days, phosphorous concentrations reached 2.26 and 2,42 g/100 g in bio-silages fermented with Lc. lactis Tw34 and Lb. plantarum Lb7, respectively, while control values remains almost stable (1,61 g/100 g). At the end of the experience, inhibitory activity of trypsin was abolished in both bio-silage while in control sample antinutritional factors remained active. The results indicated the feasibility of the use of the selected mixture as substrate for bio-silage production and the effectiveness Lc. lactis Tw34 and Lb. plantarum Lb7 as inoculants.

Actinomicetos aislados de Argopecten purpuratus productores de enzimas extracelulares y con actividad inhibitoria de patógenos marinos

espanolEl presente trabajo tiene como objetivos evaluar actinomicetos aislados de Argopecten purpuratus y su capacidad de producir enzimas extracelulares (EEC), asi como determinar su actividad antagonista frente a patogenos de importancia en acuicultura. Se aislaron 27 cepas de actinomicetos a partir de la masa visceral de especimenes adultos de A. purpuratus colectados en la localidad de Pisco y Pucusana (Lima) - Peru. El 81,5 y 59,2% de los aislados mostraron actividad proteolitica y lipolitica, respectivamente. Asimismo, las cepas senaladas como ARG 9-II, ARG 10-II, ARG 12-II y ARG 14-II mostraron mayor actividad antimicrobiana contra los patogenos Vibrio anguillarum, V. vulnificus, V. alginolitycus, Lactococcus garvieae, Streptococcus iniae, Carnobacterium piscicola y Yersinia ruckeri. La cepa ARG 4-II exhibio la mayor actividad inhibitoria. La Concentracion Minima Inhibitoria (CMI) del extracto diclorometanico de la cepa ARG 12-II frente a V. anguillarum y V. alginolyticus fue calculada en 250 y 500 µg ml-1 respectivamente. Las cepas ARG 9-II, ARG 12-II y ARG 14-II sobre la base del analisis de su ARNr 16S fueron identificadas como Streptomyces variabilis, St. labedae y St. rochei, respectivamente. Los resultados senalan a A. purpuratus como una fuente promisoria de aislamiento de nuevas cepas de Streptomyces con alta capacidad bioactiva y antagonista contra patogenos de importancia en acuicultura y con posibilidades de ser desarrolladas como potenciales agentes probioticos en el futuro. EnglishThe present study was aimed at isolating Argopecten purpuratus-associated actinomycetes strains, and evaluating their capacity of production of extracellular enzymes (ECE), as well as inhibitory compounds against relevant pathogens in commercial aquaculture. Twenty seven strains were isolated from the gut of A. purpuratus adult specimens that were collected in the city of Pisco and Pucusana (Lima) _ Peru; 81.5 and 59.2% of the isolates showed proteolytic and lipolytic activity, respectively. In addition, the strains ARG 9-II, ARG 10-II, ARG 12-II and ARG14-II evidenced broad-spectrum antimicrobial activity against the pathogens Vibrio anguillarum, V. vulnificus, V. alginolitycus, Lactococcus garvieae, Streptococcus iniae, Carnobacterium piscicola, and Yersinia ruckeri. The strain ARG 4-II produced the highest inhibitory effect against S. iniae. The Minimum Inhibitory Concentration (MIC) of the dichloromethane extract obtained from the strain ARG 12-II supernatant was 250 and 500 µg ml-1 against V. anguillarum and V. alginolyticus, respectively. Based on 16S rRNA sequence analysis, strains ARG 9-II, ARG 12-II and ARG 14-II were identified as Streptomyces variabilis, St. labedae and St. rochei, respectively. Results indicate that A. purpuratus is a promissory source for the isolation of new strains of Streptomyces with high bioactivity and antagonistic capacity against relevant pathogens in aquaculture. These strains have high potential for being developed as probiotic agents in the future.