Tailoring fungal morphology of Aspergillus niger MYA 135 by altering the hyphal morphology and the conidia adhesion capacity: biotechnological applications

Current problems of filamentous fungi fermentations and their further successful developments as microbial cell factories are dependent on control fungal morphology. In this connection, this work explored new experimental procedures in order to quantitatively check the potential of some culture conditions to induce a determined fungal morphology by altering both hyphal morphology and conidia adhesion capacity. The capacity of environmental conditions to modify hyphal morphology was evaluated by examining the influence of some culture conditions on the cell wall lytic potential of Aspergillus niger MYA 135. The relative value of the cell wall lytic potential was determined by measuring a cell wall lytic enzyme activity such as the mycelium-bound β-N-acetyl-Dglucosaminidase (Mb-NAGase). On the other hand, the quantitative value of conidia adhesion was considered as an index of its aggregation capacity. Concerning microscopic morphology, a highly negative correlation between the hyphal growth unit length (lHGU) and the specific Mb-NAGase activity was found (r = −0.915, P < 0.001). In fact, the environment was able to induce highly branched mycelia only under those culture conditions compatible with specific Mb-NAGase values equal to or higher than 190 U gdry.wt -1. Concerning macroscopic morphology, a low conidia adhesion capacity was followed by a dispersed mycelial growth. In fact, this study showed that conidia adhesion units per ml equal to or higher than 0.50 were necessary to afford pellets formation. In addition, it was also observed that once the pellet was formed the lHGU had an important influence on its final diameter. Finally, the biotechnological significance of such results was discussed as well.Fil: Colin, Veronica Leticia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET- Tucumán. Planta Piloto de Procesos Industriales Microbiológicos (i); Argentina;Fil: Baigori, Mario Domingo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET- Tucumán. Planta Piloto de Procesos Industriales Microbiológicos (i); Argentina; Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia; Argentina;Fil: Pera, Licia Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET- Tucumán. Planta Piloto de Procesos Industriales Microbiológicos (i); Argentina

Influence of culture conditions on a mycelium-bound lipase production from Aspergillus niger MYA 135

Introduction: Lipases (EC 3.1.1.3) are enzymes that hydrolyse the ester bonds of water insoluble substrates at the interface between the substrate and the water. This reaction is reversible. Lipases may also catalyze ester synthesis and transesterification in reaction mixtures with low water contents. Objective: The aim of this work was to study the influence of culture conditions on a mycelium-bound lipase production from Aspergillus niger MYA 135. Materials and methods: The fermentation medium comprised (in g/l): sucrose 10; NH4NO3 2; KH2PO4 1; MgSO4.7H2O 0.2; CuSO4.5H2O 0.06. The effect of modification in the environmental condition on lipase production was tested by changing the initial pH of the medium as well as by the addition of CaCl2, FeCl3 or Tween (20, 40, 60, and 80). Lipase activity was determined using 0.01 g of wet mycelium and p-nitrophenyl palmitate as substrate. Results and conclusions: The assayed culture conditions scientifically influences the lipase production. The highest specific activity (36.6 mU/g of DW) was obtained with either initial pH 8 or in presence of 0.5% Tween 60. This work was supported by grants PIP 6062 and PICTO 761.Fil: Colin, Veronica Leticia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Baigori, Mario Domingo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Pera, Licia Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaXXIII Jornadas Científicas de la Asociación de Biología de TucumánTafí del ValleArgentinaAsociación de Biología de Tucumá

Impact of manganese on the production of a biomass associated B-D-lucosidase activity using a thermophilic Bacilllus licheniformis strain

The â-Glucosidase (EC 3.2.1.21) constitutes a group of well-studied hydrolases. This enzyme catalyzes the hydrolysis of arylglucosides, alkylglucosides, cellobiose, and cellooligosaccharides. The interest in this biocatalyst centers on its roles in the enzymatic hydrolysis of cellulose. The rate of cellulose hydrolysis can be improved by supplementing commercial cellulases with immobilized â-D-glucosidase, which usually has high stability and can be recovered and reused. In addition, for industrial saccharification of cellulosic materials, â-glucosidases from thermophilic bacteria are also of particular interest due to their increased stability. In this work, we study the influence of manganese on the production of a biomass associate â-D-glucosidase activity using a thermophilic Bacillus licheniformis strain. Assays were performed at 45 °C in 500 ml Erlenmeyer containing 200 ml of LB medium supplemented with 0 - 1.0 mM MnCl2. The â-D-glucosidase activity was also determined at 45 °C using 3.6 mM p-nitrophenyl-â -D-glucopyranoside (Sigma) as substrate. Cells were harvested by centrifugation and washed twice with 100 mM Tris-HCl buffer (pH 7). The pellet was resuspended in the same buffer, and it was directly used as the â-D-glucosidase source. The mixture was shaken at 1000 rpm. Then, the absorbance of the supernatant was measured at 405 nm and the enzyme activity calculated and related to the biomass dry weight. One unit of the enzyme was defined as the amount needed to release 1 µmol p-nitrophenol per min. Thus, dose-response experiments showed that in the presence of 0.3 mM MnCl2 the enzyme production was increased by about 20%. Under this culture condition, a specific activity value of 19.99 U per mg of dry weight was obtaining after 4 h of cultivation. Finally, these results could be of relevance to the bioethanol industry where lignocellulosic material is used as feedstock for fermentation and, which should be treated enzymatically. The use of naturally bound enzymes is an important immobilization technique. This type of biocatalyst system is potentially cost-effective because the biomass can be directly utilized in the treatment.Fil: Abdulhamid, María Belén. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Baigorí, Mario Domingo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Pera, Licia Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaXI Congreso Argentino de Microbiología GeneralCórdobaArgentinaSociedad Argentina de Microbiología Genera

Bioemulsifier-producing Aspergillus niger MYA 135: effect of culture conditions

Bioemulsifiers are surface-active molecules synthetized by microorganisms, which play an important physiological role in hydrocarbon degradation. Few reports have shown the bioemulsifier production by filamentous fungi being the amount, quality and nature dependent not only on the microorganism but also on the culture conditions. Bioemulsifiers have the advantages of biodegradability, low toxicity, effectiveness and these properties enable their wide application on bioremediation, food, cosmetic and pharmaceutical industries, etc. The aim of this work was to study the bioemulsifier production by Aspergillus niger MYA 135 under different culture conditions. Methods: The bioemulsifier production was conducted in mineral medium during 96 hours, at different initial pH and with the addition of CaCl2 or FeCl3. The emulsification index was determinated after 24 h (E-24) in supernatants using kerosene as immiscible liquid. E-24 was estimated as the height of the emulsion layer divided by the total height and multiplied by 100. Results and conclusions: Bioemulsifier production reached maximum levels at 2 days of cultivation suggesting that its accumulation was growth-associated. Although all the emulsions were stable, the maximum values of E-24 were obtained at initial pH 2 (60.0 ± 0.71 %) and with the addition of FeCl3 (50.5 ± 0.70 %).This work was supported by grants PIP 6062 & PICTO 761Fil: Colin, Veronica Leticia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Baigori, Mario Domingo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Pera, Licia Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaXLIV Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología MolecularVilla Carlos PazArgentinaSociedad Argentina de Investigaciones Bioquímicas y Moleculare

Immobilization of a lipase activity from Aspergillus niger MYA 135 and its application in the biodiesel synthesis

Lipases have been widely used in the organic synthesis of industrially important chemicals such as emulsifiers, surfactants, wax esters, biopolymers, structured lipids, flavor-associated esters, and biodiesel. Concerning the biodiesel production, in order to get an efficient biodiesel production, the proper selection of the immobilization matrix and the subsequent reaction optimization have attracted the interest of several researches in recent years. In this work, those steps were carried out by using the one factor at a time optimization method. Thus, a culture supernatant from Aspergillus niger MYA 135 showing a lipase activity was firstly immobilized by adsorption on different low-cost supports (sand, PET and PP plastic, rubber, silicone, glass beads, silica gel and bagasse) applying a vacuum drying procedure. All biocatalysts were evaluated at 40 °C, at 800 rpm, and in the presence of different combinations of oil (soybean or waste frying oils) and alcohols (ethanol or butanol). After a three-stepwise addition of the corresponding alcohol, the biodiesel synthesis was evaluated by thin layer chromatography (TLC). The most promising reaction mixture comprised a lipase activity immobilized in silica gel as biocatalyst, and soybean oil and butanol as substrates. Then, the following parameters were analyzed: a) the enzyme concentration (1, 2, 3 and 4 ml of culture supernatant), b) the molar ratio oil:alcohol (1:3, 1:4, 1:5, 1:6, 1:7), and c) the reaction time (the addition of alcohol carried out in three equal parts every 24, 12, 6 or 3 h). In addition, the crosslinking immobilization technique was also studied. Taking into account the qualitative analysis by TLC, the best conditions for biodiesel production were: 2 ml of culture supernatant immobilized in silica, 1:4 soybean oil to butanol molar ratio, and a reaction time of 18 h. Under these optimal reaction conditions, a biodiesel yield of 93.36 % (w/w) was achieved in a solvent free system. The composition of fatty acid butyl esters was 12.97 % palmitic acid, 6.57 % estearic acid, 25.15 % oleic acid, 45.24 % linoleic acid, 4.72 % linolenic acid, 0.67 % araquidic acid, 0.34 % eicosenoic acid, and 3.83 others. Finally, it is interesting to mention that the cloud point of butyl esters is around 10 °C lower than that of methyl esters, meaning that they have better performance under cold conditions.Fil: Salvatierra, Hebe Natalia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Baigori, Mario Domingo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Pera, Licia Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaLVI Annual Meeting Argentine Society for Biochemistry and Molecular Biology and XV Annual Meeting Argentinean Society for General MicrobiologyCiudad Autónoma de Buenos AiresArgentinaSociedad Argentina de Investigación Bioquímica y Biología MolecularSociedad Argentina de Microbiología Genera

Cry genes profile and proteolytic activity of native Bacillus thuringiensis strains against Spodoptera frugiperda

Introduction: Bacillus thuringiensis (Bt) produces entomopathogenic Cry proteins which are activated to pathogenic form by proteases. Objective: Determination of cry genes and proteolytic activity in three native Bt strains. Material and methods: Total DNA was isolated with the CTAB technique. Cry 1 and 2 genes were amplified with general and specifics primers. Proteolytic activity was assayed by using azocasein as substrate. Results and Discussion: Specific cry genes and the biomass-bound protease activity are showed in the table. Bt RT displayed different cry specific content than the others strains. In addition to Cry protein, Bt is also an excellent source of protease activities. Bt RT has a proteolytic activity significantly different to that achieved for the reference strain Bt 4D1 (P> 0.05, Tukey test). This work was supported by grants PICTO-UNT 761 and PIP 6062 (CONICET).Fil: Alvarez, Analia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Pera, Licia Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Virla, Eduardo Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Baigori, Mario Domingo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaXXV Jornadas Científicas de la Asociación de Biología de TucumánTafi del ValleArgentinaAsociacion de Biologia de Tucuma

Direct DNA amplification from Fall Armyworm (Lepidoptera: Noctuidae) samples

The direct amplification by PCR of the DNA in tissue samples of eggs and neonate larvae of Spodoptera frugip erda (J. E. Smith) (Lepidoptera: Noctuidae) was accomplished, and it is a new alternative for DNA amplification from fall armyworm samples. This method is simple, fast, economic, and accelerates studies on this polyphagous pest.Fil: Loto, Flavia del Valle. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos (i); ArgentinaFil: Romero, Cintia Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos (i); ArgentinaFil: Baigori, Mario Domingo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos (i); ArgentinaFil: Pera, Licia Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos (i); Argentin

Purification and partial characterization of an extracellular lipase from Aspergillus niger MYA 135

Introducción: Las lipasas son enzimas consideradas de interés económico por su capacidad de actuar como catalizadores en reacciones de hidrólisis y síntesis. Aspergillus niger, microorganismo GRAS, es utilizado para producir lipasas con propósitos biotecnológicos. En el presente trabajo utilizamos A. niger ATCC MYA 135 para producir una lipasa extracelular inducible obtenida a partir de cultivo sumergido. Objetivos. Purificar y caracterizar parcialmente una lipasa producida por A. niger MYA 135. Materiales y Métodos: El sobrenadante de cultivo se concentró usando PEG 20.000 y se recuperó en buffer fosfato 10 mM. Posteriormente se sembró y corrió la misma en un PAGE nativo. Una vez finalizada la corrida electroforética se cortó una de las calles sembradas y se reveló por actividad lipasa. La misma fue utilizada como patrón para cortar las bandas de las calles restantes. La purificación se realizó por electroelución, la banda seleccionada de mayor peso molecular que presentó actividad lipasa fue colocada en una membrana de diálisis con buffer Tris-Gly 25 mM. Después de la electroelución se concentró la muestra nuevamente con PEG 20.000. Para comprobar la purificación se midió actividad lipasa usando p-nitrofenil palmitato y se corrieron las muestras en un PAGE, que fue revelado con α-naftilacetato y α-naftilmiristato. Se determinó el punto isoeléctrico de la banda purificada, las condiciones óptimas de temperatura, pH y la constante de Michaelis-Menten (Km) frente a distintos sustratos: p-nitrofenil-acetato, propionato, palmitato y estearato (p-NPA, p-NPPr p-NPP y p-NPE). Se calculó su peso molecular aparente en geles PAGE-SDS y su estabilidad frente a solventes y detergentes iónicos y no iónicos. Resultados y Discusión: Se purificó una lipasa con un peso molecular de 104.7 kDa y un pI de 5.1. La misma presentó un Km (µM) de 0.13, 4.08, 0.017 y 0.60 frente a pNPA, pNPPr, pNPP y pNPE, respectivamente. La actividad enzimática mostró ser estable en el rango de temperaturas 4-55°C, en el rango de pH 2-10 y en presencia de los solventes ensayados. La lipasa fue estable en Tween 60, Tween 40 y saponina. No se observó actividad en presencia de los demás detergentes estudiados. La electroelución resultó ser una técnica rápida y práctica para la purificación de proteínas. La lipasa purificada fue parcialmente caracterizada, mostrando tener un importante potencial para su aplicación biotecnológica.Fil: Romero, Cintia Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Pera, Licia Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Baigori, Mario Domingo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaXXV Jornadas Científicas de la Asociación de Biolgía de TucumánTafi del ValleArgentinaAsociación de Biología de Tucumá

Influence of calcium chloride on cellular polarity of Aspergillus Niger MYA 135

Introducción: La hifa, unidad estructural y funcional de los hongos filamentosos es una célula tubular cuya forma se conserva gracias a la existencia de una pared celular, sitio de diversas actividades enzimáticas. Dentro de las enzimas líticas de pared, la b-N-acetil-D-glucosaminidasa (NAGasa) puede ser empleada como un marcador relativo de la morfología de las hifas ya que, resultados previos muestran una interrelación entre su actividad y el grado de ramificación y/o presencia de células bulbosas en el micelio de Aspergillus niger. Considerando que la pared es esencial para mantener el balance osmótico y la forma celular y que la actividad de sus enzimas puede ser modulada, entre otras cosas, por factores ambientales; el efecto estimulante del Ca+2 sobre la actividad NAGasa se vio reflejado en un incremento del grado de ramificación del micelio y presencia de abundantes células bulbosas. Así, dentro de este marco teórico, la pérdida de polaridad celular que se observa en las células bulbosas o globosas podría ser el resultado de una pared fuertemente debilitada. Objetivo: Determinar si la polaridad celular es restaurada con el suplemento de un estabilizador osmótico al medio de cultivo. Materiales y Métodos: El microorganismo empleado en el presente trabajo es Aspergillus niger ATCC MYA 135, una cepa aislada y caracterizada en nuestro laboratorio. El micelio que desarrolla en medio salino a 30°C se considera estándar. Los cambios morfológicos se estudiaron en micelios obtenidos en presencia de 0,5 g/l de CaCl2 con y sin el suplemento de NaCl 1,5 M como de estabilizador osmótico. El análisis microscópico de la morfología (100 X) se realiza luego de 72 horas de cultivo. Resultados: En el micelio desarrollado en presencia NaCl prácticamente no se observaron células bulbosas mientras que, en ausencia del mismo, estas células fueron prominentes y abundantes. Conclusiones: La morfología celular fue restaurada en un medio de alta osmolaridad, lo que sugiere la presencia de una pared celular debilitada.Fil: Colin, Veronica Leticia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Baigori, Mario Domingo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Pera, Licia Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaXXV Jornadas Científicas de la Asociación de Biología de TucumánTafi del ValleArgentinaAsociación de Biología de Tucumá

Impact of manganese on the production of a biomass associated β-D-glucosidase activity using a thermophilic Bacillus licheniformis strain

The b-Glucosidase (EC 3.2.1.21) constitutes a group of well-studied hydrolases. This enzyme catalyzes the hydrolysis of arylglucosides, alkylglucosides, cellobiose, and cellooligosaccharides. The interest in this biocatalyst centers on its roles in the enzymatic hydrolysis of cellulose. The rate of cellulose hydrolysis can be improved by supplementing commercial cellulases with immobilized b-D-glucosidase, which usually has high stability and can be recovered and reused. In addition, for industrial saccharification of cellulosic materials, b-glucosidases from thermophilic bacteria are also of particular interest due to their increased stability. In this work, we study the influence of manganese on the production of a biomass associate b-D-glucosidase activity using a thermophilic Bacillus licheniformis strain. Assays were performed at 45 °C in 500 ml Erlenmeyer containing 200 ml of LB medium supplemented with 0 - 1.0 mM MnCl2 . The b-D-glucosidase activity was also determined at 45 °C using 3.6 mM p-nitrophenyl-b -D-glucopyranoside (Sigma) as substrate. Cells were harvested by centrifugation and washed twice with 100 mM Tris-HCl buffer (pH 7). The pellet was resuspended in the same buffer, and it was directly used as the b-D-glucosidase source. The mixture was shaken at 1000 rpm. Then, the absorbance of the supernatant was measured at 405 nm and the enzyme activity calculated and related to the biomass dry weight. One unit of the enzyme was defined as the amount needed to release 1 µmol p-nitrophenol per min. Thus, dose-response experiments showed that in the presence of 0.3 mM MnCl2 the enzyme production was increased by about 20%. Under this culture condition, a specific activity value of 19.99 U per mg of dry weight was obtaining after 4 h of cultivation. Finally, these results could be of relevance to the bioethanol industry where lignocellulosic material is used as feedstock for fermentation and, which should be treated enzymatically. The use of naturally bound enzymes is an important immobilization technique. This type of biocatalyst system is potentially cost-effective because the biomass can be directly utilized in the treatment.Fil: Abdulhamid, María Belén. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Baigori, Mario Domingo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Pera, Licia Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaXI Congreso Argentino de Microbiología GeneralCordobaArgentinaSociedad Argentina de Microbiología Genera