Producción de bioinsecticidas

El objetivo del presente trabajo fue desarrollar una tecnología nacional de producción de un insecticida biológico a base de Bacillus thuringiensis variedad kurstaki. Para alcanzar tal objetivo se debieron cumplimentar etapas parciales: a) Seleccionar condiciones de aireación adecuadas a nivel de erlenmeyers agitados que aseguraran una alta tasa de esporulación y formación de cristales. b) Estudiar las necesidades nutricionales del microorganismo para definir la composición de un medio de cultivo adecuado para su desarrollo. c) Poner a punto un ensayo biológico y un método inmunoelectroforético para el dosaje de la actividad tóxica de los preparados. d) Estudiar en escala de tanques agitados a nivel de laboratorio, diferentes sistemas de producción (cultivo discontinuo y discontinuo alimentado) con medios con alta concentración de nutrientes para alcanzar elevadas productividades.Tesis digitalizada en SEDICI gracias a la Biblioteca Central de la Facultad de Ciencias Exactas (UNLP).Facultad de Ciencias Exacta

Producción de bioinsecticidas

El objetivo del presente trabajo fue desarrollar una tecnología nacional de producción de un insecticida biológico a base de Bacillus thuringiensis variedad kurstaki. Para alcanzar tal objetivo se debieron cumplimentar etapas parciales: a) Seleccionar condiciones de aireación adecuadas a nivel de erlenmeyers agitados que aseguraran una alta tasa de esporulación y formación de cristales. b) Estudiar las necesidades nutricionales del microorganismo para definir la composición de un medio de cultivo adecuado para su desarrollo. c) Poner a punto un ensayo biológico y un método inmunoelectroforético para el dosaje de la actividad tóxica de los preparados. d) Estudiar en escala de tanques agitados a nivel de laboratorio, diferentes sistemas de producción (cultivo discontinuo y discontinuo alimentado) con medios con alta concentración de nutrientes para alcanzar elevadas productividades.Tesis digitalizada en SEDICI gracias a la Biblioteca Central de la Facultad de Ciencias Exactas (UNLP).Facultad de Ciencias Exacta

Pectinase production profile of Aspergillus foetidus in solid state cultures at different acidities

Solid-state cultures of a pectinase-producing fungus (Aspergillus foetidus NRRL 341) were performed under different acidic conditions. Glass bottles containing 5 g of wheat bran and 7.5 mL of 0.2, 0.3, 0.4, or 0.5 N HCl were autoclaved (15 min, 121°C), inoculated with a spore suspension appropriately diluted to achieve an initial concentration of 4 × 10⁴ spores per gram of wet substrate (with a 60 % humidity, on wet basis) and incubated at 30°C. Time course of pH and of different pectinase activities were determined in culture extracts. Total pectinase activity (TPA), expressed in terms of viscosimetric units per gram of wet substrate (VU.g⁻¹), was affected by the initial culture acidity. The higher the HCl concentration used, the higher the TPA achieved, but after longer cultivation times. On the other hand, when 0.5 HCl was used, no fungal growth was observed. Nevertheless, enzyme productivity increased with culture acidity. When 0.4 HCl was used, TPA reached its maximum after 36 h of cultivation (2,535 VU.g⁻¹). With 0.2 and 0.3 N HCl, TPA was the highest at 24 h (733 VU.g⁻¹) and at 30 h (1,860 VU.g⁻¹) respectively. The composition of the pectinase pool was also affected by culture acidity. The higher the acidity, the lower the pectinesterase activity and the higher both the polymethylgalacturonate lyase and polygalacturonase activities.Centro de Investigación y Desarrollo en Fermentaciones Industriale

Evaluation of Beauveria bassiana (Hyphomycetes) strains as potential agents for control of Triatoma infestans (Hemiptera: Reduviidae)

Chagas disease constitutes a major human health problem in most Latin American countries. This endemic disease is transmitted by several species of triatomine bugs, the most important being Triatoma infestans (Klug). In this article, we report on the selection of strains of the entomopathogenic fungus Beauveria bassiana (Bals.) Vuill. virulent to T. infestans for possible use as bioinsecticides. Four strains of B. bassiana isolated from Argentina (Bb 1, 10, 25, and 65) were evaluated. To calculate mortality and mean lethal time, nymphs and adults of T. infestans were treated with conidia produced on complete agar medium and wheat brain and rice husk medium (WH). The LD50 for nymphs and adults of T. infestans was calculated. The effect of different temperatures (18, 22, 26, 30, and 34°C) and relative humidities (35 and 90% RH) on mortality of nymphs were studied. We evaluated the compatibility of strains with Deltamethrin and Beta-Cypermethrin. Although the strain Bb 25 failed to grow on WH, the other three strains showed similar mortality values independent of the culture medium used to grow the microorganisms. The lowest LD50 values for nymphs were obtained with the strains Bb 10 and 65 and for adults were Bb 1, 10, and 65. The highest mean mortality was obtained with strain Bb 10, and among temperatures the highest mean mortality was observed at 26°C. Relative humidity did not affect the mortality of T. infestans nymphs with all strains and temperatures assayed. Deltamethrin did not affect any of the three strains for the four studied doses, and Beta-Cypermethrin could be used in combination with the fungus only at low doses. The strain Bb 10 was selected for future assays under natural climatic conditions.Facultad de Ciencias ExactasCentro de Investigación y Desarrollo en Fermentaciones Industriale

Evaluation of Beauveria bassiana (Hyphomycetes) strains as potential agents for control of Triatoma infestans (Hemiptera: Reduviidae)

Chagas disease constitutes a major human health problem in most Latin American countries. This endemic disease is transmitted by several species of triatomine bugs, the most important being Triatoma infestans (Klug). In this article, we report on the selection of strains of the entomopathogenic fungus Beauveria bassiana (Bals.) Vuill. virulent to T. infestans for possible use as bioinsecticides. Four strains of B. bassiana isolated from Argentina (Bb 1, 10, 25, and 65) were evaluated. To calculate mortality and mean lethal time, nymphs and adults of T. infestans were treated with conidia produced on complete agar medium and wheat brain and rice husk medium (WH). The LD50 for nymphs and adults of T. infestans was calculated. The effect of different temperatures (18, 22, 26, 30, and 34°C) and relative humidities (35 and 90% RH) on mortality of nymphs were studied. We evaluated the compatibility of strains with Deltamethrin and Beta-Cypermethrin. Although the strain Bb 25 failed to grow on WH, the other three strains showed similar mortality values independent of the culture medium used to grow the microorganisms. The lowest LD50 values for nymphs were obtained with the strains Bb 10 and 65 and for adults were Bb 1, 10, and 65. The highest mean mortality was obtained with strain Bb 10, and among temperatures the highest mean mortality was observed at 26°C. Relative humidity did not affect the mortality of T. infestans nymphs with all strains and temperatures assayed. Deltamethrin did not affect any of the three strains for the four studied doses, and Beta-Cypermethrin could be used in combination with the fungus only at low doses. The strain Bb 10 was selected for future assays under natural climatic conditions.Facultad de Ciencias ExactasCentro de Investigación y Desarrollo en Fermentaciones Industriale

High level of sporulation of Metarhizium anisopliae in a medium containing by-products

Solid-state fermentation of rice bran or rice-bran-husk mixtures byMetarhizium anisopliae proved to be highly successful in spore yield. Optimum sporulation response on bran medium occurred when the initial water activity values ranged from 0.982 to 0.999. When bran was supplemented with 50% rice husk, the spore yield almost doubled, but a narrower initial water activity range (0.997–0.999) was optimum. Under these conditions, spore yields were 5–15 times higher (depending on the strain) than those currently obtained on the basis of rice grain fermentations.Centro de Investigación y Desarrollo en Fermentaciones Industriale

Organic and inorganic nitrogen source ratio effects on Bacillus thuringiensis var.israelensis delta-endotoxin production

The influence of different organic and inorganic nitrogen source combinations and C∶N ratios was studied in connection with growth and protein production of Bacillus thuringiensis var.israelensis. Protein production was assumed to be proportional to delta-endotoxin production. Delta-endotoxin concentration increased when media were supplemented with (NH4)2SO4, but the delta-endotoxin: biomass dry weight ratio was unaffected by different C∶N ratios. Organic nitrogen source, yeast extract, could be partially replaced by (NH4)2SO4 with a significant increase in delta-endotoxin production.On a étudié l'influence de diverses sources d'azote organique et inorganique et des rapports C∶N en relation avec la croissance et la production de protéine parBacillus thuringiensis var.israelensis. On fait l'hypothèse que la production de protéines est proportionnelle à la production de delta-endotoxine. La concentration de delta-endotoxine croît quand on ajoute au milieu du (NH4)2SO4, mais le rapport delta-endotoxine: poids sec de biomasse n'est pas affecté par différents rapports C∶N. On peut remplacer partiellement la source organique d'azote, l'extrait de levure, par du (NH4)2SO4 avec une augmentation significative de production de delta-endotoxine.Centro de Investigación y Desarrollo en Fermentaciones Industriale

Effect of the media composition on the growth parameters and biological properties of Bacillus thuringiensis var. israelensis delta-endotoxin

The effects of media composition on growth parameters, total protein production (including delta-endotoxin) and its relation to the biological properties of Bacillus thuringiensis var. israelensis was investigated. The replacement of glucose by glycerol as the carbon source yielded higher concentrations of delta-endotoxin. This increase in toxicity was associated with increased amounts of the 130 kDa polypeptide fraction. The biocide activity was not related to haemolytic activity, specific growth rate nor spore count.Departamento de Ciencias Exactas y Naturale

Evaluation of Beauveria bassiana (Hyphomycetes) strains as potential agents for control of Triatoma infestans (Hemiptera: Reduviidae)

Chagas disease constitutes a major human health problem in most Latin American countries. This endemic disease is transmitted by several species of triatomine bugs, the most important being Triatoma infestans (Klug). In this article, we report on the selection of strains of the entomopathogenic fungus Beauveria bassiana (Bals.) Vuill. virulent to T. infestans for possible use as bioinsecticides. Four strains of B. bassiana isolated from Argentina (Bb 1, 10, 25, and 65) were evaluated. To calculate mortality and mean lethal time, nymphs and adults of T. infestans were treated with conidia produced on complete agar medium and wheat brain and rice husk medium (WH). The LD50 for nymphs and adults of T. infestans was calculated. The effect of different temperatures (18, 22, 26, 30, and 34°C) and relative humidities (35 and 90% RH) on mortality of nymphs were studied. We evaluated the compatibility of strains with Deltamethrin and Beta-Cypermethrin. Although the strain Bb 25 failed to grow on WH, the other three strains showed similar mortality values independent of the culture medium used to grow the microorganisms. The lowest LD50 values for nymphs were obtained with the strains Bb 10 and 65 and for adults were Bb 1, 10, and 65. The highest mean mortality was obtained with strain Bb 10, and among temperatures the highest mean mortality was observed at 26°C. Relative humidity did not affect the mortality of T. infestans nymphs with all strains and temperatures assayed. Deltamethrin did not affect any of the three strains for the four studied doses, and Beta-Cypermethrin could be used in combination with the fungus only at low doses. The strain Bb 10 was selected for future assays under natural climatic conditions.Facultad de Ciencias ExactasCentro de Investigación y Desarrollo en Fermentaciones Industriale

Biotecnología de la obtención de enzimas pectolíticas

Información extraída de http://www.cindefi.org.ar/?page_id=61&language=esFacultad de Ciencias Exacta