Blas Dorta - Academia.edu (original) (raw)

Papers by Blas Dorta

0378-1844/09/02/130-05 $ 3.00/0 (Farlow) Samson is an entomopathogenic fungus found in several co... more 0378-1844/09/02/130-05 $ 3.00/0 (Farlow) Samson is an entomopathogenic fungus found in several countries, including Brazil and Venezuela. This fungus attacks important caterpillar pests of soybean and corn such as Spodoptera frugiperda Smith (Lepidoptera: Noctuidae), causing epizootics (Ignoffo et al., 1976; Piñango et al., 2002). Environmental conditions (solar radiation, humidity, etc) greatly affect the microorganisms, decreasing their field viability and persistence. Current research

Interciencia, 2015

The fungal infection of corn plants by Rhizoctonia solani is a major pest that is responsible for... more The fungal infection of corn plants by Rhizoctonia solani is a major pest that is responsible for low yields of corn plantations. One of the strategies for t...

El presente estudio está dirigido al desarrollo de un proceso fermentativo en sustrato sólido, pa... more El presente estudio está dirigido al desarrollo de un proceso fermentativo en sustrato sólido, para ser utilizado como alternativa en la producción de esporas del hongo entomopatógeno Metarhizium anisopliae. Ello contempla evaluar la factibilidad del uso de afrecho de arroz como componente básico de bajo costo, en el diseño de medios de cultivo que ofrezcan ventajas comparativas frente a los medios, que para tal fin, han sido utilizados tradicionalmente. Se intenta la caracterización del crecimiento y la esporulación de M. anisopliae en dichos medios, tanto en términos cinéticos y estequiométricos, como a través de la identificación de los factores limitantes involucrados. Se pretende con ello obtener información básica sobre el funcionamiento del sistema, que sirva de referencia para un posible escalado del proceso.

Revista De La Sociedad Venezolana De Microbiologia Num 2 Vol 30, 2015

Artículo original Aislamiento y caracterización molecular, ribotipificación, de cepas nativas de ... more Artículo original Aislamiento y caracterización molecular, ribotipificación, de cepas nativas de Bacillus thuringiensis aisladas en suelos y larvas muertas de Hylesia metabus en la región nororiental de Venezuela

Interciencia, Feb 1, 2009

Revista Cientifica, May 1, 2006

This work was carried out with the purpose of attain a protein concentrate from microbial biomass... more This work was carried out with the purpose of attain a protein concentrate from microbial biomass with low content of nucleic acids. The yeast Kluyveromyces marxianus var. marxianus was grown on deproteinized and supplemented whey with nitrogen and vitamins sources at pH 4.5; 32 to 35°C and an aeration rate of 1.22 volumes of air fed for volume of broth per minute (VVM). The average biomass yield obtained was 0.30 g/g lactose, a lactose consumption of 93.21% and a cellular concentration of 4.15 g/L at the end of the fermentation. Two protein concentrates were obtained: the first one by alkaline extraction and isoelectric precipitation (C1) and the second one by alkaline extraction, phosphorylation and isoelectric precipitation (C2). Chemical analysis of both concentrates shown significant differences (P < 0.05) in the content of ash, fat, crude protein, non protein nitrogen, RNA and carbohydrates. There was significant (P < 0.05) the decrease in the RNA content from 4.59% (C1) to 2.71% (C2), important fact for the use of this protein concentrates for human consumption. Phosphorylation of the protein (C2) produced an increase in the water holding capacity (4.21 to 4.64 g water/g protein), solubility (32.43 to 41.74 g solubilized protein/g total protein) and emulsifying capacity (903.38 to 971.91 g oil/g protein), as well as a decrease in the oil absorption capacity (1.79 to 1.65 g oil/g protein). These characteristics are important when considering the use of such protein concentrates as ingredients in bakery or meat products.

Revista De La Sociedad Venezolana De Microbiologia, Dec 1, 2010

Revista Cientifica De Veterinaria, May 1, 2006

El presente trabajo se realizó con el propósito de obtener un concentrado proteico con un bajo co... more El presente trabajo se realizó con el propósito de obtener un concentrado proteico con un bajo contenido de ácidos nucleicos a partir de biomasa microbiana. Para ello se cultivó la levadura Kluyveromyces marxianus var. marxianus en lactosuero desproteinizado y suplementado con fuentes de nitrógeno y vitaminas a pH 4,5; 32 a 35°C y una tasa de aireación de 1,22 volúmenes de aire por volumen de medio por minuto (VVM). Se obtuvo un rendimiento promedio de: biomasa de 0,30 g/g lactosa, un consumo de lactosa del 93, 21% y concentración celular 4,15 g/L al final de la fermentación. A partir de la biomasa obtenida se elaboraron dos concentrados proteicos: uno por extracción alcalina y precipitación isoeléctrica (C1) y otro por extracción alcalina, fosforilación y precipitación isoeléctrica (C2). El análisis de los concentrados mostró diferencias significativas (P < 0,05) en los contenidos de cenizas, grasa, proteína cruda, nitrógeno no proteico, ARN y carbohidratos. Se evidenció una disminución significativa (P < 0,05) del contenido de ARN de 4,59% (C1) a 2,71% (C2) hecho importante para el uso de este concentrado proteico para el consumo humano. La fosforilación de la proteína (C2) incrementó la capacidad de absorción de agua (4,21 a 4,64 g agua/g proteína), la solubilidad (32,43 a 41,74 g proteína solubilizada/g proteína total), y la capacidad emulsionante (903,38 a 971,91 g aceite/g proteína), y disminuyó la capacidad de absorción de grasa (1,79 a 1,65 g grasa/g proteína), características éstas que deben ser consideradas para la incorporación de los concentrados proteicos como ingredientes de productos cárnicos y de panadería.

Interciencia, Mar 1, 2008

The version presented here may differ from the published version or from the version of the recor... more The version presented here may differ from the published version or from the version of the record. Please see the repository URL above for details on accessing the published version and note that access may require a subscription.

Bioagro

The entomopathogenic fungus N. rileyi has great potential to be used in Integrated Pest Managemen... more The entomopathogenic fungus N. rileyi has great potential to be used in Integrated Pest Management Programs of Spodoptera frugiperda, because of epizootics generated in some corn fields in Venezuela. However, it is necessary to emphasize research on improved formulations in order to increase commercial products efficacy. One of the most important areas is fungal compatibility with chemicals commonly used in pest control. Compatibility of N. rileyi with certain chemical pesticides was evaluated. In general, the compatibility was dose-dependent or not affected at all. The insecticides Lannate and Mimic were ineffective at any concentration tested (1/10 to 1/1000 dilutions of the commercial product); the insecticides Atabron, Karate, the adherent Nu Film 17, and the herbicide Accent affected the fungus only at high concentrations (1/10 dilution of the commercial product), the fungicide Vitavax affected the fungus at any concentration (dilutions 1/10, 1/100 and 1/1000 of the commercial ...

Microbios, 1990

The production of a bacteriostatic microcin, of molecular weight 520 kD by Salmonella typhimurium... more The production of a bacteriostatic microcin, of molecular weight 520 kD by Salmonella typhimurium LT2, strain M799-0, was studied in continuous culture. The effect of specific growth rate (mu) on microcin production was measured under aerobic and anaerobic conditions. In aerobiosis the microcin specific production rate (qp) was found to be strictly associated with cell growth. Thus, it is constitutively synthesized though at low production rate. As growth conditions become limited (i.e. anaerobiosis) its production is clearly induced and the highest yields are reached. Under the latter conditions microcin production follows a kinetic partial growth-linked process.

Soil and Sediment Contamination: An International Journal, 2014

The accuracy of the Content should not be relied upon and should be independently verified with p... more The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content.

Nucleic Acids Research, 1982

As part of a project pertaining the organization of ribosomal genes in Kinetoplastidae, we have c... more As part of a project pertaining the organization of ribosomal genes in Kinetoplastidae, we have created a data base for published sequences of ribosomal nucleic acids, with information in Spanish. As a first step in their processing, we have written a canputer program which introduces the new feature of determining the length of the fragments produced after single or multiple digestion with any of the known restriction enzymes. With this information we have detected conserved SAU 3A sites: (i) at the 5' end of the 5.8S rRNA and at the 3' end of the small subunit rRNA, both included in similar larger sequences; (ii) in the 5.8S rRNA of vertebrates (a second one), which is not present in lower eukaryotes, showing a clear evolutive divergence; and, (iii) at the 5' terminal of the small subunit rRNA, included in a larger conserved sequence. The possible biological importance of these sequences is discussed.

Molecular and Cellular Biochemistry, 1984

Purified mitochondria from rat liver were found to contain protein synthesis inhibitors, that cou... more Purified mitochondria from rat liver were found to contain protein synthesis inhibitors, that could be extracted by disruption of mitochondrial membranes and fractionated by gel filtration into two fractions of low and high molecular weight. Small size inhibitors were also released from the latter peak by high ionic strength followed by gel filtration. Both types of factors inhibit incorporation of radioactive amino acids into protein by liver cytoplasmic polysomes programmed with endogenous mRNA or poly U, and by rabbit reticulocyte lysates programmed with added globin mRNA and by incubations of Walker carcinoma cells. They decrease to the same level the cytoplasmic synthesis of proteins for the mitochondrial and extra-mitochondrial compartments in intact cells, but do not appear to inhibit substantially endogenous mitochondrial protein synthesis. Inhibitors were purified by paper chromatography and reverse phase high performance liquid chromatography into fractions which block with the same kinetics the incorporation of [14]leucine and [35]methionine into protein in systems able to initiate protein synthesis, such as reticulocyte lysates or intact cells, but differ in this respect in incubations of liver ribosomes where re-binding of mRNA is a limiting step. Some of these factors behave as oligopeptides that are assumed to inhibit in vitro primarily the initiation stage but whose function in vivo is still undetermined.

Journal of Invertebrate Pathology, 2002

Hylesia metabus larvae are susceptible to several pathogens indigenous to the area in which they ... more Hylesia metabus larvae are susceptible to several pathogens indigenous to the area in which they are found. Some larvae show symptoms characteristic of bacterial infection; they become flaccid and lethargic, and show a marked loss of appetite. We isolated and identified 29 bacterial strains from live, dead and experimentally infected H. metabus larvae, and evaluated their pathogenic activity. The bacteria which caused mortality in the larvae were: Pseudomonas aeruginosa (60-93.3%), Proteus vulgaris (20%), Alcaligenes faecalis, Planococcus sp. and Bacillus megaterium (10%), at doses of 3-4 x 10(7). Although P. aeruginosa is a well-known insect pathogen, this is the first report of its pathogenic activity on H. metabus. The potential risk to humans and low virulence make it unlikely that P. aeruginosa could be used in an augmentative biological control programme. However its natural incidence may be enhanced using parasites and predators of H. metabus as carriers.

Enzyme and Microbial Technology, 1998

Metarhizium anisopliae was grown by solid-state fermentation using a medium based on a mixture of... more Metarhizium anisopliae was grown by solid-state fermentation using a medium based on a mixture of rice bran and rice husk (1:1 on a dry weight basis) where the initial water content was fixed at a value of 47%. The experiments were performed in glass column bioreactors of three different sizes. Moist saturated air was continuously passed through the bottom of each column at a flow rate of 0.34 l h Ϫ1 g Ϫ1 initial dry matter, and cultivation was performed for two weeks at 27 Ϯ 1°C. The effect of medium packing density was studied in the columns of small size. For initial apparent densities of 0.270 and 0.357 g ml Ϫ1 , no significant differences were observed either in total biomass production or spore yields; however, when the initial apparent density was increased up to a value of 0.496 g ml Ϫ1 , both growth and sporulation were strongly affected. Thermal gradients in the medium and larger columns packed at an apparent density of 0.357 g ml Ϫ1 were observed both in the radial and axial directions. Heat build-up effects were analyzed in the larger column. In this case, there were significant differences between different segments of the column both in the water content of the fermented matter and the sporulation pattern.