Búsqueda avanzada


Área de conocimiento




6 resultados, página 1 de 1

Diversification of the kinetic properties of yeast NADP‐glutamate‐dehydrogenase isozymes proceeds independently of their evolutionary origin

JOSE CARLOS CAMPERO BASALDUA Hector Quezada LINA RAQUEL RIEGO RUIZ DARIEL MARQUEZ GUTIERREZ James González MOHAMMED EL HAFIDI BENTLAKDER MARIA ALICIA GONZALEZ MANJARREZ (2017, [Artículo])

"In the yeast Saccharomyces cerevisiae, the ScGDH1 and ScGDH3 encoded glutamate dehydrogenases (NADP‐GDHs) catalyze the synthesis of glutamate from ammonium and α‐ketoglutarate (α‐KG). Previous kinetic characterization showed that these enzymes displayed different allosteric properties and respectively high or low rate of α‐KG utilization. Accordingly, the coordinated action of ScGdh1 and ScGdh3, regulated balanced α‐KG utilization for glutamate biosynthesis under either fermentative or respiratory conditions, safeguarding energy provision. Here, we have addressed the question of whether there is a correlation between the regulation and kinetic properties of the NADP‐GDH isozymes present in S. cerevisiae (ScGdh1 and ScGdh3), Kluyveromyces lactis (KlGdh1), and Lachancea kluyveri (LkGdh1) and their evolutionary history. Our results show that the kinetic properties of K. lactis and L. kluyveri single NADP‐GDHs are respectively similar to either ScGDH3 or ScGDH1, which arose from the whole genome duplication event of the S. cerevisiae lineage, although, KlGDH1 and LkGDH1 originated from a GDH clade, through an ancient interspecies hybridization event that preceded the divergence between the Saccharomyces clade and the one containing the genera Kluyveromyces, Lachancea, and Eremothecium. Thus, the kinetic properties which determine the NADP‐GDHs capacity to utilize α‐KG and synthesize glutamate do not correlate with their evolutionary origin."

Functional diversification Glutamate dehydrogenase Kinetics Paralogous enzymes Phylogeny Yeast gene duplication BIOLOGÍA Y QUÍMICA CIENCIAS DE LA VIDA MICROBIOLOGÍA

APROVECHAMIENTO DE LAS CASCARA DE MANGO Y BAGAZO DE CAÑA PARA LA PRODUCCIÓN DE PECTINASAS EN FERMENTACIÓN EN ESTADO SOLIDO

JORGE LUIS VILLALPANDO GUZMAN (2010, [Tesis de maestría])

In this work we used shea nuts derived from Nayarit agroindustries such as mango peel and cane bagasse for the production of pectinases in a solid state fermentation. The mango shells were subjected to a process of particle reduction using a blade mill, obtaining a smooth and uniform paste, this paste was taken to a drying process with hot air to reach a humidity of 15%, the extruded mango shells were applied a supplementary drying at three temperatures 50 ° C. 60°C and 70°C up to a final moisture content of 7.8%. The pellets were used as substrate, in Solid State Fermentation (FES), with cane bagasse as support and the fungus Aspegillus awamori as producer of pectinases. Three production kinetics were performed in a solid state column fermenter. The fermentation conditions were as follows: for FES-1 a pellet at 50°C and cane bagasse (50%-50%) was considered, inoculated with 1.3x10^7 spores/ml and humidity of 75%. For FES-2 pellet at 60°C and cane bagasse (50%-50%) inoculum of 1.1x10^7 spores/ml and humidity of 75% and for FES-3 pellet at 70° and cane bagasse (50%-50%), inoculum of 1.9x10^7 spores/ml and humidity of 75%, I adjust the fermentation temperature to 3O°C. An activity kinetic was carried out, in which samples were taken every 24 hours. The pectinase activity of the extracts was determined using the DNS method, for the measurement of reducing sugars released by the pectinase activity. For the biochemical characterization of the extracts, optimal pH (3.6,4.5,5.0,6.0 and 6.5) and optimal temperatures (35°C to 70°C) were determined. Besides the thermostability at 50, 60 and 70°C (every 30 min.). The results obtained in these tests were as follows: The optimum pH found was 4.5, 6.0 and 4.5 for FES-1.2 and 3 extracts, respectively. Regarding the optimal temperatures, the best activities were detected at 60°C, 50°C and 45°C for FES-1, 2 and 3 extracts, respectively. According to the first results obtained from the enzymatic kinetics, the maximum activity of pectinase is obtained within the first 48 hours of the start of fermentation, subsequently there is no significant increase in activity. From the results, the optimization of fermentation conditions for the increase of pectinase activity was continued. The kinetics FES 4 and FES 5, did not find significant differences in the production of pectinases, with a maximum production time of 24 hours, at a pH of 6.5. Taking into account that it is not significant to use mango pellets dried at different temperatures.

En este trabajo se utilizaron esquilmos derivados de agroindustrias nayaritas tales como la cascara de mango y bagazo de caña para la producción de pectinasas en una fermentación de Estado solido. Las cascaras de mango se sometieron a un proceso de reducción de partícula empleo un molino de cuchillas, obteniendo una pasta suave y uniforme, esta pasta se llevo a un proceso de secado con aire caliente hasta llegar a una humedad del 15%, a los extrudidos de cascara de mango se les aplico un secado complementario a tres temperaturas 50°C. 60°C y 70°C hasta un contenido final de humedad del 7.8%. Los pellets fueron utilizados como sustrato, en Fermentación en Estado Solido (FES), teniendo como soporte bagazo de caña y al hongo Aspegillus awamori como productor de pectinasas. Se realizaron tres cinéticas de producción en un fermentador de estado solido de columnas, las condiciones de fermentación fueron las siguientes: para la FES-1 se considero un pellet a 50°C y bagazo de caña (50%-50%), inoculo con 1.3x10^7 esporas/ml y humedad del 75%. Para la FES-2 pellet a 60°C y bagazo de caña (50%-50%) inoculo de 1.1x10^7 esporas/ml y humedad del 75% y para la FES-3 pellet a 70° y bagazo de caña (50%-50%), inoculo de 1.9x10^7 esporas/ml y humedad del 75%, ajusto la temperatura de fermentación a 3O°C. Se realizo una cinética de actividad, en la que se tomo muestras cada 24 horas. La actividad de pectinasa de los extractos, se determino utilizo el método de DNS, para la medición de azucares reductores liberados por la actividad de pectinasa. Para la caracterización bioquímica de los extractos, se determinaron los pH óptimos(3.6,4.5,5.0,6.0 y 6.5).y las temperaturas optimas (35°C hasta 70°C). Ademas de la termoestabilidad a 50, 60 Y 70°C (cada 30 min.). Los resultados obtenidos en estas pruebas fueron los siguientes: El pH optimo encontrado fue de 4.5,6.0 y 4.5 para los extractos de la FES-1.2 y 3, respectivamente. Con respecto a las temperaturas optimas.las mejores actividades se detectaron a los 60°C ,50°C Y 45°C para los extractos de la FES-1, 2 Y 3, respectivamente. De acuerdo a los primeros resultados obtenidos de las cinéticas enzimáticas, la máxima actividad de la pectinasa se obtiene dentro de las primeras 48 horas de iniciada la fermentación, posteriormente no existe un incremento significativo de la actividad. A partir de los resultados, se continuo con la optimización de las condiciones de fermentación para la incrementación de la actividad de pectinasa. Las cinéticas FES 4 Y FES 5, no se encontraron diferencias significativas en la producción de pectinasas, siendo su tiempo máximo de producción de 24 horas, a un pH de 6.5.Tomando en cuenta que no es significativo el utilizar pellets de mango secados a diferentes temperaturas.

cascara de mango Fermentacion pectinasa esquilmos cineticas enzimaticas enzymatic kinetics pectinase Fermentation mango peel CIENCIAS AGROPECUARIAS Y BIOTECNOLOGÍA

Diseño y caracterización de microcápsulas de seleniometionina

LILIANA VALDIVIEZO MORALES (2012, [Tesis de maestría])

Tesis (Maestría en Ciencias, especialista en Ganadería).- Colegio de Postgraduados, 2012.

El objetivo del presente estudio fue diseñar y caracterizar microcápsulas de liberación controlada de seleniometionina de administración vía intramamaria, con dos diferentes de tipos de agentes encapsulantes (carboximetilcelulosa de sodio (NaCMC) y alginato de sodio (/(C6H7NaO6)n)). Las microcápsulas fueron elaboradas por el método de secado por atomización; se utilizó un secador mini Spray-dryer. La caracterización morfológica de las microcápsulas fue mediante microscopía electrónica de barrido. La distribución de las partículas por tamaño para ambos sistemas se determinó con un equipo MasterSize X (1.2b MALVERN) y etilenglicol como dispersante. Se evaluó la cantidad de seleniometionina total encapsulada, el porcentaje de rendimiento, el porcentaje de recuperación, el tamaño de la partícula y la cinética de liberación de seleniometionina desde las microcápsulas; se utilizó como testigo la liberación de la seleniometionina sin encapsular a través del vehículo de entrega (carbopol 2 %). Las variables de respuesta (SeMet total encapsulada, porcentaje de recuperación y porcentaje de rendimiento) fueron significativamente diferentes, con intervalos del 95% de confianza. Las cinéticas de liberación de ambos sistemas (SeMet/NaCMC y SeMet/(C6H7NaO6)n) tuvieron un mayor ajuste al modelo matemático de Korsmeyer. La variación de n para ambos sistemas fue entre 0.5718 y 0.6064, lo que sugirió que la naturaleza del proceso de liberación de la seleniometionina fue por un mecanismo de difusión no fickiano o anómalo. Por lo tanto, el método de secado por atomización resulta una alternativa viable para elaborar microcápsulas de SeMet, además de que el agente encapsulante carboximetilcelulosa obtuvo una mayor eficiencia para el encapsulado de la seleniometionina y protegió la SeMet de la degradación térmica. Por otro lado, la carboximetilcelulosa de sodio mostró un mayor control de la entrega del activo, así como un mayor ajuste de datos a los modelos de Higuchi (1963) y Korsmeyer et al. (1983). _______________ DESIGN AND CHARACTERIZATION OF MICROCAPSULES OF SELENOMETHIONINE. ABSTRACT: The aim of this study was to design and characterize controlled release microcapsules of selenomethionine (SeMet) of intramammary administration, with two different types of encapsulating agents (sodium carboxymethylcellulose (NaCMC), and sodium alginate). The microcapsules were prepared by applying the spray drying method, using a Mini Spray-dryer. Morphological characterization of the microcapsules was made by scanning electron microscopy. The distribution of particles by size was determined for both systems with a computer MasterSize X (1.2b MALVERN) and ethylene glycol as a dispersant. We evaluated the amount of the total encapsulated selenomethionine, the yield percentage, the recovery percentage, the particle size and the release kinetics of selenomethionine from the microcapsules. We used as control the release of unencapsulated selenomethionine through the delivery vehicle (carbopol 2%). The overall response variables of encapsulated SeMet, percentage of recovery and percentage of yield were significantly different with an interval of 95% confidence. The release kinetics of both systems (SeMet/NaCMC and SeMet/(C6H7NaO6)n) had a better fit to the mathematical model by Korsmeyer. The variation of n for both the systems were between 0.5718 and 0.6064, suggesting that the nature of the release process of selenomethionine was through a diffusion mechanism not following the Fick equation neither anomalous. Therefore, the spray drying method is a viable alternative to prepare SeMet microcapsules. In addition, the encapsulating agent of SeMet resulted more efficient and protected SeMet from thermal degradation. Moreover, NaCMC showed better control of delivery of active, as well as a further data adjustment to the models of Higuchi (1963) and Korsmeyer et al. (1983).

Seleniometionina Microcápsulas Cinética de liberación Alginato de sodio Selenomethionine Carboximetilcelulosa de sodio Microcapsules Release kinetics Sodium carboxymethylcellulose Sodium alginate Maestría Ganadería CIENCIAS AGROPECUARIAS Y BIOTECNOLOGÍA

OPTICAL COHERENCE TOMOGRAPHY AND NANOPARTICLES WITH CONCAVE SURFACES: FROM THE FOLLOWING OF NANOPARTICLES GROWTH KINETICS TO THEIR USE AS CONTRAST AGENT

Yenisey Ponce de Leon (2014, [Tesis de doctorado])

"The Optical Coherence Tomography (OCT) technique is an imaging modality that performs tomographic images with high resolutions (1-15µm) and high depth penetration capacity (12mm). It uses NIR light and is called the optical analogous of ultrasound. Its potential is based on the fact that is able to imaging transparent and highly scattering tissue samples, deeper and with better resolution than other techniques. However, tissues are optically inhomogeneous and the resulting scattering limits resolution and imaging depth; mainly in non transparent media. During the last decade, nanoparticles (NPs) have had a great impact on applications in different areas; one of them in the biomedical field as contrast agents, markers, sensors, etc. Nevertheless, most of the time the syntheses are not ideal, since they do not present high yield production and monodispersivity. In order to get a good synthesis, an understanding of the process that governs the NP growth is needed.

In this thesis an analysis of the growth kinetics of concave nanocubes by means of the Optical Coherence Tomography (OCT) technique is reported. In order to corroborate the viability of the OCT technique, UV-Vis spectroscopy and dynamic light scattering (DLS) experiments were also carried out. The results of the three techniques are very similar, confirming that OCT is a feasible technique to follow the NP growth kinetics. Furthermore, OCT shows the advantage over the UV-Vis spectroscopy technique that OCT is able to detect low concentrations of NPs, making it able to follow the synthesis since the beginning; and the monitoring is not affected by small variations in concentration. Additionally, the combination of these techniques allows getting complementary information of the synthesis without the need of expensive and sophisticated equipment. Moreover, to our knowledge, this is the first time that OCT is used to follow the NP growth kinetics."

OCT, NANOPARTICLES, GROWTH KINETICS, CONCAVE NANOCUBES CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA ÓPTICA OPTOMETRÍA

Competitive kinetics versus stopped flow method for determining the degradation rate constants of steroids by ozonation.

ALBERTO LOPEZ LOPEZ VALENTIN FLORES PAYAN ELIZABETH LEON BECERRIL LEONEL HERNANDEZ MENA RAMIRO VALLEJO RODRIGUEZ (2016, [Artículo])

"Steroids are classified as endocrine disrupting chemicals; they are persistent with low

biodegradability and are hardly degraded by conventional methods. Ozonation process

has been effective for steroids degradation and the determination of the kinetics

is a fundamental aspect for the design and operation of the reactor. This study assessed

two methods: competitive kinetics and stopped flow, for determining the degradation

kinetics of two steroids, estradiol (E2) and ethinylestradiol (EE2) in spiked water.

Experiments were performed at pH 6, 21 °C, and using tertbutyl alcohol as scavenger

of hydroxyl radicals; competitive kinetics method used sodium phenolate as reference

compound. For the stopped flow, the experiments were performed in a BioLogic SFM-

3000/S equipment. For both methods, the second order rate constants were in the

order of 106 and 105 M−1 s−1 for E2 and EE2 respectively. The competitive kinetics can

be applied with assurance and reliability but needing an additional analysis method

to measure the residual concentrations. Stopped flow method allows the evaluation

of the degradation kinetics in milliseconds and avoids the use of additional analytical

methodologies; this method allows determining the reaction times on line. The methods

are applicable for degradation of other emerging contaminants or other steroids

and could be applied in water treatment at industrial level. Finally, it is important to

consider the resources available to implement the most appropriate method, either

competitive kinetics or the stopped-flow method".

Steroids, Competitive kinetics, Stopped flow, Second order constant INGENIERÍA Y TECNOLOGÍA CIENCIAS TECNOLÓGICAS INGENIERÍA Y TECNOLOGÍA DEL MEDIO AMBIENTE OTRAS

COMPARATIVE STUDY OF COMPETITIVE KINETICS AND STOPPED FLOW METHODS ON THE DETERMINATION OF RATE CONSTANTS OF STEROIDS DEGRADATION USING OZONE

RAMIRO VALLEJO RODRIGUEZ ALBERTO LOPEZ LOPEZ LEONEL HERNANDEZ MENA ELIZABETH LEON BECERRIL VALENTIN FLORES PAYAN (2016, [Artículo])

Steroids are classified as endocrine disrupting chemicals; they are persistent with low

biodegradability and are hardly degraded by conventional methods. Ozonation process

has been effective for steroids degradation and the determination of the kinetics

is a fundamental aspect for the design and operation of the reactor. This study assessed

two methods: competitive kinetics and stopped flow, for determining the degradation

kinetics of two steroids, estradiol (E2) and ethinylestradiol (EE2) in spiked water.

Experiments were performed at pH 6, 21 °C, and using tertbutyl alcohol as scavenger

of hydroxyl radicals; competitive kinetics method used sodium phenolate as reference

compound. For the stopped flow, the experiments were performed in a BioLogic SFM-

3000/S equipment. For both methods, the second order rate constants were in the

order of 106 and 105 M−1 s−1 for E2 and EE2 respectively. The competitive kinetics can

be applied with assurance and reliability but needing an additional analysis method

to measure the residual concentrations. Stopped flow method allows the evaluation

of the degradation kinetics in milliseconds and avoids the use of additional analytical

methodologies; this method allows determining the reaction times on line. The methods

are applicable for degradation of other emerging contaminants or other steroids

and could be applied in water treatment at industrial level. Finally, it is important to

consider the resources available to implement the most appropriate method, either

competitive kinetics or the stopped-flow method.

Steroids, Competitive kinetics, Stopped flow, Second order constant INGENIERÍA Y TECNOLOGÍA