RESUMEN
Lipase from Thermomyces lanuginosus was assembled into multiple layers on polyethylenimine treated cotton flannel cloth, utilising the enzymes property of forming bimolecular aggregates via layer-by-layer (LBL) immobilization technique. An increase in lipase activity with increasing enzyme layers confirmed lipase aggregation. A study to compare the activity of enzyme bound by classical LBL technique, containing alternate layers of polyethylenimine and lipase and the modified approach indicated above, showed that more enzyme was bound to cloth in the modified approach. A total of 13 U/cm(2) of enzyme were bound to cloth till the fifth layer whereas only 10.2 U/cm(2) were bound till the fifth bilayer in the classical approach. The successful assembly of lipase molecules has shown that this modified technique is a promising approach to immobilize enzymes that aggregate through hydrophobic interactions as nano-films on cloth.
Asunto(s)
Enzimas Inmovilizadas/química , Lipasa/química , Difusión , Gossypium , Hidrólisis , Interacciones Hidrofóbicas e Hidrofílicas , Sustancias Macromoleculares , Modelos Químicos , Aceite de Oliva , Aceites de Plantas , Polietileneimina/química , Polímeros/química , Propiedades de SuperficieRESUMEN
Inner epidermis of onion bulb scales was used as a natural support for immobilization of microbial cells for biosensor application. A bacterium Sphingomonas sp. that hydrolyzes methyl parathion into a chromophoric product, p-nitrophenol (PNP), has been isolated and identified in our laboratory. PNP can be detected by electrochemical and colorimetric methods. Whole cells of Sphingomonas sp. were immobilized on inner epidermis of onion bulb scale by adsorption followed by cross-linking methods. Cells immobilized onion membrane was directly placed in the wells of microplate and associated with the optical transducer. Methyl parathion is an organophosphorus pesticide that has been widely used in the field of agriculture for insect pest control. This pesticide causes environmental pollution and ecological problem. A detection range 4-80 µM of methyl parathion was estimated from the linear range of calibration plot of enzymatic assay. A single membrane was reused for 52 reactions and was found to be stable for 32 days with 90% of its initial hydrolytic activity. The applicability of the cells immobilized onion membrane was also demonstrated with spiked samples.
Asunto(s)
Técnicas Biosensibles/métodos , Cebollas/microbiología , Células Inmovilizadas , Contaminantes Ambientales/análisis , Equipo Reutilizado , Hidrólisis , Insecticidas/análisis , Límite de Detección , Metil Paratión/análisis , Metil Paratión/metabolismo , Microscopía Electrónica de Rastreo , Cebollas/ultraestructura , Epidermis de la Planta/microbiología , Epidermis de la Planta/ultraestructura , Sphingomonas/metabolismo , Sphingomonas/ultraestructuraRESUMEN
The uranium (U) accumulation potential and ensuing biochemical responses were studied in Hydrilla verticillata (L.f.) Royle upon exposure to U (0, 20 and 100 mg L(-1)). There was a concentration-duration dependent increase in U accumulation with the maximum being 78 mg g(-1) DW at 100 mg L(-1) U after 24 h. Plants experienced an initial phase of the maximum toxicity (within 30 min) followed by almost complete recovery after 24 h. The recovery was attributed to an integrated modulation in the level of both enzymatic and molecular antioxidants (viz., guaiacol peroxidase, ascorbate peroxidase, catalase, proline, total phenolics) and also the constituents of thiol metabolism (viz., cysteine and glutathione). Thus, plants were found to be able to accumulate significant amount of U in a short time and to tolerate it efficiently. Hence, they may find application in U phytoremediation considering there accumulation ability, fast growth due to weed-like habit and world-wide distribution.
Asunto(s)
Restauración y Remediación Ambiental/métodos , Hydrocharitaceae/metabolismo , Uranio/farmacocinética , Contaminantes Radiactivos del Agua/farmacocinética , Análisis de Varianza , Antioxidantes/metabolismo , Ascorbato Peroxidasas , Catalasa/metabolismo , Cinética , Peroxidasa/metabolismo , Peroxidasas/metabolismo , Prolina/metabolismoRESUMEN
Inner epidermal membrane of the onion bulb scales was studied as a natural polymer support for immobilization of the glucose oxidase (GOD) enzyme for biosensor application. Onion epidermal membrane was used for immobilization of glucose oxidase and was associated with dissolved oxygen (DO) probe for biosensor reading. Glucose was detected on the basis of depletion of oxygen, when immobilized GOD oxidizes glucose into gluconolactone. A wide detection range between 22.5 and 450 mg/dl was estimated from calibration plot. A single membrane was reused for 127 reactions with retention of approximately 90% of its initial enzyme activity. Membrane was stable for 45 days ( approximately 90% activity) when stored in buffer at 4 degrees C. Surface structure studies of the immobilized membranes were carried under SEM. To our knowledge, this is the first report on employing inner epidermal membrane of onion bulb scales as the solid support for immobilization of enzyme.
Asunto(s)
Técnicas Biosensibles/instrumentación , Glucosa Oxidasa/química , Glucosa/análisis , Cebollas/anatomía & histología , Cebollas/química , Epidermis de la Planta/anatomía & histología , Epidermis de la Planta/química , Electroquímica/instrumentación , Enzimas Inmovilizadas/química , Diseño de Equipo , Análisis de Falla de Equipo , Microelectrodos , Oxígeno/análisis , Reproducibilidad de los Resultados , Sensibilidad y EspecificidadRESUMEN
The mechanism and chemical nature of uranium and thorium sequestration by a Pseudomonas strain was investigated by transmission electron microscopy, energy dispersive X-ray (EDX) analysis, FTIR spectroscopy and X-ray diffractometry. Atomic force microscopy (AFM) used in the tapping mode elucidated the morphological changes in bacterial cells following uranium and thorium binding. Transmission electron microscopy revealed intracellular sequestration of uranium and thorium throughout the cell cytoplasm with electron dense microprecipitations of accumulated metals. Energy dispersive X-ray analysis confirmed the cellular deposition of uranium and thorium. EDX and elemental analysis of sorption solution indicated the binding of uranium and thorium by the bacterial biomass via displacement of cellular potassium and calcium. The strong involvement of cellular phosphate, carboxyl and amide groups in radionuclide binding was ascertained by FTIR spectroscopy. X-ray powder diffraction (XRD) analyses confirmed cellular sequestration of crystalline uranium and thorium phosphates. Overall results indicate that a combined ion-exchange-complexation-microprecipitation mechanism could be involved in uranium and thorium sequestration by this bacterium. Atomic force microscopy and topography analysis revealed an undamaged cell surface with an increase in cell length, width and height following radionuclide accumulation. The arithmetic average roughness (R(a)) and root mean square (RMS) roughness (R(q)) values indicated an increase in surface roughness following uranium and thorium sequestration.
Asunto(s)
Pseudomonas/química , Pseudomonas/metabolismo , Torio/química , Torio/metabolismo , Uranio/química , Uranio/metabolismo , Microscopía de Fuerza Atómica , Microscopía Electrónica de Transmisión , Pseudomonas/ultraestructura , Espectroscopía Infrarroja por Transformada de Fourier , Difracción de Rayos XRESUMEN
The biosorption characteristics of uranium(VI) onto Catenella repens (a red alga), were evaluated as a function of pH, biosorbent size, time, biomass dosage, initial uranium concentration and temperature. Within the pH range studied (1.5-7.5), 4.5 was the optimum pH for the uptake of uranium(VI) by C. repens. Reduction in particle size did not increase the biosorption capacity. The metal removal was rapid, with more than 90% of total biosorption taking place in 30 min, and equilibrium was attained in 45 min. The maximum metal loading capacity of the alga was 303 mg/g. Within the temperature range studied (15-55 degrees C), there was no significant change in biosorption, under optimal conditions. Adsorption process could be well defined by both the Langmuir and Freundlich isotherms with r(2) of 0.94 and 0.96, respectively. The kinetic data fitted the pseudo-second-order kinetic model with the r(2) value of 0.99. At a low pH of 2.5, where most of the biomasses show either no or less metal uptake, a good (>15%) metal loading capacity of 25% was achieved. Therefore biosorption characteristics were also evaluated at pH 2.5.
Asunto(s)
Rhodophyta/metabolismo , Uranio/metabolismo , Biomasa , Concentración de Iones de Hidrógeno , Cinética , Tamaño de la Partícula , Temperatura , AguaRESUMEN
Aseptically grown Vetiveria zizanoides were evaluated for their potential for phytoremediation of phenol from Murashige and Skoog's liquid medium. Phenol was found to be completely removed from incubation medium at the end of 4 days by V. zizanoides plantlets, when medium was supplemented with 50 and 100 mg L(-1) phenol, while with 200, 500, and 1000 mg L(-1) of phenol, 89%, 76% and 70%, respectively, were removed. Phenol removal was found to be associated with inherent production of peroxidase and hydrogen peroxide. Coupled with H(2)O(2) formation, the levels of antioxidant enzymes like superoxide dismutase and peroxidase showed an enhancement when plants were exposed to phenol, whereas catalase levels initially showed a decline due to the utilization of H(2)O(2) by peroxidase for phenol oxidation. However, when peroxidase levels declined, there was an enhancement in catalase levels to minimize the presence of H(2)O(2) in the medium. Having confirmed that the removal of phenol was by V. zizanoides plantlets, in the next phase, micropropagated plantlets and well-developed plants grown in hydroponics were used under in vivo conditions to study the effect of phenol (200 mg L(-1)) on plant growth and reuse. Although plant growth was reduced in presence of phenol, the results of the reuse study indicated the possibility of plants getting adapted to phenol without any decline in potential for phenol remediation.
Asunto(s)
Chrysopogon/metabolismo , Fenol/metabolismo , Contaminantes Químicos del Agua/metabolismo , Antioxidantes/metabolismo , Biodegradación Ambiental , Catalasa/metabolismo , Chrysopogon/efectos de los fármacos , Glutatión Peroxidasa , Peróxido de Hidrógeno/metabolismo , Hidroponía , Oxidación-Reducción , Peroxidasa/metabolismo , Fenol/análisis , Fenol/toxicidad , Superóxido Dismutasa/metabolismo , Contaminantes Químicos del Agua/análisis , Contaminantes Químicos del Agua/toxicidadRESUMEN
A Pseudomonas strain identified as a potent biosorbent of uranium (U) and thorium was immobilized in radiation-induced polyacrylamide matrix for its application in radionuclide containing wastewater treatment. The immobilized biomass exhibited a high U sorption of 202 mg g(-1) dry wt. with its optimum at pH 5.0. A good fit of experimental data to the Freundlich model suggested multilayered uranium binding with an affinity distribution among biomass metal binding sites. Scanning electron microscopy revealed a highly porous nature of the radiation-polymerized beads with bacterial cells mostly entrapped on pore walls. Energy dispersive X-ray analysis (EDXA) coupled with SEM ascertained the accumulation of uranium by the immobilized biomass without any physical damage to the cells. A significant (90%) part of biosorbed uranium was recovered using sodium bicarbonate with the immobilized biomass maintaining their U resorption capacity for multiple sorption-desorption cycles. Uranium loading and elution behavior of immobilized biomass evaluated within a continuous up-flow packed bed columnar reactor showed its effectiveness in removing uranium from low concentration (50 mg U L(-1)) followed by its recovery resulting in a 4-5-fold waste volume reduction. The data suggested the suitability of radiation polymerization in obtaining bacterial beads for metal removal and also the potential of Pseudomonas biomass in treatment of radionuclide containing waste streams.
Asunto(s)
Resinas Acrílicas/química , Biomasa , Pseudomonas/metabolismo , Uranio/aislamiento & purificación , Eliminación de Residuos Líquidos/métodos , Contaminantes Químicos del Agua/aislamiento & purificación , Adsorción , Sitios de Unión , Concentración de Iones de Hidrógeno , Cinética , Microscopía Electrónica de Rastreo , Microesferas , Radiación , Espectrometría por Rayos X , Uranio/químicaRESUMEN
Uranium uptake by dried roots of Eichhornia crassipes was rapid and the biomass could remove 54% of the initial uranium present within 4 min of contact time. The process was favored at pH 5-6 and was least influenced by temperature. Biosorption data fitted to both Langmuir and Freundlich isotherm. The maximum loading capacity obtained was 371 mg U/g dry biomass. Distribution coefficient of 9336 ml/g was observed at a residual concentration of 4.9 mg U/L. Uptake increased at higher dose of biomass and reached a plateau beyond the concentration of 6 g/L. The specific metal ion uptake decreased with increasing initial uranium concentration. Anions (0.1 M) inhibited the uptake and followed the trend acetate > sulphate > nitrate > chloride. However presence of carbonate had no effect on uranium biosorption.
Asunto(s)
Raíces de Plantas/química , Uranio/farmacocinética , Contaminantes Radiactivos del Agua/farmacocinética , Adsorción , Aniones/análisis , Concentración de Iones de Hidrógeno , TemperaturaRESUMEN
Crude cell-free extract of yeast cells was mixed with sufficient amount of Jack bean meal extract so as to precipitate all the invertase. The precipitate was then cross-linked using 2% glutaraldehyde retaining over 60% of the activity. The immobilized invertase could be reused for over ten batches without loss in activity.