Determination of biosorption mechanism in biomass of agave, using spectroscopic and microscopic techniques for the purification of contaminated water

[Abstract] Lead (Pb2+) and copper (Cu2+) are polluting metals due to their toxicity; however, the extraction of these metals is essential for economic development, so it is important to look for efficient and low-cost alternatives that can remove heavy metals from the various bodies of water. One of the alternatives used in this work is biosorption, for which an agroindustrial waste (epidermis from Agave atrovirens) was used to evaluate the affinity of removal of lead and copper in aqueous solutions; in addition, spectroscopy and microscopy techniques were used to elucidate and corroborate the removal and affinity capacity of the agave epidermis for both metals studied. The optimal pH value for the removal of both metals was 3. The adsorption isotherms yielded a qmax of 25.7 and 8.6 mg/g for lead and copper, respectively. Adjusting to the Langmuir-Freundlich model, the adsorption kinetics were pseudo-second order, and it was found that the equilibrium time was at 140 min. The spectroscopy and microscopy analyses corroborated the affinity between metals and functional groups of the agave, as well as with the elemental analysis, which reported 17.38% of lead and 4.25% of copper.[Resumen] El plomo (Pb2+) y el cobre (Cu2+) son metales contaminantes debido a su toxicidad; sin embargo, la extracción de estos metales es indispensable para el desarrollo económico, por lo que es importante buscar alternativas eficientes y de bajo costo que puedan remover metales pesados de los diversos cuerpos de agua. Una de las alternativas utilizadas en este trabajo es la biosorción, para la cual se utilizó un residuo agroindustrial (epidermis de Agave atrovirens), para evaluar la afinidad de remoción del plomo y cobre en soluciones acuosas; adicionalmente, se emplearon técnicas de espesctroscopía y microscopía que permitieron elucidar y corroborar la capacidad de remoción y afinidad que tuvo la epidermis de A. atrovirens para ambos metales estudiados. El valor óptimo de pH para la remoción de ambos metales fue 3. Las isotermas de adsorción arrojaron una qmax de 25.7 y 8.6 mg/g para el plomo y cobre, respectivamente. Ajustando al modelo de Langmuir-Freundlich, las cinéticas de adsorción resultaron de pseudo-segundo orden, se encontró que el tiempo de equilibrio es a los 140 min. El análisis espectroscópico y microscópico, corroboró la afinidad entre metales y grupos funcionales del agave, así como con el análisis elemental, el cual reportó 17.38% de plomo y 4.25% de cobre

Análisis de la conductividad térmica efectiva en un generador termoeléctrico segmentado usando Bi2Te3 y PbTe

Los generadores termoeléctricos (TEG), conocidos como dispositivos de estado sólido, se utilizan para generar energía eléctrica a partir de un gradiente de temperatura. Los TEGs son de pequeño tamaño y no necesitan de mantenimiento. En este trabajo, se analiza el transporte de calor en un generador termoeléctrico segmentado compuesto de dos materiales, Bi2Te3 y PbTe, a través de la "conductividad térmica efectiva" (kef).Ésta conductividad, considera la conducción de Fourier en estado estacionario, la generación de calor de Joule y el efecto Seebeck. Además, el valor de ...... no depende de las condiciones de funcionamiento del TEG sino de las propiedades de transporte de los propios materiales semiconductores En el modelo considerado para el TEG segmentado, los resultados obtenidos muestran que los valores óptimos para la conductividad térmica efectiva, eficiencia reducida y finalmente la potencia máxima del sistema corresponden al Bi2Te3.Palabra(s) Clave(s): conductividad térmica, eficiencia, potencia, seebeck, TEG

Early detection of mechanical damage in mango using NIR hyperspectral images and machine learning

Mango fruit are sensitive and can easily develop brown spots after suffering mechanical stress during postharvest handling, transport and marketing. The manual inspection of this fruit used today cannot detect the damage in very early stages of maturity and to date no automatic tool capable of such detection has been developed, since current systems based on machine vision only detect very visible damage. The application of hyperspectral imaging to the postharvest quality inspection of fruit is relatively recent and research is still underway to find a method of estimating internal properties or detecting invisible damage. This work describes a new system to evaluate mechanically induced damage in the pericarp of ‘Manila’ mangos at different stages of ripeness based on the analysis of hyperspectral images. Images of damaged and intact areas of mangos were acquired in the range 650–1100 nm using a hyperspectral computer vision system and then analysed to select the most discriminating wavelengths for distinguishing and classifying the two zones. Eleven feature-selection methods were used and compared to determine the wavelengths, while another five classification methods were used to segment the resulting multispectral images and classify the skin of the mangos as sound or damaged. A 97.9% rate of correct classification of pixels was achieved on the third day after the damage had been caused using k-Nearest Neighbours and the whole spectra and the figure dropped to 91.4% when only the most discriminant bands were used

Morphometric and crystallinity changes on jicama starch (Pachyrizus erosus) during gelatinization and their relation with in vitro glycemic index

The effect of gelatinization on the in vitro glycemic index (GI) of starch obtained from jicama tubers was investigated, and the relationships between the starch crystallinity, granule morphology, and the GI were measured. Samples were prepared by heating an aqueous dispersion of starch (1:3 w/v) at different baking process temperatures (60, 65, 70, 75, or 80°C). Native starch granules showed spherical and polyhedral shapes, with a morphometric aspect ratio (AR) of 0.89–1.0 and sizes ranging from 3 to 21 μm. During the thermal process a change in the AR (0.21–0.88) and size (3.0–46 μm) was observed, as well as the formation of agglomerates. Native jicama starch exhibited a CA-type X-ray diffraction pattern, while those thermally treated showed a transition from the CA-type to CB-type, decreasing their crystallinity (20.8–11.5%) at higher temperatures. The gelatinization degree of the starch samples and the glycemic index showed the largest values (97.4% and 98.6% respectively) at the highest temperature (80°C), while the crystallinity percentage followed an inverse correlation to temperature (11.5%, 80°C), indicating that the thermal history affected the behavior of the starch enzymatic digestion. The in vitro glycemic index correlated positively with the gelatinization degree based on aspect ratio (R2 = 0.977), DSC gelatinization enthalpy (R2 = 0.969), and crystallinity (R2 = −0.988). Based on these results a mathematical model is proposed to determine the glycemic index as a function of the aspect ratio. However, more studies are required to validate this information.Fil: Ramírez Miranda, Mónica. Instituto Politécnico Nacional; MéxicoFil: Ribotta, Pablo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Ciencia y Tecnología de Alimentos Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Ciencia y Tecnología de Alimentos Córdoba; ArgentinaFil: Silva González, Ana Zury Zaradi. Instituto Politécnico Nacional; MéxicoFil: Salgado Cruz, María de la Paz. Consejo Nacional de Ciencia y Tecnología; MéxicoFil: Andraca Adame, José Alberto. Instituto Politécnico Nacional; MéxicoFil: Chanona Pérez, José Jorge. Instituto Politécnico Nacional; MéxicoFil: Calderón Domínguez, Georgina. Instituto Politécnico Nacional; Méxic

Effects of TiO2 Nanoparticles Incorporation into Cells of Tomato Roots

In this study, tomato plants were grown in vitro with and without incorporation of TiO2 nanoparticles in Murashige and Skoog (MS) growth medium. The aim of this study was to describe the morphological (area and roundness cell) and mechanical (Young’s Modulus) change in the different tissue of tomato root, epidermis (Ep), parenchyma (Pa), and vascular bundles (Vb), when the whole plant was exposed to TiO2 nanoparticles (TiO2 NPs). light microscopy (LM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM), wavelength dispersive X-ray fluorescence (WDXRF) techniques were used to identify changes into the root cells when TiO2 NPs were incorporated. TiO2 NPs incorporation produces changes in the area, roundness, and Young’s Modulus of the tomato root. When tomato root is exposed to TiO2 NPs, the Ep and Vb area size decreases from 260.92 µm2 to 160.71 µm2 and, 103.08 µm2 to 52.13 µm2, respectively, compared with the control area, while in Pa tissue the area size was increased considerably from 337.72 mm2 to 892.96 mm2. Cellular roundness was evident in tomato root that was exposed to TiO2 NPs in the Ep (0.49 to 0.67), Pa (0.63 to 0.79), and Vb (0.76 to 0.71) area zones. Young’s Modulus in Pa zone showed a rigid mechanical behavior when tomato root is exposed to TiO2 NPs (0.48 to 4.98 MPa control and TiO2 NPs, respectively). Meanwhile, Ep and Vb were softer than the control sample (13.9 to 1.06 MPa and 6.37 to 4.41 MPa respectively). This means that the Pa zone was stiffer than Ep and Vb when the root is exposed to TiO2 NPs. Furthermore, TiO2 NPs were internalized in the root tissue of tomato, accumulating mainly in the cell wall and intercellular spaces, with a wide distribution throughout the tissue, as seen in TEM

Ultrasound-assisted extraction of starch from frozen jicama (P. erosus) roots: Effect on yield, structural characteristics and thermal properties

Jicama roots have been studied as an alternative starch source. However, reports about the extraction yield are scarce, as well as publications about the use of pretreatment techniques for this material. Hence, the aim of this study was to analyze the effect of sonication on the starch yield as well as on the granule structure. Ultrasound was observed to have a positive effect on the starch yield, with the largest value obtained at a sonication time of 10 min (24.76 ± 2.4%). This represents a 46.9% increase over a non-treated sample (16.86 ± 0.9%), and the starch granule structure was unaffected, as confirmed by microscopy and an X-ray diffraction analysis The imperviousness of the starch granule to the sonication process is attributed to the protective effect of soluble fiber and a change in viscosity caused by the material released from parenchyma cells. More studies are required in this area

The Role of ZO-2 in Modulating JAM-A and γ-Actin Junctional Recruitment, Apical Membrane and Tight Junction Tension, and Cell Response to Substrate Stiffness and Topography

This work analyzes the role of the tight junction (TJ) protein ZO-2 on mechanosensation. We found that the lack of ZO-2 reduced apical membrane rigidity measured with atomic force microscopy, inhibited the association of γ-actin and JAM-A to the cell border, and instead facilitated p114RhoGEF and afadin accumulation at the junction, leading to an enhanced mechanical tension at the TJ measured by FRET, with a ZO-1 tension probe, and increased tricellular TJ tension. Simultaneously, adherens junction tension measured with an E-cadherin probe was unaltered. The stability of JAM-A and ZO-2 binding was assessed by a collaborative in silico study. The absence of ZO-2 also impacted the cell response to the substrate, as monolayers plated in 20 kPa hydrogels developed holes not seen in parental cultures and displayed a retarded elongation and formation of cell aggregates. The absence of ZO-2 was sufficient to induce YAP and Snail nuclear accumulation in cells cultured over glass, but when ZO-2 KD cells were plated in nanostructured ridge arrays, they displayed an increased abundance of nuclear Snail and conspicuous internalization of claudin-4. These results indicate that the absence of ZO-2 also impairs the response of cells to substrate stiffness and exacerbates transformation triggered by substrate topography