ABSTRACT
This work investigated the synthesis and characterization of alginate/starch porous materials and their application as copper ions adsorbents from aqueous media. Initially, pregel aqueous solutions with different biopolymer concentrations (1, 3, and 5% w/w) and alginate contents (25, 50, and 75% w/w) were prepared. Hydrogel formation was performed by internal and external gelation methods. Finally, the drying step was done via CO2sc leading to aerogels and via freeze-drying leading to cryogels. Process parameters influence on the final properties of materials was evaluated by BET isotherms, SEM, EDS, and TGA. Regardless the gelation method applied, interesting materials with meso- and macro-pore structure were prepared from pregel mixtures with 3% w/w biopolymer concentration and an alginate content of only 25% w/w. Low alginate content reduces the final cost of the materials. Concerning copper removal, the adsorption data were well fitted to the pseudo-second order kinetic model for aerogels and cryogels, showing aerogels the highest adsorption capacity (40 mg/g) and removal efficiency (â¼ 92%). Materials demonstrated excellent reusability throughout five consecutive adsorption/desorption cycles. Hence, environmentally friendly materials with a high practical value as low-cost bioadsorbents were synthesized, having great performance in the removal of copper ions from aqueous solution.
Subject(s)
Alginates , Copper , Water Pollutants, Chemical , Adsorption , Alginates/chemistry , Copper/chemistry , Cryogels/chemistry , Starch , Water/chemistry , Water Pollutants, Chemical/chemistryABSTRACT
Here, we build and characterize a single-stage gas-gun microparticle accelerator, where a pressurized gas expands and launches particles on a target. The microparticles in the range of 60-250 µm are accelerated by the expansion of pressurized nitrogen. By using a high-speed camera, we study how the velocity distribution of accelerated particles is modified by particle size, pressure in the gas reservoir, valve's opening time, and diaphragm's thickness and composition. We employ this microparticle accelerator to study the impact of glass particles with diameters of (69 ± 6) µm accelerated at moderate velocities â¼ (10-25) m/s, using films of poly-dimethylsiloxane as targets.
ABSTRACT
Resumen El efecto sinérgico de la microencapsulación en geles de pectina e inulina extraída de cultivos nativos de topinambur se evaluó como una estrategia natural para aumentar la supervivencia de Lactobacillus paracasei subsp. toleraos F2, bacteria seleccionada por sus propiedades probióticas sobre la trucha arco iris (Oncorhynchus mykiss). La cepa fue capaz de crecer y fermentar la inulina de topinambur en caldo MRS modificado, lo que condujo al incremento del número de células (~+5 unidades logarítmicas) y la disminución neta del pH (6,2 ±0,2 a 4,0±0,5). La encapsulación de F2 en microgeles de pectina en presencia de inulina mejoró su supervivencia no solo a lo largo del almacenamiento sino también en condiciones donde se simuló el pasaje por el tracto gastrointestinal. Después de 56 días de almacenamiento a 4 °C, se registraron números significativamente mayores de células viables microencapsuladas en presencia del prebiótico (8,2-8,4 log UFC/g) que sin él (~7,00 log UFC/g). Estos resultados alientan la aplicación de estas técnicas para la formulación de alimentos funcionales utilizando fuentes alternativas naturales de inulina que incrementan la viabilidad del probiótico almacenado y su digestibilidad.
ABSTRACT
The synergistic effect of microencapsulation in pectin microgels and inulin extracted from native crops of Jerusalem artichoke (JAI) was evaluated as a natural strategy to increase the survival of Lactobacillus paracasei subsp. tolerans F2 selected for its probiotic properties in Oncorhynchus mykiss. The strain was able to grow and ferment JAI in modified MRS broth, increasing cell population (â¼+5 log units) with a net decrease in pH (6.2±0.2 to 4.0±0.5). Encapsulation of F2 in pectin microgels in the presence of JAI improved the survival of the strain not only during storage but also after exposure to simulated gastrointestinal conditions. Viable entrapped cells in the presence of the prebiotic were significantly higher (8.2-8.4log CFU/g) than without it (â¼7.00log CFU/g) after 56 days at 4°C. These results encourage further implementation of these techniques for the formulation of functional feeds using natural alternative sources of inulin with greater viability on storage conditions and digestibility.
