Percorrer por autor "Rangel, A. O. S. S."
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- Are PGPR’s traits and the inoculum size relevant for inoculation purposes in mine affected soils?Publication . Moreira, H.; Pereira, S. I. A.; Marques, A. P. G. C.; Rangel, A. O. S. S.; Castro, P. M. L.Cadmium and Zn concentrations in soil were largely increased in past decades due to several anthropogenic activities, including mining activities. Phytotechnologies can minimize their hazardous effects through the use of plants coupled with plant growth promoting rhizobacteria (PGPR). Several factors can contribute to the failure of PGPR inoculation, such as bacteria selection and the inoculum size. This work selected five metal resistant PGPR and assessed their in vitro growth promoting traits and their ability to induce maize germination and seedlings growth under Zn and Cd increasing concentrations. Additionally, the effect of the inoculum size (10 and 20 mL) of these strains and their efficiency in promoting plants’ growth and metal accumulation was evaluated in energy maize sowed in a mine soil. Some bacteria only exhibited or enhanced PGP traits when exposed to metals. Strains ECP37 and EDP28 showed to be the most efficient in improving seedlings’ growth with increasing metal concentrations, followed by S3X. Likewise, when inoculated in energy maize grown in mine soil, these same strains outperformed the others by increasing shoot biomass and elongation, metal accumulation, and by decreasing it in roots. The most evident effect of doubling the inoculum size was the increase in Cd accumulation, which was of 17% and 31% in roots and shoots, respectively. Other effects included a slight reduction in shoots' biomass (13%) and a general decrease in P tissue content. The results obtained suggest the selection of PGPR prior to inoculation in target soils should be primarily based in seedling growth promotion under metal exposure. Additionally, the size of the inoculum applied in the soil rhizosphere appears to be important in remediation processes and should be taken into account when planning phytomanagement strategies, especially when the biomass of plants is an important demand.
- Automated analytical microsystem for the spectrophotometric monitoring of titratable acidity in winesPublication . Sández, N.; Calvo-López, A.; Vidigal, S. S. M. P.; Rangel, A. O. S. S.; Alonso-Chamarro, J.INTRODUCTION: Titratable acidity is one of the key parameters of wine due to its closed relationship with both its quality and character. Its control during wine production as well as in the final product is of great interest for wineries in order to ensure the desired characteristics. European and American official organizations, the Organisation Internationale de la Vigne et du Vin (OIV) and the Association of Official Analytical Chemists (AOAC International) respectively, propose similar methods for its determination. These methods consist in the titration of samples to a certain pH against a standard alkaline solution by potentiometric or visual titration. However, these methods are laborious and time consuming. Alternatively, other methods, including some flow-based systems, have already been proposed. Despite offering some advantages in comparison to the classical ones, these methods still present some drawbacks, including expensive instrumentation [1], or complex procedures [2], among others. Herein, we propose an automatic continuous flow spectrophotometric microanalyzer for monitoring titratable acidity in wine, displaying low reagents and sample consumption, simple instrumentation, high portability and high throughput. METHODS: The analytical determination is based on the decrease of the blue coloration of a buffered bromothymol blue (BTB) solution when it is mixed with the standard or the sample solution. This change in absorbance is monitored at 607 nm. The whole system consists of three programmable three-way microvalves, a peristaltic pump, a microfluidic platform, and a miniaturized optical detection system. The scheme of the fluidic set-up is depicted in Fig.1.A. The programmable valves permit the on-line automatic preparation of the different standard solutions, as well as the sample dilution, by multicommutation. The microfluidic platform, which was entirely fabricated using cyclic olefin copolymer (COC) as the substrate material, was constructed by using a 3D-multilayer approach. The fabrication process regarding these type of platforms is described in detail elsewhere [3]. The platform consists of three different inlets, two micromixers and a detection chamber where the absorbance measurements take place (Fig.1.A). Inside the microfluidic platform, a buffered BTB solution is mixed with deionized water. This diluted BTB solution is, then, mixed with the carrier solution where the standard or the samples are injected. The microfluidic platform perfectly fits with the miniaturized optical detection system by using a lock-and-key concept [4]. The detection system consists of a LED emitting at 607 nm and a PIN photodetector mounted in a home-made polymeric structure. The LED and the photodetector are connected to a printed circuit board (PCB), which is connected to a data acquisition card (DAQ). RESULTS: The hydrodynamic conditions for the microsystem were evaluated and optimized, establishing a total flow rate of 1500 µL min-1 and a sample injection volume of 10 μL. The chemical composition of the different solutions was also optimized: deionized water was used as the carrier solution as well as for the on-line dilution of the buffered BTB solution (35 mM phosphate buffer solution adjusted to pH 7.8, with 500 ppm BTB). A 0.50 g L-1 tartaric acid solution was used as stock solution for the on-line preparation by multicommutation of tartaric acid standard solutions of 0.05, 0.10, 0.20, 0.30 and 0.40 g L-1. Analytical characterization of the microsystem was carried out. Fig.1.B shows the obtained signal record for one of the calibrations. The obtained equation (n=6 and 95% confidence) was Abs = - 0.442 ( 0.002)[tartaric acid] - 0.0045 ( 0.0007), with r2 = 9995, and detection and quantification limits of 0.01 g L-1 and 0.03 g L-1 of tartaric acid, calculated as three and ten times the standard deviation of the blank, respectively. The linear working range was established from 0.05 g L-1 to 0.50 g L-1 of tartaric acid.
- Exploring flow analysis tools for monitoring calcium and magnesium in soil leachates from laboratory scale soil columns (LSSCs)Publication . Costa, C. F. F. A.; Mesquita, L. S.; Rocha, F. V.; Mesquita, R. B. R.; Rangel, A. O. S. S.Monitoring the soil/water interface has become fundamental for both environmental and agricultural studies. This work aimed to set up and monitor laboratory scale soil columns (LSSCs) for assessing nutrient levels and characterizing soil leachates using flow analysis methods. A flow analysis method was developed to determine calcium and magnesium concentrations, overcoming the disadvantages of conventional methods in terms of time consumption, waste production and cost. The LSSCs were set up with soil cores from distinct locations and with burned soil to verify if soil type or forest fires affect leaching behaviour. Leachates were obtained through rain simulations with rainwater. In order to establish valid comparisons, simulated rain was assessed before and after going through the LSSCs. The accommodation of both metals in the same sequential injection manifold was successfully attained, as well as the determination of ranges of calcium of 0.160–35.0 mg L-1, and a range of magnesium of 0.160–8.00 mg L-1. The developed method was successfully used to monitor different soil leachates, allowing for the assessment of both metal ions before and after going through the LSSCs. The limits of detection obtained for calcium and magnesium determinations were 7 and 8 mg L-1, respectively. Effluent production equalled 1.8 mL for the assessment of magnesium and the smaller range of calcium and 2.0 mL for the larger range.
- Flow-based method for total protein content monitoring in by-products hydrolysatesPublication . Teixeira, Raquel; Ribas, Tânia C. F.; Almeida, André; Pintado, Manuela; Rangel, A. O. S. S.For this purpose, the conventional and reliable Biuret method was used. This method was chosen for its ease of preparation and the use of reagents with associated low toxicity. The flow-based approach consisted of a double injection of the sample and reagent in a continuous stream, resulting in the reduction of the reagent consumption. For the development of the flow injection analysis (FIA) system, essential parameters, including reagent concentration, flow rate and reactor length, were optimized. The method was validated across various matrices, addressing potential interferences, and demonstrated repeatability and reproducibility. This optimized protocol offers a robust, efficient tool for the food industry, enhancing quality control and nutritional assessments.