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There are reports on resistance to metals by the Microbacteriaceae family, although few studies have focused on the Microbacterium genus. The present work is one of the first studies related to arsenic (As) resistance and removal by Microbacterium hydrocarbonoxydans . Growth curves were performed simultaneously as follows: (1) growth kinetics without As, and (2) growth kinetics added with As(III). Incubation conditions were at 30 °C and 120 rpm for 168 h, with an inoculation of bacterial culture, 107 (CFU)/ml. Absorbance was measured at 600 nm in an ultraviolet (UV)–vis spectrophotometer. The As surface adsorption and uptake into bacterial cells, exposed to As(III), were confirmed through SEM, EDX, and FTIR analyses. It was observed that the cellular morphology of M. hydrocarbonoxydans through TEM was deformed when exposed to high concentrations of arsenite. Bacterial cells growing in a rich medium with As(III) were able to oxidize 98% As(III), and the inactivated biomass of the bacterium exhibited a high removal capacity. Likewise, M. hydrocarbonoxydans was employed to test its ability to remove other toxic heavy metals such as lead, cadmium, and chromium. The order of resistance of each metal was as follows: Cr VI (2.08 gL −1 ) > Pb (1.24 gL −1 ) > Cd (0.169 gL −1 ). This work demonstrated that the strain M. hydrocarbonoxydans has high arsenic resistance and removal capacity, as well as significant As(III) oxidation potential, rendering it a promising candidate for biotechnological application in the development of affordable systems for the removal of metals/metalloids from contaminated sites.

Two bacterial consortia (C55 and C33), obtained from an industrial residue contaminated with hexavalent chromium (Cr(VI)), were used to study the behavior of their mixture for depleting this ion in liquid media. In the absence of Cr(VI), C55 showed a greater growth rate than C33, while the latter exhibited biofilm formation. In the presence of this ion, C55 showed resistance up to 800 mg·L −1 and an ability to diminish up to 400 mg·L −1 of the Cr(VI) from the medium, while for C33, these concentrations were 400 and 200 mg·L −1 , respectively. Bacterial synergism between these consortia was evaluated using different compound ratios (C55:C33 ratios of 1:1, 1:2, and 2:1), growing at 50, 100, and 200 mg·L −1 Cr(VI). The best half‐lives of Cr(VI) decrease were 16, 31, and 98 h, respectively, for the 1:1 mixture. The ability of C33 and the mixed consortia to form biofilms was verified. MiSeq sequencing revealed 4 major populations for C55 (in a total of 14) and 3 for C33 (8), most of which were common. After an isolation process, 2 bacterial strains were obtained from C55 and 4 from C33. Three of these strains (QRePLB33E, similar to Oceanobacillus profundus ; QRePLB33G, to Shouchella clausii ; and QRePLB55C, to Cellulosimicrobium funkei ) showed resistance to Cr(VI) and the ability to remove 100% of it at least up to 300 mg·L −1 . Thus, synergism between different bacterial consortia obtained from the same site is possible and can improve, by complementing their capacities, both the growth rate and the ability to diminish the xenobiotic from the medium.

One of the main concerns of humankind in the last years is the availability of energy sources. Research has been focused on finding clean and renewable ways to satisfy the energy demand worldwide. In the particular case of the state of Guanajuato, Mexico, clay industry burns each year about 15,000 m 3 of fuel oil and residual oils, and 96,000 t of wood derivatives. As a way to reduce the environmental impact of clay industry, the use of solid fuel pellets, obtained from vegetable residual material, is proposed. The raw material for the pellets is obtained from agribusiness and from the cities of the state. The solid biofuel has high density, low content of humidity, a homogeneous shape and high energy density. Nevertheless, special care must be taken about the location of the production facility and hubs, in order to make the production of the biofuel economically feasible. Furthermore, to have an environmentally friendly fuel, the supply chain and the production process must minimize the global environmental impact. In this work, a mathematical programming model is proposed to determinate the optimal location of the production facilities, the hubs, and the best distribution logistics. The problem is modelled using a general disjunctive programming approach, and then relaxed into a mixed-integer non-linear programming (MINLP) problem. It has been determined that the main plant should be located in the city of Irapuato, while secondary plants must be established in the cities of León, Irapuato, Abasolo and Salamanca. Moreover, it has been estimated that, when the residual biomass is converted into pellets, about 72,548 t/year of equivalent CO 2 are avoided in the main plant, together with 24,182 of equivalent CO 2 avoided per secondary facility.

The present study aims to investigate the low-energy consumption and high-efficiency removal of arsenic from aqueous solutions. The designed adsorbent Fe/TBC was synthesized by impregnating iron on torrefaction henequen fibers. Isothermal adsorption experiments indicated maximum adsorption capacities of 7.30 mg/g and 8.98 mg/g for arsenic(V) at 25.0 °C and 40.0 °C, respectively. The interference testing showed that elevated levels of pH, HCO 3 − concentration, and humic acid content in the solution could inhibit the adsorption of arsenic by Fe/TBC. Characterization of the adsorbent before and after adsorption using FTIR and SEM–EDS techniques confirmed arsenic adsorption mechanisms, including pore filling, electrostatic interaction, surface complexation, and H-bond adhesion. Column experiments were conducted to treat arsenic-spiked water and natural groundwater, with effective treatment volumes of 550 mL and 8792 mL, respectively. Lastly, the life cycle assessment (LCA) using OpenLCA 2.0.3 software was performed to treat 1 m 3 of natural groundwater as the functional unit. The results indicated relatively significant environmental impacts during the Fe/TBC synthesis stage. The global warming potential resulting from the entire life cycle process was determined to be 0.8 kg CO 2 -eq. The results from batch and column experiments, regeneration studies, and LCA analysis indicate that Fe/TBC could be a promising adsorbent for arsenic(V).

A gallery of hydrotalcite-type mesoporous materials with different Mg/Al molar ratios were synthesized by the coprecipitation method. The materials were activated by heat treatment to test their activity in the photodegradation of 2,4,6-trichlorophenol under UV light irradiation. The physicochemical properties of the different synthesized and activated materials were determined using XRD, physical adsorption/desorption of N2, FTIR, SEM, DTA, and TGA. Their banned band energy was determined by UV-Vis to identify their potential to be used as a semiconductor in catalytic photodegradation processes. The results of photodegradation tests of 2,4,6-trichlorophenol showed that hydrotalcites have a high degradation capacity, up to 100% for the catalyst of Mg/Al ratio = 2, with a high mineralization capacity of 80%. The degradation capacity of most of the catalysts tested is mainly due to the presence of holes and the formation of superoxide free radicals, which are the determining species within the degradation mechanism.

Arsenic release from the abandoned mines and its fate in a local stream were studied. Physicochemical parameters, metals/metalloids and arsenic species were determined. One of the mine drainages was found as a point source of contamination with 309 μg L −1 of dissolved arsenic; this concentration declined rapidly to 10.5 μg L −1 about 2 km downstream. Data analysis confirmed that oxidation of As(III) released from the primary sulfide minerals was favored by the increase of pH and oxidation reduction potential; the results obtained in multivariate approach indicated that self-purification of water was due to association of As(V) with secondary solid phase containing Fe, Mn, Ca.

In this work, the distribution of nine metals in two types of cultivated mushroom had been investigated. For Agaricus bisporus, the biomass was separated into caps and stalks, and for Pleurotus ostreatus, the entire mushrooms were taken for analysis. Electrothermal atomic absorption spectrometry was used for total element determination in acid digests. For accuracy checking, the certified reference material (NIST 1,571, citrus leaves) was analyzed. The results obtained for the two fungi species were within the ranges of concentration reported previously by other authors. Subcellular fractionation was accomplished by centrifugation of cell homogenates, which had been suspended in Tris-HCl buffer. In the first centrifugation (7,300 g, 4 degrees C, 10 min), cell walls were separated (pellet I), and the second centrifugation (147,000g, 4 degrees C, 60 min) yielded mixed membrane fraction (pellet II) and cytosol (supernatant II). Recoveries of the fractionation procedure were in the range 70--100% (with the exception of Fe). For all elements studied, the highest relative contributions were found in cytosol fractions of the fruiting bodies (63--72%, 49--76%, 44--93%, 26--87 pc, 55--85%, 50--68%, 41--78%, 39--78%, 54--67% respectively for Al, Bi, Cd, Cr, Cu, Fe, Mn, Ni, and Pb. Lower contributions were found in cell walls (respectively 22--32%, 24--44%, 6.1--47%, 12--52%, 7.3-- 37%, 7.9--32%, 19--52%, 20--42%, and 25--38%) and only minute amounts in the mixed membrane fraction (3.0--5.8%, 0.7--7.0%, 0.7--8.3%, 1.0--22%, 7.5--14%, 16--24%, 1.1--19%, and 5.1--7.7%). The results obtained indicate that small water-soluble molecules were the primary forms of nine elements in two mushroom species studied. On the other hand, the evidence has been provided on elements binding to larger, water-insoluble molecules contained in the structures of cell wall and membranes. The relative distribution was both element and fungi dependent. Thus, in P. ostreatus, total element levels were higher than in A. bisporus, with the preference for their accumulation in cytosol. On the contrary, total element content in the latter fungi was lower; however, a clear tendency toward more efficient element incorporation to the water-insoluble structures was observed (no apparent differences between stalks and caps).

The agricultural soils in Guanajuato, Mexico, are confronted with potentially toxic element (PTE) pollution due to long-term mining activities and sewage irrigation. The present study investigated PTEs, including Mn, Ni, Cu, Zn, Cr, As, Cd, Pb, and F, in soil and corresponding crops from five farms. Meanwhile, the ecological risks of PTEs were evaluated through the Igeo (geo-accumulation index), TF (transfer factor), and HRI (human health risk index) indices. Correlation analysis and principal component analysis were applied to identify the sources of PTEs. The PTE profile distribution results showed that the As concentration range in soil was 0.98–10.96 mg/kg, which exceeded the allowed limit at some farms. The evaluation of Igeo and HRI indicators further confirmed the high ecological risk of As, and principal component analysis indicated that residual substances from mining activities were a substantial source of PTEs. This study represents the initial effort to establish the distribution of PTE profiles in agricultural soils within the Guanajuato area. It also conducts contamination evaluation and source analysis, presenting a comprehensive assessment.

Malondialdehyde (MDA) is a widely accepted biomarker of lipid peroxidation. Thus, the measurement of MDA in clinical samples is useful in the evaluation of oxidative stress. In this study, a micro-extraction-spectrophotometric assay was developed, based on the formation of MDA–thiobarbituric acid (TBA) adduct. To enhance the analytical performance, Erioglaucine A was used as an internal standard (IS), and the first derivative spectra were obtained. The volume of serum sample was 20 µL and the total volume of aqueous phase 420 µL (200 µL of 0.6% TBA in acetic acid, pH 2.5 and 200 µL of 6.25·10−4% IS). The extraction of adduct and IS was carried out with 300 µL of aliquat 336 (0.06%) in ethyl acetate. The analytical signal S was defined as the ratio between the first derivative absorbances measured at 543.1 nm (adduct) and 644.4 nm (IS). In the calibration range up to 10 µmol L−1 MDA, the linear regression coefficient was 0.9998. The quantification limit was 0.19 µmol L−1 and the CV values for 2 µmol L−1 and 5 µmol L−1 MDA, respectively, were 0.8% and 0.7%. The procedure was applied to the analysis of diabetic sera and the results compared with those obtained by HPLC (derivatization with 2,4-dinitrophenylhydrazine). Lower HPLC results (about 15%) indicated that interferences from other TBA reactive substances had not been completely eliminated by the extraction procedure and derivatization of spectral data. On the other hand, the micro-procedure presents important advantages: it is simple, precise and environmentally friendly (small amounts of reagents), which makes it readily adaptable to the analysis of large sample series. The feasibility of micro-assay in the evaluation of lipid peroxidation status was demonstrated in the analysis of 156 serum samples from diabetic patients divided into three groups according to the stage of development of typical complications.