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This study deals with the characterization of exopolysaccharides (EPS) synthesized by a halophilic bacterium Salibacterium halochares STm recently isolated from saline soil in Cuatro Ciénegas Basin, Coahuila Mexico. S. halochares exhibited an EPS production of 17.38 g/L (at 72 h), using a modified ATCC 2185 culture medium (with yeast extract at 6 g/L and NaCl at 120 g/L). Chemical characterization of the EPS revealed a composition of total sugars, protein, and uronic acids contents of 83.83%, 1.59% and 2.09% (w/w), respectively. The purified EPS showed a molecular weight of 1283 kDa. Rheological studies of the EPS aqueous solutions indicated a non-Newtonian rheological behaviour which was reliably modeled by the Cross equation. The EPS showed high emulsification indexes (EI) against diverse non-polar substances and formed microemulsions with negative high ζ -potential values (up to − 46 mV). The viscoelastic behaviour data indicated the high stability of hexane–water (1:1 ratio) emulsions stabilized with EPS. The EPS retained its EI at harsh conditions of pH (4, 6.5, 7 and 12), NaCl (0, 2.0 and 4.0 M) and thermal incubation (up to 40 °C, 60 min). This is the first time that a Salibacterium genus member is reported as an EPS-producer. These results reveal the discovery of a novel polysaccharide with great potential for industrial applications, such as emulsion stabilizer, viscosity modifier and thickener. [ABSTRACT FROM AUTHOR]

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Guayusa (Ilex guayusa) is an endemic plant from the Amazon with potential medicinal applications. Indigenous people are familiar with such applications and use guayusa based on ancestral knowledge. There is a growing interest in guayusa-based products in urban areas of Ecuador and internationally. The supply cannot meet the demand. Currently, traditional practices are used for guayusa growth and the potential use of the protected forest is foreseen. This work describes a protocol for the in vitro propagation of guayusa, a sustainable solution to generate high quality plants in reduced space. Stakes obtained from stems were used as explants. Chemical sterilization with ethanol and sodium hypochlorite resulted in 100% surface-sterilized stakes. The growth medium mWPM resulted in favorable outcomes regarding shoot development and elongation, as well as rooting. Supplementation with activated charcoal resulted in reduced browning, only 10% of the shoots presented necrosis during the elongation phase. More than two thirds of shoots were able to develop roots spontaneously. Medium supplementation with the auxin indole-3-butyric acid, IBA, may be considered when rooting does not occur spontaneously. Acclimatization was performed in soil. The protocol was tested under different light spectra, revealing that guayusa growth is affected by light quality. The photobiology of this shade tolerant plant requires further characterization, but the data uncovered a potential role for green and far-red light in root development. Key message: Guayusa was propagated on mWPM medium supplemented with activated charcoal. Spontaneous root development occurred in most shoots. Light quality affected plant development, green and far-red light could influence root growth. [ABSTRACT FROM AUTHOR]

Mining is known as one of the primary economic activities where exploitation of minerals and other materials have become essential for human development. However, this activity may represent a risk to the environment, starting from deforestation and ending with production of residues that might contain potentially toxic elements. Tailing deposits from historical mining are an example of waste that may represent an environmental concern when abandoned and exposed to environmental conditions. The town of Nacozari de Garcia, in northwestern Mexico, has three abandoned mine tailings (locally known as tailings I, II, and III) located around the urban area that represent important sources of dust and pollution. Images obtained using unmanned aerial vehicles (UAV) in conjunction with geochemical data are used to assess historic erosion calculation and pollution considering contamination and hazard indexes in tailings II and III. Digital elevation models of abandoned tailings were obtained using photogrammetry with UAV. A total of 37 surficial samples were collected from mine tailings to determine elemental concentrations (As, Cu, Pb, W, Zn) using portable X-ray fluorescence. Higher concentrations were found on samples from mine tailing II. Average concentrations followed the decreasing order of Cu > Zn > W > Pb > As for tailing II, whereas decreasing order of Cu > Zn > W > As > Pb was found for tailing III. Contamination Index (CI) values obtained from tailings II and III represent a low potential of pollution, whereas efflorescent crusts from these tailings represent a high potential of polluting soils and sediments by dust generation. Hazard Average Quotient (HAQ) values on both tailings suggest a very high potential of contamination if fluids infiltrate tailings and interact with surficial water and/or groundwater. Obtained surfaces of mine tailings II and III are 146,216 and 216,689 m2, respectively, which represent around 11% of the urbanized area. A loss mass of 321,675 tons was determined for mine tailing II, whereas 634,062 tons for tailing III, accounting for 0.96 million tons of total eroded mass. Since abandonment, calculated erosion rates of 493 t ha−1 year−1 (tailing II) and 232 t ha−1 year−1 (tailing III) are in agreement with those determined in other mining areas. CI and HAQ indexes provide good estimates of pollution associated with abandoned mine tailings from Nacozari de García. Historic erosion determined in these tailings is an environmental concern since eroded material and polluted water have been incorporated into the Moctezuma River, which feeds several villages, whose major activities include agriculture and livestock raising. [ABSTRACT FROM AUTHOR]

One of the most important Mayan cities of the Classic period (A.D. 200-900) of Mesoamerica is Palenque, in Chiapas. The Mayan civilization attributed great importance to greenstone minerals, in particular jadeite. This study covers the analysis of greenstones found in royal tombs of several temples corresponding to the Classic period: the Temple of the Skull, Temple of the Cross and Temples XVIII and XVIII-A. The aim of this research is to determine the use of greenstone minerals and the raw materials' sources as a first step in understanding the development of Palenque and its relationships to other sites in the Maya region. Here, we present a non-destructive in situ study of lithic objects carried out by means of a several spectroscopic techniques, such as Raman, Fourier transform infrared (FTIR), X-ray fluorescence (XRF) and color measurements, at the Palenque site museum. FTIR and Raman allowed for the identification of minerals including jadeite, omphacite, amazonite, albite, muscovite and green quartz. Moreover, XRF was effective for in situ analysis of the elemental composition of the artifacts. This information was essential for sourcing the raw materials, in particular, jadeite. It was possible to infer the exploitation of an unknown source of jadeite for the earlier burial (A.D. 250-450). During this period the exploitation of the Verapaz and Motagua jadeite deposits also began. These sources were the primary deposits used for the manufacture of the artifacts studied from the period of A.D. 600-850. Also, a greater diversity of minerals is observed during the zenith of Palenque during this period, corresponding to the reign of Pakal. Although, between burials, the color of the artifacts is diverse, the color measurements indicated similarity in color among artifacts within individual burials. [ABSTRACT FROM AUTHOR]