División de Ciencias Ambientales
http://hdl.handle.net/11627/2
2024-03-29T14:25:33ZCaracterización taxonómica de comunidades arsenato-reductoras y su potencial para la detoxificación de arsénico
http://hdl.handle.net/11627/6483
Caracterización taxonómica de comunidades arsenato-reductoras y su potencial para la detoxificación de arsénico
Navarrete Euan, Heron
"El arsénico es un metaloide que puede estar presente en el ambiente ya sea por fuentes
naturales o antropogénicas. La exposición de los seres vivos al arsénico causa diversos
efectos nocivos, por lo que su remoción del agua o suelos resulta crítica. Para ello, se
pueden emplear bacterias capaces de transformar el arsénico y que propicien su remineralización para facilitar su remoción. Algunas bacterias, como las sulfato reductoras
tienen la capacidad de ayudar a reducir la toxicidad de arsénico ya que además de reducir
sulfato a sulfuro, pueden reducir arsenato a arsenito en un proceso respiratorio y promover
la formación de sulfuros de arsénico. Cabe señalar que las bacterias también pueden reducir
arsenato a arsenito para detoxificarlo, este proceso lo llevan a cabo muchas bacterias y está
regulado por el gen arsC. El objetivo de este trabajo fue caracterizar comunidades
microbianas cultivables expuestas al arsénico para determinar su uso potencial en sistemas
de remediación de arsénico. A partir de comunidades capaces de tolerar arsénico (10 mM)
en ausencia de sulfato con dos concentraciones distintas de lactato (10 ó 22 mM) se
observaron los cambios en la composición de las comunidades y se compararon con
cultivos donde el arsénico se encontraba ausente. De igual manera, se cuantificó el gen
arsC, donde se observó que el arsénico ejerce una presión selectiva sobre las comunidades
promoviendo un cambio en su estructura y crecimiento, favoreciendo a las bacterias que
toleran el arsénico a través de la detoxificación y que también podrían estar respirando
arsenato. Entre las géneros bacterianos favorecidos por el arsénico se encontró
Desulfosporosinus que tiene capacidad de respirar arsenato, mientras que en ausencia de
arsénico se favoreció el género Clostridium, con capacidad fermentativa primordialmente.
Se estima que la mayor parte de las bacterias encontradas en los cultivos con arsénico
poseen el gen de detoxificación; y en donde no se observó este gen, se considera que los
microorganismos podrían llevar a cabo la respiración de arsenato.
Las diferentes condiciones a las que fueron sometidas las comunidades sulfatoreductoras/arsenato-reductoras modificaron su composición de acuerdo con su capacidad de
tolerancia al arsénico y, en menor medida, se observaron cambios a una mayor
concentración de donador de electrones como el lactato. En consecuencia, estas
condiciones permitieron la selección exitosa de bacterias arsenato reductoras, encontrando
entre cinco y nueve géneros distintos, de los cuales Desulfosporosinus, Clostridium,
Pseudomonas, y Bacillus resultaron miembros clave de la comunidad y podrían ser
esenciales para futuros procesos de arsenato reducción para la biorremediación de aguas
contaminadas con este metaloide."; "Arsenic is a metalloid that can be present in the environment due to natural or
anthropogenic sources. The exposure to arsenic of living organisms can cause several
health issues, thus, its removal from water and soil must be addressed. It has been
demonstrated that some bacteria can transform arsenic and facilitate the removal of arsenic
through re-mineralization. Some bacteria, like sulfate-reducing bacteria can lessen arsenic
toxicity, because in addition of reducing sulfate to sulfide, some of them can also reduce
arsenate to arsenite through a respiratory process and promote the formation of arsenic
sulfides. It is worth noting that bacteria can also reduce arsenate to arsenite for
detoxification, which is carried out by several bacterial genera and is regulated by the arsC
gene. The objective of this work was to characterize culturable microbial communities
exposed to arsenic and determine their potential use in arsenic remediation systems.
From cultivable microbial communities capable of tolerating arsenic (10 mM) in the
absence of sulfate with two different concentrations of lactate (10 and 22 mM) as electron
donor, the changes in the community structure were observed and compared among
cultures in the presence and absence of arsenic. Additionally, by means of quantifying the
arsC gene it was observed that arsenic exerts a selective pressure over the community
structure. Suggesting that detoxification, and perhaps respiration, were used as mechanisms
to tolerate arsenic, promoting changes in the structure and growth rate favoring arsenic
resistant bacteria. Among the bacterial genera favored by arsenic, Desulfosporosinus most
likely promoted arsenate reduction through respiration, whereas the Clostridium genus used
lactate in a fermentative process favored by the absence of arsenate. It is estimated that
most of the bacteria found in the communities have the detoxification gene, and where this
gene was not observed, it is considered that microorganisms could carry out arsenate
respiration. The sulfate/arsenate reducing communities exhibited changes based on the
conditions to which they were exposed such as their capacity to tolerate arsenate, and
according to the increase in lactate concentration.
As a result, these conditions allowed the successful selection of arsenate reducing bacteria,
finding between five to nine different bacterial genera. From these genera,
Desulfosporosinus, Clostridium, Pseudomonas, and Bacillus were part of the core
community and might be essential in future projects for the bioremediation of contaminated
water with arsenic."
2023-10-12T00:00:00ZPreparation of carbon materials from chromium-tanned leather shavings for the removal of dyes from aqueous solution
http://hdl.handle.net/11627/6371
Preparation of carbon materials from chromium-tanned leather shavings for the removal of dyes from aqueous solution
Arcibar Orozco, Javier Antonio; Barajas Elías, Bertha Silvia; Baltazar Campos, Hazael; Rangel Méndez, José René
"Chromium-Tanned Leather Shavings are hazardous residues generated during leather processing. Since they contain considerable amounts of chromium, they represent a threat to life and the environment if managed improperly. The present study examines the transformation of such residues into carbon adsorbents and their use in the removal of azo dyes (methylene blue, Congo red and acid black 210) from water. The effects of temperature, holding time and the presence of an activating agent were studied, and basic characterization of the produced materials was performed. Carbon materials contain a low amount of chromium and an improved surface area that was only developed when high temperatures and an activating agent were employed. Depending on the synthesis conditions, the adsorbents’ surface charge was positive or negative, which impacts the dye uptake from aqueous solution. Both the chemical speciation of the dye and the material´s pore volume played a critical role during the adsorption process. It is possible to obtain carbon materials from Chromium-Tanned Leather Shavings, containing no hazardous chromium(VI) particles, that are capable of removing polluting dyes from water."
2022-01-01T00:00:00ZThe value of biotic pollination and dense forest for fruit set of Arabica coffee: A global assessment
http://hdl.handle.net/11627/6367
The value of biotic pollination and dense forest for fruit set of Arabica coffee: A global assessment
Moreaux, Céline; Lopes Meireles, Desiree Ayume; Sonne, Jesper; Badano, Ernesto Ivan; Classen, Alice; González Chaves, Adrian; Hipólito, Juliana; Klein, Alexandra María; Maruyama, Pietro Kiyoshi; Metzger, Jean Paul; Philpott, Stacy M; Rahbek, Carsten; Saturni, Fernanda Teixeira; Sritongchuay, Tuanjit; Tscharntke, Teja; Uno, Shinsuke; Vergara Briceño, Carlos Hernán; Felipe Viana, Blandina; Strange, Niels; Dalsgaard, Bo
"Animal pollinators are globally threatened by anthropogenic land use change and agricultural intensification. The yield of many food crops is therefore negatively impacted because they benefit from biotic pollination. This is especially the case in the tropics. For instance, fruit set of Coffea arabica has been shown to increase by 10–30% in plantations with a high richness of bee species, possibly influenced by the availability of surrounding forest habitat. Here, we performed a global literature review to (1) assess how much animal pollination enhances coffee fruit set, and to (2) examine the importance of the amount of forest cover, distance to nearby forest and forest canopy density for bee species richness and coffee fruit set. Using a systematic literature review, we identified eleven case studies with a total of 182 samples where fruit set of C. arabica was assessed. We subsequently gathered forest data for all study sites from satellite imagery. We modelled the effects of open (all forest with a canopy density of ?25%), closed (?50%) and dense (?75%) forests on pollinator richness and fruit set of coffee. Overall, we found that animal pollination increases coffee fruit set by ~18% on average. In only one of the case studies, regression results indicate a positive effect of dense forest on coffee fruit set, which increased with higher forest cover and shorter distance to the forest. Against expectations, forest cover and distance to open forest were not related to bee species richness and fruit set. In summary, we provide strong empirical support for the notion that animal pollinators increase coffee fruit set. Forest proximity had little overall influence on bee richness and coffee fruit set, except when farms were surrounded by dense tropical forests, potentially because these may provide high-quality habitats for bees pollinating coffee. We, therefore, advocate that more research is done to understand the biodiversity value of dense forest for pollinators, notably assessing the mechanisms underlying the importance of forest for pollinators and their pollination services."
2022-01-01T00:00:00ZRemoval of Heavy Metal Ions from Wastewater with Poly-?-Caprolactone-Reinforced Chitosan Composite
http://hdl.handle.net/11627/6360
Removal of Heavy Metal Ions from Wastewater with Poly-?-Caprolactone-Reinforced Chitosan Composite
Martínez, Manuel E.; Rangel Méndez, José René; Gimeno, Miquel; Tecante, Alberto; Lapidus, Gretchen T.; Shirai, Keiko
"Currently, the requirements for adsorbent materials are based on their environmentally friendly production and biodegradability. However, they are also related to the design of materials to sustain many cycles in pursuit of low cost and profitable devices for water treatments. In this regard, a chitosan reinforced with poly-?-caprolactone thermoplastic composite was prepared and characterized by scanning electron microscopy; Fourier transforms infrared spectroscopy, X-ray diffraction analysis, mechanical properties, as well as erosion and swelling assays. The isotherm and kinetic data were fitted with Freundlich and pseudo-second-order models, respectively. The adsorption equilibrium capacities at pH 6 of Zn(II), Cu(II), Fe(II), and Al(III) were 165.59 ± 3.41 mg/g, 3.91 ± 0.02 mg/g, 10.72 ± 0.11 mg/g, and 1.99 ± 0.22 mg/g, respectively. The adsorbent material lost approximately 6% of the initial mass in the adsorption-desorption processes."
2022-01-01T00:00:00Z