Papers by Author: Edgardo R. Donati

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Authors: P. Chiacchiarini, L. Lavalle, Alejandra Giaveno, Edgardo R. Donati
Abstract: This work presents an overview of the physicochemical and biological studies carried out along Rio Agrio and in different hot springs belonging to the geothermal Copahue volcano system, in Neuquén Argentina. This is an extreme environment characterized by wide ranges of temperature, pH (<1 to 8) and heavy metals concentration. In these extreme conditions chemolitho-autotrophic bacteria, archaea, heterotrophic bacteria, yeasts and filamentous fungi were detected. Members of Leptospirillum ferrooxidans, Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans and Acidianus spp., among others, were successfully cultivated and physiological properties of different isolates were determined. Additionally, bioleaching and biooxidation of regional ores were carried out using mixed native cultures.
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Authors: Alejandra Giaveno, Edgardo R. Donati
Abstract: Bioleaching of a sulfide ore was investigated using a consortium of thermophilic bacteria and archaea. The consortium was obtained through successive enrichment procedures (using M88 with tetrathionate) after isolating from two different places into the geothermal area (Baño 9 and Las Maquinitas) of the Copahue volcano (in the north of Neuquén province in Argentina). Bioleaching experiments were carried out in 250-ml shake flasks with 100 ml of media and 1 g of the sulfide ore. Flasks were incubated at 150 rpm and 70 oC. The major constituents of the ore (La Resbalosa, Argentina) were sphalerite, pyrite, chalcopyrite and galena. The sample used throughout bioleaching experiments contained 22.5 % Zn. Two different media (0K and M88) were evaluated with and without the addition of elemental sulfur. Genetic diversity analysis of the microbial community was performed by PCR amplification of bacterial 16S rDNA fragments and analyzed by DGGE (denaturing gradient gel electrophoresis). The 16S rDNA was amplified by using eubacteria and archaea primers. Metal concentration, Eh and pH were periodically analyzed. Solid residues were filtered, washed, dried and finally analyzed by XRD and XRF. After 45 days, more than 50 % of zinc and about 100 % of the copper were solubilized. Galena and jarosite were detected in the solid residues. The data indicated that the dominant acidophiles were bacteria or archaea according to the media. M88 media allowed an important decrease of pH and higher zinc extractions while the presence of sulfur did not show significant influence on the zinc recovery.
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Authors: J. Plaza, Eric Guibal, J.M. Taulemesse, M. Viera, Edgardo R. Donati
Abstract: Macrocystis pyrifera was used for the recovery of Zn2+ and Cd2+ from slightly acidic solutions (i.e., pH 4). Sorption isotherms were obtained from mono- and bi-component solutions. For the study of metal desorption, EDTA, HNO3 and Ca(NO3)2 were used as eluents. Metal release (Ca2+, Mg2+, K+ and Na+) was monitored in order to evaluate ion exchange mechanisms. After metal sorption/desorption steps the sorbent was characterized using SEM-EDAX analysis. SEM-EDAX analysis also allowed identifying the presence of elements such as Si, Al, Co, Ag, S, P, and Fe in the cell wall. Zinc desorption was almost complete when using 0.1 M nitric acid solution and the sorbent was not significantly damaged by the acidic treatment. Cadmium was completely removed from loaded sorbent when using EDTA, but at the expense of a partial degradation of the biomass as evidenced by the decrease in the intensity of the C and O peaks (SEM-EDAX).
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Authors: Orquidea Coto, Federico Galizia, Ernesto González, Ianeya Hernández, Jeannette Marrero, Edgardo R. Donati
Abstract: Cuban serpentines are known as one of the richest deposits of Ni and Co in the world. These ores are usually treated by pyrometallurgy or by hydrometallurgy. These processes generate huge volumes of mining residues, which still contains high amounts of Ni (0.25 %) and Co (0.09 %). Since metals are partially oxidized, the chances to use sulfur-oxidizing bacteria (Acidithiobacillus thiooxidans) which are able to generate sulfuric acid to leach the residues from Caron process have been evaluated. Thus, in this work, inorganic and organic acids produced in cultures with A. niger or A. thiooxidans respectively were used to study the extraction of Co and Ni from laterite tailings. The results were compared with those obtained in leaching experiments with direct inoculation of those microorganisms. 7 and 16 % of Ni and Co were leached after 3 days using A. niger and sucrose as carbon source. In stage batch one using A. thiooxidans and elemental sulfur as energy source higher percentages of metal solubilization were reached after 15 days. In stage batch two experiments were carried out using inorganic and/or organic bioacids. Metal recoveries in stage batch two using sulfuric bioacid were higher (79 % Ni and 58 % Co) than those obtained with citric bioacid (2.4 % Ni, and 38% Co). However metal recoveries using chemical leaching with citric acid were much higher (80.4 % Ni and 50 % Co using 0.5 M citric acid). Since the mineralogy composition of raw material is a parameter very important to select the leaching agent of oxide ore, the leaching of residue nickel-ferrous of the Caron process with bio-sulfuric acid produced in A. thiooxidans cultures could be an attractive alternative in the development of a sustainable technology in Cuban mining-metallurgy industry.
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Authors: María Sofía Urbieta, Elena González Toril, Ángeles Aguilera, Maria Alejandra Giaveno, Edgardo Donati, Edgardo R. Donati
Abstract: Copahue is a geothermal field located in the Northwest corner of Neuquén province in Argentina. It is dominated by the still active Copahue volcano. In the area there are many acidic pools, hot springs and solfataras with different temperature and pH conditions that influence their microbial diversity. On the surrounding rocks and the borders of the pools, where water movements and thermal activity are less intense, many biofilms can be found. They have different aspects and structure, and they present less extreme temperature and pH conditions than the ponds and hot springs. Biofilms are a different ecological niche and they have different microbial community structure. In this study carried out by molecular ecology techniques, mainly 16S and 18S rRNA sequencing, we report a strong presence of cyanobacterias, cloroflexi and eukaryotes, not detected in previous biodiversity studies done on water samples. Almost no acidophilic bacteria were found, with the exception of members of genus Thiomonas, also found in the acidic pools. Archaea were detected only in one of the biofilms and the structure of that community seems to be similar to those found in water samples, with many uncultured species mainly related to order Sulfolobales. The aim of this study is to assess microbial community diversity in the biofilms present in this acidic geothermal area, with particular emphasis on detection of cyanobacterias and eukaryotes with potential biotechnological applications like production of alternative energy sources, synthesis and accumulation of biomolecules with antiviral or antibiotic activities or potential ability to bioremediate contaminated areas.
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Authors: J. Huergo, C. Bernardelli, M. Viera, Wolfgang Sand, Edgardo R. Donati
Abstract: Bioleaching is the biological conversion of an insoluble metal compound into a water soluble form. In this process metal sulfides are oxidized to metal ions and sulfate by acidophilic microorganisms capable of oxidizing Fe2+ and/or sulfur-compounds. The metal solubilization from sulfide minerals is a chemical process which requires Fe3+ reduction. It is an environmentally friendly technique and an economical method for recovering metals that requires low investment and operation costs. In this work we studied the bioleaching of two kinds of acid-soluble copper sulfides, one easily leached by mesophilic bacteria (covellite), and the other one refractory to their activity (chalcopyrite), in acidic media with or without Fe2+ ions. We studied attached and planktonic populations of autotrophic bacteria, such as Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans and Leptospirillum ferrooxidans in pure or mixed cultures. The influence of a heterotrophic microorganism, Acidiphilium cryptum, was also studied. Attachment was evaluated with fluorescence staining and FISH using four specific probes. L. ferrooxidans showed highest initial attachment in all cases. The presence of Ap. cryptum increased the cell attachment compared with the autotrophic pure cultures. It was possible to correlate experimental data with a mechanism of bacterial-metal sulfide oxidation, the polysulfide pathway for acid- soluble metal sulfides.
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Authors: L. Lavalle, M. Portillo, P. Chiacchiarini, Edgardo R. Donati
Abstract: In recent years the use of microbial methods for decontamination or recovery of heavy metals from environment has increased. Microorganisms such as yeasts are potential bioremediators, removing metals via active or passive uptake. Pink-coloured and pigment-less yeast strains isolated from Agrio River, Patagonia Argentina, were tested for copper, nickel, cadmium and zinc tolerance. An agar-plate qualitative screening method using YNB-glucose agar at different metal concentrations was employed. The tolerance to the metals varied depending on the strain tested. A pigmented yeast strain (Agrio 16) was selected by its tolerance. The ability of this strain to copper uptake was investigated. The kinetics of bioaccumulation/biosorption with increasing copper concentrations up to 622.8 mg l-1 were carried out using viable and nonviable biomass. The values of constants k and n obtained for the Freundlich model are 0.0418 and 0.7430, respectively. The maximun sorption uptake capacity (q) for viable biomass was 81.6 mg of copper/g of biomass.
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Authors: Natasha Zurakoski, Alejandra Giaveno, Ricardo Ulloa, Teresa Laura Lavalle, María Sofía Urbieta, Edgardo R. Donati
Abstract: Microbial consortia taken from an extreme environment were grown at different temperature and enrichment media. The consortia response to environmental changes was evaluated in order to investigate their metabolic flexibility. The molecular technique, DGGE (denaturing gel gradient electrophoresis) was carried out to evaluate the biodiversity. The results show that each consortium was able to grow according to the available resources, demonstrating their flexibility. A selective development was detected when growing conditions were similar to those found in the natural environment even though some species were able to grown even in conditions far away from those present in the sampling sites.
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Authors: Ianeya Hernández Díaz, Federico Galizia, Orquidea Coto, Edgardo R. Donati
Abstract: In previous studies it has been showed that sulphuric bio-acid is a good leaching agent for laterite tailings. In this work we evaluated nickel and cobalt recoveries from tailings of Caron technology process using sulphuric acid produced by Acidithiobacillus thiooxidans cultures under different conditions. In studies where tailings were initially added to the cultures, high nickel and cobalt recoveries (about 60 % for cobalt and 85-100 % for nickel) were reached after 13 days when low pulp densities (1 % and 2.5 %) of laterite tailings were used. These high recoveries fitted very well with the low pH values measured in these cultures. However, metal recoveries were negligible when higher pulp densities were used. Due to such reason, the performance of pre-cultivation configuration was evaluated; for that laterite tailings were added to the cultures after 24 or 48 hours of bacterial growth. This configuration was very efficient even at high pulp density (like 10 %) reaching recoveries (almost 50 % for cobalt and 80 % for nickel) close to those observed where tailings at low pulp densities were initially added to the cultures.
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Authors: P. Kikot, M. Viera, C. Mignone, Edgardo R. Donati
Abstract: Metallurgical processes and mining are the main source of heavy metal contamination of water sources, rivers and lakes. There are a large number of physicochemical processes that can be applied for the immobilization of heavy metals from a liquid matrix. However, many of them are not particularly desirable because their low selectivity and inefficiency when high volumes of low metal concentration liquids must be treated. In such conditions, alternative biological processes have shown to be more useful than traditional physicochemical processes. One of those processes, bioprecipitation of metal sulphides is relevant due to the possibility of forming stable solids (very low solubility) with small volumes compared with other solids. This process is mediated by a broad group of organisms called sulphate reducers that are able to catalyze, under anaerobic conditions, the reduction of sulphate with organic compounds as electron donors. In this paper, we study the effect of the presence of various heavy metals and the pH on the ability to reduce sulphate by sulphate-reducing bacteria. We compare the reduction of sulphate by a microbial community obtained from the effluent of a tannery with a strain isolated from that community. Our results showed that sulphate reduction was significantly affected by pH changes whereas the presence of heavy metals did not show a significant effect. In addition, metal precipitation by the isolated strain was similar than that produced by the community.
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