Análise proteômica diferencial de Acidithiobacillus ferrooxidans em resposta aos sulfetos minerais calcopirita e bornita e efeito de uma proteína recombinante de A. ferrooxidans LR contendo cisteína na oxidação bacteriana da calcopirita

Pós-graduação em Biotecnologia - IQ

Estudo de genes envolvidos no processo de adesão do Acidithiobacillus ferrooxidans em calcopirita (CuFe'S.IND.2')

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Obtenção e avaliação de mutantes de Acidithiobacillus ferrooxidans quanto à capacidade de lixiviar minérios de cobre

Pós-graduação em Biotecnologia - IQ

Differential gene expression in Acidithiobacillus ferrooxidans LR planktonic and attached cells in the presence of chalcopyrite

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Dissolução redutiva de minério de ferro por Acidithiobacillus ferrooxidans para a recuperação de metais de interesse econômico

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

The effects of copper ions on the synthesis of periplasmic and membrane proteins in Acidithiobaeillus ferrooxidans as analyzed by SDS-PAGE and 2D-PAGE

The effects of 200 mM copper ions on the synthesis of membrane and periplasmic proteins were investigated in iron-grown cells of Acidithiobacillus ferrooxidans (At. ferrooxidans). Total membrane protein profiles of cells grown in the absence of copper ions (unadapted cells) and in the presence of copper ions (copper-adapted cells) were compared by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE). Crude preparations of outer membrane and periplasmic proteins were analyzed by SDS-PAGE. The synthesis of proteins was diminished or increased in the presence of copper ions. Low molecular weight proteins (< 14 kDa) were significantly repressed by copper. These proteins are probably acidic proteins located in the outer membrane. An over-expression of a periplasmic protein of about 17 kDa was detected in the copper-adapted cells and was assumed to be rusticyanin, a 16.5-kDa periplasmic copper protein present in At. ferrooxidans cells and involved in the electron-transport chain of the iron oxidation pathway. To our knowledge, this is the first report of a possible involvement of the rusticyanin and outer membrane proteins in the mechanism of copper resistance in At. ferrooxidans. (C) 2003 Elsevier B.V. All rights reserved.

The effects of bacterial leaching on metal partitioning in sewage sludge

The partitioning of Mn, Al, Zn, Cu and Ti ions in municipal sewage sludge was investigated before and after bioleaching processes effectuated by Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans. Oxidation reduction potential increase and pH decrease were obtained as a result of bacterial activity. A less pronounced and constant decrease was obtained with A. ferrooxidans, whereas A. thiooxidans presented a lag phase before a steep pH decrease. Metal solubilization was accomplished in experimental systems supplemented with energy source, Fe2+ for A. ferrooxidans and S-0 for A. thiooxidans. Solubilization efficiency differed for each metal except for Al, and was relatively similar for either organism. Metal partitioning was conducted using five-step sequential extraction procedure before and after the bioleaching. The results indicated that Zn and Mn ions were mostly associated with the organic fraction, whereas Cu, Al and Ti ions with the sulphide/ residue fraction. The bioleaching process caused prompt solubilization of metals mostly associated with the more labile fractions (exchangeable, adsorbed and organically bound metals), whereas those associated to the less labile ones (EDTA and sulphide/residue fractions) were exchanged towards more labile fractions.

Effect of anaerobic digestion and initial pH on metal bioleaching from sewage sludge

The effects of anaerobic digestion and initial pH on the bioleaching of metals from sewage sludge were investigated in shake flask experiments. A strain of Acidithiobacillus thiooxidans was employed in the assays using secondary and anaerobic sludges, which resulted in similar solubilization yields of the metals chromium, copper, lead, nickel, and zinc for both the sludges investigated. The effect of initial pH (7.0 and 4.0) on metal bioleaching was assayed by using the anaerobic sludge inoculated with indigenous sulfur-oxidizing thiobacilli. Although the time required to reach the end of the experiment (final pH close to 1.0) was shortened at initial pH of 4.0, final metal solubilization was not significantly different for both initial pH values, resulting in higher solubilization yields for copper, nickel, and zinc (higher than 80%). Chromium and lead presented solubilization yields close to 50%. The results obtained in this work showed that the metal bioleaching process can be applied to sewage sludge regardless of the type of sludge and without the requirement of pH adjustment.

Bacterial leaching of uranium ore from Figueira-PR, Brazil, at laboratory and pilot scale

A bacterial leaching program was carried out in order to evaluate the potential of applying this process to leach uranium from the ore of Figueira-PR, Brazil. The experiments were carried out in shake flasks, column percolation (laboratory and semipilot scale) and in heap leaching. In shake flasks and in column percolation experiments at laboratory scale, bacterial activity on the ore was confirmed: approximately 60% of uranium was leached, against around 30% in sterilized controls. Column percolation experiments at semipilot scale and heap leaching (850 tons of ore) showed uranium extractions of approximately 50%. In both experiments, a complementary sulfuric acid attack, after the bacterial leaching phase, was necessary to reach this level of uranium extraction.

Estudo da dissolução oxidativa microbiológica de uma complexa amostra mineral contendo pirita (FeS2), pirrotita (Fe 1-XS) e molibdenita (MoS2)

This work aims to study the oxidation of a complex molybdenite mineral which contains pyrite and pyrrotite, by Acidithiobacillus ferrooxidans. This study was performed by respirometric essays and bioleaching in shake flasks. Respirometric essays yielded the kinetics of mineral oxidation. The findings showed that sulfide oxidation followed classical Michaelis-Menten kinetics. Bioleaching in shake flasks allowed evaluation of chemical and mineralogical changes resulting from sulfide oxidation. The results demonstrated that pyrrotite and pyrite were completely oxidized in A. ferrooxidans cultures whereas molybdenite was not consumed. These data indicated that molybdenite was the most recalcitrant sulfide in the sample.

The effect of chloride ions and A. ferrooxidans on the oxidative dissolution of the chalcopyrite evaluated by electrochemical noise analysis (ENA)

It is believed that the dissolution of chalcopyrite (CuFeS2) in acid medium can be accelerated by the addition of Cl- ions, which modify the electrochemical reactions in the leaching system. Electrochemical noise analysis (ENA) was utilized to evaluate the effect of the Cl- ions and Acidithiobacillus ferrooxidans on the oxidative dissolution of a CPE-chalcopyrite (carbon paste electrode modified with chalcopyrite) in acid medium. The emphasis was on the analysis of the admittance plots (Ac) calculated by ENA. In general, a stable passive behavior was observed, mainly during the initial stages of CPE-chalcopyrite immersion, characterized by a low passive current and a low dispersion of the Ac plots, mainly after bacteria addition. This can be explained by the adhesion of bacterial cells on the CPE-chalcopyrite surface acting as a physical barrier. The greater dispersions in the Ac plots occurred immediately after the Cl- ions addition, in the absence of bacteria characterizing an active-state. In the presence of bacteria the addition of Clions only produced some effect after some time due to the barrier effect caused by bacteria adhesion. © (2009) Trans Tech Publications.

Leaching of Ni and Cu from mine wastes (tailings and slags) using acid solutions and A. ferrooxidans

The objective of this work is to evaluate the acidic and biological leaching of tailings containing Ni/Cu from a flotation and smelting plant. Acidithiobacillus ferrooxidans, strain LR, was used for bioleaching at pH 1.8 and chemical controls were run parallel to that. The acidic leaching was done within 48 hours at pH 0.5 and 1.0. In the slag inoculated flasks the redox potential was high (600 mV), thus indicating oxidative bacterial activity, however, the obtained results after 15 days showed only around 13% Ni and 8% Cu extractions, which were not different to those of the controls. For the flotation tailings bioleaching extractions were approximately 45% for Ni and 16% for Cu while differing figures were obtained for the chemical controls. These were 30% and 12% respectively. Here we could observe that the presence of bacterial activity led to a higher solubility of Ni. Acid leaching of slag showed higher nickel and copper extractions: 56% and 24% respectively at pH 0.5 and 21% and 11% at pH 1.0. However, the acid consumption was 320 and 150 Kg/ton of slag, respectively, both much higher than in bacterial assays. These results indicated that Ni and Cu solubilization from the slag is acid dependent no matter the redox potential or ferric iron concentration of the leaching solution. For flotation tailings, acid treatment showed extractions of 23% for Ni and 16% for copper at pH 0.5 and 22% and 28%, respectively at pH 1.0. The acid consumption was also higher: 220 and 120 Kg/ton, at pH 0.5 and 1.0, respectively. Based on own findings we could observe that acid leaching is found to be more effective for slag, though the acid consumption is much higher, while for the flotation tailings, bacterial leaching seems to be the best alternative. © (2009) Trans Tech Publications.

Effect of Na-chloride on the bioleaching of a chalcopyrite concentrate in shake flasks and stirred tank bioreactors

Oxidative dissolution of chalcopyrite at ambient temperatures is generally slow and subject to passivation, posing a major challenge for developing bioleaching applications for this recalcitrant mineral. Chloride is known to enhance the chemical leaching of chalcopyrite, but much of this effect has been demonstrated at elevated temperatures. This study was undertaken to test whether 100-200 mM Na-chloride enhances the chemical and bacterial leaching of chalcopyrite in shake flasks and stirred tank bioreactor conditions at mesophilic temperatures. Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans and abiotic controls were employed for the leaching experiments. Addition of Na-chloride to the bioleaching suspension inhibited the formation of secondary phases from chalcopyrite and decreased the Fe(III) precipitation. Neither elemental S nor secondary Cu-sulfides were detected in solid residues by X-ray diffraction. Chalcopyrite leaching was enhanced when the solution contained bacteria, ferrous iron and Na-chloride under low redox potential (< 450 mV) conditions. Scanning electron micrographs and energy-dispersive analysis of X-rays revealed the presence of precipitates that were identified as brushite and jarosites in solid residues. Minor amounts of gypsum may also have been present. Electrochemical analysis of solid residues was in concurrence of the differential effects between chemical controls, chloride ions, and bacteria. Electrochemical impedance spectroscopy was used to characterize interfacial changes on chalcopyrite surface caused by different bioleaching conditions. In abiotic controls, the impedance signal stabilized after 28 days, indicating the lack of changes on mineral surface thereafter, but with more resistive behavior than chalcopyrite itself. For bioleached samples, the signal suggested some capacitive response with time owing to the formation of less conductive precipitates. At Bode-phase angle plots (middle frequency), a new time constant was observed that was associated with the formation of jarosite, possibly also with minor amount or elemental S, although this intermediate could not be verified by XRD. Real impedance vs. frequency plots indicated that the bioleaching continued to modify the chalcopyrite/solution interface even after 42 days. © 2013 The Authors.

Biossolubilização da calcopirita na presença dos íons cloreto e ácidos orgânicos

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)