Papers by Keyword: Acidithiobacillus ferrooxidans

Abstract: The extraction and processing of silver minerals produce significant amounts of waste, which poses environmental challenges due to their low metal content and the potential release of toxic elements. The study investigates the application of Acidithiobacillus ferrooxidans (AF) bacteria to the bioleaching of these waste materials, with the aim of maximizing the recovery of iron, copper and arsenic. The objectives of the study include characterizing waste materials, optimizing the bioleaching process parameters and evaluating metal extraction efficiency. The samples were leached with additives (CuSO₄ 5H₂O and AgNO₃) to accelerate the kinetics of metal dissolution in solution and reduce the bacterial leaching time. The results showed that samples 1-2 and 2-2 containing additives had higher values of dissolved iron and copper in the leachate compared to samples 1-1 and 2-1 without additive application.

Abstract: Recombinant rusticyanin was produced in Pichia pastoris, then purified and immobilized on Sepharose CL-4B with periodate activation. Cellular lysate of acidophilic Acidithiobacillus ferrooxidans was applied to an affinity column with immobilized rusticyanin. Rusticyanin-binding proteins, separated using 1D PAGE and identified by mass spectrometry, included anticipated interacting partners, such as cytochromes Cyc1 and Cyc2, which are involved in the downhill electron pathway from ferrous iron to oxygen. However, the results indicate that rusticyanin’s functional protein-protein interaction (PPI) network could be more complex than expected, including various proteins involved in different cellular processes. Although affinity purification coupled to mass spectrometry should mostly detect proteins that bind stably, and thus are likely participants in functional in vivo PPIs, further verification is needed to exclude non-functional interactants. Nevertheless, our preliminary PPI data confirm some previous experimental findings and indicate potentially fruitful directions for probing additional roles of rusticyanin in sulfur metabolism, copper resistance, anaerobic iron reduction, iron transport, and oxidative stress in extreme acidophiles.

Abstract: Due to the advancing development of new technologies and consumer goods the future demand for raw materials will rise significantly. The finite primary raw materials will not be able to meet the demand quickly enough or the prices for the extraction will rise enormously. In consequence, a recycling of process waste and end of life products will be in future an essential step in order to meet the demand. Y₂O₃:Eu fluorescent phosphor was identified as the main composition in phosphor waste fractions and was chemical leached and bioleached with A. ferrooxidans. A selective leaching towards Y in bioleaching batches was observed and already after four days 100 % could be leached. The bioleaching with the bacteria showed no significant differences in comparison to the abiotic control without microorganism. Initial Fe³⁺ in the medium was identified as the driving force and lower extraction efficiencies of the biotic batches were attributed to a biosorption process and to high pH-values. This work showed that the extraction of yttrium out of waste products with high Y₂O₃:Eu content by chemical leaching with Fe-addition under mild conditions offers a good perspective to support the material demand of Y in the future growing market. In comparison to bioleaching of other fluorescent phosphors and waste fractions leaching efficiencies up to 100% were achieved and it was identified that the microorganisms can positively influence the leaching effect. Furthermore, it became obvious that the leaching behavior of microorganisms was highly dependent on the sample material. As relevant parameters mainly the structural composition of the phosphor was identified.

Abstract: Anionic ion species occur in gangue minerals and impact the bioleaching efficiency even at low concentrations. Recently, the detrimental influence of fluoride ions on bioleaching microorganisms has caused great attention in research. However, the tolerance mechanisms of bioleaching microorganisms for fluoride are still unclear. In order to reveal fluoride tolerance, culture experiments with different concentrations of fluoride and ferrous iron-grown Acidithiobacillus ferrooxidans were carried out. The results showed that oxidation-reduction potential, oxidation capacity of iron and cell density were all negatively correlated to the fluoride concentration. The growth of A. ferrooxidans showed a longer delayed time and a slower growth rate when fluoride concentration increased. The fluoride tolerance for A. ferrooxidans could be attributed to the generated ferric ions from ferrous oxidation. Ferric ions reacted with HF to decrease the concentration of F^- and finally reduced the toxicity of fluoride on A. ferrooxidans.

Abstract: The ability of Acidithiobacillus ferrooxidans to remove chromium and other metals from LD slag was examined. Additionally the option to retrieve P from LD slag was evaluated. Due to the facts that A. ferrooxidans is a facultative anaerobic microorganism and LD slag is an alkaline and oxidic material, both oxidative and reductive bioleaching experiments were carried out. In the reductive mode, four different gas atmospheres (nitrogen, carbon dioxide, air and a mixture of N₂ and CO₂) were considered. Promising results were obtained by reductive bioleaching with A. ferrooxidans and a pure carbon dioxide atmosphere, 83 % chromium could be removed. In comparison, only 27 % Cr were removed by oxidative bioleaching. The degree of P removal could not be easily determined due to imbalanced data obtained.

Abstract: Small quantities of organic substances are inevitably entrained and dissolve in the aqueous raffinate during a copper solvent extraction (SX) operation. These organic substances contaminate the bioleaching environment through the loopback of the raffinate. The attachment of cells of Acidithiobacillus ferrooxidans (At. ferrooxidans) to the low grade chalcopyrite ores and the bioleaching of the ores under the influence of solvent extraction organic substances were investigated. The results showed that the cells of At. ferrooxidans were apt to attach on the SX organics-contaminated chalcopyrite ores with an adsorption ratio of about 83%, larger than that of 44% on the uncontaminated ores as a control. However, the bioleaching efficiency decreased from 25% to 15% under the influence of the SX organic substances. Obviously, an improvement of the cells attachment did not improve the bioleaching efficiency of the low grade chalcopyrite ores by At. ferrooxidans in the present of the SX organic substances. The SX organic substances impacted the metabolism of At.ferrooxidans and their bioleaching ability.

Abstract: Ferric iron may act as a thermodynamically favourable electron acceptor during elemental sulfur oxidation by Acidithiobacillus ferrooxidans in extremely acidic anoxic environments. A loss of anaerobic ferric iron reduction ability has been observed in ferrous iron-grown A. ferrooxidans CCM 4253 after aerobic passaging on elemental sulfur. In this study, iron-oxidising cells aerobically adapted from ferrous iron to elemental sulfur were still able to anaerobically reduce ferric iron, however, following aerobic passage on elemental sulfur it could not. Preliminary quantitative proteomic analysis of whole cell lysates of the passage that lost anaerobic ferric iron-reducing activity resulted in 150 repressed protein spots in comparison with the antecedent culture, which retained the activity. Identification of selected protein spots by tandem mass spectrometry revealed physiologically important proteins including rusticyanin and outer-membrane cytochrome Cyc2, which are involved in iron oxidation. Other proteins were associated with sulfur metabolism such as sulfide-quinone reductase and proteins encoded by the thiosulfate dehydrogenase and heterodisulfide reductase complex operons. Furthermore, proteomic analysis identified proteins directly related to anaerobiosis. The results indicate the importance of iron-oxidising system components for anaerobic sulfur oxidation in the studied microbial strain.

Abstract: Mobile phone PCBs (MPPCBs) is one of the most important targets in e-waste from both economical and environmental threat points attention to their high dense composition of metals. Because of the inhibitory effect of metals especially copper on gold recovery, for gold extraction from MPPCBs a successive two stage bioleaching using Acidithiobacillus ferrooxidans and Bacillus megaterium, was applied. At the first stage, it was tried to extract copper and nickel from the waste. Then using B. megaterium the gold extraction from MPPCBs was examined. The amount of gold which extracted was about 64 g/ton while the average amount of gold in a mine in the world is about 8-10 g/ton. For both of stages the optimum condition was determined using response surface methodology.

Abstract: Heterodisulfide reductase (Hdr), is an iron-sulfur protein which in anaerobic methanogenic archaea catalyzes the reduction of the disulphide bond between coenzyme M and coenzyme B and is coupled to methane formation. In aerobic acidophilic chemolithotrophic bacteria (e.g., biomining bacteria) the function of this enzyme is unclear. Inspection of the genomic sequences of Acidithiobacillus ferrooxidans DSM 16786 and Acidithiobacillus thiooxidans DSM 17318 and reverse transcriptase-PCR results revealed a cluster of six co-transcribed genes, hdrC1, hdrB1, hdrA, orf1, hdrC2 and hdrB2, encoding proteins with high similarity to catalytic Hdr subunits. Additionally, microarray expression profiling and quantitative RT-PCR experiments demonstrated that the hdr genes of A. ferrooxidans and A. thiooxidans were highly expressed when bacteria are grown in the presence of sulfur and tetrathionate. Moreover, hdr genes in A. ferrooxidans were greatly up-regulated when this microorganism was grown in sulfur compared to ferrous medium. These results strongly support a role for Hdr in oxidative metabolism of reduced sulfur compounds in aerobic chemolithotrophic bacteria.

Abstract: The proteomics of the extracellular proteins (EPs), outer membrane proteins (OMPs) and the periplasmic proteins (PPs) of Acidithiobacillus ferrooxidans ATCC 23270 grown on Fe²⁺ and S⁰ substrates, respectively, were comparatively studied. 39 expression up-regulated proteins (including 13 EPs, 9 OMPs and 17 PPs) were identified and 70% of them contain cysteine residues in sequence. Some of the selected proteins especially the EPs contain abundant of the cysteine residues and one or more-CXXC-functional motifs. The thiol groups on the At. ferrooxidans cell surface were selectively marked by Ca²⁺ and SR-μ-XRF mapping in situ observation revealed that the number of thiols on the surface of the cells grown on S⁰ was about five times as that grown on Fe²⁺ substrate. When 0.01 g/L surfactant Tween-80 was added in the S⁰ culture medium, the adsorption and activation related EPs were down-regulated and the sulfur metabolism related proteins was up-regulated. The same phenomenon was observed when the cells were grown on the more easily adhesion sulfur allotrope μ-S. It indicates that the thiol-rich proteins played important roles in adhesion and sulfur oxidation process of At. ferrooxidans.