Solid State Phenomena Vol. 262

Abstract: In the course of the decline of high-grade ore deposits, new effective and eco-friendly bioleaching techniques are of interest. In-situ leaching is an auspicious method, but composition of leaching community should be adapted to the respective external conditions and the ore material. In this study several sulfidic minerals were inoculated into acidic mine water of a mine in eastern Germany, housing members of well-known iron oxidizing bacteria like Acidithiobacillus, Leptospirillum and Ferrovum. The attachment tests were performed in batch and in a continuous way at different temperatures. The analysis of the extracted DNA from adhered cells showed an enrichment of Ferrovum spp. on chalcopyrite surface under in-situ conditions at 11°C. For laboratory batch conditions an accumulation of Leptospirillum spp. was detected for adhered cells probably due to the changes of the physicochemical parameter of the mine water. In more detailed analyses we aim to elucidate possible preferential attachment of the mine water community members to certain minerals.

Abstract: While bioleaching is a proven technology for the efficient recovery of base metals from sulphide minerals, its sustenance is dependent on the continuous availability of ferric ion, Fe³⁺, in soluble form, in bioleach liquor. However, the solubility of ferric ion is low at higher pH thus resulting in the formation of various types of ferric ion precipitates, which decreases leaching efficiency by trapping the leached metals in solution through an adsorption. The effect of initial solution pH on the surface properties of ferric ion precipitates was investigated with a view to establish a relationship between operational pH and surface charge on precipitate and to relate this to the precipitates metal adsorption properties. Ferric ion precipitates recovered from a typical biooxidation process were characterized by XRD, SEM, PSD and zeta potential. Potassium-hydronium jarosite were the main phases identified by X-ray diffraction (XRD) analyses. The SEM results revealed that the precipitates had smooth surfaces with development of sharp edges on the precipitates formed at high pH. The precipitates formed at higher pH had less positive charge and scavenged more copper ions due to the high electrostatic attraction forces. The results from this study revealed that surface charge on a precipitate can give an indication of its metal adsorption capacity and that in order to prevent metal loss and improve extraction efficiency, solution conditions should be maintained such that the resulting precipitates have high positive surface charge to promote high electrostatic repulsion forces.

Abstract: A DFT study of H⁺ effect on CoO(0 1 0) surface was carried out. What could be seen from the inter atomic distance and the density of states (DOS) was: Co-O bonds were broken strongly and H-O bonds formed strongly when one H⁺ was adsorbed on the O atom, and Co-O bonds were not broken and H-O bond not formed strongly when two H⁺ were adsorbed on the O atom, so the Skutterudite acid leaching process cannot be described as two H⁺ were adsorbed on the O atom and formed the H₂O molecules to enter the solution. But that can be described as one H⁺ was adsorbed on the O atom and formed the OH^- to enter the solution, the OH^- was combined with the H⁺ in the solution to form the H₂O molecule.

Abstract: Marinobacter sp. DS40M6 produces the siderophores marinobactins, which are amphiphilic and contain hydroxamate functional groups responsible for a strong complexation of iron(III). First tests about growth and production conditions showed on the one hand a high rate for both growth of bacteria and siderophore production at 25°C. The pH value, on the other hand, demonstrated a contrary effect, thus the optimal pH 7.0 for growth was not the most efficient pH value for siderophore production.

Abstract: The differences of superficial (about 10 nm) extracellular polymeric substances (EPS) composition of thermoacidophilic archaea Acidianus manzaensis YN-25 acclimated with different energy substrates (FeS₂, CuFeS₂, S⁰, FeSO₄) were analyzed in situ for the first time by synchrotron radiation (SR) based carbon K-edge X-ray absorption near edge structure (XANES) spectroscopy. The results showed that there are clear associations between the energy substrates and the changes in organic composition in terms of typical function groups (-C=O, -C-O and -C-N). The archaea acclimated with chalcopyrite and pyrite contain higher proportion of proteins but less polysaccharides compared to cells acclimated with S⁰.The archaea acclimated with FeSO₄ contains the highest proportion of protein which is positively associated with the iron oxidation process, while archaea acclimated with S⁰ contains more lipids and polysaccharides, which may be favorable to the hydrophobic S⁰ adsorption and utilization processes.

Abstract: The depletion of rare metals is an issue of major concern since rare metals are limited in the abundance but essential for high technology industry. However, the present rare metal recovery technical by chemical methods has high environmental impact, poor selectivity, and is too expensive to be practical. To resolve these problems, this study aimed to create a rare metal recover system using yeast, and molybdenum was selected as the first target. A molybdenum binding protein, ModE, which was derived from Escherichia coli was selected. A fusion gene was generated by linking partial modE with a secretion signal and a domain of α-agglutinin to display the ModE on the surface of yeast cells. The expression of fusion protein on the cell surface was detected by immunofluorescence labeling. As for the recovery experiment, the engineered yeast cells were incubated in 10 mM of sodium molybdate solution for 2 h, and the recovery of molybdenum ion was measured by ICP-AES. The results of fluorescence micrographs showed that the designed fusion protein was successfully expressed on yeast cell surface. According to the results of ICP-AES, the cell surface engineered yeast adsorbed molybdenum and the cells after 72~84 h incubation gave the best adsorption. Besides, the results suggested that the optimization of each functional domain in the fusion protein was important. The selectivity and the lower limit of recoverable concentration are under investigation, while this study provides a preliminary result of bio-extraction technology using cell surface engineered yeast.

Abstract: Over the past years, the traditional cultivation-independent genomic approaches which rely on the preexisting knowledge about gene sequence, have significantly promoted our understanding of the structural and functional diversity of bioleaching microorganisms in extremely acidic environments. However, high-throughput sequencing technology as a comprehensive and rapid method is now being ported to bioleaching systems for microbial community and gene expression analysis. Years of research have demonstrated that high-throughput sequencing technology has the potential to dramatically accelerate biological research, by enabling the comprehensive analysis of genomes and transcriptomes. This paper aims to introduce the high-throughput sequencing methodology, particularly focusing on the application of high-throughput sequencing technology on bioleaching microorganisms and the challenges associated with its applications.

Abstract: Dispersal between genomes of certain mobile genetic elements and their gene cargo depends on conjugative type IV secretion systems. In this work, variants of these nanomachines, tra and trb, have been profiled in publicly available genomes of the genus Acidithiobacillus and in a set of relevant strains. Our analyses show that the trb system is of broad distribution, being present in most of the strains analyzed. In turn, the tra type is present in fewer strains of A. ferrooxidans, A. ferrivorans, A. ferriphilus and A. thiooxidans, and generally correlates with the presence of larger ICE in the respective genomes. Herein, sequence conservation, genomic context, integration site and synteny analyses are performed to infer functionality of the T4SS systems of the acidithiobacilli.

Abstract: We studied the surface properties of F. acidiphilum DSM 28986 by attenuated total reflection-Fourier transformed infra-red (ATR-FTIR) spectroscopy and microbial adhesion to hydrocarbon (MATH) techniques. In addition, extracellular polymeric substances (EPS) were extracted and characterized by conventional colorimetric analysis and fluorescence lectin-binding analysis (FLBA). Results showed that: 1) cells selectively adhered to mineral surfaces and showed maximum attachment to pyrite of approx. 50% within 30 min; 2) EPS synthesis by F. acidiphilum DSM 28986 was influenced by growth substrates; and 3) tightly-bound EPS (capsular EPS) were composed of carbohydrates and proteins. In contrast, loosely-bound EPS (colloidal EPS) were mainly characterized as carbohydrates. Monosaccharides like glucose, fucose, arabinose, galactose, mannose, and sialic acid were detected in the EPS of F. acidiphilum DSM 28986. This study provides first insight into surface characterization of the cell wall-lacking archaeon F. acidiphilum and facilitates the understanding of interactions of this organism with other acidophiles and metal sulfides.

Abstract: In this work we report the metagenome-derived draft genomic sequence of an enrichment culture dominated by A. ferrooxidans obtained from an airlift bioreactor inoculated with the microbial consortium recovered from the “Relave Viejo” tailing. The genome of this culture was assembled de-novo and by reference, generating a consensus assembly of 3.0 Mb. On the basis of 16S rRNA (100 % identity), average nucleotide identity analysis (99.33% identity) and in silico DNA-DNA hybridization against A. ferrooxidans ATCC 23270^T (97.9%), the recovered genome is confirmed to pertain to A. ferrooxidans species. Comparative genomics results are presented to uncover the genetic traits of the variant surviving lime treatment and to further explore the genomic diversity of these model iron oxidizing species.