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Susana S.R.,University of Adelaide | Susana S.R.,Católica del Norte University | Glonek G.,University of Adelaide | Soto P.,Católica del Norte University | And 3 more authors.
Advanced Materials Research | Year: 2013

A descriptive mathematical model is a valuable tool that can help understand the relationship between the bioheap leaching process at the Escondida mine in Chile, the microbial community that participates in the process, and the physical characteristics of the heap, such as the arrangement and the mineral composition of the individual leaching strips. However, the bioleaching process at Escondida is a system, which presents many challenges to modelling. The main challenges relate to the heap's design and mineral characteristics, the complex interactions between biological and physicochemical parameters, and the unexpected changes in the heap's operational conditions. The heap is sampled periodically, and more than 20 variables, including 16S rRNA gene copy number for 16 different microorganisms, are recorded. The data exhibit complex behaviour, including variable dynamics between strips, systematic differences between lifts of the heap, and spatial and temporal correlations. In this work, we develop a non-linear descriptive model for the microbial population trajectory along the leaching cycle and across the different strips. The parameterisation of the model considers the different dynamics between lifts, and strip specific parameters characterise the behaviour of data from individual strips. The parameterisation also allows for spatial correlation by incorporating the effect of adjacent strips on the microbial population trajectory. The model is found to provide a good fit to the data and captures its behaviour across strips. Residuals showed no systematic patterns of departure between the observed and modelled response. The R2 values ranged from 0.53 to 0.71, indicating a reasonable level of predictive power. © (2013) Trans Tech Publications, Switzerland.


Soto-Rojo S.,University of Adelaide | Soto-Rojo S.,Católica del Norte University | Glonek G.,University of Adelaide | Demergasso C.S.,Católica del Norte University | And 6 more authors.
Advanced Materials Research | Year: 2013

Heap bioleaching is an established technology for recovering copper from low-grade sulphide ores. Recently, genetics-based approaches have been employed to characterize mineralprocessing bacteria. In these approaches, data analysis is a key issue. Consequently, it is of fundamental importance to provide adequate mathematical models and statistical tools to draw reliable conclusions. The present work relates to current studies of the consortium of organisms inhabiting the bioleaching heap of the Escondida mine in Northern Chile. These studies aim to describe and understand the relationship between the dynamics of the community and the performance of the industrial process. Here, we consider a series of quantitative real-time Polymerase Chain Reaction (PCR) experiments performed to quantify six different microorganisms at various stages of the bioleaching cycle. Establishing the reliability of the data obtained by real-time PCR requires the estimation of the error variance at several different levels. The results obtained show that the sampling component of the error variance is the dominant source of variability for most microorganisms. An estimate for the proportional reduction in residual standard deviation from the use of extraction and real-time PCR triplicates was found to range from 3% to 27% for the different organisms. This result suggests that triplicate assays would produce only a modest reduction in error variance compared to more frequent sampling from the heap. © (2013) Trans Tech Publications, Switzerland.


Salazar C.N.,Católica del Norte University | Acosta M.,Católica del Norte University | Galleguillos P.A.,Católica del Norte University | Galleguillos P.A.,Research Center Cientifica y Tecnologica para la Mineria | And 3 more authors.
Advanced Materials Research | Year: 2013

Acidithiobacillus ferrooxidans strain D2 was isolated from a copper bioleaching operation in Atacama Desert, Chile. Copper is widely used as cofactor in proteins but high concentrations of copper are toxic. Cells require certain mechanisms to maintain the copper homeostasis and avoid toxic effects of high intracellular concentration. The molecular response of A. ferrooxidans strain D2 grown in the presence/absence of copper was examined using a A. ferrooxidans whole-genome DNA microarrays. Roughly 23% of 3,147 genes represented on the microarray were differentially expressed; about 9% of them were upregulated in the presence of copper. Among the upregulated genes, those encoding for the copper efflux protein (CusA) and for the copper-translocating P-type ATPase (CopA) were upregulated. The expression of genes encoding proteins related to iron transport was repressed. Similarly, genes related with assimilative metabolism of sulfur (L-cysteine biosynthesis) cysB, cysJ, cysI, CysD-2 and cysN were upregulated. Our results show that when A. ferrooxidans strain D2 was challenged with high copper concentrations, genes related to copper stress response were upregulated as well as others that have not been reported to be related to that mechanism. In addition, some genes related to other metabolic pathways were repressed, probably because of the energy cost of the stress response. © (2013) Trans Tech Publications, Switzerland.


Demergasso C.,Católica del Norte University | Demergasso C.,Research Center Cientifica y Tecnologica Para la Mineria | Galleguillos F.,Católica del Norte University | Soto P.,Católica del Norte University | And 4 more authors.
Hydrometallurgy | Year: 2010

The paper Bacterial succession in bioheap leaching (Brierley, 2001) showed the search for methods to analyze the microbial dynamics in bioleaching industrial processes as a key challenge for advancing commercial bioheap applications. "Chemical and physical conditions within bioheaps change radically from the time the bioheap is stacked and inoculated until bioleaching is completed." The results from a comprehensive monitoring program by culturing and molecular techniques in an industrial bioleaching process for run-of-mine (ROM) low grade copper sulfide ore in Chile is summarized. The analysis of the compiled information permits an understanding of changes in microbial substrates availability, chemical and physical conditions. A data mining technique, called decision trees was used to analyze the information and to establish rules that represent patterns in the data. The bacterial succession in bioheap leaching solutions allowed the leaching cycle stages to be described as: i) Acid conditioning and soluble copper releasing, ii) Chalcocite Bacterial leaching (ferrous oxidation); iii) Chalcocite Bacterial leaching (ferrous and reduced sulfur compounds - RISC oxidation); iv) Bacterial leaching of sulfide minerals with higher rest potentials (pyrite and covellite), and v) Bacterial oxidation of remnant sulfide minerals and RISC. The impact of other factors on microbiology, such as the solvent-extraction process, aspects of the industrial design and operation are also discussed. © 2010 Elsevier B.V. All rights reserved.


Araya G.,Católica del Norte University | Acosta M.,Católica del Norte University | Demergasso C.S.,Católica del Norte University | Demergasso C.S.,Research Center Cientifica y Tecnologica para la Mineria
Advanced Materials Research | Year: 2013

Acidithiobacillus ferrooxidans is a chemiolithoautotrophic Gram-negative bacterium widely spread in ambient temperature bioleaching processes. Several strains of At. ferrooxidans were isolated and studied and, some time later, questions arise about whether it was a species with a wide metabolic variation or a group of closely related species. Advances in molecular biology, phylogeny and genomics have shed some light on At. ferrooxidans strains and allows their grouping according to their relations. However, significant challenges remains to be met, such as understanding how a particular strain faces environmental challenges and how a particular kind of adaptive response affects the growth and activity of the strain. The purpose of this study was to identify differential expression signals between At. ferrooxidans strains-with different abundances and dynamics-present in the bioleaching system at Escondida mine. Culture characterization and DNA macroarrays techniques provided some answers. Analysis of growth curves showed that IESL 32 had the highest anaerobic growth rate, while aerobic growth was similar for all strains. It was shown that though the phylogenetic analysis based on 16S rRNA sequences suggested a close relation between IESL 32 and the type strain ATCC 23270, the growth curves and the expression profile showed that the type strain and strain D2 had the closest similarity. Growth experiments under different conditions, together with the comparative analysis of gene expressions in At. ferrooxidans, could be a springboard for future investigations of strain characterization to broaden our knowledge about adaptation, metabolic strategies, regulation and microbial diversity in industrial processes. © (2013) Trans Tech Publications, Switzerland.


Soto P.E.,Católica del Norte University | Galleguillos P.A.,Católica del Norte University | Galleguillos P.A.,Research Center Cientifica y Tecnologica Para la Mineria | Seron M.A.,Católica del Norte University | And 5 more authors.
Hydrometallurgy | Year: 2013

The industrial run of mine (ROM) bioleaching heap of Escondida mine is monitored monthly from Pregnant Leach Solution (PLS) to assess concentration of microorganisms, microbial activity and physicochemical parameters generating a huge amount of information. To obtain a better description of the iron microbial activity and the dissolution rate of sulfide ores occurring in the leaching cycle, iterative process based on "Knowledge Discovery in Databases" (KDD) was used. A data mining technique, called "hierarchical clustering", was employed with mineralogical characteristics of the ores loaded in the heap as input. Three different groups of strips were distinguished by this model. Chalcocite and chalcopyrite contents were the most relevant parameters selected by "decision tree" technique. The results showed that there was a good coincidence between the three groups defined and the metallurgical performance in terms of copper recovery. Moreover, another decision tree analysis was performed including the three mineralogical groups, the gathered data about physicochemical parameters and the microbial community composition and function from the PLS. The PLS temperature and the MPN were the most relevant factors selected to explain the differences between the operation of the defined groups of strips. The group with the lowest chalcocite and highest chalcopyrite content, reached the highest PLS temperature and the highest MPN of ferrous iron oxidizing microorganisms and also the fastest kinetics of copper recovery. The estimated temperature inside the heap following conservatively the available models for heaps loaded with agglomerated material, together with the sustainable occurrence of a moderate thermophile population and the confirmation of some chalcopyrite dissolution by analysis of tail allowed us to account the chalcopyrite as a microbial substrate in that industrial scale operation. Those results confirmed the relationship between the microbial community function and the copper release and the hypothesis that the substrate availability is an important parameter to describe the microbial activity. Nevertheless, the model is not yet able to explain the low bacterial growth in the group with the highest chalcocite content that is considered a good microbial substrate. Then it is needed to perform another cycle of the KDD process to complete the model. This kind of information should be considered in defining models to describe and to predict copper recovery in ROM industrial bioleaching processes. © 2012 Elsevier B.V. All rights reserved.


Soto P.,Católica del Norte University | Soto P.,Research Center Cientifica y Tecnologica Para la Mineria | Demcrgasso C.,Católica del Norte University | Demcrgasso C.,Research Center Cientifica y Tecnologica Para la Mineria | And 2 more authors.
WMSCI 2010 - The 14th World Multi-Conference on Systemics, Cybernetics and Informatics, Proceedings | Year: 2010

In the context of a bacterial assisted leaching system, understanding the kinetics of microbial oxidation is essential to explore alternatives for process optimization. On a laboratory scale, there are empirical-analytic models that fit well to the dynamic of bacterial populations. However, at industrial level, the bioleaching process complexity together with the limited understanding of the relationship among biological, physicochemical and operational variables, have made their modeling elusive. In this paper we present the results of the characterization of the oxidizing activity of a microbial community in an industrial bioleaching operation. Based on an ad-hoc data mining process defined for this problem, decision trees are firstly constructed and then a set of rules are selected to characterize the oxidizing activity of a subset of strips in a bioleaching system. Following the same process of decision tree generation and then rule selection, a second subset of strips are characterized and results are compared between both subsets of bioleaching strips.


Acosta M.,Católica del Norte University | Galleguillos P.,Católica del Norte University | Galleguillos P.,Research Center Cientifica y Tecnologica Para la Mineria | Ghorbani Y.,Católica del Norte University | And 8 more authors.
Hydrometallurgy | Year: 2014

A comprehensive monitoring program has been performed at an industrial bioleaching heap at the Escondida mine in Chile since 2006, in order to study possible changes to the indigenous microbial population. In the initial stage of the bioleaching heap operation, the microbial population was dominated by mesophilic microorganisms. When the height of the heap increased, the microbial population changed from predominantly mesophilic to thermotolerant and moderate thermophilic microorganisms. The results of molecular analyses indicated that under these conditions Leptospirillum ferriphilum and Sulfobacillus thermosulfidooxidans are the most abundant microorganisms. Those results obtained show that the highest ferrous iron oxidation activity at the third lift occurs at the same operational temperature window as that of the thermotolerant and moderate thermophiles. An increase in the expression of genes (including rfaF1) associated with cell envelope biogenesis was indicative of the active growth of L. ferriphilum. We conclude that the increasing heap height and the consequent increase in temperature within the heap triggered a change in the microbial community from mesophilic to moderate thermophilic microorganisms. Further, this shift had a relevant impact on the metallurgical performance of the industrial bioheap process at Escondida mine. © © 2014 Elsevier B.V. All rights reserved.


Issotta F.,Fundacion Ciencia and Vida | Galleguillos P.A.,Católica del Norte University | Galleguillos P.A.,Research Center Cientifica y Tecnologica para la Mineria | Moya-Beltran A.,Fundacion Ciencia and Vida | And 14 more authors.
Standards in Genomic Sciences | Year: 2016

Leptospirillum ferriphilum Sp-Cl is a Gram negative, thermotolerant, curved, rod-shaped bacterium, isolated from an industrial bioleaching operation in northern Chile, where chalcocite is the major copper mineral and copper hydroxychloride atacamite is present in variable proportions in the ore. This strain has unique features as compared to the other members of the species, namely resistance to elevated concentrations of chloride, sulfate and metals. Basic microbiological features and genomic properties of this biotechnologically relevant strain are described in this work. The 2,475,669 bp draft genome is arranged into 74 scaffolds of 74 contigs. A total of 48 RNA genes and 2,834 protein coding genes were predicted from its annotation; 55 % of these were assigned a putative function. Release of the genome sequence of this strain will provide further understanding of the mechanisms used by acidophilic bacteria to endure high osmotic stress and high chloride levels and of the role of chloride-tolerant iron-oxidizers in industrial bioleaching operations. © 2016 Issotta et al.


Ghorbani Y.,University of Exeter | Ghorbani Y.,Research Center Cientifica y Tecnologica Para la Mineria | Montenegro M.R.,Research Center Cientifica y Tecnologica Para la Mineria
Hydrometallurgy | Year: 2016

Although heap leaching using sulfuric acid was introduced to the uranium industry in the 1950s, sodium carbonate-bicarbonate (alkaline) heap leaching of low-grade Ca-carbonate-rich uranium ores has recently gained popularity. This study presents the results of two column tests on a calcrete-type uranium-vanadium (carnotite) ore using a mixture of sodium carbonate and bicarbonate (Na2CO3/NaHCO3) as the leach solution. This data was kindly supplied by Toro Energy Ltd. The experimental data comprised physical-chemical leach information and two different irrigation rates (10 and 20 L/h·m2). The experimental data indicated that the carnotite ore with high calcium carbonate (CaCO3) can be leached effectively using the alkaline leach solution. The increase in the irrigation rate increased the uranium and vanadium extraction and decreased their concentration in the effluent. The column leach data was therefore fitted to a simplified first-order kinetic model using two approaches, a general form and a second based on the reagent consumption per unit mass of the initial valuable species (U and V). As reagent consumption is a key economic factor in the heap leaching process, having a kinetic leaching model incorporating reagent consumption would provide useful techno-economic information. In this regards a new leaching index of (β) is also introduced. Both approaches of the first order kinetic model provide a good agreement with the column testing data. © 2016 Elsevier B.V. All rights reserved.

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