ABSTRACT
Thermoacidophiles can exist in a state of dormancy both in moderate temperatures and even in cold conditions in heap leaching. Sulphide mineral ores such as chalcopyrite produce sulfuric acid when exposed to the air and water. The produced sulfuric acid leads to the decrease of pH and exothermic reactions in heap leaching causing the temperature to increase up to 55 °C and the activation of thermoacidophilic microorganisms. The aim of the present study was to isolate indigenous extreme thermoacidophilic microorganisms at ambient temperature from Sarcheshmeh Copper Complex, to adapt them to the high pulp density of a chalcopyrite concentrate, and to determine their efficiency in chalcopyrite bioleaching in order to recover copper. In this study samples were collected at ambient temperature from Sarcheshmeh Copper Complex in Iran. Mixed samples were inoculated into the culture medium for enrichment of the microorganisms. Pure cultures from these enrichments were obtained by subculture of liquid culture to solid media. Morphological observation was performed under the scanning electron microscope. Isolates were adapted to 30% (w/v) pulp density. For the bioleaching test, the experiments were designed with DX7 software. Bioleaching experiments were carried out in Erlenmeyer flasks and a stirred tank reactor. The highest copper recovery in Erlenmeyer flasks was 39.46% with pulp 15%, inoculums 20%, size particle 90 pm and 160 rpm. The lowest recovery was 3.81% with pulp 20%, inoculums 20%, size particle 40 pm and 140 rpm after 28 days. In the reactor, copper recovery was 32.38%. Bioleaching residues were analyzed by the X-ray diffraction (XRD) method. The results showed no jarosite (KFe3(SO4)2(OH)6) had formed in the bioleaching experiments. It seems that the antagonistic reactions among various species and a great number of planktonic cells in Erlenmeyer flasks and the stirred tank reactor are the reasons for the low recovery of copper in our study.
Los microorganismos termoacidófilos pueden estar en estado latente tanto a temperatura moderada como baja, en lixiviación en pilas. Los minerales sulfurosos, como la calcopirita, producen ácido sulfúrico cuando se exponen al aire y al agua. El ácido sulfúrico producido conduce a la disminución del pH y a reacciones exotérmicas durante la lixiviación en pilas, lo que hace que la temperatura aumente hasta 55 °C y se activen los microorganismos termoacidófilos. El objetivo del presente estudio fue aislar del complejo de cobre Sarchesh-meh (Irán) microorganismos termoacidófilos extremos que proliferan a temperatura ambiente e investigar su adaptación a la alta densidad de pulpa del concentrado de calcopirita, así como su eficiencia para biolixiviarese mineral, con el objeto de recuperar el cobre. Se recogieron muestras a temperatura ambiente del citado complejo, y luego muestras mixtas se inocularon en un medio de cultivo de enriquecimiento. A partir de estos enriquecimientos, mediante el subcultivo del cultivo líquido a medio sólido, se obtuvieron cultivos puros. La observación morfológica se realizó bajo microscopio electrónico de barrido. Los aislados estaban adaptados al 30% p/v de densidad de pulpa. Para la prueba de biolixiviación, los experimentos fueron diseñados con el software DX7. Los experimentos de biolixiviación se llevaron a cabo en Erlenmeyers y en un reactor tanque con agitación. La mayor recuperación de cobre en los Erlenmeyers fue del 39,46% y se obtuvo con la pulpa al 15%, un inóculo del 20%, un tamaño de partícula de 90 µm y una agitación de 160 rpm. La menor recuperación fue del 3,81% y se obtuvo con la pulpa al 20%, un inóculo del 20%, un tamaño de partícula de 40 µm y una agitación de 140 rpm, después 28 días. En el reactor, la recuperación del cobre fue del 32,38%. El análisis de difracción de rayos X (XRD) no mostró que se formara jarosita (KFe3-#91;SO4-#93;2-#91;OH-#93;6) en los experimentos de biolixiviación. Dicha técnica sirve para determinar la estructura cristalina de una sustancia desconocida. Al parecer, las reacciones antagónicas entre las diversas especies y el mayor número de células planctónicas en los Erlenmeyers y en el reactor fueron las causas de la baja recuperación de cobre observada en este estudio.
Subject(s)
Percolation/analysis , Chemical Reactions/analysis , Copper/economics , Causality , Adaptation to Disasters , Hydrogen-Ion ConcentrationABSTRACT
Background: β-lactam resistance is more prevalent in Gram negative bacterial isolates worldwide, particularly in developing countries. In order to provide data relating to antibiotic therapy and resistance control, routine monitoring of corresponding antibiotic resistance genes is necessary. Aims: The aim of this study was the characterization of β-lactam resistance genes and its plasmid profi le in bacteria isolated from urinary tract infection samples. Materials and Methods: In this study, 298 Gram negative bacteria isolated from 6739 urine specimens were identifi ed by biochemical standard tests. Antimicrobial susceptibility testing was performed by the disk diffusion method. Extendedspectrum β-lactamase (ESBL)-producing strains were also detected by the double-disk synergy test. The presence of blaTEM and blaSHV genes in the strains studied was ascertained by polymerase chain reaction. Results: Of all Gram negative bacteria, Escherichia coli (69.1%) was the most common strain, followed by Klebsiella sp. (12.1%), Enterobacter sp. (8.4%), Proteus sp. (4.4%), Citrobacter (4%) and Pseudomonas sp. (2%). The most antibiotic resistance was shown to tetracycline (95.16%), nalidixic acid (89.78%) and gentamycin (73.20%) antibiotics. Among all the strains tested, 35 isolates (11.75%) expressed ESBL activity. The prevalence of TEM and SHV positivity among these isolates was 34.29%, followed by TEM (31.43%), TEM and SHV negativity (20.0%) and SHV (14.29%), respectively. Conclusions: Regular monitoring of antimicrobial drug resistance seems necessary to improve our guidelines in the use of the empirical antibiotic therapy.