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
An extremely thermoacidophilic isolate K4-1 was obtained from an acidic hot spring in Teng- chong Rehai, Yunnan province. Morphology, growth characteristics, utilization of carbon compounds, en- ergy sources and 16S rRNA gene sequence of K4-1 were studied. Cells of K4-1 are irregular cocci with monotrichous flagella. The strain grew aerobically in either a lithotrophic or a heterotrophic mode. Growth on elemental sulfur occurred through oxidation of sulfur. It grew optimally at 75?C and pH 3.5. On the basis of 16S rRNA gene sequence similarity, strain K4-1 was shown to belong to genus Sulfolobus, being related to the type strains of genus Sulfolobus (86.6%~94.3% similarity), and being most closely related to strain Sulfolobus tengchongensis RT8-4 (98.9% similarity). The GenBank accession number of strain K4-1 16S rRNA gene sequence is EU729124.
ABSTRACT
A moderately thermoacidophilic iron-oxidizing bacterium,designated as strain MLY,was isolated from a coal spoil heap in China.The optimum of temperature for growth is 50℃～54℃.The optimum of pH is 1.2～1.4.The strain MLY is facultative autotroph and grows heterotrophically on yeast extract.It is able to oxidize ferrous iron(Fe 2+ ),pyrite(FeS 2),and elemental sulfur(S 0) autotrophically and mixotrophically in the presence of yeast extract.Autotrophic oxidation of elemental sulfur is relative weak.The comparison of ferrous iron and pyrite oxidation between strain MLY and A10 Thiobacillus ferrooxidans,strain indicated that MLY is one time faster than A10.
ABSTRACT
Objective To determine the best method to detect thermo-acidophilic bacteria in apple juice concentrate. Methods L 16 (4 5) orthogonal test was applied to analyse the four factors, including culture medium, ways of heat shock, dilution degrees of AJC and pH value. The results were comprehensively scored according to the number of colonies. Results The isolated bacteria were polymorphous. A better method was as follows: after being diluted to 1∶10, the AJC was submitted to a heat shock at 80 ℃ for 10 min, and then spread on k agar with a pH value of 3.5. Samples were incubated at 45 ℃ for 3 days, and then enumerated. Conclusion This method can considerably improve the sensitivity of detecting thermo-acidophilic bacteria in apple juice concentrate.