Effects of Acidiphilium cryptum on biosolubilization of rock phosphate in the presence of Acidithiobacillus ferrooxidans

The bioleaching of pyrite and biosolubilization of rock phosphate (RP) in 9K basal salts medium were compared by the following strains of an autotrophic acidophilic bacterium, Acidithiobacillus ferrooxidans, a heterotrophic acidophilic bacterium, Acidiphilium cryptum, and mixed culture of At. ferrooxidans and A. cryptum. The results show that A. cryptum is effective in enhancing the bioleaching of pyrite and biosolubilization of RP in the presence of At. ferrooxidans, although it could not oxidize pyrite and solubilize RP by itself. This effect is demonstrated experimentally that A. cryptum enhances a decrease in pH and an increase in redox potential, concentration of total soluble iron and planktonic part bacterial number in the broth during pyrite bioleaching processes by At. ferrooxidans. The mixed culture of At. ferrooxidans and A. cryptum leads to the most extensive soluble phosphate released at 30 °C. Pulp density exceeding 3% is shown to adversely influence the release of soluble phosphate by the consortium of At. ferrooxidans and A. cryptum. It is essential to add pyrite to the 9K basal salts medium for the biosolubilization of RP by the mixed culture of At. ferrooxidans and A. cryptum, and the percentage of soluble phosphate released is the greatest when the mass ratio of RP to pyrite is 1:2 or 1:3.     

嗜酸兼性异养菌Acidiphilium sp.DX1-1的分离、特征及其浸矿行为(英文)

研究了一株源自江西德兴铜矿矿区的中温嗜酸兼性异养菌Acidiphilium sp.DX1-1的分离、鉴定、特征及其浸矿行为。菌株Acidiphilium sp.DX1-1为短杆状革兰氏阴性菌,最适合的生长温度为30℃,最适合的生长pH约为3.5。该菌株具有广泛的底物利用特性,可以利用有机物进行异养生长并在细胞内积累聚羟基丁酸酯,也可以利用单质硫、三价铁等无机物进行自养生长。系统发育分析表明DX1-1属于Acidiphilium属,与Acidiphilium cryptum and Acidiphilium multivorum的同源性大于99%。在铁闪锌矿生物浸出过程中,Acidiphilium sp.DX1-1表现出极强的浸矿能力,其作用不仅仅是之前报道的作为其他自养嗜酸浸矿细菌的辅助者。在初始pH3.5时,DX1-1能够在一个月内单独地浸出铁闪锌矿中40%的锌。该浸出率高于它与A.ferrooxidans混合以及A.ferrooxidans单独浸出铁闪锌矿(初始pH均为2.0)的浸出率。     

Transformation of iron in pure culture process of extremely acidophilic microorganisms

Jarosite and extracellular polymer substance generated during pure culture and bioleaching process have been widely accepted the main transformation of decreasing iron in the medium. In the present work, acidophilus bioleaching organisms Ferroplasma thermophilum, Leptospirillum ferriphilum and Acidithioobacillus ferrooxidans were cultured. It was found that they can live in low pH environment, and more than 10 particles in each cell intracellular nano-particles are synthesized in the cells. By analyzing the morphology and chemical composition of nano-particles, they were found to contain iron, and the three microorganisms belonged to high-yielding strains. The results show that the transformation of the decreasing iron ions is not only generating jarosite, but also taken into cells and synthesizing ferruginous nano-particles.     

转鼓和搅拌槽反应器中氧化亚铁硫杆菌氧化Fe2+的比较（英文）

研究转鼓和搅拌槽反应器中氧化亚铁硫杆菌在不同Al2O3粉末含量下对Fe2+的氧化。结果表明:未添加Al2O3粉末时,氧化亚铁硫杆菌在搅拌槽中的生物活性比在转鼓中的生物活性高。当Al2O3粉末含量从0增加到50%(质量分数)时,Fe2+的生物氧化速率从0.23g/(L·h)显著降低到0.025g/(L·h),可能是搅拌槽中的固体颗粒碰撞和研磨作用导致氧化亚铁硫杆菌失活。转鼓中Al2O3的含量增加对氧化亚铁硫杆菌的生物活性仅有较小的负面影响,这是由于两个反应器不同的混合机制所致。在相同的Al2O3含量下,Fe2+在转鼓反应器中的生物氧化速率比在搅拌槽中的生物氧化速率更高,尤其在较高的固体含量下,表明转鼓反应器能允许较高的固体含量和维持较高的生物活性。由于Al2O3粉末与真实硫化矿具有不同的物理化学性质,因此转鼓反应器用于硫化矿生物浸出的可行性还需进一步验证。     

可见光和Cd2+对黄铜矿生物浸出的催化作用(英文)

利用扫描电镜(SEM)、同步辐射X射线衍射(SR-XRD)和X射线光电子能谱(XPS)研究在酸性氧化亚铁硫杆菌存在下,可见光和镉离子(Cd²⁺)对黄铜矿生物浸出的影响。生物浸出28天后的结果表明,光照下铜的溶解提高4.96%;Cd²⁺单独存在对黄铜矿的浸出有轻微的抑制作用;可见光和50mg/LCd²⁺同时存在时,溶解铜的浓度提高14.70%。化学浸出结果表明,可见光能促进体系中铁元素的循环。SEM结果显示,Cd²⁺在可见光下促进酸性氧化亚铁杆菌在黄铜矿表面的附着。综合SR-XRD和XPS结果可知,可见光和Cd²⁺促进黄铜矿的浸出,但不会抑制钝化物的形成。提出可见光和Cd²⁺对黄铜矿生物浸出协同催化作用机制的模型。     

Enhancing recovery of uranium column bioleaching by process optimization and kinetic modeling

This research aimed to enhance the column bioleaching recovery of uranium ore by Acidithiobacillus ferrooxidans. Seven factors were examined for their significance on bioleaching using a Plackett–Burman factorial design. Four significant variables ([Fe²⁺]_initial, pH, aeration rate and inoculation percent) were selected for the optimization studies. The effect of these variables on uranium bioleaching was studied using a central composite design (CCD). The optimal values of the variables for the maximum uranium bioleaching recovery (90.27±0.98)% were as follows: [Fe²⁺]_initial=2.89 g/L, aeration rate 420 mL/min, pH 1.45 and inoculation 6% (v/v). [Fe²⁺]_initial was found to be the most effective parameter. The maximum uranium recovery from the predicted models was 92.01%. This value was in agreement with the actual experimental value. The analysis of bioleaching residue of uranium ore under optimum conditions confirmed the formation of K-jarosite on the surface of minerals. By using optimal conditions, uranium bioleaching recovery is increased at column and jarosite precipitation is minimized. The kinetic model showed that uranium recovery has a direct relation with ferric ion concentration.     

铁闪锌矿的Leptospirillum ferrooxidans菌浸出及电化学性能(英文)

采用纯种L.ferrooxidans菌研究矿浆浓度、pH及外加Fe3+离子对铁闪锌矿生物浸出的影响。结果表明,锌的浸出率随着矿浆浓度的降低而增加。在生物浸出过程中调节pH值到1.6对铁闪锌矿的溶解有促进作用。外加Fe3+离子加速了铁闪锌矿的生物浸出,但当外加Fe3+离子浓度超过2.5g/L时,促进作用变弱。这是因为高浓度的Fe3+离子会对细菌生长产生抑制作用且促进黄钾铁矾的生成。在L.ferrooxidans菌存在条件下,利用电化学测试方法进一步了解有、无外加Fe3+离子时铁闪锌矿的溶解过程。实验数据表明,外加Fe3+离子可以增加腐蚀电流密度,有利于锌的提取。交流阻抗谱表明,添加Fe3+离子后没有改变反应过程的控制步骤。     

一种用于嗜酸性氧化亚铁硫杆菌液氮保藏的新型保护剂的保藏效果(英文)

对一种用于嗜酸性氧化亚铁硫杆菌液氮冷藏新型保护剂GP的保藏效果进行研究。依据最大细胞复苏率及最高亚铁氧化活性确定该新型保护剂的最佳使用浓度。结果表明,保护剂的最佳浓度为30%,在此浓度下细胞复苏率达到84.4%,且能在120h内完全氧化培养基中的亚铁,培养6d后菌体浓度达到5.8×107cell/mL。此外,解冻细胞在9K培养基中培养6d后,对活细胞复苏的最佳GP残留浓度为0.6%(体积分数)。在此浓度下,菌株DC完全氧化亚铁需要108h,并且最终菌体浓度为6.8×107cell/mL.因此,GP是一种简单、有效的嗜酸性氧化亚铁硫杆菌液氮保藏的冷冻保护剂。     

Photogenerated-hole scavenger for enhancing photocatalytic chalcopyrite bioleaching

The effects of photogenerated-hole scavengers (ascorbic acid, oxalic acid, humic acid and citric acid) on chalcopyrite bioleaching in the presence of visible light were studied using Acidithiobacillus ferrooxidans (A. ferrooxidans). Four sets of bioleaching experiments were performed: (1) visible light + 0 g/L scavenger, (2) visible light + 0.1 g/L of different scavenger (ascorbic acid, oxalic acid, humic acid and citric acid), (3) dark + 0.1 g/L of different scavenger (ascorbic acid, oxalic acid, humic acid and citric acid), and (4) dark + 0 g/L scavenger (control group). The results showed that ascorbic acid and oxalic acid could act as photogenerated-hole scavengers and significantly enhance chalcopyrite bioleaching under visible light. The dissolved copper in the light group without scavenger was only 18.7% higher than that of the control group. The copper extraction rates of the light groups with oxalic acid and ascorbic acid were respectively 30.1% and 32.5% higher than those of the control group. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) analyses indicated that ascorbic acid and oxalic acid as photogenerated-hole scavenger could capture photo-generated holes and inhibit jarosite formation on the chalcopyrite surface, thereby enhancing bioleaching of chalcopyrite under visible light.     

Effect of Cu ions on bioleaching of marmatite

The effect of Cu^2＋ ions on bioleaching of marmatite was investigated through shake leaching experiments. The bacteria inoculated are a mixed culture ofAcidithiobacillusferrooxidans, Acidithiobacillus thiooxidans and Lepthospirillumferrooxidans. The results show that zinc is selectively leached, and the addition of appropriate content of Cu^2＋ ions has positive effect on the bioleaching of marmatite. SEM and EDX analyses of the leaching residue reveal that a product layer composed of iron sulfide, elemental sulfur and jarosite forms on the mineral surface. The biooxidation of elemental sulfur is catalyzed by the Cu^2＋ ions, which eliminate the barrier to bioleaching of marmatite and keep low pH value. With the addition of 0.5 g/L Cu^2＋ ions, the maximum zinc extraction rate reaches 73% after 23 d at the temperature of 30 ℃ with the pulp density of 10%, while that of iron is only about 10%.     

EPS-contact-leaching mechanism of chalcopyrite concentrates by A. ferrooxidans

The effect of extracelluar polymeric substances（EPS） on the bioleaching chalcopyrite concentrates in the presence of ironand sulphur-oxidizing bacteria （A. ferrooxidans） was studied. The bacterial number, pH, redox potential, and the concentrations of Fe^2＋ and Cu^2＋ ions were investigated. The leached residues were analyzed by the X-ray diffraction and FT-IR. The results indicate that the EPS makes the bacteria adhere to the chalcopyrite surface easily and it is helpful for bacteria in disadvantageous environment At the same time, EPS film layer with Fe^3＋ deposits on the surface of chalcopyrite and becomes a barrier of oxygen transfer to chalcopyrite to passivate chalcopyrite, and creates the high redox potential space through concentrating Fe^3＋ ions to accelerate bioleaching pyrite in chalcopyrite concentrates. The results suggest that EPS formation promotes bioleaching pyrite and inhibits bioleaching chalcopyrite, especially under high potential condition.     

嗜酸氧化亚铁硫杆菌（ATCC 23270）浸出黄铜矿过程中的EPS、Cu2+和Fe3+的相互作用机制（英文）

采用超声-离心方法提取嗜酸氧化亚铁硫杆菌(ATCC 23270)胞外多聚物(EPS)、EPS中的Cu2+、Fe3+离子,研究生物浸出黄铜矿过程中Cu2+、Fe3+和EPS的相互作用机制。结果表明:与Fe3+离子相比,Cu2+离子可刺激细菌产生更多的EPS;当Cu2+离子浓度从0.01mol/L增加到0.04mol/L时,EPS中Fe3+/Cu2+质量比从4:1降低到2:1;从1%黄铜矿的无铁9K介质中提取的EPS中铜铁含量是从含0.04mol/LCu2+离子的9K介质中提取的量的2倍。在生物浸出黄铜矿过程中,黄铜矿表面结合黄铁钾钒的EPS层减弱了Cu2+、Fe3+离子的迁移,逐渐成为离子扩散壁垒。     

Bioleaching of pyrite by A. ferrooxidans and L. ferriphilum

Pyrite oxidation rates were examined under various conditions in the presence of A. ferrooxidans and L. ferriphilum, in which different pulp concentration, inoculation amount, external addition of Fe^3＋ and initial pH value were performed. It is found that A. ferrooxidans and L. ferriphilum show similar behaviors in the bioleaching process. The increasing pulp concentration decreases the leaching rate of iron, and external addition of high concentration Fe^3＋ is also adverse to leaching pyrite. The increased inoculation amount and high initial pH value are beneficial to leaching pyrite, and these changed conditions bring more obvious effects on leaching pyrite by L. ferriphilum than by A. ferrooxidans. The results also show that adjusting the pH values in leaching process baffles leaching pyrite due to the formed jarosite. Jarosite formed in leaching process was observed using XRD, SEM and energy spectrum analysis, and a considerable amount of debris with a crystalline morphology is present on the surface of pyrite. The results imply that the indirect action is more important for bioleaching pyrite.     

Effect of pH values on extracellular protein and polysaccharide secretions of Acidithiobacillus ferrooxidans during chalcopyrite bioleaching

The effect of pH values on the extracellular protein and polysaccharide secretions of Acidithiobacillus ferrooxidans was comparatively investigated in different phases of bacterial growth during chalcopyrite bioleaching. The results indicate that the extracellular protein is always more than the extracellular polysaccharide secreted by attached cells on the chalcopyrite, on the contrary, and is always less than the extracellular polysaccharide secreted by free cells in the solution at bacterial adaptive phase, logarithmic phase and stationary phase whenever pH value is at 1.0, 1.5, 2.0 or 2.5; free cells are mainly through the secretion of extracellular polysaccharide rather than the extracellular protein to fight against disadvantageous solution environment, such as high concentration of metal ions and unsuitable pH solution; both amounts of polysaccharide and protein secreted by attached cells are mainly positively related to the solution acidity rather than the total concentration of soluble metal ions. The experimental results imply that bacteria are mainly through secreting more extracellular polysaccharide to fight against disadvantageous environment and the extracellular protein perhaps plays an important role in oxidation–reduction reactions in the bioleaching system.     

Bioleaching of anilite by Acidithiobacillus ferrooxidans

In order to characterize the efficiency of copper bioleaching from anilite using pure cultures of Acidithiobacillus ferrooxidans in the absence and presence of ferrous sulphate, the experiments were carried out in shake flasks with or without 4 g/L ferrous sulphate (FeSO₄·7H₂O) at pH 2.0, 150 r/min and 35°C. The tests show that Acidithiobacillus ferrooxidans is unable to attack anilite in iron-free 9K medium. Anilite is rapidly oxidized by bacterial leaching when ferrous sulphate is added. Chemical oxidation of anilite is slow compared with Acidithiobacillus ferrooxidans initiated solubilization in the presence of iron. The EDAX analysis of the surfaces of anilite confirms that sulfur coating layer is present as a reaction product on the surface of the bacterially leached mineral.     

Isolation and characterization of acidophilic bacterium from Gaofeng Mine in China

An acidophilic, chemolithotrophic and ferrous oxidizing bacterium strain GF was isolated from the acid mine drainage （AMD） of Gaofeng Mine, Guangxi Province, China using 9K enrichment medium, and then purified on solid ferrous-agarose medium. The physiological experiments show that it can use ferrous or sulfur as sole energy and a low level （0.1%, w/v） of peptone can accelerate the growth of the isolated strain. The optimum pH and temperature for growth are 2.0 and 30 ℃, respectively. The isolated strain shares 99.64% identities of 16S rRNA gene with the type strain Acidthiobacillusferrooxidans ATCC 23270 and 100% identities of iro gene （CDS） with A.ferrooxidans strain Fe-1. These results show that the strain can be considered as A cidthiobacillus ferrooxidans. Because of the high activity of oxidizing ferrous and sulfide mineral, strain GF was used in bioleaching of marmatite. The Zn concentration is 0.273 g/L under the steriled control and 7.30 g/L with adapted GF strain incubated after 29 d in leaching marmatite. The isolated strain GF can be used to leach marmatite in industry application.     

Purification and enzymatic characteristics of cysteine desulfurase, IscS, in Acidithiobacillus ferrooxidans ATCC 23270

A cysteine desulfurase protein, IscS, was encoded by the operon iscSUA in Acidithiobacillusferrooxidans. The gene of IscS from Acidithiobacillus ferrooxidans ATCC 23270 was cloned and expressed in Escherichia coil The protein was purified by one-step affinity chromatography to homogeneity. The final protein yield after affinity chromatography was 12.9%. The enzyme was characterized for thermal stability, pH and kinetic parameters. The molecular mass of recombinant lscS was 46 ku by SDS-PAGE. The optimum pH was 8.0-8.5. The enzyme had a temperature optimum at 30 ℃ and was relatively stable at 40 ℃, with 67% loss of activity. 1,5-I-AEDANS significantly inhibited IscS activity. Kinetic parameters Km and Vmax were found to be 0.11 mmol/L and 2.57 μmol/（L.min）.     

Acidithiobacillus ferrooxidans enhanced heavy metals immobilization efficiency in acidic aqueous system through bio-mediated coprecipitation

This study investigated the promotion effect of A. ferrooxidans on complex heavy metals coprecipitation process. A. ferrooxidans significantly enhanced the ferrous oxidation, which also promoted the formation of iron-oxyhydroxysulphate. Cu(II) concentration reduced to 0.058 mmol/L in A. ferrooxidans inoculated system, and Cd also reduced to the lowest concentration (0.085 mmol/L). Pb was mainly immobilized as anglesite and iron-oxyhydroxysulphate promoted the removal of remanent Pb in solution. The precipitates are characterized by XRD, SEM, and FTIR analysis. The main component of the iron-oxyhydroxysulphate was well crystallized jarosite. A. ferrooxidans contributed to the formation of schwertmannite in later monovalent cation lack stage. Higher ferrous iron oxidation rate and Fe(III) supply rate in A. ferrooxidans inoculated system facilitated polyhedron crystal formation and the increase of particle diameter. Complex heavy metals could be incorporated into iron oxyhydroxysulphate crystal, and efficiently removed from acidic wastewater through A. ferrooxidans mediated coprecipitation.     

Corrosion of carbon steel C1010 in the presence of iron oxidizing bacteria Acidithiobacillus ferrooxidans

In this study, corrosion behaviors of carbon steel C1010 in the presence of an acidophilic, iron-oxidizing bacterial species Acidithiobacillus ferrooxidans were examined. Results showed that A. ferrooxidans cells, with or without attaching to C1010 steel, accelerated its corrosion at a rate of 3–6× those of acidic water, at a pH of 2, without cells. A. ferrooxidans oxidized Fe²⁺ to Fe³⁺ as an energy source and the produced Fe³⁺ rapidly oxidized Fe⁰ to Fe²⁺ was proposed and verified as the reason. In addition, severe pitting corrosion was found on the C1010 steel surface in solutions containing A. ferrooxidans cells.     

Ferrous ion oxidation by Thiobacillus ferrooxidans immobilized on activated carbon

1 Introduction One of the main applications of biotechnology to hydrometallurgy is based on the ability of bacteria such as Thiobacillus ferrooxidans, Thiobacillus thiooxidans and Leptospirillum ferrooxidans to oxidize sulfide minerals to soluble compone…