Effect of surfactant Tween-80 on sulfur oxidation and expression of sulfur metabolism relevant genes of Acidithiobacillus ferrooxidans

The effects of surfactant Tween-80 on the growth, sulfur oxidation, and expression of selected typical sulfur metabolism relevant genes of Acidithiobacillus ferrooxidans ATCC 23270 were investigated. The results showed that in the presence of 10-2 g/L Tween-80, the growth of A. ferrooxidans and its metabolism on the insoluble substrate S0 and CuFeS2 were promoted. After 24 d of bioleaching, the copper extraction yield of chalcopyrite at 10-2 g/L Tween-80 increased by 16% compared with the bioleaching experiment without Tween-80. FT-IR spectra analysis revealed that the result was probably caused by the extracellular polymeric substances whose composition could be changed by the surfactant addition. RT-qPCR was used to analyze the differential expressions of 17 selected sulfur metabolism relevant genes in response to the addition of Tween-80. Down-regulation of the extracellular protein genes indicated the influence of Tween-80 on bacteria-sulfur adsorption. Variation of the expression level of the enzymes provided a supplement to sulfur metabolism investigation.

Effect of EPS on adhesion of Acidithiobacillus ferrooxidans on chalcopyrite and pyrite mineral surfaces

Extracellular polymeric substances （EPS） were extracted from Acidithiobacillus ferrooxidans through sonication method associated with centrifugation, which was evaluated tentatively with 2-keto-3-deoxyoctonic acid （KDO） as the indicator of EPS by spectrophotometry. Then the effect of EPS of A. ferrooxidans on the adhesion on chalcopyrite and pyrite surfaces was studied through a series of comparative experiments. The untreated cells and EPS-free cells of A. ferrooxidans were mixed with EPS suspension, Fe^2＋ or Fe^3＋, respectively. The planktonic cells were monitored in 2 h during bioleaching. The results indicate that the presence of EPS on the cell is an important factor for the adhesion to chalcopyrite and pyrite. A decrease of attachment of A. ferrooxidans to minerals was produced by the deficiency of EPS, which can recover mostly when the EPS was re-added into the EPS-free cells. The restoring extent is more obvious in pyrite than in chalcopyrite. The extent of cell adhesion to chalcopyrite increased when EPS and Fe^3＋ added, and decreased when Fe^2＋ added, which imply the electrostatic interaction plays a main role in initial adhesion between bacteria and minerals and it is a driving force for bacteria to produce EPS probably as a result of regaining their attachment ability to copper sulphides.

Differential utilization and speciation transformation of orthorhombic α-S_8 and amorphous μ-S by substrate-acclimated mesophilic Acidithiobacillus ferrooxidans

The utilization and speciation transformation of α-S8 and μ-S by the typical mesophilic acidophilic strain Acidithiobacillus ferrooxidans ATCC 23270 were investigated.A.ferrooxidans cells first acclimated to the energy source α-S8 or μ-S,respectively.The results of cell growth and sulfur oxidation behavior showed that the strain grown on α-S8 entered slowly（about 1 d later） into the exponential phase,while grew faster in the exponential phase and attained higher maximal cell density and lower p H value than that on μ-S.After bio-corrosion,both of the two sulfur samples were evidently eroded and modified by A.ferrooxidans cells.After growth of A.ferrooxidans,the surface composition of amorphous μ-S became 63.1% μ-S and 36.9% α-S8,and that of orthorhombic α-S8 became 68.3% α-S8 and 31.7% μ-S,while the surface compositions of α-S8 and μ-S in sterile experiment were not changed,indicating that these two elemental sulfur species can be interconverted by A.ferrooxidans.

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.

Acidithiobacillus ferrooxidans氧化分解毒砂的次生产物研究

毒砂是常见的含砷硫化物矿物。在金属硫化物矿山环境中,含毒砂矿石和尾矿的风化会导致严重的重金属污染,在其风化过程中,微生物能够显著促进毒砂的氧化分解。本文实验研究了Acidithiobacillus ferrooxidans氧化分解毒砂矿物的现象,利用X射线衍射和扫描电子显微镜,分析了毒砂微生物氧化作用形成的次生矿物类型,发现毒砂表面存在As含量明显不同的2类次生产物,观察到黄钾铁矾、臭葱石、自然硫和施威特曼石等矿物;借助光电子能谱仪重点分析了微生物作用前后毒砂晶面的表面化学组成,基本查明了Fe、As和S三种元素的价态变化,初步探讨了毒砂表面次生矿物成因和As的化学态转化。

Experimental measurements of short-term adsorption of Acidithiobacillus ferrooxidans onto chalcopyrite

The influencing factors in adsorption such as adsorption time, pulp concentration, bacterial concentration, pH as well as ionic strength were investigated to explore the relationship among them and bacterial adsorption. The adsorption was a rapid process for bacterial adhesion to chalcopyrite. The extent of adsorption increased with increasing initial bacterial concentration and pulp concentration. The optimal pH for Acidithiobacillusferrooxidans adsorption onto chalcopyrite surfaces was in the range of pH 1-3. The increase of ionic strength led to decrease in bacterial adsorption, which can be well explained by electric double layer theory. The adsorption behavior appeared to be controlled by both hydrophobic and electrostatic interactions at the interface of bacteria and mineral,

天然闪锌矿光催化协同Acidithiobacillus ferrooxidans生长及抑制自身分解作用实验研究

对天然闪锌矿光催化协同下的Acidithiobacillus ferrooxidans生长,以及此过程中天然闪锌矿的光催化作用对其自身分解的影响进行了研究。结果表明,天然闪锌矿的光催化作用能够将光能以电子的形式转移给A.ferrooxidans并且促进了其生长,这一过程以Fe2+/Fe3+这一氧化还原对作为媒介;有光照组的A.ferrooxidans细胞浓度达到了8×108 cell/mL,而无光照和体系无电流的2组对照组A.ferrooxidans细胞浓度分别为6×108 cell/mL和4.95×108 cell/mL。通过电感耦合等离子体发射光谱仪测定3组不同条件实验体系中Zn2+的溶出量可以发现,在光照条件下Zn2+的溶出量只有3.5×10-6,而无光照条件下Zn2+溶出量达到了5×10-6。天然闪锌矿光催化作用一方面可以促进A.ferrooxidans的生长,另一方面也能够抑制其自身的分解和金属离子向水体中的释放。研究结果为酸性矿山废水地区抑制硫化物矿物溶蚀提供了新的思路。

固定化Acidithiobacillus ferrooxidans对Fe^(2+)氧化及其生物反应器研究进展

Acidithiobacillus ferrooxidans对Fe2+的生物氧化是一个非常重要的反应过程,在生物浸矿、H2S等废气的脱硫、含重金属污泥和酸性矿坑废水的处理等领域有着重要的应用。近些年来,大量的研究主要集中A.ferrooxidans及其反应过程等方面,然而,A.ferrooxidans对Fe2+的催化氧化速率缓慢和稳定性欠佳等问题仍然限制了其商业应用。因此,对A.ferrooxidans的固定化及其生物反应器研究是该技术进一步发展的关键。评述了A.ferrooxidans最新应用、存在的问题和解决办法,重点比较了目前文献中报道的各种A.ferrooxidans固定材料、方法,并对目前采用的各种固定化A.ferrooxidans生物反应系统的效率和结构等方面进行了讨论和分析。

Preservation efficiency of new cryoprotectant used for Acidithiobacillus ferrooxidans in liquid nitrogen

The efficiency of a new cryoprotectant,GP,for the preservation of Acidithiobacillus ferrooxidans（A.ferrooxidans） strain DC in liquid nitrogen was investigated.The optimal concentration of this new cryoprotectant for the maximal viable cell recovery and the highest ferrous ion oxidation activity was determined.The results show that 30%（volume fraction） GP is optimal for the cryopreservation with 84.4% of cells surviving,completely oxidizing ferrous ions within 120 h,and growing to a final density of 5.8×107 cell/mL after 6 d in the culture.Furthermore,the optimal residual GP concentration for viable cell recovery after culture of thawed cells in 9K medium for 6 d is 0.6%（volume fraction）.At this concentration,strain DC completely oxidizes ferrous ions within 108 h and grows to a final cell density of 6.8×107 mL-1.Thus,GP is a simple,effective cryoprotectant for the preservation of A.ferrooxidans strain DC in liquid nitrogen.

Acidithiobacillus ferrooxidans-硫酸酸溶联合浸出金川铜镍硫化矿尾矿砂实验研究

金川铜镍硫化矿尾矿砂富含Cu、Ni和Co等金属,为对其进行回收,对新尾矿库不同深度的尾矿砂分别进行了直接硫酸酸溶浸出与A.f.-硫酸酸溶联合浸出实验,利用ICP-AES分析了不同阶段浸出液中Cu2+、Ni2+、Co2+含量。实验结果表明,A.f.-硫酸酸溶联合浸出工艺对尾矿砂中有价金属Cu、Ni和Co的浸出效果优于单独酸溶浸出工艺。其中,A.f.-硫酸酸溶联合浸出法对1m深度的尾矿砂中Cu、Ni、Co的浸出率最高,分别达到95.78%、98.01%和75.13%,而单独硫酸酸溶作用的离子浸出率分别为75.69%、74.33%和42.33%。

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.

Comparison of Fe^(2+) oxidation by Acidithiobacillus ferrooxidans in rotating-drum and stirred-tank reactors

Fe2＋ oxidation by Acidithiobacillus ferrooxidans（At.ferrooxidans） under different solid contents by adding inert Al2O3 powder was examined in rotating-drum and stirred-tank reactors.The results show that the bioactivity of At.ferrooxidans in the stirred-tank is higher than that in the rotating-drum in the absence of Al2O3 powder,but the biooxidation rate of Fe2＋ decreases markedly from 0.23 g/（L·h） to 0.025 g/（L·h） with increasing the content of Al2O3 powder from 0 to 50%（mass fraction） in the stirred-tank probably due to the deactivation of At.ferrooxidans resulting from the collision and friction of solid particles.The increase in Al2O3 content has a little adverse effect on the bioactivity of At.ferrooxidans in the rotating-drum due to different mixing mechanisms of the two reactors.The biooxidation rate of Fe2＋ in the rotating-drum is higher than that in the stirred-tank at the same content of Al2O3 powder,especially at high solid content.The higher bioactivity of At.ferrooxidans can be maintained for allowing high solid content in the rotating-drum reactor,but its application potential still needs to be verified further by the sulfide bioleaching for the property differences of Al2O3 powder and sulfide minerals.

Fe^(2+)浓度对Acidithiobacillus ferrooxidans耐铜性的影响

嗜酸性氧化亚铁硫杆菌(Acidithiobacillus ferrooxidans)是铜矿生物冶金中应用最广泛的微生物之一。但在冶金过程中淋滤出来的Cu2+等重金属逐渐积累,达到一定的浓度后就会抑制A.ferrooxidans的生长,从而降低冶金的效率。本文着重研究了Fe2+初始浓度对A.ferrooxidans耐铜性的影响。实验中ρ(Cu2+)变化范围为0～5.0 g/L。结果表明,当ρ0(Fe2+)为6.7 g/L时,A.ferrooxidans仅在Cu2+为0～0.4 g/L的体系中能显著地氧化Fe2+进行生长;当Cu2+≥0.5 g/L时,A.ferrooxidans生长完全受到抑制。将ρ0(Fe2+)增加到8.9 g/L,A.ferroox-idans在0.5、1.0、2.0和3.0 g/L Cu2+的培养基中也能明显氧化Fe2+,并最终将其完全氧化,Cu2+对A.ferrooxidans生长抑制作用仅出现在4.0和5.0 g/L Cu2+的体系中。因此提高体系中亚铁离子的浓度能提高菌体对Cu2+的耐受力。研究结果对铜矿的生物冶金具有重要意义。

喷淋塔中固定化Acidithiobacillus ferrooxidans对Fe^(2+)的生物氧化特性研究

为了增大嗜酸氧化亚铁硫杆菌细胞密度以提高其对Fe^(2+)的氧化速率,利用泰勒花环填料为载体,在喷淋塔中固定嗜酸氧化亚铁硫杆菌,考察固定化细胞对Fe^(2+)的生物氧化性能。采用扫描电子显微镜对载体表面进行形貌表征,X射线衍射仪和傅里叶红外光谱仪对填料表面沉淀进行成分分析。结果表明:在改良的9 K培养基中,嗜酸氧化亚铁硫杆菌被成功的固定在泰勒花环填料上,并伴有少量黄铵铁矾沉淀,这些沉淀和菌体细胞一起构成了生物反应系统的生物膜。嗜酸氧化亚铁硫杆菌在喷淋塔中完成固定化后,溶液初始pH值和温度是影响氧化速率的主要原因,其优化结果分别为2.25和34℃。在此条件下,整个生物反应系统能长期保持稳定的氧化特性,Fe^(2+)的氧化速率为4.27 g/L/h。

Really active form of fluorine toxicity affecting Acidithiobacillus ferrooxidans activity in bioleaching uranium

In order to determine the mechanism of bacterial tolerance to fluorine,Acidithiobacillus ferrooxidans ATCC 23270 was domesticated and studied under the conditions of different fluorine concentrations and pH values with or without treatment by Proteinase K.The bacterial activities were observed through measuring the changes of solution potentials by platinum electrode with Ag/AgCl reference electrode and the intracellular fluorine was determined by-uorine ion-selective electrode.The results indicated that the tolerance of Acidithiobacillus ferrooxidans ATCC 23270 to fluorine could be obviously improved by domestication,HF was the effective form of fluorine to affect the bacterial activity,and pH increase or concentration change of ions of strong complex ability with fluorine ions in solution could result in false appearance of high fluorine-resistant strain.Some proteins located in cell wall or cell membrane were intimately relative with the bacterial fluorine tolerance.

Bioleaching of low-grade copper sulfide ores by Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans

The grown conditions of Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans were investigated,and then experiments were conducted to research the bioleaching behaviors of crude ore of copper sulfide and hand-picked concentrates of chalcopyrite by Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans.The experimental results show that the bacteria grow best when the temperature is(30±1) °C and the pH value is 2.0.The bacteria concentration is 2.24×107 mL-1 in this condition.It is found that the copper extraction yield is affected by the inoculum size and the pulp density and the extraction yield increases as the inoculum size grows.The bioleaching rates reach their highest point in sulfide copper and chalcopyrite with a pulp density of 5% and 10%,respectively.Column flotation experiments of low-grade copper sulfide ores show that the bioleaching recovery reaches nearly 45% after 75 days.

Cu^2+胁迫对Acidithiobacillus ferrooxidans亚铁氧化代谢及胞外电子传递影响

为了查明Cu^2+胁迫影响Acidithiobacillus ferrooxidans(At.ferrooxidans)亚铁氧化代谢机制,本研究设计了由低到高Cu^2+浓度(0~25 g/L)胁迫环境,利用邻菲啰啉分光光度法、实时荧光定量PCR和循环伏安法等分析手段分别探究了不同Cu^2+浓度胁迫下At.ferrooxidans亚铁氧化率、亚铁氧化电子传递链rus operon相关基因表达及胞外电子传递的响应情况。结果表明:Cu^2+胁迫浓度由0 g/L增加至25 g/L时,At.ferrooxidans菌亚铁氧化活性显著降低(25 g/L Cu^2+,对应下24 h亚铁氧化抑制率约为50%),rus operon相关基因表达显著下调(尤其是细胞内膜蛋白编码基因Cyc1和细胞色素c氧化酶编码基因CoxBACD分别下调12.4倍和4~6倍),Fe2+氧化胞外传递电子能力也降低(循环伏安曲线还原峰值29.0μA(对照组,0 g/L Cu^2+)和26.5μA(25 g/L Cu^2+))。综上所述,高浓度Cu^2+胁迫引起At.ferrooxidans菌亚铁氧化代谢Rus operon相关基因表达显著下调,造成胞外电子传递速率降低,最终导致At.ferrooxidans菌亚铁氧化率降低。

Bioleaching of marmatite flotation concentrate by Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans

Bioleaching of marmatite flotation concentrate by Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans was investigated at 35 ℃, the initial pH value of 2.0 on an orbital shaker with 160 min-1 over a period of 10 days. Experimental results indicate that the adapted strains increase markedly the dissolution rate and the leaching ratio of marmatite. Pulp density also affects the bioleaching of marmatite. Massive elemental sulfur and jarosite form during the leaching process in the systems inoculating the adapted strains in pure and mixed cultures; and acid product is enhanced, which decreases the pH below to 2.0 in latter leaching period. Marmatite preferentially dissolves during the bacterial leaching of complex sulfides. Compared with the pure cultures of original and adapted strains, the adapted strains of Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans in mixed cultures are more efficient in the oxidation of marmatite.

Catalytic mechanism of manganese ions and visible light on chalcopyrite bioleaching in the presence of Acidithiobacillus ferrooxidans

The bioleaching of chalcopyrite is low cost and environmentally friendly,but the leaching rate is low.To explore the mechanism of chalcopyrite bioleaching and improve its leaching rate,the effect and mechanism of manganese ions(Mn^(2+))and visible light on chalcopyrite mediated by Acidithiobacillus ferrooxidans(A.ferrooxidans)were discussed.Bioleaching experiments showed that when both Mn^(2+)and visible light were present,the copper extraction was 14.38%higher than that of the control system(without Mn^(2+)and visible light).Moreover,visible light and Mn^(2+)promoted the growth of A.ferrooxidans.Scanning electron microscopy(SEM)and energy dispersive spectrometer(EDS)analysis revealed that Mn^(2+)promoted the formation of extracellular polymeric substance(EPS)on the surface of chalcopyrite,changed the morphology of A.ferrooxidans,enhanced the adsorption of bacteria on chalcopyrite surface with light illumination,and thus promoted the bioleaching of chalcopyrite.UV–vis absorbance spectra indicated that Mn^(2+)promoted the response of chalcopyrite to visible light and enhanced the catalytic effect of visible light on chalcopyrite bioleaching.Based on X-ray photoelectron spectroscopy(XPS),the relevant sulfur speciation of chalcopyrite before and after bioleaching were analyzed and the results revealed that visible light and Mn^(2+)promoted chalcopyrite bioleaching by reducing the formation of passivation layer(S_(n)^(2-)/S0).Investigation into electrochemical results further indicated that Mn^(2+)and visible light improved the electrochemical activity of chalcopyrite,thus increasing the bioleaching rate.

Microbiologically influenced corrosion of cable bolts in underground coal mines:The effect of Acidithiobacillus ferrooxidans

Reports on corrosion failure of cable bolts,used in mining and civil industries,have been increasing in the past two decades.The previous studies found that pitting corrosion on the surface of a cable bolt can initiate premature failure of the bolt.In this study,the role of Acidithiobacillus ferrooxidans(A.ferrooxidans)bacterium in the occurrence of pitting corrosion in cable bolts was studied.Stressed coupons,made from the wires of cable bolts,were immersed in testing bottles containing groundwater collected from an underground coal mine and a mixture of A.ferrooxidans and geomaterials.It was observed that A.ferrooxidans caused pitting corrosion on the surface of cable bolts in the near-neutral environment.The presence of geomaterials slightly affected the p H of the environment;however,it did not have any significant influence on the corrosion activity of A.ferrooxidans.This study suggests that the common bacterium A.ferrooxidans found in many underground environments can be a threat to cable bolts'integrity by creating initiation points for other catastrophic failures such as stress corrosion cracking.