Kinetics of growth and elemental sulfur oxidation in batch culture of thiobacillus ferrooxidans

The kinetics of oxidation of elemental sulfur by Thiobacillus ferrooxidans in a batch reactor was followed by measuring the concentration of adsorbed cells on the sulfur surface, the concentration of free cells in liquid medium, and the amount of sulfur oxidized. As the elemental sulfur was oxidized to sulfate, the liquid-phase concentration of free cells continued to increase with time, whereas the surface concentration of adsorbed cells per unit weight of sulfur approached a limiting value, i.e., the maximum adsorption capacity. During sulfur oxidation, there was a close correlation between the concentrations of adsorbed and free cells, and these data were well correlated with the Langmuir isotherm. The observed rates of batch growth and sulfur oxidation were consistent with a kinetic model, assuming that the growth rate of batch growth and sulfur oxidation were consistent with a kinetic model. Assuming that the growth rate of adsorbed bacteria is proportional to the product of the concentration of adsorbed cells and the fraction of adsorption sites unoccupied by cells. The kinetic and stoichiometric parameters appearing in the model were evaluated using the experimental data and were compared with parameters determined previously for a few metal sulfides. (c) 1994 John Wiley & Sons, Inc.     

Effect of carbon dioxide concentration on the bioleaching of a pyrite-arsenopyrite ore concentrate

The effect of carbon dioxide concentration on the bacterial leaching of a pyrite-arsenopyrite ore concentrate was studied in continuous-flow reactors. Steady-state operation with two feed slurry densities, 6 wt% and 16 wt% solids, were tested for the effect of carbon dioxide concentration. Bacterial growth rates were estimated via the measurement of carbon dioxide consumption rates. Aqueous-phase carbon dioxide concentrations in excess of 10 mg/L were found to be inhibitory to bacterial growth. (c) 1993 John Wiley & Sons, Inc.     

不同培养基中氧化亚铁硫杆菌生长及沉淀研究

为减缓氧化亚铁硫杆菌在9K培养基中培养时产生的沉淀,通过改变9K液体培养基的组成成分,研究了培养基成分的改变对细菌生长特性的影响及沉淀产生情况,并利用X射线衍射仪对沉淀进行了物相鉴定。结果表明,最佳培养基组成为(NH4)2HPO43.00g,KCl 0.10g,MgSO4.7H2O 0.50g,FeSO4.7H2O 44.3g,蒸馏水1 000ml,pH 2.0。在该培养基中,氧化亚铁硫杆菌不仅能保持其较高的氧化活性(其Fe2 氧化速率最高为0.3376 g/L.h-1),而且生长过程中沉淀出现的时间最迟,产生的沉淀量最少,且沉淀为非晶型物质。     

The Effect of the Facultative Chemolithotrophic Bacterium Thiobacillus acidophilus on the Leaching of Low-Grade Cu-Ni Sulfide Ore by Thiobacillus ferrooxidans

The purpose of this investigation was to determine the effect of Thiobacillus acidophilus on the leaching of a low-grade Cu-Ni sulfide ore by Thiobacillus ferrooxidans. A sample of low-grade Cu-Ni sulfide ore containing 0.36% Cu, 0.48% Ni, and 7.87% Fe was pulverized and initially leached for a 21-day period using two different pure cultures of T. ferrooxidans, an environmental strain (F2) and a strain from the American Type Culture Collection (ATCC 23270). Samples of the ore slurries were drawn and the pH was monitored over the course of the leaching period. The concentrations of Cu and Ni leached by each strain were determined and compared. No significant differences were observed in the concentrations of Cu and Ni leached by the two pure cultures of T. ferrooxidans. Subsequently, the ore was leached with mixed cultures of T. ferrooxidans and T. acidophilus to determine the effect of the latter on the concentrations of Cu and Ni leached from the ore. The environmental strain F2 of T. ferrooxidans was used in combination with both a type strain (ATCC 27807) and an environmental strain (64) of T. acidophilus. After 21 days, the mixed cultures of T. ferrooxidans and T. acidophilus leached significantly greater amounts of copper than the pure strain alone, but no such difference was observed for the leaching of nickel.     

Bacterial Oxidation of Refractory Sulfide Ores for Gold Recovery

Abstract

The microbiological leaching of refractory sulfide ores (pyrite, arsenopyrite) for recovery of gold is reviewed in this article. The underlying physiological, biochemical, and genetic fundamentals of the bacteria involved (Thiobacillus and Sulfolobus spp.) are complex and have yet to be elucidated in depth. The chemistry of acid and biological leaching of pyrite and arsenopyrite minerals is also complex, and many of the individual reactions are not known in detail. Bacterial leaching is discussed in relation to chemical speciation at acid pH values. Attempts to develop models for a better understanding of bioleaching processes are summarized. The importance of pH, redox potential, temperature, sulfur balance, and toxic metals is evaluated for optimizing conditions for bacterial activity. Gold is finely disseminated in refractory sulfide ores, thereby decreasing Au recoveries upon conventional cyanidation for gold dissolution. In the bioleaching process, bacteria remove the sulfide minerals by oxidative dissolution and thus expose Au to extraction with cyanide solution. Stirred tank reactors appear most suited for this biological leaching process. The overall oxidation of the sulfides is an important variable for gold recovery. Pilot- and commercial-scale bioleaching processes for gold-containing pyrite and arsenopyrite ores are reviewed. This application of mineral biotechnology competes favorably with pressure leaching and roasting processes, both of which are problematic and energy-intensive alternatives for pretreatment of auriferous pyrite/arsenopyrite ores.     

Mechanism of microbial flotation using Thiobacillus ferrooxidans for pyrite suppression

Microbial desulfurization might be developed as a new process for the removal of pyrite sulfur from coal sluries such as coal-water mixture (CWM). An application of iron-oxidizing bacterium Thiobacillus ferrooxidans to flotation would shorten the periods of the microbial removal of pyrite from some weeks by leaching methods to a few minutes. The floatability of pyrite in flotation was mainly reduced by T. ferrooxidans itself rather than by other microbial substances in bacterial culture as additive of flotation liquor. Floatability was suppressed within a few seconds by bacterial contact. The suppression was proportional to increasing the number of cells observed between bacterial adhesion and the suppression of floatability. If 25% of the total pyrite surface area covered with the bacteria, pyrite floatability would be completely depressed. Bacteria that lost their iron-oxidizing activities by sodium cyanide treatment were also able to adhere to pyrite and reduced pyrite floatability as much as normal bacteria did. Thiobacillus ferrooxidans ATCC 23270, T-1, 9, and 11, which had different iron-oxidizing abilities, suppressed floatability to similar-levels. The oxidizing ability of bacteria did not influence the suppressing effect. These results showed the mechanism of the suppression of pyrite floatability by bacteria. Quick bacterial adhesion to pyrite induced floatability suppression by changing the surface property from hydrophobic. The quick adhesion of the bacterium was the novel function which worked to change the surface property of pyrite to remove it from coal. (c) 1993 John Wiley & Sons, Inc.     

氧化亚铁硫杆菌生物冶金的新进展

综述了Thiobacillus ferrooxidans生物冶金的催化作用机制,能量变化,细胞外多聚物和基底金属在浸出过程中的作用和影响,以及温度,矿物的大小,空气分离器,pH,细菌载体的影响。     

Microorganisms and the aquatic environment

The important role of bacteria in sediments is reviewed. The problems in estimating bacterial biomass in sediments are highlighted. Recent developments in studying substrate transformations in the laboratory, under conditions simulating the nutrient status occurring in nature, are also discussed.     

Further Readings in Geomicrobiology

The Biology of Cyanobacteria. N. G. Carr and B. A. Whitton (eds.). Botanical Monographs, Vol. 19. Blackwell Scientific Publications, Oxford, U.K., 1982 (also University of California Press), xi + 688 pp., $75.00 (U.S.); £42.00 sterling, hardcover.

Earth's Earliest Biosphere: Its Origin and Evolution. J. William Schopf (ed.). Princeton University Press, Princeton, NJ, 1983. With 67 tables, 97 figures, and 47 photographs, xxv + 543 pp. Cloth, $95.00; paper, $42.50.     

Bioleaching of zinc sulfide concentrate by Thiobacillus ferrooxidans

The kinetics of the bioleaching of ZnS concentrate by Thiobacillus ferrooxidans was studied in a well-mixed batch reactor. Experimental studies were made at 30 degrees C and pH 2.2 on adsorption of the bacteria to the mineral, ferric iron leaching, and bacterial leaching. The adsorption rate of the bacteria was fairly rapid in comparison with the bioleaching rate, indicating that the bacterial adsorption is at equilibrium during the leaching process. The adsorption equilibrium data were correlated by the Langmuir isotherm, which is a useful means for predicting the number of bacteria adsorbed on the mineral surface. The rate of chemical leaching varied with the concentration of ferric iron, and the first-order reaction rate constant was determined. Bioleaching in an iron-containing medium was found to take place by both direct bacterial attack on the sulfide mineral and indirect attack via ferric iron. In this case, the ferric iron was formed from the reaction product (ferrous iron) through the biological oxidation reaction. To develop rate expressions for the kinetics of bacterial growth and zinc leaching, the two bacterial actions were considered. The key parameters appearing in the rate equations, the growth yield and specific growth rate of adsorbed bacteria, were evaluated by curve fitting using the experimental data. This kinetic model allowed us to predict the liquid-phase concentrations of the leached zinc and free cells during the batch bioleaching process.     

Dynamics of bacterioplankton in oligotrophic and eutrophic aquatic environments: bottom-up or top-down control?

Measurements of bacterial biomass, production and mortality have been carried out in a large range of aquatic environments, including eutrophic and oligotrophic ones. The general trends of variations of bacterial biomass, size, specific growth rate and mortality rate in all these environments are examined. The overall flux of bacterial production is taken as an index of the flux of organic matter available to bacteria, thus characterizing the richness of the environment. Bacterial biomass is roughly proportional to richness, while mean cell size increases with it. The turnover rate of biomass, as revealed either by growth or by mortality rates, appears to be fairly independent of richness.These observations are compatible with a simple resource-limited (bottom-up controlled) model of the dynamics of bacterioplankton. On the other hand, they are in contradiction with the predictions of a predator-controlled (top-down controlled) model.     

Limited diffusive fluxes of substrate facilitate coexistence of two competing bacterial strains

Soils are known to support a great bacterial diversity down to the millimeter scale, but the mechanisms by which such a large diversity is sustained are largely unknown. A feature of unsaturated soils is that water usually forms thin, poorly-connected films, which limit solute diffusive fluxes. It has been proposed, but never unambiguously experimentally tested, that a low substrate diffusive flux would impact bacterial diversity, by promoting the coexistence between slow-growing bacteria and their potentially faster-growing competitors. We used a simple experimental system, based on a Petri dish and a perforated Teflon membrane to control diffusive fluxes of substrate (benzoate) whilst permitting direct observation of bacterial colonies. The system was inoculated with prescribed strains of Pseudomonas, whose growth was quantified by microscopic monitoring of the fluorescent proteins they produced. We observed that substrate diffusion limitation reduced the growth rate of the otherwise fast-growing Pseudomonas putida KT2440 strain. This strain out-competed Pseudomonas fluorescens F113 in liquid culture, but its competitive advantage was less marked on solid media, and even disappeared under conditions of low substrate diffusion. Low diffusive fluxes of substrate, characteristic of many unsaturated media (e.g. soils, food products), can thus promote bacterial coexistence in a competitive situation between two strains. This mechanism might therefore contribute to maintaining the noncompetitive diversity pattern observed in unsaturated soils.     

细菌毒素-抗毒素系统的研究进展

毒素-抗毒素系统(toxin-antitoxin system,TA)由两个共表达的基因组成,其中一个基因编码不稳定的抗毒素蛋白(antitoxin),另一个基因编码稳定的毒素蛋白(toxin).毒素-抗毒素系统最早发现于一些低拷贝的质粒,用来维持低拷贝质粒在菌群中的稳定存在.随后的研究表明,毒素-抗毒素系统广泛存在于细菌,包括一些致病菌的染色体上.在营养缺乏等不良生长条件下,由于基因表达的抑制和蛋白酶的降解作用,不稳定的抗毒素蛋白减少,从而产生游离的毒素蛋白,导致细菌的生长抑制和死亡.毒素-抗毒素系统的生理功能目前还存在争议,有学者认为细茼染色体上的毒素-抗毒素系统可以在不良生长状况下介导细菌的死亡,即细茼程序性细胞死亡(baeterial programmedcell death).但也有证据显示,毒素-抗毒素系统的功能更偏向于应激状态下的生理调节方面,即只起应激状态下的抑菌作用而不是杀菌作用.对细菌生长调控中毒素-抗毒素系统的作用机理进行综述,并探讨毒素-抗毒素系统研究的理论和应用价值.     

Enhancement of Copper Dissolution from a Sulfide Ore by Using Thiobacillus thiooxidans

Copper dissolution from a sulfide ore (with covellite as the main copper phase) was investigated in cultures of Thiobacillus ferrooxidans or Thiobacillus thiooxidans and in abiotic controls. In unsupplemented media, T. ferrooxidans was more efficient than T. thiooxidans. In the presence of ferric iron, the dissolution of covellite was not significantly different in cultures inoculated with T. ferrooxidans or T. thiooxidans. However, the most extraction was found in T. thiooxidans cultures supplemented with ferrous sulfate. The first results were explained by the mechanism proposed by Schippers and Sand (Appl Envir Microbiol 65:319-321, 1999), which involves polysulfides and sulfur as intermediates. This mechanism was extended to explain the behavior of T. thiooxidans culture supplemented with ferrous iron.