Search Results (98)

Systematic studies were conducted at one of the uranium deposits in Kazakhstan. Native strains of Acidithiobacillus ferrooxidans bacteria were found in leaching solutions at the deposit. The modeling of iron species in the culturing medium was analyzed using Medusa software v.2.0.5. To intensify the process, the bacterial strains were propagated in laboratory conditions, and strains available in the laboratory were added. The ability of bacteria to oxidize divalent iron to trivalent iron at 8 °C in laboratory conditions was established, but the oxidation rate was low. It was found that the limiting stage of bioleaching use in deposit conditions is the temperature mode, the content of divalent iron, and oxygen. A biomass volume of 15 L was initially cultivated under laboratory conditions, and subsequently scaled up to 3 m³ in production using three 1 m³ pachucas with air aeration. In addition, pilot tests were carried out directly in production conditions and biomass in the volume of over 30 m³ was produced. The kinetics of the oxidation process of divalent iron to trivalent iron in 1 g/h under production conditions was established. The features of the bioleaching process at the field are shown as follows: since production, the solution contains the main microelements for the nutrition and reproduction of bacteria, and recommendations for the use of bioleaching are proposed. Research has established that under conditions of a shortage of divalent iron in the solution, sulfuric acid is formed due to sulfur-containing substances. It was observed that for the effective conversion of divalent iron to trivalent iron, bacteria of the provided strain and air (oxygen) supply are sufficient. The corresponding recommendations were issued during the work. Full article

As humanity embarks on interplanetary exploration and envisions future colonies beyond Earth, understanding the impact of extreme environments on life becomes paramount. Among these factors, the hypomagnetic field (HMF)—a condition where the protective geomagnetic field is absent—remains poorly understood, especially regarding its effects on (micro)organisms. To our knowledge, this is the first study to examine how short-term exposure to an HMF (24 h to 7 days) affects the growth of three different microorganisms, Saccharomyces cerevisiae, Acidithiobacillus ferrooxidans, and Lactobacillus plantarum, using a specialized hypomagnetic chamber and advanced spectrophotometric analysis. We demonstrate significant growth inhibition in S. cerevisiae (23%) and A. ferrooxidans (68%), with L. plantarum remaining unaffected. This inhibitory effect appears reversible, diminishing as organisms return to normal geomagnetic conditions. These findings reveal that the HMF acts as a temporary environmental stressor, underscoring the need for deeper exploration of its biological effects. Our work sets the stage for further research into how the space environment may shape microbial ecosystems critical to future human endeavors in space. Full article

Lithium is a critical mineral resource. With the development of high-end manufacturing industry, the demand for high-performance lithium-containing chemical raw materials continues to grow. At present, lithium needs to be acquired from a large amount of lepidolite ore, constrained by the existing lithium resource supply limitation quandary, and the industry urgently needs to develop more efficient beneficiation and extraction methods for lepidolite. Findings have suggested mixed collectors (e.g., DDA/SDBS) achieve a 4.99% Li₂O grade and 98% recovery at neutral pH, reducing reagent use by 20–30%. Microwave-assisted roasting boosts Li recovery to 95.9% and cuts energy use by 26.9%. Bioleaching with Acidithiobacillus ferrooxidans (A.F.) and rhamnolipid releases 6.8 mg/L Li with a lower environmental impact. Sulfuric acid baking recovers Li (97.1%), Rb (96.0%), and Cs (95.1%) efficiently. Despite challenges in fine-particle recovery and reagent costs, integrated strategies like nanobubble flotation, green collectors, and AI optimization offer sustainable, high-efficiency extraction. This work provides insights for advancing lepidolite processing, balancing economics and environmental stewardship. Full article

Acid mine drainage (AMD) is the result of the oxidation of pyrite and other sulfide ores, and the catalytic action of microorganisms accelerates the generation of AMD. In this paper, the interaction between 2-mercaptobenzimidazole (MBI) and pyrite in the presence of Acidithiobacillus ferrooxidans (At. ferrooxidans) was studied. The results of leaching experiments showed that when the dosage of MBI was more than or equal to 6 g/kg, the oxidation of pyrite was obviously inhibited, and the inhibition rate of 9 g/kg MBI was the best, reaching 97.1%. Electrochemical tests show that when the amount of MBI exceeds 16.8 mg, the pyrite surface treated with MBI will show good oxidation corrosion resistance, and the corrosion resistance will be enhanced with the increase in MBI dosage. Subsequently, the influence of MBI on bacterial growth was ruled out by experiments, and the surface of passivated pyrite was observed and characterized. The results showed that MBI could chelate with iron on the surface of pyrite through -C=N and -SH in the molecule, which enhanced the hydrophobicity of pyrite, thus reducing the contact between pyrite and the external environment and effectively inhibiting the oxidation of pyrite. Full article

Magnetosomes are magnetic nanocrystals synthesized by bacteria that have important application value in biomedicine. Therefore, it is very important to evaluate their biocompatibility. It has been reported that the extremophilic acidophilic bacterium Acidithiobacillus ferrooxidans, which is aerobic, can synthesize intracellular Fe₃O₄ magnetosomes. In this paper, we performed a comprehensive and systematic evaluation of the biocompatibility of magnetosomes with an average particle size of 53.66 nm from Acidithiobacillus ferrooxidans, including pharmacokinetics, degradation pathways, acute systemic toxicity, cytotoxicity, genotoxicity, blood index and immunotoxicity. The phase composition of the magnetosomes was identified as Fe3O4 through XRD and HRTEM analyses. Biocompatibility evaluation results showed that magnetosomes metabolized rapidly in rats and degraded thoroughly in major organs, with almost no residue. When the injection concentration was low (40 mg/kg, 60 mg/kg), magnetosomes would not cause pathological changes in the major organs of mice, basically. At the same time, magnetosomes had low cytotoxicity, genotoxicity, immunotoxicity and hemolysis rate, which proved that the magnetosomes synthesized by Acidithiobacillus ferrooxidans are magnetic nanomaterials with good biocompatibility. This research provides an important theoretical basis for the large-scale application of bacterial magnetosomes as functional magnetic nanomaterials. Full article

Acid mine drainage (AMD) has serious impacts on the environment. To inhibit the generation of AMD from copper sulfide tailings at the source, in this paper, a strategy is developed for promoting the biopassivation of copper sulfide tailings using algal biochar, and the effects of the pyrolysis temperature and concentration of algal biochar on the passivation efficiency and stability are investigated. The results reveal that the introduction of algal biochar during the biopassivation of copper sulfide tailings significantly enhances the tailings passivation effect of the tested Acidithiobacillus ferrooxidans strain and greatly stabilizes the formed passivation layer. Algal biochar prepared with a pyrolysis temperature of 300 °C and applied at a concentration of 6 g/L not only optimizes biopassivation but also significantly improves the stability of the passivation layer. The complex mechanisms of algal biochar in this system include regulating the pH and oxidation‒reduction potential of the reaction system, effectively adsorbing microbial cells, efficiently aggregating metal cations in solution, stimulating the synthesis of extracellular polymeric substances, and accelerating electron transfer. This research offers a novel method for the benign treatment of copper sulfide tailings and resource utilization of algae. Full article

Ionic rare earth ore (IREO) has a high abundance of medium and heavy rare earth elements (REEs), making it a vital strategic resource for China. In this work, two typical microorganisms, Aspergillus niger and Acidithiobacillus ferrooxidans, were used to study the interaction mechanism during the bioleaching of IREO under acidic conditions. The results revealed some differences in the interaction and leaching effects of A. niger and A. ferrooxidans on ionic rare earth minerals. A. niger mainly forms rare earth complexes with rare earth ions in IREO by secreting metabolites such as organic acids, thereby promoting the release of REEs, and it has a strong adsorption capacity for Yb. A. ferrooxidans promotes the release of REEs from rare earth minerals, primarily through iron–sulfur oxidation. The differential expression of metabolic genes (e.g., gpmL, FabF, FASN) associated with major metabolite secretion indicates their correlation with the leaching process. The above results reveal the role of the typical acid-producing microorganisms A. niger and A. ferrooxidans and their metabolites in the leaching of IREO, which is valuable for understanding the interaction mechanisms between microorganisms and IREO under acidic conditions. Full article

Acidithiobacillus ferrooxidans is a Gram-negative bacterium that thrives in extreme acidic conditions. It has emerged as a key player in biomining and bioleaching technologies thanks to its unique ability to mobilize a wide spectrum of elements, such as Li, P, V, Cr, Fe, Ni, Cu, Zn, Ga, As, Mo, W, Pb, U, and its role in ferrous iron oxidation and reduction. A. ferrooxidans catalyzes the extraction of elements by generating iron (III) ions in oxic conditions, which are able to react with metal sulfides. This review explores the bacterium’s versatility in metal and elemental mobilization, with a focus on the mechanisms involved, encompassing its role in the recovery of industrially relevant elements from ores. The application of biomining technologies leveraging the bacterium’s natural capabilities not only enhances element recovery efficiency, but also reduces reliance on conventional energy-intensive methods, aligning with the global trend towards more sustainable mining practices. However, its use in biometallurgical applications poses environmental issues through its effect on the pH levels in bioleaching systems, which produce acid mine drainage in rivers and lakes adjacent to mines. This dual effect underscores its potential to shape the future of responsible mining practices, including potentially in space, and highlights the importance of monitoring acidic releases in the environment. Full article

Due to the emission of hazardous chemicals and heat, the traditional smelting method used to extract critical minerals from ore and mine slag/tailings is considered bad for the environment. An environmentally friendly procedure that can stabilize sulfur emissions from mine waste without endangering the environment is bioleaching. In the present study, sequential oxidative (Oxi) and reductive (Red) bioleaching of acid-pretreated copper smelter slag using iron-oxidizing/reducing Acidithiobacillus ferrooxidans was applied to investigate critical minerals’ recovery for the dissolution of copper smelter slag. In this batch flask experiment, up to 55% Cu was recovered on day 11 during the Oxi stage, which increased to 80% during the Red stage on day 20. A sequential oxidative and reductive bioleaching of an acid-pretreated copper smelter slag at pH (1.8) and 30 °C positively affects the extraction of Cu (80%), Zn (77.1%), and Al (65.3%). In contrast to the aerobic bioleaching experiment, the reduction of Fe³⁺ iron under anaerobic conditions resulted in a more significant release of Fe²⁺ and sulfate, limiting the development of jarosite, surface passivation, and the subsequent loss of metal recovery due to co-precipitation with Fe³⁺. Overall, the Oxi-Red bioleaching process combined with acid pretreatment showed promising results toward creating a method for recovering valuable metals from metallurgical waste that is economical and environmentally beneficial. Full article

Bacterial leaching is a well-known green technology proposed for the extraction of valuable metals into solution. However, this biotechnology has some “bottle neck” problems too. Arsenopyrite, a gold-bearing ore, is a refractory mineral material that is hardly soluble and contains toxic arsenic compounds which decrease any bioleaching production. The most common biotechnology used for this process is provided with the species Acidithiobacillus ferrooxidans: autotrophic and acidophilic bacterial strains including ones resistant to inorganic arsenic compounds. Common attempts to dissolve arsenopyrite with increasing volumes of sulfuric acid provoke acidification of the environment and its pollution with toxic compounds. In our research, we compared two A. ferrooxidans strains of different origin: TFBk isolated from arsenopyrite ore (pre-adopted to arsenic), the Republic of Kazakhstan, and ShA-GNK isolated from silicate nickel-ferrous ore (laterite, without arsenic), the Russian Federation. The studied genomes of both strains showed the presence of the same genes providing defense against arsenic compounds, but the resistance to toxic compounds was higher in the strain that had never been exposed to any high As concentration under the natural conditions. Both strains showed a weak oxidation of the arsenopyrite flotation concentrate (AFC). In accordance with the published data, supplementation of the medium with formate stimulated bacterial growth in the culturing medium. However, this supplementation to the leaching solution decreased the arsenopyrite oxidation during the first stage of the AFC leaching because formate was used as an alternative energy substrate, but subsequently gave a higher iron yield later. Full article

Acid mine drainage (AMD), containing large quantities of heavy metals and acidic components, poses a severe threat to the environment and human health. Acidithiobacillus ferrooxidans (A. ferrooxidans) plays a crucial role in the treatment of AMD, but its activity is significantly influenced by environmental conditions. This study systematically analyzes the stress effect of high phosphorus concentration on A. ferrooxidans during AMD treatment and its biomineralization effect. The results indicate that with phosphorus concentrations ranging from 0 g/L to 2 g/L, the system’s pH and Fe²⁺ oxidation rate initially decrease and then increase, with higher phosphorus concentrations delaying the time of increase. When the phosphorus concentration exceeds 2 g/L, both pH and Fe²⁺ oxidation rates generally show a downward trend. The morphology and elemental composition of the precipitates obtained under different phosphorus concentrations exhibit significant differences, indicating that phosphorus concentration notably affects the oxidation activity of A. ferrooxidans and its mediated biomineralization process. Under high phosphorus concentrations, the activity of A. ferrooxidans is inhibited, hindering the Fe²⁺ oxidation process and resulting in the formation of a large quantity of amorphous ferric phosphate precipitates. The findings provide a scientific basis for optimizing AMD treatment technologies, suggesting that reasonable control of phosphorus concentration in practical applications can improve AMD treatment efficiency and pretreatment effects. Full article

From an engineering standpoint, investigating the effects of rotation speed and fulvic acid concentration on the development of secondary high-iron minerals is crucial for treating acid mine drainage. The Fe²⁺ oxidation mechanism by Acidithiobacillus (A.) ferrooxidans to synthesise secondary high-iron minerals was examined in this study using shaking flask tests under various conditions: fulvic acid concentrations of 0, 0.2, or 0.4 g/L and rotation speeds of 180 r/min or 100 r/min. The pH, Fe²⁺ oxidation rate, total iron precipitation rate, secondary high-iron mineral functional groups and ore equivalent indicators were also investigated. The results demonstrated that at a fulvic acid concentration of 0 g/L, the pH decreased from 2.5 to 2.17 at 180 r/min. At 0.2 g/L, it decreased from 2.5 to 2.05. Finally, at 0.4 g/L, it decreased from 2.5 to 2.07. Fe²⁺ was completely oxidised after 48 h, and the final total iron precipitation rate ranged from 26.2% to 33.4%. The synthesised secondary high-iron minerals were uniformly dispersed in the solution. When the rotation speed was 100 r/min, the pH reduced from 2.5 to 2.25 at a fulvic acid concentration of 0 g/L, from 2.5 to 2.14 at 0.2 g/L, and from 2.5 to 2.19 at 0.4 g/L. Notably, Fe²⁺ was completely oxidised within 72 h. The experiment’s final iron precipitation rate ranged from 23.6 to 29.6%. The synthesised secondary high-iron minerals were blocky and adhered to the bottom of the shaking flask. In summary, at a rotation speed of 180 r/min or 100 r/min, the Fe²⁺ oxidation rate and total iron precipitation rate of the experimental group with a fulvic acid concentration of 0.2 g/L were higher than those of the control group and the experimental group with a fulvic acid concentration of 0.4 g/L. A fulvic acid concentration of 0.2 g/L enhanced the activity of A. ferrooxidans. The minerals obtained from these experiments were characterised and identified as schwertmannite and jarosite. Full article

This study presents findings regarding the kinetics of ferrous iron oxidation in solution mediated by Acidithiobacillus ferrooxidans bacteria within a continuous-flow bioreactor employing diverse types of immobilizers. The objective is to augment the rate of ferrous iron oxidation in solutions utilizing an immobilizer for Acidithiobacillus ferrooxidans strains. Immobilization represents a promising avenue for enhancing the efficiency of Fe²⁺ oxidation via acidophilic ferrooxidizing bacteria, leading to a several-fold increase in oxidation rate. A comparative analysis was conducted to evaluate the efficacy of different types of immobilizer in facilitating iron oxidation within a continuous-flow bioreactor, including the application of wood chips coated with Fe(OH)₃. The results indicate that wood chips coated with iron hydroxide serve as effective type of immobilizer, facilitating the robust attachment of Acidithiobacillus ferrooxidans via electrostatic interactions between negatively charged bacteria and positively charged surfaces. Experimental investigations were conducted using novel immobilization matrices in pilot-scale tests simulating the underground borehole leaching (UBL) of uranium. The bioactivation of leaching solutions enhances the efficiency and environmental compatibility of UBL compared to conventional chemical oxidation methods. The relationships between redox potential and ferric iron content in bioactivated solutions during the UBL of uranium were delineated. The significance of this study lies in its elucidating the pivotal role of Fe²⁺ oxidation in uranium extraction processes, particularly in the context of UBL. By employing bioactivation mediated by Acidithiobacillus ferrooxidans, the study demonstrates not only enhanced uranium extraction efficiency, but also markedly improved environmental sustainability compared to traditional chemical oxidation methods. The findings reveal crucial correlations between redox potential and ferric iron concentration in bioactivated solutions. Full article

Recycling and reusing phosphorus in agriculture can reduce the consumption of natural phosphorus resources, which are continuing to shrink. Phosphorus fertilizers made from renewable raw materials (sewage sludge ash, animal bones, dried animal blood) and activated with phosphorus solubilizing microorganisms (Bacillus megaterium, Acidithiobacillus ferrooxidans) offer an alternative to conventional fertilizers. These products should meet consumer and environmental safety standards. In this paper, based on field experiments conducted in northeast Poland, the effects of waste-derived biofertilizers on selected parameters of wheat yield quality are discussed. The study focuses on the technological properties of the grain (hectoliter weight, hardness index, Zeleny index, starch, wet gluten, and protein content), the content of proteogenic amino acids, macro- and micronutrients, and selected toxic elements in the grain. The quality parameters of wheat grain were not affected by the tested biofertilizers applied in P doses up to 35.2 kg ha⁻¹, nor by conventional fertilizers. Full article

Acidophiles are capable of surviving in extreme environments with low pH. Acidithiobacillus ferrooxidans is a typical acidophilic bacterium that has been extensively studied when grown chemoautotrophically, i.e., when it derives energy from oxidation of Fe²⁺ or reduced inorganic sulfur compounds (RISCs). Although it is also known to grow with electrons supplied by solid electrodes serving as the sole source of energy, the understanding of its electroautotrophic growth is still limited. This study aimed to compare the growth characteristics of A. ferrooxidans under electroautotrophic (ea) and chemoautotrophic (ca) conditions, with an attempt to elucidate the possible mechanism(s) of extracellular electron flow into the cells. Jarosite was identified by Raman spectroscopy, and it accumulated when A. ferrooxidans used Fe²⁺ as the electron donor, but negligible mineral deposition occurred during electroautotrophic growth. Scanning electron microscopy (SEM) showed that A. ferrooxidans possesses more pili and extracellular polymeric substances (EPSs) under electroautotrophic conditions. A total of 493 differentially expressed genes (DEGs) were identified, with 297 genes being down-regulated and 196 genes being up-regulated in ea versus ca conditions. The genes known to be essential for chemoautotrophic growth showed a decreased expression in the electroautotrophic condition; meanwhile, there was an increased expression of genes related to direct electron transfer across the cell’s outer/inner membranes and transmembrane proteins such as pilin and porin. Joint analysis of DEGs and differentially expressed metabolites (DEMs) showed that galactose metabolism is enhanced during electroautotrophic growth, inducing A. ferrooxidans to produce more EPSs, which aids the cells in adhering to the solid electrode during their growth. These results suggested that electroautotrophy and chemoautotrophy of A. ferrooxidans have different extracellular electron uptake (EEU) pathways, and a model of EEU during electroautotrophic growth is proposed. The use of extracellular electrons as the sole energy source triggers A. ferrooxidans to adopt metabolic and subsequently phenotypic modifications. Full article