Acidithiobacillus Ferrooxidans Culture Research Articles

Simplification of the Acidithiobacillus ferrooxidans Culture Process for Expanding the Field of Biomachining.

Biomachining is an eco-friendly metal processing method with broad application potential. Nevertheless, the bacterial culture methods that are currently involved in biomachining require the intensive use of chemical reagents, especially FeSO4, specialized equipment, and professional-level skills in the field of biology. Herein, the differences between two cultures with and without sterilization were evaluated. Acidithiobacillus ferrooxidans was cultured with iron instead of FeSO4 in the culture medium. The chemical and biochemical parameters of the culture were analyzed by studying the area of exposed iron and continuously regulating the pH. Eliminating the sterilization and sterile inoculation of the medium is feasible for culturing A. ferrooxidans. The key to achieving a high bacterial density in culture with iron was to maintain the solution pH. The possibility of mass culturing A. ferrooxidans with steel cuttings was evaluated in a custom bioreactor, and the bacterial concentration reached 9 × 107 cells/mL.

A comparative study on psychrophilic and mesophilic biooxidation of ferrous iron by pure cultures of Acidithiobacillus ferrooxidans and Acidithiobacillus ferrivorans

Biological oxidation of ferrous sulfate by Acidithiobacillus ferrooxidans and Acidithiobacillus ferrivoransis an important process in the bioleaching of minerals and the treatment of acid mine drainage. The rate at which biooxidation reactions take place is directly related to the microorganisms’growth temperature. Decreasing the temperature of reaction causes both a decrease on the chemical reactions rates and a decrease on bacterial growth. In this study, the effects of pH and temperatures on oxidation of ferrous sulfate by a native At. ferrooxidans and At. ferrivorans strains were investigated. The biooxidation tests conducted in shake flasks at 28 °C and 8 °C and at initial pH 1.6 for 5 days. During the experiment, the mesophilic iron oxidizers were capable of growing on ferrous iron at concentrations of 4.5 g/L at low and optimum temperature. However, the rate of mesophilic biooxidation of ferrous iron was higher than that observed in the psychrophilic biooxidation. In conclusion, during the experiment the At. ferrivorans strain 535 showed high activity in oxidizing at low temperature than other strains. It means even at very low temperatures, microorganisms play an important role in the oxidation and leaching of sulphide ores.

Effect of biogenic jarosite on the bio-immobilization of toxic elements from sulfide tailings

The discharge of toxic elements from tailings soils in the aquatic environments occurs chiefly in the presence of indigenous bacteria. The biotic components may interact in the opposite direction, leading to the formation of a passivation layer, which can inhibit the solubility of the elements. In this work, the influence of jarosite on the bio-immobilization of toxic elements was studied by native bacteria. In batch experiments, the bio-immobilization of heavy metals by an inhibitory layer was examined in the different aquatic media using pure cultures of Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans. A variety of analyses also investigated the mechanisms of metals bio-immobilization. Among different tests, the highest metal solubility yielded 99% Mn, 91% Cr, 95% Fe, and 78% Cu using A. ferrooxidans in 9KFe medium after ten days. After 22 days, these percentages decreased down to 30% Mn and about 20% Cr, Fe, and Cu, likely due to metal immobilization by biogenic jarosite. The formation of jarosite was confirmed by an electron probe micro-analyzer (EPMA), X-ray diffraction (XRD), and scanning electron microscope (SEM). The mechanisms of metal bio-immobilization by biogenic jarosite from tailings soil confirmed three main steps: 1) the dissolution of metal sulfides in the presence of Acidithiobacillus bacteria; 2) the nucleation of jarosite on the surface of sulfide minerals; 3) the co-precipitation of dissolved elements with jarosite during the bio-immobilization process, demonstrated by a structural study for jarosite. Covering the surface of soils by the jarosite provided a stable compound in the acidic environment of mine-waste.

Бактериально-химическое выщелачивание золотоносной руды месторождения шокпар культурой aciditiobacillus ferrooxidans

Бактериально-химическое выщелачивание золотоносной руды месторождения шокпар культурой aciditiobacillus ferrooxidans

Effects of Conventional Flotation Frothers on the Population of Mesophilic Microorganisms in Different Cultures

Bioleaching is an environment-friendly and low-investment process for the extraction of metals from flotation concentrate. Surfactants such as collectors and frothers are widely used in the flotation process. These chemical reagents may have inhibitory effects on the activity of microorganisms through a bioleaching process; however, there is no report indicating influences of reagents on the activity of microorganisms in the mixed culture which is mostly used in the industry. In this investigation, influences of typical flotation frothers (methyl isobutyl carbinol and pine oil) in different concentrations (0.01, 0.10, and 1.00 g/L) were examined on activates of bacteria in the mesophilic mixed culture (Acidithiobacillus ferrooxidans, Leptospirillum ferrooxidans, and Acidithiobacillus thiooxidans). For comparison purposes, experiments were repeated by pure cultures of Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans in the same conditions. Results indicated that increasing the dosage of frothers has a negative correlation with bacteria activities while the mixed culture showed a lower sensitivity to the toxicity of these frothers in comparison with examined pure cultures. Outcomes showed the toxicity of Pine oil is lower than methyl isobutyl carbinol (MIBC). These results can be used for designing flotation separation procedures and to produce cleaner products for bio extraction of metals.

Formation and characterization of ternary (Na, NH4, H3O)-jarosites produced from Acidithiobacillus ferrooxidans cultures

The purpose of this study was to characterize a series of (Na, NH4, H3O)-jarosites produced with various combinations of NH4+ + Na+ in cultures of Acidithiobacillus ferrooxidans that simulated acid solutions from bioleaching systems. The solution concentrations utilized were 6.1, 80, 160 and 320 mM for NH4+ and 0, 50, 100, 250 and 500 mM for Na+ as their respective sulfates. Media at pH 2.2 were inoculated with iron-oxidizing A. ferrooxidans and incubated in shake flasks at 22 ± 2 °C. As the bacteria oxidized ferrous sulfate, ferric iron hydrolyzed and precipitated as schwertmannite (idealized formula Fe8O8(OH)6(SO4).nH2O) and/or as solid solution jarosites [(Na, NH4, H3O)-Fe3(SO4)2(OH)6)] depending on the relative and absolute concentrations of NH4+ and Na+. The precipitates were characterized by elemental analysis, X-ray diffraction, specific surface area, and Munsell color. Schwertmannite was the dominant mineral product at low combinations of Na+ (≤50 mM) and NH4+ (≤80 mM) in the media after 2 weeks of aging. At higher single or combined concentrations and with aging for 6 and 11 weeks, the formation of yellowish, solid solution jarosites was enhanced. Precipitation of jarosite-group minerals was favored by NH4+ relative to Na+. Color (Munsell hue) was a useful tool for assessing sample mineralogy after extended aging, but the presence of abundant, poorly crystalline schwertmannite tended to mask the color of admixed jarosite-group minerals after only 2 weeks of contact with the culture media. The purest samples of jarosite-type minerals had specific surface areas <1.0 m2/g. Unit cell edge lengths and cell volume calculations from powder XRD data indicated that the jarositic phases produced were ternary (Na, NH4, H3O)-solid solutions. Most products also appeared to be deficient in structural Fe, especially at low NH4 contents. Thus, ferric iron precipitation from the simulated bioleaching systems yielded solid solutions of jarosites with chemical compositions that were dependent on the relative concentrations of Na+ and NH4+ in the synthesis media. No phase separations involving discrete, end-member Na-, NH4-, or H3O-jarosites were detected.

Recovery of phosphorus from source separated urine by Acidithiobacillus ferrooxidans culture supernatant

In the present study, Acidithiobacillus ferrooxidans (At. ferrooxidans) culture supernatant was used for phosphate (PO43−) removal and recovery from source separated urine. The results indicated that the solution pH and ferric ion (Fe3+) concentration influenced the PO43− precipitation. The 5.6 pH was found optimum for PO43− recovery. An increase in Fe3+ concentration increased PO43− recovery. Recovered iron phosphate (FePO4) was characterized by X-ray diffraction (XRD), and scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDX). Source separated urine can be a renewable source for phosphate recovery using At. ferrooxidans culture supernatant. This will help in sustainable agricultural development.

Fate of extracellular polymeric substances of anaerobically digested sewage sludge during pre-dewatering conditioning with Acidithiobacillus ferrooxidans culture

This study investigated the fate of extracellular polymeric substances (EPS) of anaerobically digested saline sewage sludge during its preconditioning. Sludge was conditioned with Acidithiobacillus ferrooxidans (AF) culture for 24h in the presence and absence of Fe2+ as an energy substrate. pH decreased from 7.24 to 3.12 during sludge conditioning process. The capillary suction time (CST) of conditioned sludge significantly decreased to <10s, and specific resistance to filtration (SRF) was reduced by >94% as compared with control within 4h of conditioning with or without Fe2+, indicating a significant (P<0.001) improvement in sludge dewaterability. A noticeable decrease in extractable EPS was observed in conditioned sludge. The EPS contents showed a significant negative correlation with dewaterability of sludge (P<0.05). The results suggest that bioacidification treatment using A. ferrooxidans effectively improved sludge dewaterability through modification of sludge EPS.

Natural Organic Matter Affects the Treatment of Mine Tailings through Bioleaching Processes

In the present study, the effects of natural organic matter (NOM) on metal bioleaching from mine tailings were investigated. NOM can enter into the bioleaching process either through mine tailings being exposed in the natural ground surface conditions or through the water quality in the bioleaching process. An analysis of the conditions resembling the interaction between NOM and mine tailings was conducted through the variation of the concentration of suspended NOM (0, 20, 50 ppm) and the amount of NOM (0, 20, 50 ppm) attached to the mine tailings surface. Different concentrations of Suwannee River Humic Acid (SRHA) were considered as the main source of NOM for the bioleaching experiments. The flask experiments were conducted using bacterial cultures of Acidithiobacillus ferrooxidans (1x107 cells/mL) grown in DSMZ medium 882 at a constant temperature of 30 °C, shaking speed of 150 rpm, and 1.8 as initial pH. The solid concentration was fixed at 0.5 % w/v of mine tailings (particle size of 100-150 µm), which were obtained from Janggun Mine, Gyeongsang, South Korea. No differences in extraction efficiency were observed in relation to variation of NOM concentration (0–50 ppm SRHA) attached to the surface of mine tailings. On the other hand, a reduction of approximately 10% to 15% of metal bioleaching efficiency (Zn) was observed due to the increment of suspended NOM concentrations, 20 and 50 ppm of SRHA, respectively.

Critical values of the volumetric oxygen transfer coefficient and oxygen concentration that prevent oxygen limitation in ferrous iron and elemental sulfur oxidation by Acidithiobacillus ferrooxidans

Biochemical and biotechnological aspects of aeration conditions in iron- and sulfur-oxidizing Acidithiobacillus ferrooxidans cultures were studied. The critical values of volumetric oxygen transfer coefficient, (kLa)crit, and oxygen concentration, Ccrit, were used to define the conditions necessary for minimum aeration and to eliminate potential oxygen limitation during substrate oxidation by the model bioleaching culture. The Michaelis constants for oxygen were 1.07 and 0.61μmol O2 l−1 for the oxidation of ferrous iron and elemental sulfur, respectively. The Ccrit values, below which oxygen limitation may occur, were 6.250 and 3.125μmol O2 l−1, determined in respirometric experiments for the oxidation of ferrous iron and elemental sulfur, respectively. The rates of iron and sulfur oxidation were also determined at the Ccrit values by measuring the formation of ferric iron and protons in the corresponding cell suspensions. Neither iron nor sulfur oxidation was limited by oxygen at Ccrit. The (kLa)crit values required to maintain oxygen-unlimited oxidation of ferrous iron and elemental sulfur were 7.70 and 4.88h−1, respectively.

Experimental Study of Microbial Pyrite Oxidation: A Suggestion for Geologically Useful Biosignatures

The oxidation of pyrite in cultures of Acidithiobacillus ferrooxidans (A.f) was studied. The experiments were performed at an initial pH of 2.5 at 28°C. The concentrations of total dissolved iron in solution and the pH were monitored during the first 36 days. Pyrite surfaces were examined by scanning electron microscopy and energy-dispersive spectrometry (SEM-EDS) after 100 days. The concentrations of total dissolved iron and hydrogen ions increased significantly in the presence of bacteria. SEM examination indicated that the crystal surfaces were subjected to two types of dissolution phenomena. Cracks were observable on the of crystal surfaces under both biotic and abiotic conditions, whereas rounded and polygonal pits appeared additionally on the surfaces under biotic conditions. The co-occurrence of the rounded and polygonal pits on the crystal surfaces and the presence of A.f at the pyrite surface suggests that A.f promotes pyrite oxidation by a contact mechanism. We propose that the rounded and polygonal pits be considered to represent a practical biosignature for tracing the evolution of microbial iron oxidation in the remote past.

Synthesis and properties of ternary (K, NH4, H3O)-jarosites precipitated from Acidithiobacillus ferrooxidans cultures in simulated bioleaching solutions

The purpose of this study was to synthesize a series of solid solution jarosites by biological oxidation of ferrous iron at pH2.2–4.4 and ambient temperature in media containing mixtures of K+ (0, 1, 4, 6, 12, 31mM) and NH4+ (6.1, 80, 160, 320mM). The starting material was a liquid medium for Acidithiobacillus ferrooxidans comprised of 120mM FeSO4 solution and mineral salts at pH2.2. Following inoculation with A. ferrooxidans, the cultures were incubated in shake flasks at 22°C. As bacteria oxidized ferrous iron, ferric iron hydrolyzed and precipitated as jarosite-group minerals (AFe3(SO4)2(OH)6) and/or schwertmannite (idealized formula Fe8O8(OH)6(SO4)·nH2O). The precipitates were characterized by X-ray diffraction (XRD), elemental analysis, and Munsell color. Schwertmannite was the dominant mineral product at low combinations of K+ (≤4mM) and NH4+ (≤80mM) in the media. At higher single or combined concentrations, yellowish jarosite phases were produced, and Munsell hue provided a sensitive means of detecting minor schwertmannite in the oxidation products. Although the hydrated ionic radii of K+ and NH4+ are similar, K+ greatly facilitated the formation of a jarosite phase compared to NH4+. Unit cell and cell volume calculations from refinements of the powder XRD patterns indicated that the jarosite phases produced were mostly ternary (K, NH4, H3O)-solid solutions that were also deficient in structural Fe, especially at low NH4 contents. Thus, ferric iron precipitation from the simulated bioleaching systems yielded solid solutions of jarosite with chemical compositions that were dependent on the relative concentrations of K+ and NH4+ in the synthesis media. No phase separations involving discrete, end-member K-jarosite or NH4-jarosite were detected in the un-aged precipitates.

Microbial community shifts during the process of marmatite bioleaching

Predefined mixed cultures of Acidithiobacillus ferrooxidans, Acidithiobacillus caldus and Acidithiobacillus thiooxidans strains were used to stimulate marmatite bioleaching under different temperatures. Changes in this simple bacterial community over time during the leaching process were evaluated using denaturing gradient gel electrophoresis (DGGE) analysis of PCR-amplified 16S rRNA gene fragments. A. ferrooxidans and A. caldus were detected in all samples taken at 5-d intervals during a 41–46days bioleaching process. The presence of A. thiooxidans in the initial inoculum stimulated bioleaching, however the relative population of A. thiooxidans gradually declined, and this species was not detected after 30day (at 30°C) or 15days (at 35°C). Scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDX) analyses revealed the production of S0 and jarosite during bioleaching. Bacteria were observed to be attached to mineral surfaces. Results suggested that A. ferrooxidans and A. caldus together could perform marmatite bioleaching, and that A. thiooxidans could promote the bioleaching of marmatite by A. ferrooxidans and A. caldus. This study improves the understanding of marmatite bioleaching at different temperatures.

Enhanced dewaterability of anaerobically digested sewage sludge using Acidithiobacillus ferrooxidans culture as sludge conditioner

Role of Acidithiobacillus ferrooxidans culture in bioacidification and dewaterability of anaerobically digested sewage sludge (ADS) was investigated. A. ferrooxidans culture grown in 9K medium along with Fe2+ produced iron flocculant containing, secondary iron minerals and biopolymeric substances as confirmed by FT-IR, XRD, and SEM-EDX. Bioacidification of ADS was performed using 10% (v/v) A. ferrooxidans culture, isolated cells and cell-free culture filtrate; and dewaterability was assessed using the capillary suction time (CST) and specific resistance to filtration (SRF). Isolated bacterial cells significantly (P<0.05) reduced the sludge dewaterability when supplemented with Fe2+ while the whole culture and cell-free filtrate rapidly acidified the sludge without Fe2+ and showed significant reduction of CST (71.3–73.5%) and SRF (84–88%). Results clearly indicated that the culture and filtrate of the A. ferrooxidans facilitated rapid sludge dewaterability while the cells supplemented with Fe2+ also enhanced dewaterability but required 2–4days.

Fate of extracellular polymeric substances during flocculation of anaerobically digested sludge using biogenic flocculant

This study investigated the fate of extracellular polymeric substances (EPS) of anaerobically digested saline sewage sludge during its conditioning with a biogenic flocculant produced by Acidithiobacillus ferrooxidans culture before dewatering. Sludge was conditioned for 24h with the biogenic flocculant in presence and absence of Fe2+ as energy substrate. During the sludge conditioning process, pH dropped from 7.24 to 3.12. The capillary suction time of sludge was <10s and specific resistance to filtration (SRF) was reduced by more than 94% of its original SRF in the biogenic flocculent treatments within 4h of incubation with or without FeSO4 indicating a significant (P<0.001) improvement in sludge dewaterability. A significant decrease in extractable EPS was observed in treatments with biogenic flocculant and the EPS contents showed a significant negative correlation with dewaterability of sludge (P<0.05). The results suggest that the biogenic flocculant effectively improved sludge dewaterability through modification of sludge EPS.

Minimum Aeration in &lt;i&gt;Acidithiobacillus ferrooxidans&lt;/i&gt; Cultures Required to Maintain Substrate Oxidation without Oxygen Limitation

The volumetric oxygen transfer coefficient (kLa) was used to define the conditions necessary for minimum aeration and to eliminate potential oxygen limitation in bioleaching cultures ofAcidithiobacillus ferrooxidans. The Michaelis constants for oxygen were 1.07 and 0.71 μmol O2l-1for the oxidation of ferrous iron and elemental sulphur, respectively. The critical oxygen concentration, below which oxygen limitation occurred, was determined to be 6.25 and 3.125 μmol O2l-1for the oxidation of ferrous iron and elemental sulphur, respectively. The (kLa)critvalues required to maintain oxygen-unlimited substrate oxidation for ferrous iron and elemental sulphur were 7.70 and 4.88 h-1, respectively.

Solid-phase controls on lead partitioning in laboratory bioleaching solutions

The purpose of the work was to examine the co-precipitation of Fe(III) and Pb(II) in Acidithiobacillus ferrooxidans cultures under ambient temperature conditions. The competitive formation of plumbojarosite (PbFe6(SO4)4(OH)12) and anglesite (PbSO4) was of particular interest with respect to defining the phase(s) controlling Pb solubility. The medium contained no K+ and a low level of 6.06mM NH4+. Precipitates were prepared in two phases. In the first phase (8days), A. ferrooxidans cultures oxidized ferrous iron to ferric iron (pH2.4), which partially precipitated as schwertmannite (Fe8O8(OH)5.5(SO4)1.25). In the second phase, lead nitrate (up to 100mmol Pb/l) was added to the schwertmannite-containing culture solutions, and the suspensions were held for an additional 22days. X-ray diffraction analysis indicated that lead precipitated as anglesite, and ferric iron was associated with schwertmannite and hydronium jarosite. No characteristic X-ray diffraction peaks for plumbojarosite were evident.

Cellular ATP Changes in Acidithiobacillus ferrooxidans Cultures Oxidizing Ferrous Iron and Elemental Sulfur

Cellular ATP content of Acidithiobacillus ferrooxidans cultures was determined with a bioluminescence assay in relation to batch growth and oxidation of ferrous iron and elemental sulfur. Inhibitory effects of inorganic substrates and products on luciferase were eliminated. Extracellular ATP levels were negligible. The ATP content of sulfur-grown cells decreased anomalously due to a culture pH increase at the stationary phase. Although the rates of growth and sulfur oxidation reached the original levels, the ATP content of the culture remained constant because of gradual decrease in the cellular ATP. The maximum ATP levels in A. ferrooxidans grown with Fe2+ and S0 were 1.16 and 0.33 amol per cell, respectively. The results defined conditions under which biomass growth could be monitored by the ATP assay to study biogeochemical activities of acidophilic iron- and sulfur-oxidizing bacteria.

Extraction of silver from spent silver oxide–zinc button cells by using Acidithiobacillus ferrooxidans culture supernatant

Abstract The silver extraction from spent silver oxide–zinc button cell battery was investigated by using Acidithiobacillus ferrooxidans ( A. ferrooxidans ) culture supernatant. Parameters such as duration of leaching, volume of culture supernatant, pH, initial shaking speed, and temperature were optimized for the silver extraction. About 98% silver was dissolved in 1 h, at an initial pH of 2.5, 30 °C temperature, 150 rpm shaking speed and by using 50 mL culture supernatant. The use of only culture supernatant for silver extraction indicated that an indirect non-contact leaching was the predominant mechanism for metal solubilization. There was no need for bacteria themselves to be present for the silver extraction. Hence the role of A. ferrooxidans was most likely to regenerate Fe 3+ as an oxidant. The reported method could be considered the first step to recycle spent silver oxide–zinc button cell batteries to overcome pollution problems.

Bioflotation of sulfide minerals with Acidithiobacillus ferrooxidans in relation to copper activation and surface oxidation

Surface oxidation of sulfides and copper (Cu) activation are 2 of the main processes that determine the efficiency of flotation. The present study was developed with the intention to ascertain the role of the phenomena in the biomodification of sulfides by Acidithiobacillus ferrooxidans culture (cells and growth media) and their impact in bioflotation. Surface characteristics of chalcopyrite, sphalerite, and pyrrhotite, alone and in mixtures, after interaction with A.ferrooxidans were evaluated. Chalcopyrite floatability was increased substantially by biomodification, while bacteria depressed pyrrhotite floatability, favoring separation. The results showed that elemental sulfur concentration increased because of the oxidation generated by bacterial cells, the effect is intensified by the Fe(III) left in the culture and by galvanic contact. Acidithiobacillus ferrooxidans culture affects the Cu activation of sphalerite. The implications of elemental sulfur concentration and Cu activation of sphalerite are key factors that must be considered for the future development of sulfide bioflotation processes, since the depressive effect of cells could be counteracted by elemental sulfur generation.