Manzaensis YN-25 Research Articles

Effect of pine oil on the adhesion and biofilm formation of Acidianus manzaensis on chalcopyrite

Pine oil, commonly used as a flotation frother, could affect the bioleaching process. The attachment and biofilm development of acidophiles on metal sulfides were essential for bioleaching. This study focused on the role of pine oil in the early adhesion and biofilm development by Acidianus manzaensis YN-25 on the chalcopyrite surface. It was revealed that pine oil had a negative effect on the adhesion amount of A. manzaensis on the chalcopyrite surface. After having reached adhesion equilibrium, the percentage of attached cells decreased as the concentration of pine oil increased. The addition of pine oil was found to decrease the negative charge of chalcopyrite and cells, resulting in a higher attraction of acid-base interaction energy and total interaction force. This ultimately led to a stronger adhesion force between chalcopyrite and A. manzaensis. While the addition of pine oil initially delayed the formation of cell microcolonies during the first stage of biofilm formation, which ultimately resulted in larger biofilm coverage compared with the control group. The microcolonies on the mineral surface were also larger and the corrosion pits were bigger with the addition of pine oil. Furthermore, the addition of pine oil weakened the passivation effect and promoted the biological dissolution of chalcopyrite. This study offers a better understanding of the effect of pine oil on the bioleaching of chalcopyrite.

Low concentration of Tween-20 enhanced the adhesion and biofilm formation of Acidianus manzaensis YN-25 on chalcopyrite surface

Although Tween-20 was used as an important catalyst to increase chalcopyrite bioleaching rate by acidophiles, the effect of Tween-20 on initial adhesion and biofilm development of acidophiles on chalcopyrite has not been explored until now. Herein, the role of Tween-20 in early attachment behaviors and biofilm development by Acidianus manzaensis strain YN-25 were investigated by adhesion experiments, adhesion force measurement, visualization of biofilm assays and a series of analyses including extended Derjaguin Landau Verwey Overbeek (DLVO) theory, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The bacterial adhesion experiments showed that 2 mg/L of Tween-20 increased the adhesion percentage (by 8%) of A. manzaensis YN-25. Tween-20 could promote the early adhesion of A. manzaensis YN-25 by changing the Lewis acid-base interaction and electrostatic force to increase total interaction energy and adhesion force. Besides, the functional groups on the surface of cells (carboxyl, hydroxyl and amino functional groups) contributed to the adhesion of A. manzaensis YN-25 on chalcopyrite. Furthermore, the promotion of biofilm formation by Tween-20 was mainly attributed to the reduction of S0 passivation layer formation and complexing more Fe3+ on chalcopyrite surface, contributing to the erosion of chalcopyrite and creating more corrosion pits. Live/dead staining showed low live/dead ratio (ranged from 0.35 to 1.32) during the biofilm development process. This report offers a better understanding of the effects of Tween-20 on attachment and biofilm development of acidophilic microorganisms and would lay a theoretical foundation for the better application of catalyst in bioleaching.

Ag+ significantly promoted the biofilm formation of thermoacidophilic archaeon Acidianus manzaensis YN-25 on chalcopyrite surface

Silver ion (Ag+) is an important catalyst to improve chalcopyrite bio-dissolution, but its effects on initial adhesion behaviors and biofilm formation of acidophiles onto metal sulfide were still unknown. In this study, initial attachment behavior and adhesion force in the presence of Ag+ (0, 1, 2, 5, 10 and 20 mg/L) were comparatively analyzed for Acidianus manzaensis YN-25. Biofilm was observed by fluorescent images in the presence of 0, 1 and 2 mg/L Ag+. X-ray photoelectron spectroscopy (XPS) corroborated the catalytic mechanisms of Ag+ to biofilm formation. Results showed that Ag+ could significantly promote the attachment of cells on chalcopyrite, and the optimum concentration of Ag+ was 2 mg/L with the biggest percentage of attached cells (74%), followed by 5 mg/L (71%), whereas that for the control (0 mg/L) was only 61%. Ag+ significantly increased the interaction force between A. manzaensis YN-25 and chalcopyrite. Compared with the control, larger coverage of biofilm (up to 40% versus 32%) and more corrosion pits were observed on chalcopyrite in the presence of 2 mg/L Ag+. Moreover, Ag+ catalyzed chalcopyrite corrosion and accelerated biofilm formation by producing a loose porous Ag2S layer and Ag0 to decrease the resistivity. The live/dead ratio was small with a range of 0.31–1.38, suggesting that dead cells were a great slice during the whole life-cycle of biofilm on chalcopyrite. This report offers a profound insight into the promotion mechanism of Ag+ on adhesion behaviors and biofilm formation by thermoacidophilic archaeon under extremely acidic conditions.

Comparative analysis of early-stage adsorption and biofilm formation of thermoacidophilic archaeon Acidianus manzaensis YN-25 on chalcopyrite and pyrite surfaces

The early-stage attachment behaviors of acidophiles on mineral surfaces and the subsequent biofilm formation play important roles in acid mine drainage production, and also can improve the leaching efficiency of metal sulfides. However, despite significant advances in correlational researches of mesophilic bacteria, studies on thermoacidophilic archaeon are still limited. In this study, the early attachment behaviors and biofilm formation of the thermoacidophilic archaeon Acidianus manzaensis YN-25 on chalcopyrite and pyrite were investigated. Experiments showed that A. manzaensis YN-25 attached quickly on chalcopyrite and pyrite within a short adsorption equilibrium time of about 20 min. After the adsorption equilibrium, the percentage of attached cells was higher on chalcopyrite than on pyrite (59 % versus 54 %). And the early-stage adsorption of Acidianus manzaensis YN-25 on chalcopyrite and pyrite surfaces was occurred through multilayer adsorption. Also, the measured adhesion forces (0.41 nN versus 0.31 nN) showed more affinity of A. manzaensis YN-25 to chalcopyrite than to pyrite. Furthermore, in the process of biofilm formation, more cells colonized on the chalcopyrite than pyrite, suggesting that the biofilm formation was positively correlated with the initial adhesion. Moreover, during the entire life cycle of A. manzaensis YN-25 biofilm, dead cells have accounted for a big proportion.

Heavy metal ions removed from imitating acid mine drainages with a thermoacidophilic archaea: Acidianus manzaensis YN25.

Metals in acid mine drainages (AMD) have posed a great threat to environment, and in situ economic environment-friendly remediation technologies need to be developed. Moreover, the effects of acidophiles on biosorption and migrating behaviors of metals in AMD have not been previously reported. In this study, the extremely thermoacidophilic Archaea, Acidianus manzaensis YN25 (A. manzaensis YN25) was used as a bio-adsorbent to adsorb metals (Cu2+, Ni2+, Cd2+ and Zn2+) from acidic solutions which were taken to imitate AMD. The values of their maximum biosorption capacities at both high (1mM) and low (0.1mM) metal concentrations followed the order: Cu2+>Ni2+>Cd2+>Zn2+. With the elevations of temperature and pH value, the adsorption amounts of metals increased. The results also indicated that A. manzaensis YN25 had the highest adsorption affinity to Cu2+ in coexisting system of quaternary metals. Acid-base titration data revealed that carboxyl and phosphoryl groups provided adsorption sites for metals via deprotonation. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) further corroborated that amino played an important role in the biosorption process. The fitted Langmuir model illustrated monolayer adsorption occurring on cell surface. The possible adsorption mechanism of A. manzaensis YN25 mainly involved in electrostatic attraction and complexes formation. This study gives a profound insight into the biosorption behavior of heavy metals in acidic solution by thermoacidophilic Archaea and provides a probable novel strategy for in situ remediation of heavy metals pollution in AMD.

Adsorption characteristics of Acidianus manzaensis YN25 on chalcopyrite: Surface thermodynamics and the extended DLVO theory

The adsorption of Acidianus manzaensis YN25 on chalcopyrite was investigated experimentally and theoretically. A. manzaensis showed high adhesion affinity to the chalcopyrite under acidic condition, but low adhesion affinity under neutral and alkaline conditions. The microbe-mineral adhesion was assessed by the surface thermodynamics and the extended DLVO theory. The experimental results were in agreement with the theory. Moreover, A. manzaensis grown on chalcopyrite, sulfur, and ferrous ion showed similar adsorption phenomena. The adsorptive capacity of A. manzaensis increased with increasing temperature and decreasing pH respectively, and within the range of investigation, the best adsorption was achieved at pH 2.0 and 65 °C. This study provided new insights for bio-catalytic oxidation of sulfide minerals by the thermophilic acidophilic archaea.

In situ characterization of change in superficial organic components of thermoacidophilic archaeon Acidianus manzaensis YN-25

For the first time, synchrotron radiation (SR) -based carbon K-edge X-ray absorption near edge structure (XANES) spectroscopy in-situ characterization was conducted to evaluate the evolution of superficial (about 10 nm) organic components of extracellular polymeric substances (EPS) of thermoacidophilic archaeon Acidianus manzaensis YN-25 acclimated with different energy substrates (FeS2, CuFeS2, S0, FeSO4). The atomic force microscopy (AFM) morphology scanning showed that the strain acclimated with different energy substrates varied a lot in EPS amount. XANES results showed clear associations between the energy substrates and the changes in organic composition in terms of typical function groups (CO, CO and CN). The chalcopyrite- and pyrite-acclimated cells contained higher proportion of proteins but less proportion of polysaccharides than the S0-acclimated cells. The FeSO4-acclimated cells contained the highest proportion of proteins, while the S0-acclimated cells contained more lipids and polysaccharides. The results of linear-combination and peak fitting of the K-edge XANES for the extracellular superficial organic component C is consistent with the trend in comparison with the results of FTIR and spectrophotometric determination, but there are significant differences in the values. These differences are caused by the inconsistencies of measurement depth between XANES and the latter two characterization methods.

<i>In Situ</i> Characterization of Superficial Organic Composition Changes of Thermoacidophilic Archaea <i>Acidianus manzaensis</i> YN-25 in Response to Energy Substrate

The differences of superficial (about 10 nm) extracellular polymeric substances (EPS) composition of thermoacidophilic archaea Acidianus manzaensis YN-25 acclimated with different energy substrates (FeS2, CuFeS2, S0, FeSO4) were analyzed in situ for the first time by synchrotron radiation (SR) based carbon K-edge X-ray absorption near edge structure (XANES) spectroscopy. The results showed that there are clear associations between the energy substrates and the changes in organic composition in terms of typical function groups (-C=O, -C-O and -C-N). The archaea acclimated with chalcopyrite and pyrite contain higher proportion of proteins but less polysaccharides compared to cells acclimated with S0.The archaea acclimated with FeSO4 contains the highest proportion of protein which is positively associated with the iron oxidation process, while archaea acclimated with S0 contains more lipids and polysaccharides, which may be favorable to the hydrophobic S0 adsorption and utilization processes.

Bioleaching of chalcopyrite by Acidianus manzaensis under different constant pH

The bioleaching of pure chalcopyrite by thermophilic Archaea strain Acidianus manzaensis YN-25 under different constant pH was first comparatively investigated. Then the relevant sulfur speciation was analyzed by synchrotron radiation based X-ray diffraction (SR-XRD) and S K-edge X-ray absorption near edge structure (XANES) spectroscopy. The acidity of the leaching solution was monitored at 3-h intervals to make it steady at pH 1.25, 1.50, 1.75, 2.00, 2.25 and 2.50, respectively. Leaching results showed that the copper ion extraction increased during chemical leaching but decreased during bioleaching when pH value decreased from 2.50 to 1.25. SR-XRD analysis showed that, during bioleaching, new elemental sulfur (S0) phase was detected at all tested pH cases; new jarosite phase was detected at cases of pH 1.50 to 2.50; and jarosite gradually became a major phase when pH value increased. XANES analysis further showed that covellite was detected during bioleaching at cases of pH 1.25 to 2.00 at higher redox potential (ORP) value, while chalcocite and bornite were detected at cases of pH 2.25 and 2.50 at lower ORP value. These results suggested that the formation of S0 was mainly accounting for hindering the dissolution of chalcopyrite while the formation of bornite could accelerate the dissolution of chalcopyrite by A. manzaensis.

Evidence of cell surface iron speciation of acidophilic iron-oxidizing microorganisms in indirect bioleaching process.

While indirect model has been widely accepted in bioleaching, but the evidence of cell surface iron speciation has not been reported. In the present work the iron speciation on the cell surfaces of four typically acidophilic iron-oxidizing microorganism (mesophilic Acidithiobacillus ferrooxidans ATCC 23270, moderately thermophilic Leptospirillum ferriphilum YSK and Sulfobacillus thermosulfidooxidans St, and extremely thermophilic Acidianus manzaensis YN25) grown on different energy substrates (chalcopyrite, pyrite, ferrous sulfate and elemental sulfur (S(0))) were studied in situ firstly by using synchrotron-based micro- X-ray fluorescence analysis and X-ray absorption near-edge structure spectroscopy. Results showed that the cells grown on iron-containing substrates had apparently higher surface iron content than the cells grown on S(0). Both ferrous iron and ferric iron were detected on the cell surface of all tested AIOMs, and the Fe(II)/Fe(III) ratios of the same microorganism were affected by different energy substrates. The iron distribution and bonding state of single cell of A. manzaensis were then studied in situ by scanning transmission soft X-ray microscopy based on dual-energy contrast analysis and stack analysis. Results showed that the iron species distributed evenly on the cell surface and bonded with amino, carboxyl and hydroxyl groups.

Differential Surface Properties and Iron Distribution of <i>Acidianus manzaensis</i> YN25 Grown on Four Different Energy Substrates

The surface properties and iron distribution of Acidianus manzaensis YN25 grown on four different energy substrates (chalcopyrite, pyrite, S0, and Fe2+) were comparatively studied. The results showed different growth and absorption features of A. manzaensis grown on different energy substrates. Results also showed that Zeta potentials, adsorption forces and cell surface acid-base properties were significantly influenced by the growth condition. Studies based on FT-IR and UV-vis spectroscopy indicated that the differences in cell surface properties may result from the different amounts of proteins and iron distribution on the cell surface of A. manzaensis grown on different growth conditions. The SR-μ-STXM images showed that the cell surface densities of iron spread on the cells grown on chalcopyrite, pyrite, S0 or Fe2+ were 4.31×10-5 - 23.25×10-5 g/cm2, 4.43×10-5 - 20.24×10-5 g/cm2, 0.10×10-5 - 0.29×10-5 g/cm2, and 6.45×10-5 - 24.06×10-5 g/cm2, respectively, further indicating that the surface of A. manzaensis cells grown on chalcopyrite, pyrite and Fe2+ had an iron-contained compounds, which might be the reason why the surface of A. manzaensis cells grown on chalcopyrite, pyrite and Fe2+ carried weak positive charges at pH 2 while negative for the cells grown on S0.

Comparative study of sulfur utilization and speciation transformation of two elemental sulfur species by thermoacidophilic Archaea Acidianus manzaensis YN-25

The sulfur utilization and speciation transformation of two elemental sulfur species (orthorhombic α-S8 and amorphous μ-S) by thermoacidophilic Archaea strain Acidianus manzaensis YN-25 was comparatively studied. The results of cell growth and sulfur oxidation behavior showed that A. manzaensis cultured on μ-S grew faster (about 24h earlier to reach stationary phase than that on α-S8) and produced more H+ and SO42−. Results of scanning electron microscopy indicated that the surfaces of μ-S and α-S8 were differently bio-corroded by A. manzaensis into loose porosities and pits, respectively. Fourier transform-infrared spectroscopy analysis indicated both μ-S and α-S8 were adsorbed by the cells. X-ray diffraction and Raman spectra analysis indicated that μ-S was mostly converted into α-S8 after A. manzaensis cell growth while α-S8 was not transformed into a different allotrope. The fitted result of sulfur K edge XANES spectra further showed that the μ-S after growth of A. manzaensis were composed of 92.1% α-S8 and 7.9% μ-S, while no change in composition for α-S8 was found.

Effect of sodium chloride on sulfur speciation of chalcopyrite bioleached by the extreme thermophile Acidianus manzaensis

The influence of sodium chloride on dissolution of chalcopyrite and surface sulfur speciation during bioleaching of chalcopyrite with the extreme thermophile Acidianus manzaensis YN-25 was studied. The addition of sodium chloride accelerated the dissolution of chalcopyrite by reducing the accumulation of elemental sulfur layers on the mineral surface, resulting in an increase in the concentration of copper ions from 2.37g/L to 2.67g/L. Jarosite and elemental sulfur were found in the bioleached residues, while the amount of elemental sulfur accumulating on the mineral surface decreased drastically from 25.4% to 3.0% when 0.66g/L of sodium chloride was present during bioleaching. Therefore, the accumulation of elemental sulfur on the mineral surface is likely mainly responsible for the slowdown in the dissolution rate. The results indicated that bioleaching chalcopyrite with extreme thermophiles possessing high sulfur oxidation activity likely enhances dissolution of chalcopyrite by effectively removing elemental sulfur accumulating on the mineral surface.

Bioleaching of chalcopyrite with Acidianus manzaensis YN25 under contact and non-contact conditions

In order to investigate the contributions of contact and non-contact cells of Acidianus manzaensis ( A. manzaensis) YN25 to the bioleaching of chalcopyrite, three experiments were carried out in the modified shake flasks. The redox potential, pH, cell density, copper and iron ions in the solution were monitored, and the morphological feature and chemical composition of the leached residues were analyzed. The highest leaching efficiency of Cu and Fe was reached in the experiment where the A. manzaensis YN25 could contact the surface of the chalcopyrite. There was no precipitation of jarosite in the leached residues of three experiments, but there was elemental sulfur in the leached residues when the cells could not contact the chalcopyrite. From these results, it is apparent that the leaching of the chalcopyrite is the cooperative action of the contact and non-contact A. manzaensis YN25.

Effect of activated carbon on chalcopyrite bioleaching with extreme thermophile Acidianus manzaensis

The effect of activated carbon on chalcopyrite bioleaching by extreme thermophile Acidianus manzaensis YN25 at 65 °C was evaluated, together with the investigation of the sulfur speciation transformation on the mineral by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and sulfur K-edge X-ray absorption near edge structure (XANES) spectroscopy. Bioleaching experiments show activated carbon significantly accelerated the dissolution of copper from chalcopyrite concentrate. The optimum concentration of activated carbon enhancing copper dissolution is 2 g/L, under which the copper yields increased from 64% to 95%. The catalysis could mainly be attributed to the galvanic interaction between activated carbon and chalcopyrite. Jarosite, elemental sulfur and chalcocite were detected in the solid phase, and the formation of potassium jarosite was prior to ammonio-jarosite. Activated carbon did not change the species of sulfur-containing compounds, but accelerated the formation of them.

Surface analysis of sulfur speciation on pyrite bioleached by extreme thermophile Acidianus manzaensis using Raman and XANES spectroscopy

Sulfur speciation on the surface of pyrite leached by extreme thermophile Acidianus manzaensis YN-25 was investigated by using scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy and sulfur K-edge X-ray absorption near edge structure spectroscopy (XANES). SEM micrographs showed leaching products with numerous holes were formed into the surface of leached pyrite. XRD spectra indicated that the leach residues were mainly composed of pyrite and jarosite. The sulfur K-edge XANES indicated that elemental sulfur, thiosulfate and/or thiosulfate-like species and jarosite were formed on the mineral surface. Raman spectroscopy further verified the presence of jarosite, elemental sulfur and thiosulfate. Jarosite formed in pyrite leaching appeared much later than in chalcopyrite leaching by the same strain. Jarosite on the mineral surface may account for the passivation of pyrite oxidation, with the passivation effect of elemental sulfur which is less important. In addition, the thiosulfate detected in this study provided novel evidence for surface-bound thiosulfate involved in the stepwise oxidation of pyrite by the extreme thermophile A. manzaensis.

Growth and surface properties of new thermoacidophilic Archaea strain Acidianus manzaensis YN-25 grown on different substrates

The growth and surface properties of new thermoacidophilic Archaea strain Acidianus manzaensis YN-25 isolated from an acid hot spring in Tengchong, Yunnan Province, China were investigated cultured on different substrates including soluble substrate ferrous sulfate and nonsoluble solid substrates S 0, pyrite and chalcopyrite. The growth characteristics of the cells in each substrate were characterized with the changes in cell number, pH, E h, and concentrations of Fe 2+ or SO 4 2−, or ratios of [Fe 2+] to [Fe 3+], and the surface properties were characterized and analyzed in terms of Zeta-potential, hydrophobicity, and surface FT-IR spectra of the cells. The results show that the cells grown on solid substrates have higher value of isoelectric points. They are more hydrophobic and express more surface proteins than ferrous sulfate grown cells.