The variation of main parameters including ion concentration, pH value, potential and biomass was examined in bioleaching pyrite. The pH value of the solution decreased obviously. Most of T.ferrooxidans adhered to the...The variation of main parameters including ion concentration, pH value, potential and biomass was examined in bioleaching pyrite. The pH value of the solution decreased obviously. Most of T.ferrooxidans adhered to the surface of pyrite. The surface properties of pyrite and leached products were determined by SEM, EDS and XRD. Pyrite was corroded selectively by T.ferrooxidans and sulfur in pyrite was leached preferentially. The primary product for bioleaching pyrite was jarosite. Based on these results, it can be found that pyrite is oxidized mainly through the direct role of T.ferrooxidans . A band model for bioleaching pyrite was built, by which the bioleaching process was explained theoretically. The model shows that the holes, which are injected into the valence band of pyrite through adhered T.ferrooxidans , result from dissolved oxygen in the solution.展开更多
Coenzyme Q10 (CoQ10), an important antioxidant molecule playing a major role in electron transport chain, has been commercially produced by fermentation process for the use in oral nutraceutical formulations. Construc...Coenzyme Q10 (CoQ10), an important antioxidant molecule playing a major role in electron transport chain, has been commercially produced by fermentation process for the use in oral nutraceutical formulations. Constructing the high-yielding CoQ10 producing strains is a pre-requisite for cost-effective production. A superior mutant strain P-87 generated from Paracoccus denitrificans ATCC 19367, which showed 1.25-fold improvement in specific CoQ10 content higher than the wild type strain at shake flask level, was selected to carry out the studies on CoQ10 yield improvement through fermenter process optimization. In the course of study, initially the cane-molasses-based medium and fed-batch fermentation strategy using pHBA in combination with sucrose were standardized in shake flask using wild type strain. This strategy was subsequently translated at 2 L laboratory fermenter while optimizing the fermentation process parameters using improved mutant strain P-87. Under optimized fermentation condition, mutant strain P-87 produced 49.85 mg/L of CoQ10 having specific content of 1.63 mg/g of DCW, which was 1.36 folds higher than the specific CoQ10 content of wild-type strain under similar optimized condition. The temperature and DO were found to be critical parameters for CoQ10 production by mutant strain P-87. The optimum temperature was found to be 32°C and the optimum DO concentration to be maintained throughout the fermentation cycle was found to be 30% of air saturation. Overall, a new cost-effective process has been established for the production of CoQ10 using the cheaper substrate “cane molasses” and higher CoQ10 producing mutant strain P-87.展开更多
Thiobacillus ferrooxidans might be the most important bacteria used in biometallurgy. The foundation way of its growth process is oxidizing ferrous in order to obtain energy needed for metabolism, but the variation of...Thiobacillus ferrooxidans might be the most important bacteria used in biometallurgy. The foundation way of its growth process is oxidizing ferrous in order to obtain energy needed for metabolism, but the variation of ferrous concentration and mixed potential of the culture media would have crucial effect on the bacteria growth. Based on the characteristics of Thiobacillus ferrooxidans growth and redox potential of ferric and ferrous, an electrochemical cell was designed conventionally to study growth rule and the relationship between redox potential and bacteria growth was built up, and some growth kinetics of Thiobacillus ferrooxidans were elucidated. It demonstrates that the variation of open potential of electrochemical cell Δ E shows the growth tendency of Thiobacillus ferrooxidans , at the initial growth stage, the value of Δ E increases slowly, when at logistic growth stage, it increases drastically, and the growth rate of bacteria is linear with the oxidation rate of ferrous. The bacteria growth kinetics model is proposed using Monod and Michealis-Menten equation, and the kinetics parameters are got. The consistence of the measured and the calculated results proves that it is proper to use the proposed kinetics model and the electrochemical cell method to describe the growth rule of Thiobacillus ferrooxidans .展开更多
The variation of main parameters was examined in bioleaching arsenopyrite, such as arsenic concentration, solution pH value, potential and biomass. Solution pH value decreased slightly and few T ferrooxidans adhered t...The variation of main parameters was examined in bioleaching arsenopyrite, such as arsenic concentration, solution pH value, potential and biomass. Solution pH value decreased slightly and few T ferrooxidans adhered to the surface of arsenopyrite. The surface properties of arsenopyrite and leached products were determined by using modern measurement techniques including SEM, EDS and XRD. The corrosion characteristic of arsenopyrite surface is of uniformity, and arsenic in arsenopyrite was preferential to be dissolved. Element sulfur, jarosite and scorodite are the primary products in bioleaching arsenopyrite. It can be drown from above that arsenopyrite is oxidized mainly through the indirect role of T ferrooxidans. A band model for bioleaching arsenopyrite was built, by which illustrated the bioleaching process theoretically. The model shows that the holes, which are provided by ferric ion, inject into the valence band of arsenopyrite to result in the dissolution of arsenopyrite.展开更多
The corrosion behaviors of steel A3 in synergistic action of Thiobacillus ferrooxidans(T.f)and electrochemically accelerated corrosion were studied by electrochemical,microbiology and surface analysis methods.The open...The corrosion behaviors of steel A3 in synergistic action of Thiobacillus ferrooxidans(T.f)and electrochemically accelerated corrosion were studied by electrochemical,microbiology and surface analysis methods.The open circuit potential(E_(ocp))and electrochemical impedance spectroscopy(EIS)of the steel A3 electrodes were measured in leathen culture medium without and with T.f(simply called T.f solution in the following paper) in immersion electrode way at the time of the 2nd,5th,10th,20th and 30th days,respectively.It was found that E_(ocp) of the electrode for immersion in leathen culture medium shifted negatively with the immersion time while that for immersion in T.f solutions shifted negatively,then positively and finally negatively.On the 20th day,the corrosion of steel A3 for immersion in culture medium was in pitting initiation stage while that for immersion in T.f solutions was in pitting growth stage.It was found that the corrosion of steel A3 was accelerated by T.f.The morphology of corrosion product of steel A3 immersion in T.f solutions observed through scanning electron microscopy(SEM)transformed from solid globules to tabular plates and to spongy globules and plates.展开更多
Through the study by electronic probe it was found that many new cracks and holes appear on the surface of gold bearing arsenopyrite crystal oxidized by Thiobacillus ferrooxidans, which are along with some directions....Through the study by electronic probe it was found that many new cracks and holes appear on the surface of gold bearing arsenopyrite crystal oxidized by Thiobacillus ferrooxidans, which are along with some directions. Then the selective bio oxidation model of gold bearing arsenopyrite was set up. The selective bio oxidation resulting from the submicro battery effect of gold/ arsenopyrite mineral pairs naturally forms in the gold bearing arsenopyrite crystal. Thiobacillus ferrooxidans has priority to oxidize the place of gold rich and oxidizes selectedly along with the crystal border, crystal face and crack. The bacteria oxidation process of gold bearing arsenopyrite is divided into three stages: the first stage is the surface oxidation, the second stage is restraining oxidation and the third stage is the filament oxidation, bacteria oxidize along with cracks of arsenopyrite.展开更多
By using thiobacillus ferrooxidans (T.f) from Qixiashan, Hubei Province, China, the adsorption characteristics of T.f on surface of sulfide mineral were studied. The influences of adsorption time, pH value, temperatur...By using thiobacillus ferrooxidans (T.f) from Qixiashan, Hubei Province, China, the adsorption characteristics of T.f on surface of sulfide mineral were studied. The influences of adsorption time, pH value, temperature, initial inoculated concentration of bacteria, concentration of sulfide mineral powder, and variety of minerals on the adsorption characteristics were firstly investigated by using the ninhydrin colorimetric method, and the changes of contact angles and Zeta potentials of mineral surface during the bacterial adsorption were then determined. The results show that when the leaching experiments are performed for a long time from several days to a month, the maximal quantity of adsorption of T.f on the surface of pyrite is obtained under the following conditions: leaching for 20 d, pH value in range of 12 and temperature at 30 ℃, respectively; when the bio-leaching experiments are performed for a shorter leaching time, the maximal quantity of adsorption is obtained under the conditions: bio-leaching for 2 h, at 2.4×107 cell/mLof initial inoculated bacteria concentration, and at 10% of mineral powder concentration; and the adsorption quantities are different form one sulfide mineral to another, and the adsorption of T.f on the surface of sulfide minerals includes three phases: increasing phase, stationary phase and decreasing phase.展开更多
1 Introduction Radioactive pollution is increasingly serious and radioactive pollution can not be repaired immediately once it breaks out.Strontium contamination is a research hot point as one of the typical radioacti...1 Introduction Radioactive pollution is increasingly serious and radioactive pollution can not be repaired immediately once it breaks out.Strontium contamination is a research hot point as one of the typical radioactive pollution。展开更多
A new method of processing and manufacturing certain parts of instruments through biological approach is studied.Knowledge of feasibility of micro-manufacturing is obtained by comparing experimental results of etching...A new method of processing and manufacturing certain parts of instruments through biological approach is studied.Knowledge of feasibility of micro-manufacturing is obtained by comparing experimental results of etching surfaces of copper,aluminium alloy,brass,steel and stainless steel using strain of Thiobacillus ferrooxidans(T.f.).Our experimental results show that certain metals can be etched using T.f.,the most feasible material is copper,followed by brass,etc.,with stainless steel the least.The surface of the stainless steel material is nearly unchanged during surface-etching.Micro parts made of copper or brass can be satisfactorily processed with T.f.and the rate of processing on copper is about 14 μm/h.Furthermore,surface roughness and processing speed are controlled by pH value and temperature of etching liquid,in addition to swing rate of the the swing bed.展开更多
The experimental studies on the microbial flotation of a pure pyrite sample using Thiobacillus ferrooxidans was conducted in the laboratory.The results indicate that Thiobacillus ferrooxidans has strong depression eff...The experimental studies on the microbial flotation of a pure pyrite sample using Thiobacillus ferrooxidans was conducted in the laboratory.The results indicate that Thiobacillus ferrooxidans has strong depression effect on the flotation of pyrite.Thiobacillus ferrooxidans can adsorb on the surface of pyrite in a very short time (a few min.),changing the surface from hydrophobic into hydrophilic and making the pyrite particles to lose their floatability.Therefore, Thiobacillus ferrooxidans is an effective microbial depressant of pyrite.It has also been pointed out that the depression of pyrite by Thiobacillus ferrooxidans is caused by the adsorption of the microbial colloids, but not by the oxidation effect.展开更多
Bioflotation of pyrite with bacteria Thiobacillus ferrooxidans in the presence or absence of potassium ethyl xanthate was studied on a pure pyrite through microflotation and electrophoretic light scattering measuremen...Bioflotation of pyrite with bacteria Thiobacillus ferrooxidans in the presence or absence of potassium ethyl xanthate was studied on a pure pyrite through microflotation and electrophoretic light scattering measurements. The experimental results showed that in the absence of xanthate, pyrite flotation is slightly enhanced by Thiobacillus ferrooxidans. However, with xanthate as a collector, pyrite flotation is strongly depressed after being exposed to the bacteria. The longer is the time when the pyrite is exposed to the bacteria, the stronger the depression is. The mechanism of the depression might be due to the formation of the biofilms of Thiobacillus ferrooxidans on pyrite surfaces, preventing the adsorption of xanthate on pyrite surfaces in the form of dixanthogen or xanthate ions.展开更多
文摘The variation of main parameters including ion concentration, pH value, potential and biomass was examined in bioleaching pyrite. The pH value of the solution decreased obviously. Most of T.ferrooxidans adhered to the surface of pyrite. The surface properties of pyrite and leached products were determined by SEM, EDS and XRD. Pyrite was corroded selectively by T.ferrooxidans and sulfur in pyrite was leached preferentially. The primary product for bioleaching pyrite was jarosite. Based on these results, it can be found that pyrite is oxidized mainly through the direct role of T.ferrooxidans . A band model for bioleaching pyrite was built, by which the bioleaching process was explained theoretically. The model shows that the holes, which are injected into the valence band of pyrite through adhered T.ferrooxidans , result from dissolved oxygen in the solution.
文摘Coenzyme Q10 (CoQ10), an important antioxidant molecule playing a major role in electron transport chain, has been commercially produced by fermentation process for the use in oral nutraceutical formulations. Constructing the high-yielding CoQ10 producing strains is a pre-requisite for cost-effective production. A superior mutant strain P-87 generated from Paracoccus denitrificans ATCC 19367, which showed 1.25-fold improvement in specific CoQ10 content higher than the wild type strain at shake flask level, was selected to carry out the studies on CoQ10 yield improvement through fermenter process optimization. In the course of study, initially the cane-molasses-based medium and fed-batch fermentation strategy using pHBA in combination with sucrose were standardized in shake flask using wild type strain. This strategy was subsequently translated at 2 L laboratory fermenter while optimizing the fermentation process parameters using improved mutant strain P-87. Under optimized fermentation condition, mutant strain P-87 produced 49.85 mg/L of CoQ10 having specific content of 1.63 mg/g of DCW, which was 1.36 folds higher than the specific CoQ10 content of wild-type strain under similar optimized condition. The temperature and DO were found to be critical parameters for CoQ10 production by mutant strain P-87. The optimum temperature was found to be 32°C and the optimum DO concentration to be maintained throughout the fermentation cycle was found to be 30% of air saturation. Overall, a new cost-effective process has been established for the production of CoQ10 using the cheaper substrate “cane molasses” and higher CoQ10 producing mutant strain P-87.
文摘Thiobacillus ferrooxidans might be the most important bacteria used in biometallurgy. The foundation way of its growth process is oxidizing ferrous in order to obtain energy needed for metabolism, but the variation of ferrous concentration and mixed potential of the culture media would have crucial effect on the bacteria growth. Based on the characteristics of Thiobacillus ferrooxidans growth and redox potential of ferric and ferrous, an electrochemical cell was designed conventionally to study growth rule and the relationship between redox potential and bacteria growth was built up, and some growth kinetics of Thiobacillus ferrooxidans were elucidated. It demonstrates that the variation of open potential of electrochemical cell Δ E shows the growth tendency of Thiobacillus ferrooxidans , at the initial growth stage, the value of Δ E increases slowly, when at logistic growth stage, it increases drastically, and the growth rate of bacteria is linear with the oxidation rate of ferrous. The bacteria growth kinetics model is proposed using Monod and Michealis-Menten equation, and the kinetics parameters are got. The consistence of the measured and the calculated results proves that it is proper to use the proposed kinetics model and the electrochemical cell method to describe the growth rule of Thiobacillus ferrooxidans .
文摘The variation of main parameters was examined in bioleaching arsenopyrite, such as arsenic concentration, solution pH value, potential and biomass. Solution pH value decreased slightly and few T ferrooxidans adhered to the surface of arsenopyrite. The surface properties of arsenopyrite and leached products were determined by using modern measurement techniques including SEM, EDS and XRD. The corrosion characteristic of arsenopyrite surface is of uniformity, and arsenic in arsenopyrite was preferential to be dissolved. Element sulfur, jarosite and scorodite are the primary products in bioleaching arsenopyrite. It can be drown from above that arsenopyrite is oxidized mainly through the indirect role of T ferrooxidans. A band model for bioleaching arsenopyrite was built, by which illustrated the bioleaching process theoretically. The model shows that the holes, which are provided by ferric ion, inject into the valence band of arsenopyrite to result in the dissolution of arsenopyrite.
文摘The corrosion behaviors of steel A3 in synergistic action of Thiobacillus ferrooxidans(T.f)and electrochemically accelerated corrosion were studied by electrochemical,microbiology and surface analysis methods.The open circuit potential(E_(ocp))and electrochemical impedance spectroscopy(EIS)of the steel A3 electrodes were measured in leathen culture medium without and with T.f(simply called T.f solution in the following paper) in immersion electrode way at the time of the 2nd,5th,10th,20th and 30th days,respectively.It was found that E_(ocp) of the electrode for immersion in leathen culture medium shifted negatively with the immersion time while that for immersion in T.f solutions shifted negatively,then positively and finally negatively.On the 20th day,the corrosion of steel A3 for immersion in culture medium was in pitting initiation stage while that for immersion in T.f solutions was in pitting growth stage.It was found that the corrosion of steel A3 was accelerated by T.f.The morphology of corrosion product of steel A3 immersion in T.f solutions observed through scanning electron microscopy(SEM)transformed from solid globules to tabular plates and to spongy globules and plates.
文摘Through the study by electronic probe it was found that many new cracks and holes appear on the surface of gold bearing arsenopyrite crystal oxidized by Thiobacillus ferrooxidans, which are along with some directions. Then the selective bio oxidation model of gold bearing arsenopyrite was set up. The selective bio oxidation resulting from the submicro battery effect of gold/ arsenopyrite mineral pairs naturally forms in the gold bearing arsenopyrite crystal. Thiobacillus ferrooxidans has priority to oxidize the place of gold rich and oxidizes selectedly along with the crystal border, crystal face and crack. The bacteria oxidation process of gold bearing arsenopyrite is divided into three stages: the first stage is the surface oxidation, the second stage is restraining oxidation and the third stage is the filament oxidation, bacteria oxidize along with cracks of arsenopyrite.
文摘By using thiobacillus ferrooxidans (T.f) from Qixiashan, Hubei Province, China, the adsorption characteristics of T.f on surface of sulfide mineral were studied. The influences of adsorption time, pH value, temperature, initial inoculated concentration of bacteria, concentration of sulfide mineral powder, and variety of minerals on the adsorption characteristics were firstly investigated by using the ninhydrin colorimetric method, and the changes of contact angles and Zeta potentials of mineral surface during the bacterial adsorption were then determined. The results show that when the leaching experiments are performed for a long time from several days to a month, the maximal quantity of adsorption of T.f on the surface of pyrite is obtained under the following conditions: leaching for 20 d, pH value in range of 12 and temperature at 30 ℃, respectively; when the bio-leaching experiments are performed for a shorter leaching time, the maximal quantity of adsorption is obtained under the conditions: bio-leaching for 2 h, at 2.4×107 cell/mLof initial inoculated bacteria concentration, and at 10% of mineral powder concentration; and the adsorption quantities are different form one sulfide mineral to another, and the adsorption of T.f on the surface of sulfide minerals includes three phases: increasing phase, stationary phase and decreasing phase.
基金supported by the National Natural Science Foundation of China“The study on size effect of respirable mineral fine particles and common bacteria research (No. 40072020)
文摘1 Introduction Radioactive pollution is increasingly serious and radioactive pollution can not be repaired immediately once it breaks out.Strontium contamination is a research hot point as one of the typical radioactive pollution。
基金Sponsored by the Ministerial Level Advanced Research Foundation(631092)
文摘A new method of processing and manufacturing certain parts of instruments through biological approach is studied.Knowledge of feasibility of micro-manufacturing is obtained by comparing experimental results of etching surfaces of copper,aluminium alloy,brass,steel and stainless steel using strain of Thiobacillus ferrooxidans(T.f.).Our experimental results show that certain metals can be etched using T.f.,the most feasible material is copper,followed by brass,etc.,with stainless steel the least.The surface of the stainless steel material is nearly unchanged during surface-etching.Micro parts made of copper or brass can be satisfactorily processed with T.f.and the rate of processing on copper is about 14 μm/h.Furthermore,surface roughness and processing speed are controlled by pH value and temperature of etching liquid,in addition to swing rate of the the swing bed.
文摘The experimental studies on the microbial flotation of a pure pyrite sample using Thiobacillus ferrooxidans was conducted in the laboratory.The results indicate that Thiobacillus ferrooxidans has strong depression effect on the flotation of pyrite.Thiobacillus ferrooxidans can adsorb on the surface of pyrite in a very short time (a few min.),changing the surface from hydrophobic into hydrophilic and making the pyrite particles to lose their floatability.Therefore, Thiobacillus ferrooxidans is an effective microbial depressant of pyrite.It has also been pointed out that the depression of pyrite by Thiobacillus ferrooxidans is caused by the adsorption of the microbial colloids, but not by the oxidation effect.
文摘Bioflotation of pyrite with bacteria Thiobacillus ferrooxidans in the presence or absence of potassium ethyl xanthate was studied on a pure pyrite through microflotation and electrophoretic light scattering measurements. The experimental results showed that in the absence of xanthate, pyrite flotation is slightly enhanced by Thiobacillus ferrooxidans. However, with xanthate as a collector, pyrite flotation is strongly depressed after being exposed to the bacteria. The longer is the time when the pyrite is exposed to the bacteria, the stronger the depression is. The mechanism of the depression might be due to the formation of the biofilms of Thiobacillus ferrooxidans on pyrite surfaces, preventing the adsorption of xanthate on pyrite surfaces in the form of dixanthogen or xanthate ions.
