南通嗜铜菌X1^(T)对丙溴磷手性对映体的选择性降解特性

有机磷杀虫剂已被广泛用于控制农业害虫,其在农产品与环境样本中的残留引起人们的关注。课题组前期筛选了一株有机磷杀虫剂高效降解菌株,南通嗜铜菌X1^(T)(Cupriavidus nantongensis X1^(T))。研究了菌株X1^(T)对手性有机磷杀虫剂丙溴磷对映体在不同底物浓度、菌量、pH、金属离子条件下的降解特性。结果表明,菌株X1^(T)可以优先选择性降解高毒低效对映体S-丙溴磷。随着底物浓度的升高,菌株X1^(T)对丙溴磷对映体的降解速率逐渐减慢;菌株X1^(T)降解丙溴磷的最适pH为7.5;金属离子价态是影响丙溴磷降解的重要影响因素,其中Cr^(3+)与Fe^(3+)等3价金属阳离子显著抑制菌株对丙溴磷降解,Ca^(2+)、Mn^(2+)、Mg^(2+)、Co^(2+)、Ni^(2+)等2价金属阳离子显著促进菌株对S-丙溴磷降解。同时,菌株X1^(T)中降解酶粗酶与异源表达的纯酶对丙溴磷手性对映体的降解速率无显著性差异。结果为丙溴磷残留污染的生物修复技术提供理论依据。

柿竹园某尾矿区嗜铜微生物的初步研究

目的:通过对采集的6层样本(A、B、C、D、E、F)进行嗜铜菌筛选培养及铜离子测定,为筛选嗜铜菌提供依据.方法:利用嗜铜菌筛选培养基和火焰原子吸收光谱法对所采集的样本进行嗜铜菌初筛和铜离子含量测定.结果:共培养出13种嗜铜菌,其中有菌丝的8种,有芽孢的2种,短杆的4种,球状的1种;铜离子含量由第1层至第6层依次递减;初步鉴定为8个土壤微生物菌属.结论:筛选的13种嗜铜菌为嗜铜金属修复工程菌研究奠定了基础,对重金属污染地区的土地复垦和生态植被恢复具有指导意义.

Surface characterization of chalcopyrite interacting with Leptospirillum ferriphilum

The alteration of surface properties of chalcopyrite after biological conditioning with Leptospirillum ferriphilum was studied by adsorption,zeta-potential,contact angle and bioleaching tests.The strains of L.ferriphilum cultured using different energy sources（either soluble ferrous ion or chalcopyrite） were used.The adhesion of bacteria to the chalcopyrite surface was a fast process.Additionally,the adsorption of substrate-grown bacteria was greater and faster than that of liquid-grown ones.The isoelectric point（IEP） of chalcopyrite moved toward that of pure L.ferriphilum after conditioning with bacteria.The chalcopyrite contact angle curves motioned diversely in the culture with or without energy source.The results of X-ray diffraction patterns（XRD）,scanning electron microscopy（SEM） and energy-dispersive X-ray spectroscopy（EDS） analysis indicate that the surface of chalcopyrite is covered with sulfur and jarosite during the bioleaching process by L.ferriphilum.Furthermore,EDS results imply that iron phase dissolves preferentially from chalcopyrite surface during bioleaching.The copper extraction is low,resulting from the formation of a passivation layer on the surface of chalcopyrite.The major component of the passivation layer that blocked continuous copper extraction is sulfur instead of jarosite.

Effect of pH values on extracellular protein and polysaccharide secretions of Acidithiobacillus ferrooxidans during chalcopyrite bioleaching

The effect of pH values on the extracellular protein and polysaccharide secretions of Acidithiobacillus ferrooxidans was comparatively investigated in different phases of bacterial growth during chalcopyrite bioleaching. The results indicate that the extracellular protein is always more than the extracellular polysaccharide secreted by attached cells on the chalcopyrite, on the contrary, and is always less than the extracellular polysaccharide secreted by free cells in the solution at bacterial adaptive phase, logarithmic phase and stationary phase whenever pH value is at 1.0, 1.5, 2.0 or 2.5; free cells are mainly through the secretion of extracellular polysaccharide rather than the extracellular protein to fight against disadvantageous solution environment, such as high concentration of metal ions and unsuitable pH solution; both amounts of polysaccharide and protein secreted by attached cells are mainly positively related to the solution acidity rather than the total concentration of soluble metal ions. The experimental results imply that bacteria are mainly through secreting more extracellular polysaccharide to fight against disadvantageous environment and the extracellular protein perhaps plays an important role in oxidation？reduction reactions in the bioleaching system.

Adsorption and leaching behaviors of chalcopyrite by two extreme thermophilic archaea

The adsorption and leaching of chalcopyrite by two extreme thermophilic archaea(A.brierleyi and S.metallicus)and their mixture were studied.The results revealed that the chalcopyrite leaching rate of S.metallicus was slightly higher than that of A.brierleyi;the mixed system showed the highest rate.Community structure analysis during the leaching process showed that S.metallicus was maintained in a predominant state.However,the proportion of A.brierleyi in the community increased during leaching.Copper concentrations,which increased faster in the mixed system than in the single-organism systems during later stages,was related to the change of A.brierleyi in the community.Langmuir parameter analysis revealed no competitive adsorption between these two thermophilic archaea.Furthermore,qPCR(quantitative polymerase chain reaction)confirmed that adsorption was promoted between A.brierleyi and S.metallicus during mixed leaching.These findings can improve our understanding of the adsorption behaviors of mixed extreme microbial populations on mineral surfaces.

Stepwise dissolution of chalcopyrite bioleaching by thermophile A.manzaensis and mesophile L. ferriphilum

Chalcopyrite dissolution was evaluated by bioleaching and electrochemical experiments with thermophile A. manzaensis（Acidianus manzaensis） and mesophile L. ferriphilum（Leptospirillum ferriphium） cultures at 65 ℃ and 40 ℃, respectively. It was investigated that the bioleaching of chalcopyrite was stepwise. It was reduced to Cu2 S at a lower redox potential locating in the whole bioleaching process by A. manzaensis at high temperature while only at initial days of bioleaching by L. ferriphilum at a relative low temperature. No reduced product was detected when the redox potential was beyond a high level（e.g., 550 m V（vs SCE）） bioleached by L. ferriphilum. Chalcopyrite bioleaching efficiency was substantially improved bioleached by A. manaensis compared to that by L. ferriphilum, which was mainly attributed to the reduction reaction occurring during bioleaching. The reductive intermediate Cu2 S was more amenable to oxidation than chalcopyrite, causing enhanced copper extraction.

Formation of jarosite and its effect on important ions for Acidithiobacillus ferrooxidans bacteria

The precipitation of jarosite adversely affects the bio-leaching of copper sulfides in the Sarcheshmeh heap bio-leaching process. The variables of the initial concentration of ferrous iron in the growth medium, pH, and temperature were examined in the laboratory to determine how they affect the precipitation of jarosite in the presence of Acidithiobacillus ferrooxidans bacteria. It was found that the maximum ferric precipitate occurred at a ferrous sulfate concentration of 50 g/L, a temperature of 32 ℃, and an initial pH value of 2.2. The effects of the precipitation of ferric iron on the quantities of ions that are important for A. ferrooxidans bacteria in aqueous phase, i.e., ferric, sulfate, potassium, phosphate, and magnesium ions, also were assessed. The results showed relatively similar patterns for the ferric and potassium ions, and then reason might have been the co-precipitation of these ions as constituent elements of jarosite mineral. At pH values greater than 1.6, the solubility of phosphate ions decreased dramatically due to the co-precipitation of phosphate ions with the jarosite precipitate and due to the significant growth rate of A. ferrooxidans bacteria in this pH range. Due to the dissolution of a gangue constituent in the ore, the magnesium levels increased in the first few days of the bio-leaching process;thereafter, it decreased slightly.

Bioleaching of low-grade copper sulfide ore by extremely thermoacidophilic consortia at 70℃in column reactors

The effects of introducing M.sedula derivatives having different Cu^2+-resistance on bioleaching capacity of a defined consortium(consisting of A.brierleyi DSM1651 and M.hakonensis HO1-1)were studied in column reactors at 70℃.Introducing M.sedula copA mutant,a copper sensitive derivative,only had negligible effects on bioleaching.While introducing M.sedula ARS50-2,a Cu^2+resistant strain,substantially consolidated bioleaching process,with 27.77%more copper recovered after 58 d of bioleaching.Addition of M.sedula ARS50-2 likely enhanced the sulfur oxidation capacity of consortium after the 24th day under the Cu^2+stress.The majority of extreme thermoacidophiles were attached on minerals surface as indicated by quantitative PCR(qPCR)data.Successions of microbial community of extremely thermoacidophilic consortia that attached on surface of minerals were different from those in leachate.M.hakonensis HO1-1 was the dominant species attached on minerals surface in each column reactor throughout bioleaching process.The sessile M.sedula ARS50-2 remained as a major species till the 34th day.A.brierleyi DSM1651 was the most abundant planktonic species in leachate of each column reactor.These results highlight that higher Cu^2+-resistance is a beneficial trait for extreme thermoacidophiles to process copper minerals.

Bio-dissolution of Cu,Mo and Re from molybdenite concentrate using mix mesophilic microorganism in shake flask

The application of the response surface methodology and the central composite design（CCD） technique for modeling and optimization of the influence of some operating variables on copper,molybdenum and rhenium recoveries in a bioleaching process was investigated.Three main bioleaching parameters,namely pH,solid concentration and inoculum percent,were changed during the bioleaching tests based on CCD.The ranges of the bioleaching process variables used in the design were as follows：pH1.46-2.14,solid concentration 0.95%-11.05%,and inoculum percent 1.59%-18.41%.A total of 20 bioleaching tests were carried out by the CCD method according to software-based designed matrix.Empirical model equations were developed according to the copper,molybdenum and rhenium recoveries obtained with these three parameters.Model equations of responses at the base of parameters were achieved by using statistical software.The model equations were then individually optimized by using quadratic programming to maximize copper,molybdenum and rhenium recoveries individually within the experimental range.The optimum conditions for copper recovery were pH 1.68,solid concentration 0.95% and the inoculum 18.41%（v/v）,while molybdenum and rhenium recoveries were 2.18% and 24.41%,respectively.The predicted values for copper,molybdenum and rhenium recoveries were found to be in good agreement with the experimental values.Also jarosite formation during bioleaching tests was also investigated.