A new strain Leptospirillum ferriphilum YTW315 for bioleaching of metal sulfides ores

A new strain named YTW315 was isolated from Dexing area using the double-layer culture technique. The morphological, biochemical and physiological characteristics of YTW315 were studied. Physiological investigation indicates that the strain YTW315 is a strict (obligate) chemolithoautotroph, metabolizing ferrous iron and pyrite. The optimal growth conditions for the strain are 40 ℃ and pH 1.6. A phylogenetic analysis based on 16S rRNA sequences shows that the isolate is clustered to Leptospirillum ferriphilum with 99.8% similarity to Leptospirillum ferriphilum strain Fairview and ATCC 49881. The molar fraction of DNA (G+C) of the isolate is 58.1%. The strain can tolerate high concentration of Fe(Ⅲ) and As(V) (500 mmol/L and 50 mmol/L, respectively). Bioleaching experiment indicates that the strain can oxidize Fe(Ⅱ) efficiently, and after 30 d, 44.56% of copper and 95.31% of iron are extracted from chalcopyrite and pyrite, respectively.     

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~...     

Identification and fermentation optimization of protopectinase-overproducing strain Aspergillus niger CD-01 for pectin production

In order to solve the citrus peel resource waste problem and minimize the drawbacks of chemical extraction of pectin, a protopectinase-overproducing strain CD-01 for pectin production was isolated from a pit soil dumped with perished orange in Changde City, Hunan Province of China. The strain CD-01 had the same morphology and 28S rRNA gene sequence (FJ184995) as that of Aspergillus niger (ATCC 64028). It was thus identified and named as Aspergillus niger CD-01. The fermentation condition was optimized based on L₉(3⁴) orthogonal experimental design and the variances analyses. The results show that the optimal condition for producing pectin is as follows: time 36 h, temperature 35 °C, pH 5, and urea as the nitrogen source. Under this condition, the pectin yield can reach up to 24.5%. This shows a great potential of Aspergillus niger CD-01 in pectin extraction from citrus. Foundation item: Projects(50621063, 50674101) supported by the National Natural Science Foundation of China     

Biosorption mechanism of Cr (Ⅵ) onto cells of Synechococcus sp.

The biosorption mechanism of Cr (Ⅵ) ions on Synechococcus sp. biosorbent was studied by analyzing the biosorption kinetics as well as speciation change and bond formation during the biosorption process. The kinetics study shows that the adsorption process of Cr (Ⅵ) consists of a very fast stage in the first several minutes, in which more than half of the saturation adsorption is attained, and a slower stage that approximately follows the first order kinetic model, basically Freundlich isotherm models were observed. Comparative studies of FT-IR spectra of K_2Cr_2O_7, free cells of Synechococcus sp., and Cr-bound cells of Synechococcus sp. show that the speciation of chromium that binds to the cells of Synechococcus sp. is Cr (Ⅲ), instead of Cr (Ⅵ), and the carboxylic, alcoholic, amido and amino groups may be involved in the binding of Cr (Ⅲ). Integrative analyses of the surface electric potential, the effect of pH value on adsorption behavior of Cr (Ⅵ), and the results of FT-IR show that the biosorption of Cr (Ⅵ) follows two subsequent steps, biosorption of Cr_2O_(7~)2-))by electrostatical force at the protonated active sites and reduction of Cr_2O_(7~(2-)) to Cr3+ by the reductive groups on the surface of the biosorbents.     

古菌生物浸出黄铜矿过程中的表观硫氧化活性表征

对4株纯的极端嗜热古菌及它们的混合菌在生物浸出黄铜矿过程中的硫氧化活性进行对比研究。结果表明,混合菌比纯菌拥有更高的硫氧化活性,它大幅度促进黄铜矿浸出率的提高。表征嗜热古菌硫氧化活性的参数值通常受很多因素的影响,以致在不同的硫氧化菌和不同的条件下生物浸出黄铜矿时,这些参数很难准确地反映出相应的硫氧化活性。因此,期待找到一种能有效表征浸矿菌硫氧化活性的方法。     

3种典型能量代谢菌浸出黄铜矿及其硫形态的转化

比较了3种典型嗜中温铁/硫代谢菌——Acidithiobacillus ferrooxidans、Leptospirillum ferriphilum及Acidithiobacillus thiooxidans单独及混合浸出黄铜矿过程中细菌硫氧化、铁氧化情况。同时利用XRD、硫的K边X射线吸收近边结构光谱(XANES)等分析手段研究3种细菌单独/混合浸出黄铜矿过程中矿物组成成分和矿物表面硫的形态变化。结果表明:在浸出初期电位低于400 mV(vs SCE)时,黄铜矿的浸出速率较快,此后电位迅速升高至540 mV,黄铜矿浸出速率明显变慢。混合菌浸出时体系的硫/铁氧化活性较单一菌高,根据XANES拟合分析发现,混合菌浸出时矿物表面元素硫及黄钾铁矾积累量明显减少,浸出初期辉铜矿产量明显高于单一细菌浸出的。     

磁黄铁矿自诱导浮选电化学的研究

考察了磁黄铁矿自诱导浮选基本行为,得出了不同pH条件下,回收率一矿浆电位关系和浮选电位上下限—pH关系。结果表明,磁黄铁矿在pH<13,在一定电位范围内,均可实现自诱导浮选。通过循环伏安曲线测量,阐明了磁黄铁矿表面氧化的机理。中性硫是主要疏水体,E-pH图计算,证明了可浮区间内的重要组分。     

Preparation, optical properties and cell staining of water soluble amine-terminated PAMAM G2.0-Au nanocomposites

The solution chemical and optical characteristics of formation of amine-terminated polyamidoamine dendrimer G2.0（NH2-PAMAM G2.0）-Au nanocomposites in the aqueous solution of NH2-PAMAM G2.0 at various mole ratios of Au（Ⅲ） to NH2-PAMAM G2.0 were studied by both UV-visible spectrometry and fluorospectrometry. The NH2-PAMAM G2.0-Au nanocomposites, with a type of structure in which one Au nanoparticle is surrounded by several NH2-PAMAM G2.0 dendrimers, emit strong bluish violet fluorescence, and are uniform, water soluble and biocompatible as well as very stable in frozen conditions. The size of gold nanoparticles in the nanocomposites is about 2.5 nm and decreases with the increase of NH2-PAMAM G2.0 concentration. The NH2-PAMAM G2. 0 plays an important role in acting as host or micro-reactor for Au（Ⅲ） before Au（Ⅲ） reduction and acting as dispersant and stabilizer for gold nanoparticles after Au（Ⅲ） reduction. Preliminary experiments of cells staining to human embryonic lung fibroblast cell lines show that the NH2-PAMAM G2.0-Au nanocomposites can be used as optical imaging markers for bioanalyses and medical diagnoses.     

Biosorption mechanism of Cr （Ⅳ） onto cells of Synechococcus sp.

The biosorption mechanism of Cr （Ⅳ） ions on Synechococcus sp. biosorbent was studied by analyzing the biosorption kinetics as well as speciation change and bond formation during the biosorption process. The kinetics study shows that the adsorption process of Cr （Ⅳ） consists of a very fast stage in the first several minutes, in which more than half of the saturation adsorption is attained, and a slower stage that approximately follows the first order kinetic model, basically Freundlich isotherm models were observed. Comparative studies of FT-LR spectra of K2Cr2O7, free cells of Synechococcus sp., and Cr-bound cells of Synechococcus sp show that the speciation of chromium that binds to the cells ofSynechococcus sp. is Cr （Ⅲ）, instead of Cr （Ⅳ）, and the carboxylic, alcoholic, amido and amino groups may be involved in the binding of Cr （Ⅲ）. Integrative analyses of the surface electric potential, the effect of pH value on adsorption behavior of Cr （Ⅵ）, and the results of FT-IR show that the biosorption of Cr （Ⅵ） follows two subsequent steps, biosorption of Cr2O7 ^2- by electrostatical force at the protonated active sites and reduction of Cr2O7^2- to Cr^3＋ by the reductive groups on the surface of the biosorbents.