Papers by Keyword: Microcalorimetry

Abstract: Bacillus thuringiensis (BT) was the typical environmental microorganism.To explore the environmental behavior of lithium, the growth metabolism of BT under Li+ was investigated by microcalorimetry. The power-time curve showed the growth metabolic power-time curve of BT was divided into the bacterial growth phase and sporulation process. Lithium at 0.1-12mmol L-1 revealed no obvious effect to the bacterial growth phase of BT . Li+ at 0.1-4mmol L-1 stimulated the sporulation production and Li+ at 12-16mmol L-1 inhibited that respectively. While the time for initiation to produce sporulation was not influenced. However, the time for initiation to produce sporulation was earlier than the control induced by 8 mmol L-1 of Li+. The interest turning point of microcalorimetric result was confirmed by the following SEM detection. Besides the proof on environmental behavior of lithium, present results may bring related information for BT spores biological engineering transformation.

Abstract: A novel actinomycete, Streptomyces sp. Dagang-2 was isolated from the oil contaminated soil, which has a high homology of 98.59% with Streptomyces macrosporeus strain AM2-8. Purple pigment was purified from this strain, which showed a high chemical stability of acid-base, heat and light. Escherichia coli and Staphylococcus aureus were selected to evaluate the inhibition ability of purple pigment combined with microcalorimetric analysis and oxford cup method. The purple pigment showed a striking inhibition effect on Gram-positive bacteria S. aureus, however, it did not emerge an obvious antimicrobial activity against Gram-negative bacteria E. coli. It also could reflect the dynamic process of inhibiting effect to bacteria from purple pigment using microcarlorimetric technique. These results of this study might be useful for gaining more understanding of inhibition mechanisms from purple pigment.

Abstract: Low grade copper ores containing chalcopyrite are increasingly used for copper recovery via biomining. Since metal sulfide oxidation is an exothememic process, bioleaching activity can be measured due to the heat output by microcalorimetry, which is a non-destructive and non-invasive method. The bioleaching activity of pure cultures of Sulfolobus metallicus, Metallosphaera hakonensis and a moderate thermophilic enrichment culture on high grade chalcopyrite was evaluated. Chalcopyrite leaching by microorganisms showed a higher copper recovery than sterile controls. Chemical chalcopyrite leaching by acid produced heat due to the exothermic reaction, the heat output was increased while metal sulfide oxidation by microorganisms.

Abstract: In this study, an isothermal microcalorimetry was used to demonstrate the long-term impact of dimethyl phthalate (DMP), dipropyl phthalate (DBP), dioctyl phthalate (DOP) and dicyclohexyl phthalate (DEHP) on the soil microbial activity. Generally, the toxicity order of four phthalate esters (PAEs) is DBP>DMP>DOP>DEHP. The PAEs show inhibitory effect when the soil was exposed to PAEs for 10 days and the PAEs will have a small stimulate effect after 30 days, and then the PAEs inhibit the soil microorganisms again. The effect of PAEs on soil microbial activity is almost the same as those on urease activity.

Abstract: A series of microcalorimetric experiments were performed to evaluate the As(III), Fe(II), P and their joint effects by analyzing the thermodynamic parameters, microbial growth rate constant k, total heat evolution QT, inhibitory ratio I and highest heat flow Pmax. They were obtained from power-time curves of the growth of P. fluorescens. The effect of mixed As(III), Fe(II) and P were moderate, compared with control, single As(III) or Fe(II). In addition, FT-IR spectra of dry P. fluorescens after the adsoption of As(III) and Fe(II) and their mixture showed that Fe influenced the C-H bonds of the functional groups on the cellwall, the As(III) caused litter effect.

Abstract: Taken the nanoparticles Fe3O4 as the magnetic carrier, and styrene ( St ) and Methyl Acrylate (MA) as the monomers, the magnetic polystyrene-methyl acrylate (P(St-MA)) microspheres were prepared by microsuspension copolymerization. The effect of various parameters(e.g. reaction temperature, initiator, Fe3O4/styrene ratio and disperser) on the properties of the P(St-MA) microspheres were studied.The microspheres were characterized by different techniques (e.g. SEM, VSM, TG-DSC, FTIR, ). The interaction of magnetic microspheres and BSA were studied by microcalorimetry. The results showed the P(St-MA) microspheres, with abundant –COOH, superparamagnetic and high magnetic content, were possessed much higher protein adsorbance compared to those of magnetic polystyrene(PS) microspheres.

Abstract: In this study, the adsorption mechanism of cethyltrimethylammounium bromide (CTAB) onto quartz surface from aqueous solution was investigated and also some thermokinetic parameters such as isosteric adsorption enthalpy and entropy for this system were determined through thermogenesis curves determination by microcalorimetry. In addition, the contribution of adsorption to the surface wettability is illustrated according to the experimental results of surface electrical behavior and wetting behavior. This study shows that the wetting behavior of CTAB on quartz surface is determined by the process of its adsorption.

Abstract: The largest lignite mining area in Europe is located 150 km southeast of Berlin. Acidic lakes exist in this area, known to be caused by marcasite oxidation. Thirty-two samples from the open-pit brown coal-mine Jaenschwalde were analyzed for microorganisms. Cell numbers determined after separation from sand particles revealed concentrations of 102 to 107 microorganisms per g sample. In samples exposed to the air within an hour, up to 4x107 cells were counted. Measurement of metabolic activity by microcalorimetry showed for such samples up to 50 µW per g sand, whereas in heap samples (with low moisture) low or even no activity was measurable. DNA extraction was successful for 28 samples. In 26 samples microbial 16S rRNA genes were amplified by PCR. Acidithiobacillus ferrooxidans and At. thiooxidans specific amplificates were detected by nested PCR in 23 and 10 cases, respectively. A specific signal indicating Leptospirillum ferrooxidans was obtained with nine samples. Random samples were sequenced and showed 96 to 99 % identity with published data of all three species. Surprisingly, in four samples archaeal 16S rRNA genes were amplified by PCR. Sequencing of two samples showed 99 % identity with unidentified or uncultured archaea found in NCBI-databases. Molecular biology results for At. ferrooxidans as well as for At. thiooxidans were supported by successful isolations of pure cultures in 23 cases. Cultivation of the archaea failed so far. These data indicate that iron- and sulfur-oxidizing microorganisms occur at these sites in large numbers. If in addition the evidence for archaea can become verified, a screening for hot spots as the sites of their occurrence would become interesting.

Abstract: In this work, we studied the surface/water interaction properties of a pure calcium hydroxyapatite (HA) and their modifications as a consequence of the partial Ca2+/Mg2+ (MHA) substitution by means of IR spectroscopy and microcalorimetry of adsorbed water. IR data indicated that water molecules in direct contact with the surface of HA are coordinated to surface cations and experience H-bond significantly stronger than in liquid water. The heats of adsorption associated to such interactions are very high, being twice-triple the heat of liquefaction of water. Interestingly, water experiences H-bond higher than in its bulk liquid state also in the second layer. Finally the entering in the material of Mg2+ ions was shown to significantly affect the affinity of the material toward water and the properties of its hydration layers.

Abstract: Both, the employment of leaching bacteria for metal winning as well as the mitigation of bioleaching processes at AMD/ARD sites, require reliable monitoring methods for assessing bacterial activities. Therefore, we have developed a robust and rapid test system combining two sensitive analytical techniques: quantification of heat evolution by microcalorimetry and determination of all relevant inorganic sulfur species by chromatographic methods (IC and HPLC). Generally, only about 1 g of sample is sufficient for a complete analysis. The combined test has been applied to various leaching biotopes such as bioreactors, columns, heaps and natural sites. The bacterial activity of diverse sulfidic materials such as lignite and coal wastes, pure metal sulfides and complex ores has been investigated. In our labs, microcalorimetry can be performed in the range of 5 to 80 °C, covering most of the temperature spectrum of leaching bacteria. Hence, the heat evolution values of samples as a direct measure for calculating leaching rates can be obtained at nearly all relevant in situ temperatures. The combination with sulfur species determination results in additional information on leaching mechanisms (thiosulfate or polysulfide pathway) and general leaching performance (e. g. accumulation of sulfur intermediates).