Effect of applied potentials on the activity and growth of Thiobacillus ferrooxidans

The effect of applied DC potentials both in the positive and negative range, on the activity and growth of Thiobacillus ferrooxidans, is discussed. In general, application of positive potentials up to +1000 mV in an acid bioleaching medium was found to be detrimental to bacterial activity, while the impression of negative potentials enhanced both their activity and growth through electrochemical regeneration of ferrous ions and an increase in the biomass. Ferrous-ferric ratios in a bioleaching medium could be monitored through Eh measurements. Among the base sulfide minerals such as pyrite, chalcopyrite, and sphalerite, sphalerite could be selectively bioleached if an impressed potential of -500 mV (SCE) could be maintained in the leaching medium. Electrochemical bioleaching tests carried out under an applied potential of -500 mV with sphalerite in the presence and absence of noble minerals such as pyrite and chalcopyrite indicated enhanced zinc dissolution with negligible copper and iron in solution. Probable mechanisms and advantages of the electrochemical bioleaching process developed in the laboratory are outlined

Molecular cloning and analysis of the NAG1 cDNA coding for glucosamine-6-phosphate deaminase from Candida albicans

Candida albicans and other pathogenic Candida species can use N-acetylglucosamine as a sole carbon source for growth. GlcNAc induces the enzymes of GlcNAc catabolic pathway; besides, under certain conditions, GlcNAc also induces a change from the yeast to germ tube morphology. Glucosamine-6-phosphate deaminase (EC 5.3.1.10) is the terminal enzyme of the GlcNAc catabolic pathway. We have purified the deaminase from C. albicans and studied its characteristics. The size of the deaminase estimated from SDS-polyacrylamide gel electrophoresis is 28 kDa. N-Acetylglucosamine 6-phosphate, an allosteric activator of the Escherichia coli deaminase, has no effect on the activity of the C. albicans enzyme. The deaminase is induced over 100-fold by GlcNAc and its level is about 0.3-0.5% of the proteins in crude extract. Three cDNA clones were obtained from a lambda gt11 expression library by immunoscreening with deaminase antiserum. C. albicans genomic DNA blot hybridization revealed that the NAG1 gene, encoding the glucosamine-6-phosphate deaminase, is present in a single copy. Hybrid-selected translation and immunoprecipitation experiments revealed that the purified deaminase and the protein encoded by the clones were similar in size and in their antigenicity. DNA sequencing revealed that the largest cDNA clone contained the complete open reading frame, which can code for a 27.5-kDa protein. The NH2-terminal sequence (35 residues) determined from the purified deaminase was identical to the sequence of the deduced protein. The Nag1 protein has about 47% identity with the sequence of the E. coli glucosamine-6-phosphate deaminase. Furthermore, RNA blot hybridization showed that GlcNAc induces the expression of NAG1 gene

Bacterial leaching: biotechnology in the mining industry

Bacterial leaching is the extraction of metals from their ores using microorganisms. Microbial technology offers an economic alternative for the mining industry, at a time when high-grade mineral resources are being depleted

Electrochemical aspects of grinding media-mineral interaction on sulphide flotation

Galvanic interaction between electrically conducting minerals may affect the mineral surface and influence their flotabilities. The metallographic examinations as well as hardness measurements have been made with grinding media. Rest potential, combination potential, galvanic current and polarization studies were made to understand the probable electrochemical interaction between grinding media and chalcopyrite. The galvanic contact lowered the flotability of chalcopyrite. AES and ESCA indicated that galvanic coupling of chalcopyrite with grinding media resulted in the formation of oxy-hydroxide species of iron on the chalcopyrite surface. Scanning electron microscopy was used to study the surface morphological changes on the grinding media due to galvanic interaction with chalcopyrite

Dichloro(diphenylarsino)ruthenium(III) & Its Reactions with Some Nitrogen Donors

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Effect of internal-marketing-mix on customer-pyramid-oriented banking service performance: an Indian experience

The study proposes marketing support facility provided by all three categories of bank employees each as a commitment to service performance. IM has proved its results in human resource management implications and it is proposed to yield in the marketing as well as business development function in banking service performance in form of added values in an organizatio

Stability of copper tolerance in Thiobacillus ferrooxidans

A strain of Thiobacillus ferrooxidans MAL-4-1 was adapted to grow at higher concentrations of copper by repeated subculturing in the presence of increasing levels of added cupric ions in 9K medium. The strains adapted to copper were found to be more efficient in bioleaching of copper from concentrates. When copper tolerant strains were back cultured repeatedly in 9K medium without cupric ions, the initially developed metal tolerance was observed to be lost. This indicates that the copper tolerance developed is stress-dependent and not a permanent trait of the adapted strain

HYALURONAN-A NOVEL POLYMER ISOLATED FROM MUTATED CLINICAL BACTERIAL ISOLATE

Objective: This study was done to optimize the production parameters involved in the isolation of hyaluronan (HA) from UV mutated a clinical strain of Klebsiella pneumonia (M 3020).Methods: Glucose and nitrogen enriched media (D-glucose, L-glutamic acid, and peptone) were utilized to cultivate the clinical isolate K. pneumoniae. The strain was Ultra Violet (UV) radiation mutated (254 nm, 25 min) and HA production was optimized by parameters such as pH and temperature. The isolated HA from the fermented broth was subjected to purification by isopropyl alcohol and silica gel and further dried by lyophilization. Produced HA was confirmed with UV and Fourier Transform Infra-Red (FT-IR) spectroscopy.Results: UV treated strain at 254 nm for 25 min predominantly produce a high quantity of HA (3.5 g/l) in 37 °C, 300 rpm and pH 6.8 at 24 h run. UV and IR spectrum of produced HA showed strong similarity with the standard hyaluronan.Conclusion: To conclude, high quantity and quality of HA can be isolated from mutated clinical strains of K. pneumoniae