Düsseldorf, Universiẗat, Diss., 2004.

[pt] Nos últimos anos, vários estudos têm sido realizados na aplicação dos microrganismos na biotecnologia mineral, atuando como coletores, depressores ou espumantes amigáveis com o meio ambiente, e induzindo propriedades hidrofóbicas, uma vez que eles podem-se aderir seletivamente sobre a superfície do mineral. O objetivo deste trabalho é estudar e avaliar o comportamento da cepa Rhodococcus ruber com a hematita. Entre os estudos efetuados estão à adesão microbiana à superfície mineral, medida do potencial zeta e análise no infravermelho antes a após interação do biorreagente com a hematita, assim como o estudo dos ensaios de microflotação. A amostra foi condicionada com a suspensão de biomassa por meio de agitação sob condições específicas, tais como tamanho das partículas, concentração da biomassa, pH da solução e tempo de condicionamento. Os resultados mostraram uma mudança no perfil do potencial zeta da hematita após interação com a R.ruber, e sua adesão na superfície do mineral foi maior ao redor do pH 3, e na concentração de 0.60g.L(-1) (10(9) células). Estudos de flotação foram realizados na célula de flotação modificada Partridge-Smith de 0.23L, e a maior valor de flotabilidade (84 por cento) foi atingido na fração menos 53 mais 38 um. Estudos complementários de flotabilidade foram realizados utilizando o espumante comercial Flotanol D24 combinado com a biomassa R.ruber, encontrando resultados interessantes em função do tamanho de partícula. Assim esta pesquisa visa avaliar a eficiência da bioflotação de minerais, particularmente da hematita, e do uso potencial do Rhodococcus ruber como biocoletor, projetando-se a uma futura aplicação na indústria da flotação mineral. / [en] In the recent years, research has been developed in the application of microorganisms in mineral technology, acting as environmental friendly collectors, depressors and/or frothers and inducing hydrophobic properties, since they can be selectively adhere onto the surface of the mineral. This research work deals with the fundamental aspects of hematite flotation using the bacterial strain Rhodococcus ruber. The aim of this research was to study and evaluate the behavior of Rhodococcus ruber strain before and after interaction with hematite particles. The sample was conditioned with the biomass suspension by stirring under specific conditions such as particle size, biomass concentration, pH solution and conditioning time. Among the studies conducted are the microbial adhesion to the mineral surface, zeta potential measurements and analysis of infrared spectra before and after interaction of Rhodococcus ruber with hematite, as well as microflotation studies. The results showed a change in hematite zeta potential profile after interaction with Rhodococcus ruber, and its adhesion onto the mineral surface was higher at pH 3 and at concentration of 0.60 g.L(-1) (10(9) cells). Flotation studies were carried out in a 0.23L modified Partridge-Smith flotation cell, and the highest floatability (84 percent) was achieved at size fraction any less 53 more 38 um. Also, floatability studies were performed using frother Flotanol D24 combined with the Rhodococcus ruber biomass, concluding with interesting results in function of the particle size range. This work aims to evaluate the efficiency of bioflotation of minerals, particularly hematite, and the potential use of Rhodococcus ruber as biocollector, projecting its future application in mineral flotation industry.

Universiẗat, Diss., 2003--Stuttgart.

[pt] Neste estudo, as propriedades bacterianas da estirpe Rhodococcus ruber in natura e ativada com NaOH 0,1M, foram analisadas. O estudo avaliou a influência dos cátions metálicos (Al3 positivo, Cr3 positivo, Fe3 positivo, Co2 positivo, Mg2 positivo e Ni2 positivo) sob o comportamento da estirpe bacteriana, no intervalo de concentração entre 10(-3) a 10(-6) mol/L. As amostras bacterianas foram caracterizadas por espectroscopia na faixa do infra-vermelho com transformada de Fourier (FTIR). O ponto isoelétrico (PIE) da estirpe R. Ruber foi obtido através das análises de potencial zeta. Os resultados demonstraram um PIE com pH igual 2,4 para a estirpe in natura, já quando ativada com NaOH 0,1M o PIE não foi evidenciado. A superfície bacteriana da estirpe ativada se apresentou levemente mais negativa do que a superfície da bactéria in natura. Para todas as amostras, observou-se alteração no potencial zeta durante a interação bacteriana com os íons estudados. Os resultados não apresentam diferenças significativas entre a bactéria in natura e ativada. As amostras permaneceram carregadas negativamente nos pH estudados, para todos os cátions, exceto Fe3 positivo. Por fim, diante dos resultados apresentados, acredita-se que a estirpe Rhodococcus ruber é uma opção viável para estudos voltados ao tratamento de efluentes contaminados por metais. / [en] In this study, the Rhodococcus ruber bacterial strain properties of in nature and activated with 0.1M NaOH were analyzed. The study evaluated the influence of metal ions (Al3 plus, Cr3 plus, Fe3 plus, Co2 plus, Mg2 plus and Ni2 plus) on the behavior of the bacterial strain in the concentration range from 10(-3) to 10(-6) mol/L. Bacterial samples were characterized by infra-red spectroscopy - Fourier transform Infra-red (FTIR). The isoelectric point (IEP) of the bacterium R. ruber was obtained by analysis of zeta potential. The results showed an IEP at pH equal 2.4 to strain in nature, in the other hand the IEP of activated strain (0.1M NaOH) was not observed. Bacterial surface-active strain showed slightly more negative than the surface of the bacterium in nature. All samples demonstrated changes in pH zeta potential during bacterial interaction with the analyzed ions. Samples remained negatively charged at the pH studied to all cations except Fe3 plus. Finally, it s believed that the bacterium Rhodococcus ruber is a viable option for the treatment of metal contaminated wastewater.

Nature uses inorganic elements for biological processes based on the useful chemistry, abundance, and availability of each metal. Transition metals are critical in the biogeochemical cycling of essential elements and the bioinorganic chemistry of organisms. Hydrolysis-prone metals such as iron and titanium are abundant on Earth but are mostly insoluble in oxic aqueous environments. Nearly every organism requires iron for survival, therefore Nature evolved to stabilize iron from hydrolysis and hydrolytic precipitation through protein and small molecule mechanisms. Like iron, titanium primarily exists as insoluble mineral oxides and is second only to iron as the most abundant transition metal in the Earth’s crust. Despite the reputation as an inert and insoluble metal, titanium can be solubilized and made bioavailable through by chemical and biological weathering. Currently there is no known native role for titanium, however it is quite bioactive. As a stronger Lewis acid, titanium can compete with iron in binding to biomolecules and proteins. It is of interest to investigate the interactions between hydrolysis-prone metals and biological systems, from whole cell organisms to proteins and small molecules. The non-pathogenic bacterium Rhodococcus ruber GIN-1 was isolated for its ability to strongly adhere to titanium dioxide (TiO2) over other metal oxides, providing an opportunity to study the interactions between whole bacterial cells and metal oxides. The GIN-1 strain incorporates Ti(IV) ions into its biomass after adherence to anatase, rutile, and a mixture of the two morphologies. Six metals were quantitated in TiO2-exposed and control (unexposed) cells by inductively coupled plasma optical emission spectroscopy. The exposure to TiO2 caused a significant uptake of titanium with concomitant loss of iron, zinc, and possibly manganese. A collaborative project with the Strongin laboratory at Temple University works to develop stable, biomaterial photocatalysts for environment remediation of toxic inorganic contaminants. Ferritins are a class of proteins that mineralizes and stores iron as a non- toxic ferrihydrite nanoparticle. These proteins can be photoactivated with ultraviolet light to release iron from its core to remediate environmental contaminants. Ferritin can be sensitized with plasmonic gold nanoparticles to extend the photoactivity of the catalyst to the visible spectrum. Work in this thesis highlights the contribution to this collaboration from the Valentine laboratory, included the expression and purification of proteins in E. coli (human H-chain ferritin, human L-chain ferritin, and bacterial DNA protection from starved cells protein), mutation of proteins to improve sensitization of catalyst, and biomineralization with iron and titanium. The trafficking of hydrolysis prone metals is vital for the survival of nearly every organism. Iron transport proteins such as transferrins are studied to understand how nature utilizes a difficult essential metal across the domains of life. Most transferrins have two homologous lobes and are believed to have evolved from a gene duplication of a monolobal transferrin. The ascidian Ciona intestinalis has genes for both a bilobal and monolobal transferrin. Nicatransferrin (nicaTf), the monolobal transferrin from C. intestinalis, is a primitive protein that may provide insight on the evolution of transferrins in higher organisms. It is advantageous to use E. coli expression systems to produce recombinant proteins, however protein misfolding and aggregation can be a concern. To improve expression of nicaTf in E. coli, codon optimization and disulfide bonded protein expression were used. Finally, siderophores are small, high affinity iron-chelating molecules secreted from lower organisms that scavenge iron in iron-limiting conditions. R. ruber GIN-1 and R. ruber DSM 43338 strains both secrete siderophores in artificial seawater media. There are several siderophores identified from Rhodococcus species, however none have been reported from any R. ruber strain. A new siderophore was isolated and preliminary work has been done to purify and characterize the molecule. Understanding the siderophore- metal ion interactions may help elucidate the mechanism of how R. ruber cells obtain titanium from the metal-oxide particles. / Chemistry