Papers by Keyword: Trehalose

Abstract: Chloride leaching is considered a promising alternative method to recover copper from chalcopyrite and other primary copper sulfides, because it favors the leaching kinetics and avoids passivation of minerals. Nevertheless, chloride ions are highly toxic for iron-oxidizing microorganisms that participate in the bioleaching process. A comparative genomic analysis was carried out based on the complete genomes of bacteria belonging to Nitrospirae, Firmicutes, Actinobacteria and Proteobacteria phyla, and of archaea belonging to Euryarchaeota and Crenarchaeota was carried out to identify molecular determinants involved in chloride tolerance of acidophilic iron-oxidizing microorganisms. The results obtained showed that representative Nitrospirae and Firmicutes harbor genes for the biosynthesis and uptake of compatible solutes such as ectoine, trehalose and potassium, which have been shown to have a role in salt tolerance. Microorganisms belonging to other phyla harbor genes for potassium transporters, but no genes for compatible solutes were detected. In agreement with the bioinformatic results, minimum inhibitory concentration (MIC) determinations and growth kinetics experiments showed that Leptospirillum ferriphilum (Nitrospirae) was more tolerant to NaCl than Acidithiobacillus ferrooxidans (Proteobacteria). Furthermore, it was observed that the addition of 0.5 mM ectoine to the L. ferriphilum culture stimulated growth in the presence of 100 mM NaCl. On the contrary, ectoine had no effect on the growth of At. ferrooxidans. These results suggest that ectoine and likely trehalose could play a key role in chloride tolerance in L. ferriphilum. conferring adaptative advantages compared to A. ferrooxidans and possibly other iron-oxidizing microorganisms.

Abstract: Here, we describe a new method for the separation of trehalose after its enzymatic production. Compound mutagenesis of the Angel strain of Saccharomyces cerevisiae using ultraviolet irradiation and N-ethyl-N’-nitro-N-nitrosoguanidine resulted in three strains with high levels of maltose consumption, as determined by measurement of the residual maltose content of the culture medium. After 48 h of cultivation, the amount of residual maltose in the non-fermentation medium was 12.63%, a seven-fold reduction compared with that obtained with the original, non-mutated strain. Mutant strain G-4C3 produced trehalose with a purity of up to 96.69%.

Abstract: Trehalose (α-D-glucopyranosyl-1,1-α-D-glucopyranoside) is a non-reducing disaccharide. It is currently thought that just trace level of trehalose was detected in plants, and that trehalose metabolic pathway was significantly related to stress tolerance. In this study, we report that expression levels of three genes with regard to trehalose metabolic pathway were measured in Arabidopsis thaliana, including AtTPS1, AtTPPA and AtTRE1. As a result, transcriptional levels of these genes are the highest in floral organ, and the expression of AtTRE1 is much more than AtTPS1 and AtTPPA. Additionally, we present transcriptional response analyses in drought and heat stresses, which have shown the changes of these genes expression from tolerance in early stress to senescence in later stress.

Abstract: To obtain porous TiO2 film, the precursor sol was prepared by hydrolysis of Ti isopropoxide and then complexed with trehalose dihydrate. The porous TiO2 film was fabricated by dip-coating method on quartz glass substrates using this sol. The TiO2 films were calcined at 500-900 °C. The photocatalytic activities of the films were evaluated by examining decomposition of methylene blue in aqueous solution under UV light irradiation. The photocatalytic activity of the porous TiO2 film showed a different tendency according to the irradiation wavelength of UV light. The activity of the film evaluated under UV light irradiation with a wavelength of 254 nm was not affected a great deal by the clacination temperature. In the case of UV light irradiation with a wavelength of 365 nm, the activity of the film increased with increasing calcination temperature and that of the film calcined at 800 °C was the highest.

Abstract: To obtain porous and thick TiO2 film, the precursor sol was prepared by hydrolysis of Ti isopropoxide and then complexed with trehalose dihydrate. The porous TiO2 film was fabricated by dip-coating technique on quartz glass substrates using this sol. The TiO2 films were calcined at 500-700 °C. The photocatalytic activity of the films was evaluated by examining decomposition of methylene blue in aqueous solution under UV light irradiation. The TiO2 film prepared from the sol with trehalose was more active than TiO2 film prepared from the sol without trehalose. The trehalose addition to the dip-coating solution was effective in improving the photocatalytic activity of the TiO2 film.

Abstract: To obtain porous TiO2 film, the precursor sol was prepared by hydrolysis of Ti isopropoxide and then complexed with trehalose dihydrate. The porous TiO2 film was fabricated by dip-coating technique on glass substrates using this solution. The TiO2 film was calcined at 500 °C. The maximum thickness of the film by one–run dip-coating was ca. 740 nm. The film was composed of nanosized particle and pore. The porosity of the TiO2 film was increased by the addition of trehalose dihydrate to the sol. The porous TiO2 films were calcined at various temperatures. The effects of the calcination temperature on the microstructure of the porous TiO2 film were investigated. The porous film prepared from sol containing trehalose still kept the porous structure for calcination at 950 °C. The phase transition temperature from anatase to rutile of the film was shifted from 650 to 700 °C by trehalose addition to the sol.

Abstract: To fabricate porous and thick alumina films, we prepared an aqueous alumina hydroxide sol containing trehalose. The alumina films were deposited by dip-coating technique on glass substrates and heating at 500 °C. The maximum thickness of the film obtained by one-run dip-coating using the sol containing trehalose was over 1000 nm. The film was an aggregate of alumina particles with a diameter of 20-40 nm and pores were interstices between the particles. The porosity of alumina film can be controlled in the range of 48-65 % by changing trehalose concentration in the dip-coating solution.

Abstract: The precursor solutions containing TiO2 sol for nanoporous films were prepared by hydrolyzing titanium(IV) isopropoxide and adding trehalose dihydrate. The porous and thick TiO2 film was prepared by dip-coating technique on glass substrate and heating at 500 °C. The film was composed of nano sized particles (10-20 nm) and pores (7 nm). The specific surface area of the film was 163 m2/g. The film had humidity-sensitive electrical resistance at room temperature.