Suchergebnisse

In the present work, the influence of the competitive effect of inorganic ligands (carbonates, chlorides, fluorides, phosphates, nitrates and sulphates), which can be present in real multi-metal electroplating effluents, on the biosorption of chromium, copper, nickel and zinc ions by yeast cells of Saccharomyces cerevisiae was rationally examined. Additionally, chemical speciation studies allowed optimizing the amount of yeast biomass to be used in the treatment of effluents contaminated with nickel. The applicability of chemical simulation studies was tested using two simulated effluents and validated using one real electroplating effluent, all containing high concentrations of nickel (about 303 μmol l−1). For nickel removal, heat-killed biomass of a brewing flocculent strain of S. cerevisiae was used, in a batch mode. After the implementation of the bioremediation process (12 g dry weight l−1 of yeast cells), the concentration of nickel in the real effluent (34 μmol l−1) reached the quality criteria for industrial effluents discharge, after the second or third batch according to the U.S.-Environmental Protection Agency and Portuguese law, respectively. This corresponded to a removal of nickel of 89%. ; The authors thank to the "Fundacao para a Ciencia e a Tecnologia" (FCT) from Portuguese Government for the financial support of this work with FEDER founds, by the Project POCTI/CTA/47875/2002. Manuela D. Machado is also gratefully acknowledged for a grant scholarship financed under the same project and another grant from FCT ...

The use of buffers to maintain the pH within a desired range is a very common practice in chemical, biochemical and biological studies. Among them, zwitterionic N-substituted aminosulfonic acids, usually known as Good's buffers, although widely used, can complex metals and interact with biological systems. The present work reviews, discusses and updates the metal complexation characteristics of thirty one commercially available buffers. In addition, their impact on biological systems is also presented. The influences of these buffers on the results obtained in biological, biochemical and environmental studies, with special focus on their interaction with metal ions, are highlighted and critically reviewed. Using chemical speciation simulations, based on the current knowledge of the metal-buffer stability constants, a proposal of the most adequate buffer to employ for a given metal ion is presented. ; This work has been supported by Fundação para a Ciência e a Tecnologia (FCT), from the Portuguese Government, through the grants Strategic project-LA23/2013-2014 (IBB) and PEST-C/EQB/ LA0006/2011 (REQUIMTE). Soares EV also thanks the Project "BioInd-Biotechnology and Bioengineering for improved Industrial and Agro-Food processes", REF. NORTE-07-0124-FEDER- 000028 Co-funded by the Programa Operacional Regional do Norte (ON.2 – O Novo Norte), QREN, ...

Siderophore production by Bacillus megaterium was detected, in an iron-deficient culture medium, during the exponential growth phase, prior to the sporulation, in the presence of glucose; these results suggested that the onset of siderophore production did not require glucose depletion and was not related with the sporulation. The siderophore production by B. megaterium was affected by the carbon source used. The growth on glycerol promoted the very high siderophore production (1,182 μmol g−1 dry weight biomass); the opposite effect was observed in the presence of mannose (251 μmol g−1 dry weight biomass). The growth in the presence of fructose, galactose, glucose, lactose, maltose or sucrose, originated similar concentrations of siderophore (546–842 μmol g−1 dry weight biomass). Aeration had a positive effect on the production of siderophore. Incubation of B. megaterium under static conditions delayed and reduced the growth and the production of siderophore, compared with the incubation in stirred conditions. ; The authors thank Porto University/Totta Bank for their financial support through the project "Microbiological production of chelating agents" (Ref: 180). The authors also thank the Fundacao para a Ciencia e a Tecnologia (FCT) through the Portuguese Government for their financial support of this work through the grants Strategic project-LA23/2013-2014 (IBB) and PEST-C/EQB/LA0006/2011 (REQUIMTE). Manuela D. Machado gratefully acknowledges the postdoctoral (SFRH/BPD/72816/2010) grant from ...