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André L.F. Souza,Adriana L. Invitti,Fabiane G.M. Rego,Rose A. Monteiro,Giseli Klassen,Emanuel M. Souza,Leda S. Chubatsu,Fábio O. Pedrosa,Liu U. Rigo 한국미생물학회 2010 The journal of microbiology Vol.48 No.1
The pathway of electron transport to nitrogenase in the endophytic β-Proteobacterium Herbaspirillum seropedicae has not been characterized. We have generated mutants in two nif-associated genes encoding putative ferredoxins, fdxA and fdxN. The fdxA gene is part of the operon nifHDKENXorf1orf2fdxAnifQmodABC and is transcribed from the nifH promoter, as revealed by lacZ gene fusion. The fdxN gene is probably cotranscribed with the nifB gene. Mutational analysis suggests that the FdxA protein is essential for maximum nitrogenase activity, since the nitrogenase activity of the fdxA mutant strain was reduced to about 30% of that of the wild-type strain. In addition, the fdxA mutation had no effect on the nitrogenase switch-off in response to ammonium. Nitrogenase activity of a mutant strain lacking the fdxN gene was completely abolished. This phenotype was reverted by complementation with fdxN expressed under lacZ promoter control. The results suggest that the products of both the fdxA and fdxN genes are probably involved in electron transfer during nitrogen fixation.
Osvaldo Pezoti Jr,Andre´ L. Cazetta,Isis P.A.F. Souza,Karen C. Bedin,Alessandro C. Martins,Tais L. Silva,Vitor C. Almeida 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.6
The present study reports the preparation of an activated carbon produced from buriti shells (ACb) usingZnCl2 as activating agent and its ability to removemethylene blue dye (MB) from aqueous solutions. Theobtained ACb was characterized by N2 adsorption–desorption isotherms, SEM and FT-IR. The resultsshow that ACb presents microporous features with BET surface area (SBET) of 843 m2 g-1 and functionalgroups common in carbonaceous materials. Adsorption studies were carried out and experimental datawere fitted to three isotherm models (Langmuir, Freundlich, and Redlich–Peterson) and four kineticmodels (pseudo-first order, pseudo-second order, Elovich, and intraparticle diffusion). The isothermmodel which best fitted to experimental data was Redlich–Peterson. However, the g parameter of thismodel indicated that the adsorption of MB onto ACb occurs according to the mechanism proposed byLangmuir, which showed maximum monolayer adsorption capacity of 274.62 mg g-1. Kinetic studiesdemonstrated that the Elovich model is suitable to describe the experimental data. Moreover, it wasfound that the intraparticle diffusion is the limiting step of adsorption process.