a b s t r a c tMercury is a highly hazardous water contaminant; both organic and inorganic forms are cumulatively and extremely toxic. In this context, this study describes the application of TiO 2 -based systems modified with 5, 8, 10 and 15 wt% Fe using the impregnation method for the photocatalytic reduction of Hg
2+. Characterization of TiO 2 and synthesized materials was performed by using Brunauer, Emmett and Taller area, pore diameter and pore volume, scanning electron microscopy, point zero charge, X-ray diffraction (XRD), Fourier transform infrared spectroscopy, photoacoustic and Mössbauer spectroscopy. The photocatalytic reduction of Hg 2+ was performed in batch stirred tank reactor and compound parabolic collector solar photoreactor, in the presence of catalysts, under four different reaction conditions. The process of heterogeneous photocatalysis was studied in the treatment of synthetic wastewater containing mercury chloride (HgCl 2 ) in different reaction conditions. In particular, the influence of oxygen and formic acid was analyzed. The results showed that an addition of 8% to the iron weight improved the performance of the photocatalytic titania in the reduction of Hg 2+ (artificial radiation). In the presence of this catalyst, and reaction medium containing only mercuric chloride in an aqueous solution containing oxygen, Hg 2+ was 100% reduced, after 3 h of reaction. However, under solar radiation, the reduction of Hg 2+ obtained was 67%.
The current study focuses on the evaluation of culture parameters on the enzymatic hydrolysis of Ipomoea batatas (L.) Lam fl our by Candida homilentoma strains.A 2-factor-5-level CCRD was used to evaluate the effect of pH and temperature on the hydrolysis process. For the S-47 strain, pH and both studied parameters were signifi cant at 48 h and 96 h, respectively. Regarding S-81 strain, temperature was the only factor affecting the process, at 96 hours. The regression models were signifi cant, and no lack of fi t was observed for them.
This study describes the application of ZnO commercial oxide and ZnO/ZnFe 2 O 4 mixed oxides to reduce the mercury ion (Hg 2+) in the aqueous phase. The catalysts synthesized were characterized by thermogravimetric analysis, adsorption and desorption of N 2 , scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, photoacoustic spectroscopy and Mössbauer spectroscopy. The heterogeneous photocatalysis process was studied in synthetic effluent treatment containing mercury chloride (HgCl 2) in a batch and solar reactor. The results indicated that commercial ZnO catalyst totally reduced the Hg (II), in all conditions and reaction systems studied. On the other hand, for the mixed oxides (ZnO/ZnFe 2 O 4), there was a decrease in the reduction efficiency in the batch reactor, indicating no ability to reduce Hg(II) in the presence of sunlight.
Amylase production from starch sources is associated with the nature of this carbon source, particle size and crystalline architecture of natural starch granules. The aim of this work was to evaluated the amylase production by Saccharomyces diastaticus ATCC 13007, using different CaCO3 concentration and corn starch (Zea mays) and cassava starch (Manihot esculenta) as inducers. A 22 Central Composite Rotatable Design with three replications at the center point was used to determine the influence of calcium and starch concentrations on the production process. Besides, the partial characterization of the crude enzymatic extracts obtained was investigated. Ca2+ influenced the α-amylase production by both evaluated carbon sources. The production of glucoamylase was not influenced by the variables under study. Partial characterization of crude extracts indicated that, for corn substrate, the enzyme showed maximum activity at pH 5.0, and no influence of temperature was observed. Regarding cassava starch, the results showed that conditions at central point (pH 6.5 and 50ºC) should be avoided in order to maximize enzyme activity.
Etanol pode ser produzido a partir de diversas fontes amiláceas, bem como dos resíduos oriundos das mesmas. Assim, em vista da variedade de matéria-prima para produção de etanol, faz-se necessário estudar e selecionar linhagens de microrganismos selvagens que demonstrem a capacidade de hidrolisar o amido em açúcares fermentescíveis. Desta forma, o presente estudo consiste em investigar a influência de parâmetros de cultivo sobre a atividade de amilases, produzidas por leveduras isoladas do processamento de farinha de puba. O delineamento de Plackett e Burman (PB) foi aplicado com o intuito de selecionar e avaliar a influência da temperatura, do pH inicial e das concentrações de inóculo, amido, peptona e extrato de levedura sobre a atividade enzimática. Por meio dos resultados para tal delineamento, verificou-se influência estatisticamente significativa (p < 0,10) da temperatura e das concentrações de amido e inóculo. Em relação aos resultados do Delineamento Composto Central Rotacional (DCCR), observou-se que o efeito linear da temperatura e da concentração de amido foram significativos (p < 0,05) sobre a atividade enzimática. Com a metodologia de superfície de resposta observou-se que a condição ótima para atividade da enzima amilase é obtida quando se aumenta a temperatura e a concentração de amido do meio. Assim, os resultados obtidos no presente estudo sugerem que as amilases produzidas pela linhagem PB-34 apresentam potencial para estudos futuros visando a produção de etanol a partir de materiais amiláceos.
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