Michael Ramos Nunes

Effect of the support size on the properties of β-galactosidase immobilized on chitosan: advantages and disadvantages of macro and nanoparticles.

The effect of the support size on the properties of enzyme immobilization was investigated by using chitosan macroparticles and nanoparticles. They were prepared by precipitation and ionotropic gelation, respectively, and were characterized by Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), transmission electron microscopy (TEM), light scattering analysis (LSA), and N(2) adsorption-desorption isotherms. β-Galactosidase was used as a model enzyme. It was found that the different sizes and porosities of the particles modify the enzymatic load, activity, and thermal stability of the immobilized biocatalysts. The highest activity was shown by the enzyme immobilized on nanoparticles when 204.2 mg protein·(g dry support)(-1) were attached. On the other hand, the same biocatalysts presented lower thermal stability than macroparticles. β-Galactosidase immobilized on chitosan macro and nanoparticles exhibited excellent operational stability at 37 °C, because it was still able to hydrolyze 83.2 and 75.93% of lactose, respectively, after 50 cycles of reuse.

Active carbon preparation from treads of tire waste for dye removal in waste water

Treads of scrap tires present low contents of inorganic fillers and a large amount of carbon black. In this work, this material was treated with potassium hydroxide and zinc chloride followed by pyrolysis at 500 and 700 °C. The ability to remove methylene blue and methyl orange were investigated under environmental conditions of pH and concentration. Carbons obtained with KOH at 700 °C present superior adsorption capacity. A simulation of this process permitted the characterization of the gases which contributed to surface development. The obtained products present a mesoporous structure and narrow particle size distribution. The presence of contaminants originated from these carbons was investigated in the aqueous media. The absence of zinc and sulfur releasing and the excellent ability to remove organic dye make these materials useful in the treatment of waste water.

Antioxidant and antimicrobial methylcellulose films containing Lippia alba extract and silver nanoparticles

Methylcellulose is a biopolymer, which can be used in the preparation of films for the production of biodegradable active packaging. In this work, the methylcellulose films containing biosynthesized silver nanoparticles (AgNPs) were developed using Lippia alba extract. The physico-chemical, antioxidant, and antimicrobial properties of the films were studied. The insertion of Lippia alba compounds was verified using infrared spectroscopy (FTIR), with the appearance of a band at 1595 cm-1 and 1410 cm-1 which is characteristic of CCC stretches of the aromatic ring, and the increase in the hydrophobicity of the films containing the extract in relation to the control film. The films containing AgNPs presented a decrease in tensile strength and elastic modulus, but increased elongation. It was observed that the films that contain AgNPs presented superior antioxidant activity compared to the other films, besides antimicrobial activity against the tested microorganisms.