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Lipase immobilization using adsorption on magnetic nanoparticles, cross-linked enzyme aggregates (CLEA), and a combination of both techniques was investigated. Experimental designs were used for the optimization of the immobilization observing that the pH and ionic strength play a principal role during the lipase immobilization and its activity. For adsorption on magnetic nanoparticles and CLEA synthesis the optimal condition was pH and 100 mM. Besides, during the CLEA synthesis, glutaraldehyde concentration showed to be a significant effect on the enzyme activity. A comparison between a magnetic CLEA prepared with (Lip@mCLEA) and without (mCLEA) biological functionalized magnetic nanoparticles was made observing that the use of functionalized support showed the best performance activity. All biocatalytic systems developed gives to the enzyme thermal stability between 45 and 70 °C, being Lip@mCLEA the more stable biocatalyst. Similar behavior was observed at different pH, where both Lip@mCLEA and mCLEA showed stability at a range of pH 5 to 8. The immobilized biocatalysts showed the same affinity of the subtract that the free enzyme suggested that the enzyme structure not modified the active site. The combination of both types of immobilization show evidenced the importance of the biological functionalization of the support when magnetic CLEA is produced.

Lipases (EC 3.1.1.3) are very used industrial enzymes but presents drawbacks such as lack of stability, and poor recyclability. Most of these obstacles can be solved by lipase immobilization. The objective of this work was evaluated to magnetic magnesium spinel nanoparticles as support for lipase immobilization by covalent bound. The techniques used for nanoparticles synthesis presented advantages in the size selection of the nanoparticles obtained (60-100 nm). The immobilization of Candida rugosa lipase (CRL) was optimized. The optimal conditions were determined to be pH 3.7, enzyme concentration of 1.1 mg/mL at 4 °C and an ionic strength of 100 mM. The CRL@MgFe

Y[Fe(CN)6]·4H2O has been synthesized and characterized. The crystal structure was refined by Rietveld analysis using X-ray powder diffraction data. Y[Fe(CN)6]·4H2O crystallizes in the orthorhombic crystal system, space group Cmcm. Y3+ ion is eight-coordinated forming a bicapped distorted trigonal prism YN6O2. Fe3+ ion is six-coordinated in the form of an irregular octahedra FeC6 group and cyanide linkages between YN6O2 and FeC6 groups build an infinite polymeric array. The vibrational spectrum shows two bands corresponding to antisymmetric and symmetric stretching 12C14N in the CN stretching region. These bands are accompanied by four weak isotopic bands at lower frequency due to the presence of 13C and 15N in relative natural abundance. The HOH bending band split into three bands around 1600 cm−1 due to the presence of two kinds of water molecules in the structure. The thermal decomposition has been followed by thermogravimetric and differential thermal analysis, IR spectroscopy and powder XRD. The size and morphology of the complex and its thermal decomposition products were evaluated by scanning electron microscopy. The magnetic measurements confirm that Y[Fe(CN)6]·4H2O shows an antiferromagnetic order at low temperatures.

In order to investigate the formation of the multiferroic BiFeO3, the thermal decomposition of the inorganic complex Bismuth hexacyanoferrate (III) tetrahydrate, Bi[Fe(CN)6]·4H2O has been studied. The starting material and the decomposition products were characterized by IR spectroscopy, thermal analysis, laboratory powder X-ray diffraction, and microscopic electron scanning. The crystal structures of these compounds were refined by Rietveld analysis. BiFeO3 were synthesized by the decomposition thermal method at temperature as low as 600 °C. There is a clear dependence of the type and amount of impurities that are present in the samples with the time and temperature of preparation.