O polímero híbrido derivado de siloxano e quitosana foi obtido pela técnica sol-gel, tendo como precursor o tetraetilortosilicato (TEOS). O suporte híbrido obtido foi modificado quimicamente com epicloridrina e utilizado para imobilizar lipase de Burkholderia cepacia. O híbrido SiO 2 -quitosana deu origem a uma nova estrutura macromolecular na qual as partículas inorgânicas encontramse dispersas em escala nanométrica na matriz orgânica e ligadas à matriz por meio de ligações covalentes. Foi realizado um estudo comparativo entre a lipase livre e a imobilizada quanto à influencia do pH e temperatura, parâmetros cinéticos e estabilidade térmica. O pH ótimo para a atividade máxima de hidrólise da lipase imobilizada foi de 6,1, enquanto que para a lipase livre foi de 7,0. A temperatura ótima permaneceu em 50 ºC mesmo depois da imobilização. Os perfis de estabilidade térmica indicaram que o processo de imobilização foi favorável à estabilização da enzima e o derivado epóxi SiO 2 -quitosana foi cerca de 30 vezes mais estável que a lipase livre a 60 ºC.A hybrid polymer derived from siloxane and chitosan was obtained by sol-gel technique using tetraethoxysilane (TEOS) as a precursor. The hybrid support was chemically modified with epichlorohydrin and used to immobilize lipase from Burkholderia cepacia. The hybrid SiO 2 -chitosan formed new macromolecular structure in which the inorganic particles are dispersed at the nanometer scale in the organic host matrix and bounding through covalent bonds. A comparative study between free and immobilized lipase was provided in terms of pH, temperature, kinetic parameters and thermal stability. The pH for maximum hydrolysis activity shifted from 7.0 for the soluble lipase to 6.1 and the optimum temperature remained at 50 °C after immobilization. The patterns of heat stability indicated that the immobilization process provided the stabilization of the enzyme and the epoxy SiO 2 -chitosan derivative was almost 30-fold more stable than soluble lipase at 60 °C.

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The objective of this work was to select an efficient methodology for preparing active samples of Candida rugosa lipase immobilized in wood cellulignin, to be applied in hydrolysis and ester reactions. For this purpose, lipase was immobilized in the matrix by physical adsorption (pure cellulignin) and covalent binding (activated cellulignin with glutaraldeyde or carbonyldiimidazole [CDI]) in the presence or absence of polyethylene glycol (PEG) (Molecular mass of 1500 Daltons) as stabilizing agent. The activating agent and the presence of PEG-1500 in the immobilization procedure showed a strong influence on enzyme retention in the support. The values for enzyme retention ranged from 20 to 68%, and the highest yield was obtained when the enzyme was immobilized in cellulignin activated with CDI in the presence of PEG-1500. This immobilized derivative presented high hydrolytic (193.27 microM/[mg.min]) and synthetic (522.92 microM/[g.min]) activities when compared with those obtained by other techniques. The superiority of this immobilized system was confirmed by additional analyses, such as infrared spectroscopy and elemental analysis, which demonstrated an appropriate enzyme fixation and the highest level of protein incorporation in the support. Further information on the immobilized derivative was obtained by assessing the recycle potential in both aqueous and nonaqueous media.