Síntese do oleato de etila catalisada pela lipase nativa de Aspergillus Niger imobilizada em nanotubos de carbono

Abstract

The use of enzymes as catalysts has long been exploited in recent years due to their advantages in comparison with conventional catalysts can highlight its high specificity control the formation of byproducts, in addition, enzymes work under mild conditions of temperature and pressure. A special class of enzymes are lipases, which are capable of catalyzing esterification reactions in appropriate environments. The esterification reactions catalyzed by lipases is a very important industrial process nowadays to obtain methyl and ethyl esters produced from long chain fatty acids have been used in the production of biodiesel. The development of immobilization techniques have been important for providing re-use of enzymes to facilitate separation of the product, increasing stability in organic solvents and reduce the cost of the process. In recent years, research on nanomaterials, including carbon nanotubes have attracted much attention due to its ability for applications as carriers for immobilization of enzymes. Thus this paper presents the study of oleic acid and ethanol esterification reaction, using as a biocatalyst native lipase from Aspergillus niger, in its free and immobilized form carbon nanotubes multi-walled (MWCNTs) and nanocomposites (MWCNTs / PVA). For this study was undertaken to optimize the reaction conditions with the lipase in its free form using the factorial design, varying the temperature, mass of the native A. niger lipase and molar ratio of oleic acid: ethanol, obtaining parameters as optimal for esterification reaction mass of 15 mg of lipase from A. niger ratio oleic acid: ethanol 1: 1 and temperature of 30 ° C, wherein the ethyl oleate is obtained with 66% conversion quantitated by Lowry-Tinsley method and 91% quantified by GC-FID, 6 hours of reaction. The native lipase from Aspergillus niger immobilized in MWNTCs / PVA and MWNTCs brackets, with and without functionalization of MWNTCs peroxide (H2O2) and basic medium (KOH) showed up inactive when immobilized in nanocomposites, not being observed the formation of ethyl oleate. But by immobilizing lipase from A. niger MWCNTs in the absence of PVA, conversions in ethyl oleate was 0-16%. So results showed that the immobilized lipase from A. niger has undergone partial or total inactivation, relative to obtain ethyl oleate, showing the influence of substrate-enzyme-supported relationship. On the other hand when using the native lipase in free form conversions were the ethyl oleate from good to excellent, being 31-97% under favorable reaction conditions in 6 hours of reaction, showing as an effective catalyst for the reaction esterification between oleic acid and ethanol.