Avaliação do potencial de preparado enzimático sólido de Yarrowia lipolytica em reações de síntese de ésteres alquílicos de ácidos graxos

Abstract

Biodiesel is a biodegradable and non-toxic biofuel that is an alternative to the use of fossil fuels. Usually, biodiesel is produced by alkali-catalyzed transesterification, though the formation of glycerol complicates separation and purification of the product. This route requires high purity oils (acid content < 0.5%) since free fatty acids (FFA) can react with the basic catalyst and generate soaps. Thus, the enzymatic route has been widely studied due to the possibility of the use of cheaper oils with high levels of FFA, since the employed catalysts (lipases) can catalyze both the esterification of FFA and transesterification of triacylglycerols (TAG). In the enzymatic route, the traditional approach for the production of biodiesel has been the use of commercial immobilized microbial lipases. However, the cost of these preparations is still high. Thus, in this work, the use of a fermented and dry soybean cake with lipase activity from Yarrowia lipolytica, obtained by solid state fermentation, was investigated. The solid enzymatic preparation (SEP) was studied in an esterification model reaction to evaluate the possibility of its use as biocatalyst in a pre-step to the current route of biodiesel production from acid oils. Initially, for the selection of the biocatalyst, different strains of Yarrowia lipolytica (Yarrowia lipolytica IMUFRJ 50682, Yarrowia lipolyticawild Po1g and Yarrowia lipolytica Po1g modified with the lipase gene of Yarrowia lipolytica IMUFRJ 50682 (modified Po1g)) were evaluated in the esterification of oleic acid (OA) with ethanol. The progress of the reactions was followed by neutralization volumetry and by gas chromatography. The higher conversion of OA was observed for SEP of IMUFRJ 50682. After the selection of the biocatalyst, the following effects were investigated on acid conversion: amount, type and mode of the addition of alcohol, temperature, content and mode of the addition of biocatalyst, amount of water in ethanol, and influence of acid chain. The best condition was the esterification of OA with anhydrous ethanol at 30°C for 24 h, using 30 wt.% of SEP in a single addition, alcohol/OA molar ratio equal to 1, with the addition of alcohol in a single step at the beginning of the reaction. Under these conditions, the conversion of OA was 85%, showing the potential of SEP of IMUFRJ 50682 to be used as a catalyst to reduce the content of FFA in cheaper oils, technically enabling its use in biodiesel production. Finally, the biocatalyst was reused and the influence of the solvent (water, ethanol, n-hexane) employed for wash the used catalyst was investigated. The wash of SEP with water led to the higher retention of catalytic activity and after the tenth batch, the biocatalyst kept 31% of its initial activity