Síntese e caracterização de óxidos do tipo espinélio como suporte para imobilização de lipases

Abstract

Lipases have gained prominence in catalytic studies, as they represent a versatile biocatalyst capable of acting in different reactions. However, its application needs to be improved because of the high costs of obtaining it and the risk of denaturation. Some of the alternatives for solving these problems are the use of agroindustrial residues as substrates for their production, as well as their immobilization on low-cost supports, which offer more excellent stability to the enzyme when compared to its free form and allow easy recovery, allowing it to be reused several times. This study aimed to test the efficiency of supports made from cobalt nanoparticles, impregnated with zinc aluminate and celite in different stoichiometric proportions, as new supports for immobilizing lipases. These enzymes were produced by the fungus Botryosphaeria ribis EC-01 in media containing soybean cake and glycerol, agroindustry byproducts, by submerged fermentation under previously optimized conditions. The cobaltites (NiCo2O4, ZnCo2O4 and Ni0,5Zn0,5Co2O4), produced by the sol-gel method, the cobalt oxide nanoparticles (Co3O4), as well as those incorporated into zinc aluminate and different proportions of Celite, as well as the zinc aluminate particles, produced by calcination, were characterized by FTIR, XRD, BET and SEM,and applied for enzyme immobilization. The lipases immobilized on the supports were also characterized by FTIR. After selecting the best supports for immobilization, Ni0,5Zn0,5Co2O4 and ZnAl2O4-Co3O4 were chosen to investigate their response as support for immobilization at different times and temperatures, with the aid of factorial designs (2²) with central points and axial points, in addition to being analytically evaluated using Response Surface Methodology (RSM). The predictive model showed that low temperatures and contact times would increase the immobilization of lipases on Ni0,5Zn0,5Co2O4, achieving an activity of 1054 ± 320 U gNi-Zn-Co-1 at 15 ºC and 15 min. of reaction while for the ZnAl2O4-Co3O4 support, the model predicted an optimum condition at 38 ºC and 75 min. Of enzyme-support contact, they were achieving 579 U gZn-Al-Co-1 for these conditions, demonstrating immobilization efficiency. These supports were evaluated for thermal stability (40 to 55 ºC) and in solvents (water, glycerol, and ethanol), achieving stability for up to 24 h at 55 ºC and good stability in ethanol and water, making this biocatalyst promising for applications, as well as the fungal biomass resulting from the fermentation process.