Obtenção de lipase microbiana a partir de sementes de abóbora e avaliação do potencial de imobilização da enzima

Abstract

The enzymes, due to their catalytic properties have been widely used in industrial processes in the free or immobilized forms. Among them, are the lipases, acting on ester bonds presents in acylglycerols and may be produced by solid state fermentation (SSF), allowing the use of agro-industrial residues. The aim of this work was to evaluate the potential of pumpkin seed flour to obtain lipase from Aspergillus niger and subsequent immobilization of the enzyme in hydrophobic matrices. The fermentations were performed according to experimental design varying the substrate moisture between 30 and 60% and the temperature between 30 and 40 °C. The interaction between temperature and moisture was the parameter that most influenced the fermentative process at 95% confidence, with the maximum hydrolytic activity obtained at temperatures between 26,0 and 33,5 °C and initial moisture content of the residue between 20 and 30%. Lipase pre-purified immobilization by adsorption on silica showed highest yield (81,85%) among the tested matrices. Free enzyme showed highest hydrolytic activity at pH 4,0, showing acidic character, and at 37 °C. However, when immobilized on silica the pH and temperature of greater hydrolytic activity were at 11,0 and 50 °C, respectively. Free lipase was stable at pH 6,0 at 30 °C and the immobilized biocatalyst (BI) at pH 4,0, 6,0 and 11,0 at 37 °C for four hours. Under conditions of olive oil hydrolysis, BI showed a lower speed of reaction (Vmáx =0,020 U/ mg) and lower afinity for the substrate, characterized by the higher value of Km (130,1 mmol) than those obtained by the free enzyme (Vmáx =0,028 U/ mg; Km =119,0 mmol). Biochemical characterization and kinetic parameters allow determination of the most appropriate conditions for future applications of the enzyme in processes of industrial interest. Pumpkin seeds, which have about 43% lipids, showed potential for use as natural substrate in SSF in order to obtain lipase from Aspergillus niger.