Imobilização de células de Aspergillus Oryzae IPT-301 em esponja vegetal para a síntese enzimática de fruto-oligossacarídeos

Abstract

The fructooligosaccharides (FOS) are classified as prebiotic sugars that have several benefits for human health and nutrition. They are synthesized industrially, due to the occurrence of transfructosylation in sucrose molecules catalyzed by fructosyltransferase enzymes (FTases, E.C.2.4.1.9) adhered to microbial cells. The immobilization of cells on support materials makes it possible to obtain biocatalysts that are heterogeneous, robust and resistant to adverse conditions in the reaction medium. The loofa sponges are suitable supports for immobilization because they have a size and distribution of pores that enable gaseous and substrate diffusion, essential for microbial growth. Furthermore, they are biodegradable and low cost. Therefore, the objective of this work was to evaluate the production of A. oryzae IPT-301 cells, by submerged cell culture, and their concomitant immobilization in a loofa sponge. For this, the production of microbial cells, immobilized in loofa sponge, occurred in synthetic culture medium, pH 5.5, 200 rpm at 30 ºC. The microbial growth curve showed that the best cell culture time occurred during the 28h process. The temperature of 50 ºC, the pH of 5.75 and the concentration of 400 g L-1 were the parameters of the reaction medium that provided maximum enzymatic activities. The immobilized biocatalytic cells exhibited greater thermostability when compared to the in natura biocatalytic cells, as indicated by the values of the thermodynamic parameters obtained for the heterogeneous biocatalyst. Furthermore, cells immobilized in loofa sponge have a wide range of pH stability (5.00 to 7.00) and good operational performance. Tests in a packed bed reactor demonstrated an enzymatic productivity of 11.7 U g-1 min-1, whose conversion and yield values obtained were equal to 8.31% and 6.63%, respectively. Regarding the value of the maximum productivity parameter, we obtained 1.89 g FOS gcells-1 h -1 for the continuous reaction system. This set of results obtained highlights the technological innovation present in this study to obtain biocatalysts from the immobilization of cells in loofa sponge, both for the synthesis of FOS, as well as in the advancement of the segment of bioproducts of industrial interest and in the implementation of diverse bioprocesses.