Implementação de reator de leito fixo empacotado com células de Aspergillus oryzae IPT - 301 imobilizadas em esponja de poliuretano para a produção enzimática de fruto-oligossacarídeos

Abstract

Fructooligosaccharides (FOS) have a wide range of applications in the food industry due to their physiological and functional properties. Its production occurs through a transfructosylation reaction in sucrose molecules catalyzed by fructosyltransferase enzymes (FTase, E.C.2.4.1.9) adhered to microbial cells. The immobilization of cells on support materials allows obtaining heterogeneous biocatalysts that are robust and resistant to adverse conditions in the reaction medium. Polyurethane sponges (EPU) are supports recommended for immobilization as they have thermal and mechanical stability, in addition to the size and distribution of pores that enable gaseous and substrate diffusion, essential for microbial growth. Currently, FOS production is conducted in batch bioreactors, a slow and costly process. Therefore, it is necessary to implement continuous reaction systems in fixed bed reactors (PBR) that increase the FOS production volume and reduce operating costs. Therefore, this work proposed to implement a continuous reaction system to produce FOS in a PBR reactor from Aspergillus oryzae IPT-301 cells immobilized in EPU, using commercial sucrose as substrate, with an upward feed flow. For this, the reactor was packed with the microbial cells cultivated and concomitantly immobilized, by batch process, in cubic EPU matrices using synthetic culture medium, pH 5.5, 200 rpm, 30 ºC for 32 h. For the continuous process, the influence of volumetric flow rate (1.0 mL.min-1 to 10.0 mL.min-1), substrate concentration (200 g.L-1 to 600 g.L-1), medium temperature was evaluated. reaction (30 ºC to 60 ºC) and biocatalytic bed mass in the transfructosylation (TA) activity profiles. Finally, operational stability studies were carried out with and without recycle in the PBR reactor for 12 h of reaction. The operating condition that provided the highest AT values used a sucrose concentration of 400 g.L-1, flow rate of 10 mL.min-1 for the enzymatic reaction conducted at 50 ºC, pH 5.5 with the reactor packed with 0.8 g of immobilized microbial cells. The operational stability results showed high and stable AT values throughout the reaction, reaching FOS productivities equal to 115.0 g.L-1h-1 and 5.0 g.L-1h-1 in the reactor operated with and without recycle current, respectively. The results showed that the implementation of a continuous reaction system can be promising for the enzymatic synthesis of FOS.