Imobilização de células de Aspergillus oryzae IPT-301 em suportes inorgânicos e sua aplicação como biocatalisadores para a produção de fruto-oligossacarídeos

Abstract

Fructo-oligosaccharides (FOS) are fructose oligomers consisting of fructose units linked to sucrose. These sugars exhibit non-cariogenic, anticancer properties and contribute to the balance of the intestinal microbiota. FOS can be produced from the transfructosylation reaction of sucrose, catalyzed by fructosyltransferase enzymes (FTase, E.C.2.4.1.9), which are extracellular or present in microbial cells. The use of cells with transfructosylation activity (AT) has become a promising alternative for FOS production, especially when immobilized in porous supports, as they form highly stable heterogeneous biocatalysts. The performance of these biocatalysts depends on the characteristics of the cell, the reaction conditions, and the support used. Therefore, the objective of this study was to evaluate the immobilization, via submerged cell culture, of Aspergillus oryzae IPT-301 cells in aluminum and titanium oxides. The immobilization of the microbial cells on the oxides occurred in a synthetic culture medium at pH 5.5, 200 rpm, and 30°C. The cell growth capacity over time and transfructosylation activity for both supports were evaluated, along with regeneration and reuse tests of the support to determine the most suitable one for further experiments. Stability tests were conducted for pH, thermal, storage, and operational conditions in batch and fixed-bed reactors. Additionally, the influence of sucrose concentration in the reaction medium on transfructosylation activity profiles was determined. The microbial growth curve showed that the optimal cell culture time was 32 hours for both supports. The regeneration test for the oxides indicated that only titania (TI40) could be reused in the cell culture process, as it did not present fractures during the various stages that could affect its morphology. The pH stability test indicated an optimal pH of 5.5 with the highest transfructosylation activity value of 1990.12 ± 45.5 U g-1. The storage stability showed that the activity was maintained only until the first day, progressively decreasing up to 60 days. The sucrose concentration that yielded the highest activity was 480 g L-1, with a value of 262.89 ± 25.49 U g-1. The thermodynamic parameters obtained in the thermal stability test indicated greater thermostability for the immobilized cell compared to the free cell. Finally, the cells immobilized on titania exhibited stable enzymatic activity in the batch reactor for 20 consecutive 1-hour reaction cycles and in the fixed-bed reactor for 24 hours under continuous flow. These results highlight the potential application of A. oryzae IPT-301 cells immobilized on titanium oxide for FOS production, emphasizing the support's regeneration potential and the high operational stability of the biocatalyst.