Fructooligosaccharides (FOS) are mainly produced by microbial fructosyltransferases (FTase, E.C.2.4.1.9), and Aspergillus oryzae IPT-301 has shown high fructosyl transferring and low hydrolytic activities, which leads to high FOS production yields, but the main operating parameters for its best performance have been scarcely studied. Thus, this work aimed to evaluate the cellular growth, production and characterization of mycelial and extracellular FTases by Aspergillus oryzae IPT-301. Experimental design showed that the extracellular FTase performance was optimized (high transfructosylation activity and low hydrolytic activity) for reaction pH 5.5-6.75 and temperature of 45-50 °C and was fitted by the Michaelis-Menten model, while the mycelial FTase showed better performance at pH below 6.5 and temperature above 46 °C and was better fitted by the Hill model. The results obtained showed that the fungus represents a promising source for FOS production on a laboratorial scale.

BACKGROUNDFructooligosaccharides (FOS) are sweeteners produced through the use of enzymes called fructosyltransferases (FTases) (EC 2.4.1.9). However, FTase reuse is meagre and the cost of the enzyme production is high, making FOS production economically unfeasible. In order to address these issues, this study aims to immobilize cells from Aspergillus oryzae IPT‐301, containing FTase enzyme previously glutaraldehyde‐crosslinked, by means of entrapment in calcium alginate beads. The conditions to obtain the particles, such as alginate type, mycelium mechanical dispersion, degree of crosslinking, size of the beads, and their reflections on transfructosylation activity (AT) were evaluated previously.RESULTSThe highest AT used low‐viscosity alginate solution (4.0% w/w) crosslinked with calcium chloride (0.2 mol L−1) and beads of mean diameter 2.15 mm. The entrapment conditions were complemented by conducting the reaction under different temperatures, pH values, substrate concentrations and by reusing the beads. The highest transfructosylation activities were obtained under reaction conditions of 50 °C, pH 5.5 and substrate concentration 400 g L−1.CONCLUSIONThe AT levels found with the glutaraldehyde‐crosslinked and entrapped cells in calcium alginate were ≈70% higher than the ones obtained with free cells, not glutaraldehyde‐crosslinked. Moreover, the immobilized cells (crosslinked+entrapped) retained their AT up to the third cycle of total sucrose depletion in the reaction medium, attesting to the potential use of the beads in continuous FOS production. © 2020 Society of Chemical Industry

BACKGROUND Fructooligosaccharides (FOS) are prebiotic sugars used in the production of functional foods. These sugars can be produced by the transfructosylation reaction of sucrose catalyzed by fructosyltransferase enzymes (FTase, E.C.2.4.1.9). The aim of this work was to evaluate the use of cells of Aspergillus oryzae IPT‐301 as biocatalysts for the sucrose transfructosylation reaction in a packed bed reactor (PBR). RESULTS The morphology of the cells was observed by scanning electron microscopy, and BET specific surface areas were examined by nitrogen physisorption The highest transfructosylation activity (660 U g−1) of the cells was obtained at 25 min of reaction by adopting a reaction temperature of 50 °C, sucrose concentration of 470 g L−1, and volumetric flow of 15 mL min−1. The rise in volumetric flow provided an increase in the transfructosylation activity, but also a faster deactivation of the biocatalyst. Enzyme kinetics was described using the Michaelis–Menten model, with a Vmax of 632.8 U g−1 and a km of 160.7 g L−1. The cells showed constant enzymatic activity for 12 h of reaction in the PBR operated with discontinuous flow at flow rates of 5 mL min−1 and 11.5 mL min−1, and in the PBR operated with continuous flow at a flow rate of 5 mL min−1. The transition from diffusional to kinetic regimes was observed starting from 11.5 mL min−1. CONCLUSION The results obtained suggest a high potential of application of the whole A. oryzae IPT‐301 cells for continuous FOS production in PBR. © 2022 Society of Chemical Industry (SCI).