Abstract
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.
Highlights
Nowadays, there is a continuous and growing attention for dietary prebiotics-oligosaccharides (PO), mainly due to their proven beneficial effects on human and animal health
The present study focused on laboratory-scale production of Aspergillus oryzae IPT-301 extracellular and mycelial FTases by submerged fermentation using synthetic culture medium and characterization studies of the process parameters and on enzymatic kinetic parameter determination
Effect of pH and temperature on stability enzymatic The stability of the extracellular FTase showed the highest relative transfructosylation activity at pH 6.0 (Fig.3A), whereas the mycelial FTase occurred between pH 5.0 - 8.0 (Fig. 3B)
Summary
There is a continuous and growing attention for dietary prebiotics-oligosaccharides (PO), mainly due to their proven beneficial effects on human and animal health. FOS can be found in different plants such as onion, garlic, banana, Jerusalem artichoke and some grasses (Maiorano et al, 2008) Their commercial production is predominantly based on microbial extracellular/mycelial enzymes called fructosyltransferases (FTases EC.2.4.1.9) (MuñizMárquez et al, 2016) in the presence of sucrose. Various FOS synthesized from sucrose include 1-kestose (GF2), nystose (GF3), and 1F -β-fructofuranosylnystose (GF4) where 1-3 units of fructose are attached via β-(2-1) linkage to the sucrose (Hernández et al, 2017; Gujar et al, 2018). These enzymes possess both transfructosylating and hydrolytic activities (Huang et al, 2016). High transfructosylation activity allows a high conversion of sucrose to FOS, while a high (At/Ah) is required to avoid the FOS molecule hydrolysis (Hidaka et al.,1988; Cuervo-Fernandez et al 2004; Cuervo-Fernandez et al 2007)
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