Effects of the Addition of Substrate and Salts in Both the Fructosyltransferase Immobilization and Its Catalytic Properties

Abstract

The partially purified extracellular fructosyltransferase from Rhodotorula sp. LEB-V10 immobilized in niobium particles in the presence of 4 and 8% (w/v) of sucrose showed no differences concerning fructooligosaccharide (FOS) synthesis, concluding that the enzymatic active sites are not related to immobilization. When immobilized in the presence of 5 and 10 mM CuSO4, this enzyme presented a slight increase in FOS yield (9–12%). In addition, no FOS molecule was produced when the synthesis was conducted with 10 mM CuSO4. This result might suggest that, besides the strong stabilization, the interaction between salt and enzyme should result in a “safer” conformational structure for the enzymatic active sites. FOS synthesis was also affected by the presence of 10 mM MnCl2 or NaCl, but only in a small scale than with CuSO4. Practical Applications The fructosyltransferase (FTase) from Rhodotorula sp. immobilized in niobium has proven to be a promising biocatalyst for fructooligosaccharide (FOS) production, a prebiotic sugar. Adsorption, a technique for FTase immobilization, presents several advantages, but it can, unfortunately, provide a biocatalyst with lower enzymatic activity depending on how the enzyme is linked to the support particles. Exploring the possibility of increasing FOS production by adding compounds such as sucrose (substrate) or CuSO4 (capable of promoting stability) during the process of adsorption has a great importance because it permits one to evaluate the interactions between enzyme and compound. Furthermore, the addition of salts (also capable of increasing stability) into the reactive medium for FOS production is also important to evaluate in order to understand if stability and higher yields are possible to be achieved together.