Thermal stability of the immobilized fructosyltransferase from Rhodotorula sp

Abstract

The thermal stability of the extracellular fructosyltransferase (FTase) from Rhodotorula sp., recovered from cultivation medium by ethanol precipitation and immobilized onto niobium ore, was studied by Arrhenius plot, half-life profile, half-inactivation temperature (T50) and thermodynamic parameters. The Arrhenius plot showed two different behaviors with different deactivation energies (Ead) only after immobilization, the transition occurring in the temperature interval between 51 and 52°C. T50 for the free enzyme was estimated to be around 62°C and, after immobilization, 66°C. After 15 minutes at 52°C, it was also possible to observe enzymatic activation for both the free and immobilized forms, but greater activation was achieved at pH 4.5 with the immobilized enzyme. Between 47-51°C the immobilized enzyme was more stable than the free enzyme, with pH 6.0 being the more stable condition for the immobilized enzyme. However, above 52°C the free form was more stable.