Thermostabilization of Bacillus subtillis CCMI 966 xylanases with trehalose : Study of deactivation kinetics

Abstract

The effect of trehalose (0.5 M) on the thermal stability of two endo-1,3(4)-β-xylanases, alkaline Xyl I (p I>9.3) and a neutral Xyl II (p I 7.5), purified from the culture broth of Bacillus subtilis CCMI 966 was studied at 60 and 70 °C. Thermal deactivation kinetics of Xyl I and Xyl II were analyzed in the absence and in the presence of trehalose. Suitable mechanisms were proposed to describe the deactivation process. Trehalose not only stabilized both enzymes at 60 and 70 °C, but also increased their initial activity. Addition of trehalose allowed both isoenzymes to attain a final state with residual activity. In contrast, without trehalose, the final state had no activity. At 60 and 70 °C, the Xyl I half-lives increased 2.5- and 2-fold, respectively, in the presence of trehalose. The half-life for Xyl II at 60 °C, increased about eightfold. At 70 °C, the half-life increased about twofold and gave rise to a final state with residual activity of about 35%.