Generating favorable nano-environments for thermal and solvent stabilization of immobilized beta-galactosidase.

Abstract

beta-Galactosidase (Escherichia coli) was immobilized through its thiol groups on thiolsulfinate-agarose gel. After enzyme immobilization, different nano-environments were generated by reacting the excess of gel-bound thiolsulfinate moieties with 2-mercaptoethanesulfonic acid (S-gel), glutathione (G-gel), cysteamine (C-gel), and mercaptoethanol (M-gel). Concerning thermal stability at 50 degrees C, the G-gel and the M-gel derivatives were the most stable with residual activity values of 67% and 45%, respectively. The stability in several solvent systems was studied: ethyl acetate (1.6% vol/vol), ethylene glycol (50% vol/vol), and 2-propanol (50% vol/vol). In ethyl acetate, both the M-gel and S-gel were highly stabilized; the time required for activity to decay to 80% of the initial activity was increased 29-fold for the M-gel and 20-fold for the S-gel with respect to the soluble enzyme. The G-gel was the least stable of all the derivatives. The different behaviors of the derivatives in thermal and solvent stability studies suggest that each nano-environment contributes differently to the enzyme stability, depending on the denaturing conditions. Therefore, it may be possible to tailor the matrix surface to maximize enzyme stability in particular applications.