Thermal Deactivation Kinetics of Pseudomonas fluorescens Lipase Entrapped in AOT/Isooctane Reverse Micelles

Thermostability of the lipase (EC 3.1.1.3) was found to be increased by the enzyme entrapment in 50 mM AOT/isooctane reverse micelles. The half-life (15.75 h) of Pseudomonas fluorescens lipase entrapped in reverse micelles at 70 degrees C was 9.72- and 11.41-fold longer than those solubilized in a glycerol pool or in 10 mM phosphate buffer (pH 8.0), respectively. The enzyme deactivation model considering a two-step series-type was employed, and deactivation constants for the second step (k(2)) at all temperatures were drastically decreased after the lipase was entrapped in reverse micelles. In particular, k(2) (0.0354 h(-1)) at 70 degrees C in reverse micelles was 12.33- and 13.14-fold lower than in a glycerol pool or in the phosphate buffer, respectively. The deactivation energies (from k(1), k(2)) for the lipase entrapped in the reverse micelles, solubilized in a glycerol pool, or in the aqueous buffer were 7.51, 26.35 kcal/mol, 5.93, 21.08 kcal/mol, and 533, 1737 kcal/mol, respectively.