Thermal and operational deactivation of Aspergillus fumigatus β-glucosidase in ethanol/water pretreated wheat straw enzymatic hydrolysis

The stabilization effects on a novel commercial beta-glucosidase preparation from Aspergillus fumigatus during saccharification of ethanol-water pretreated wheat straw were analysed in comparison to this enzyme stability during cellobiose hydrolysis. For this purpose, the kinetics of beta-glucosidase residual activity during cellobiose hydrolysis from 40 till 70 degrees C were studied, resulting in the fitting of a first-order partial deactivation model. Furthermore, a subsequent fitting of a kinetic model including this first-order deactivation equation and a Michaelis-Menten equation with double competitive inhibition by glucose and uncompetitive inhibition by cellobiose to released glucose was successful. Finally, global enzyme deactivation and prospective deactivation of enzyme remaining in the liquid phase were evaluated during wheat straw hydrolysis at 50 degrees C as a relevant saccharification process. Results suggest that the presence of a solid substrate dramatically reduces the global deactivation rate of the enzyme and, in addition, there is no loss the stability of the enzyme in the liquid phase along the saccharification process, even for 72 h.