Abstract
The beta-glucosidase activities of nine commercial enzymatic preparations were compared by evaluating the effects of pH, thermal stability, kinetic parameters, and glucose tolerance. The pH value of the reaction medium strongly influenced the activities, stabilities, and glucose inhibition of the assayed beta-glucosidases. Celluclast (R) 1.5 L showed the highest activity on pNPG hydrolysis (70.55 U mL(-1) and 0.69 U mg(-1)), whereas Lallzyme Beta produced the highest yields on cellobiose hydrolysis (93.4%). Regarding the glucose tolerance and the pH, Pectinex Ultra SP-L presented the maximum glucose tolerance at pH 3.0, keeping 54% of its initial activity in the presence of 167 mmol L-1 of glucose, whereas at pH 7.0, Pectinex Smash XXL presented 44% of activity at 222 mmol L-1 of glucose. Pectinex Smash XXL showed the highest K-I (19.75 mol L-1), whereas Celluclast (R) 1.5 L presented the highest K-I/K-M (19). Our results suggest that these commercial preparations are promising sources of beta-glucosidases, being Pectinex Smash XXL indicated for applications at neutral pH because of its glucose tolerance and thermal stability at this pH value, whereas Celluclast (R) 1.5 L, Lallzyme Beta, and Pectinex Ultra SP-L are more recommended for applications at acid pH, such as in fruit juices and wine productions.