Abstract:
This research was undertaken to determine biochemical properties of beta-glucosidase (beta-D-glucoside glucohydrolase, EC 3.2.1.21) isolated from Muscat of Bornova grape. The optimum pH for beta-glucosidase activity was found to be 5.0, and the enzyme showed high activity over a broad pH range of 4.5-6.0. However, due to low activity at pH 3.0, the enzyme is expected to exhibit only a fraction of the maximum activity during grape juice fermentation due to low pH of grape juice. As the temperature increased from 30 to 55 degrees C, the activity increased, too, the maximum activity occurring at 55 degrees C which implies that the enzyme is expected to exhibit a low activity at grape juice fermentation. According to thermal inactivation studies, k(D) values increased as the temperature increased, whereas half-life and D values decreased. Energy of activation (E-a) and Z values were found to be 120.99 kj mol(-1) (r(2) = 0.9776) and 18.08 degrees C (r(2) = 0.9750), respectively. d-glucose and ethyl alcohol inhibited the enzyme at varying degrees depending on the concentration.
