difficult in the acidic medium. Maximum GA and 3-oxo-GA
yieldsof 51.45 and 18.25 %, respectively, corresponding
to total bioconversion efficiency of 69.7 %, were recorded
at initial pH of 6.5. In agreement with the present results,
Akao (1997) found that GL was hydrolyzed in the rat
intestinal tract between pH 6 and 7. However, Akao et al.
(1987), El-Menoufy (1988), Akao (1999a) and Kim et al.
(1999) reported that the optimal pH value of GL β–
glucuronidase activity was 5.6.
It is noteworthy to mention that, relatively good activities
(52.57 %) were recorded on performing the transformation
process in phosphate buffered medium (pH 6) (Figure 4).
However, the capacity of the microorganism to transform
GL was greatly suppressed in acetate buffered medium at
pH values from 3.6 to 5.6, indicating the deleterious effect
of the buffer constituents (data not shown).