DISCUSSION
Attempts have previously been made to construct recombinant
T. reesei expressing b-glucosidase to overcome the inhibition
of cellobiose conversion. Nakazawa et al. (21) successfully constructed
a recombinant T. reesei strain X3AB1 expressing AaBGL1
under the control of a xyn3 promoter that displays high specific
activity. The enzyme preparation called JN11 from this X3AB1
strain showed higher cellobiase activity than that of its parent
strain. The efforts to express BGL targets in T. reesei are limited by
the availability of cellulase-inducible promoters (42). Therefore, a
better strategy is to introduce the cellulase gene into a noncellulolytic
organism that exhibits high product yield, such as
Saccharomyces (43e46). A previous study reported the expression
of AaBGL1 in S. cerevisiae (37), but these studies lacked information
on the specific cellobiase or the pNPGase activity of the
recombinant protein. So, we set out to characterize this recombinant
AaBGL1 in terms of its specific activity as well as its ethanol
production ability