Trichoderma reesei is an industrial filamentous fungus widely used for cellulase production. However

the difficulty in genetic modification of the high-production mutants limits the strain improvement. Firstly

the pyr4 gene was successfully deleted by target integration strategy in T. reesei QM9414 to construct a uracil auxotroph strain QP4. Compared with those in the parental strain

not only the genetic transformation efficiency was improved

but also the cellulase production was not influenced in QP4. The β-glucosidase (BGL) encoding gene bgl1 was further overexpressed in the QP4 strain. The transformants QPB4 and QPB5 with increased BGL activity were obtained by rapid screening based on the esculin plate. The BGL activities in the culture supernatants of QPB4 and QPB5 exhibited 10.01- and 8.26- fold higher than that in QP4

respectively. The crude enzyme preparations were used to saccharify two types of differently pretreated corncob residues. The glucose yields from saccharification of acid-pretreated corncob by QPB4 and QPB5 were 60.98% and 52.44% higher than that by QP4

respectively

while using the delignined corncob as substrate

the glucose yields by QPB4 and QPB5 were improved 80.01% and 86.00%

respectively. These results suggested that improvement of the genetic manipulation system in T. reesei greatly facilitated the strain improvement and increased the saccharification efficiency.