AUTHOR=Qian Yuanchao , Zhong Lixia , Hou Yunhua , Qu Yinbo , Zhong Yaohua 

TITLE=Characterization and Strain Improvement of a Hypercellulytic Variant, Trichoderma reesei SN1, by Genetic Engineering for Optimized Cellulase Production in Biomass Conversion Improvement

JOURNAL=Frontiers in Microbiology

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2016.01349

DOI=10.3389/fmicb.2016.01349

ISSN=1664-302X

ABSTRACT=<p>The filamentous fungus <italic>Trichoderma reesei</italic> is a widely used strain for cellulolytic enzyme production. A hypercellulolytic <italic>T. reesei</italic> variant SN1 was identified in this study and found to be different from the well-known cellulase producers QM9414 and RUT-C30. The cellulose-degrading enzymes of <italic>T. reesei</italic> SN1 show higher endoglucanase (EG) activity but lower β-glucosidase (BGL) activity than those of the others. A uracil auxotroph strain, SP4, was constructed by <italic>pyr4</italic> deletion in SN1 to improve transformation efficiency. The BGL1-encoding gene <italic>bgl1</italic> under the control of a modified <italic>cbh1</italic> promoter was overexpressed in SP4. A transformant, SPB2, with four additional copies of <italic>bgl1</italic> exhibited a 17.1-fold increase in BGL activity and a 30.0% increase in filter paper activity. Saccharification of corncob residues with crude enzyme showed that the glucose yield of SPB2 is 65.0% higher than that of SP4. These results reveal the feasibility of strain improvement through the development of an efficient genetic transformation platform to construct a balanced cellulase system for biomass conversion.</p>