The role of the transcription factor creA-mediating carbon catabolite repression in Trichoderma orientalis EU7-22 was investigated for cellulase and hemicellulase production. The binary vector pUR5750G/creA::hph was constructed to knock out creA by homologous integration, generating the ΔcreA mutant Trichoderma orientalis CF1D. For strain CF1D, the filter paper activities (FPA), endoglucanase activities (CMC), cellobiohydrolase activity(CBH), β-glucosidase activity (BG), xylanase activity (XYN), and extracellular protein concentration were 1.45-, 1.15-, 1.71-, 2.51-, 2.72, and 1.95-fold higher in inducing medium and were 6.41-, 7.50-, 10.27-, 11.79-, 9.25-, and 3.77-fold higher in glucose repressing medium, respectively, than those in the parent strain after 4 days. SDS-PAGE demonstrated that the extracellular proteins were largely secreted in the mutant CF1D. Quantitative reverse-transcription polymerase chain reaction indicated that the expressions of cbh1, cbh2, eg1, eg2, bgl1, xyn1, and xyn2 were significantly increasing for the mutant CF1D not only in the inducing medium but also in the repressing medium. Those results indicated that creA was a valid target gene in strain engineering for improved enzyme production in T. orientalis.
Keywords: Cellulase; Extracellular protein; Hemicellulase; Trichoderma orientalis; creA.