Trichoderma reesei is used for industry-scale production of enzymes, in particular cellulases.The ancestor of most currently used industry strains is Rut-C30, which was isolated after two rounds of mutagenesis by screening for high secretion of cellulases, and was consequently described as cellulase hyperproducing strain.Later it was found that Rut-C30 bears a truncated version of the Carbon catabolite repressor 1 (Cre 1)-encoding gene.Cre1 is responsible for repression of both, xylanase-and cellulase-encoding genes.