Transgressive phenotypes from outbreeding between the <i>Trichoderma reesei</i> hyper producer RutC30 and a natural isolate

The filamentous fungus <i>Trichoderma reesei</i> produces cellulolytic enzymes that are essential for the hydrolysis of lignocellulosic biomass into monomerics sugars. The filamentous fungus <i>T. reesei</i> produces cellulolytic enzymes that are essential for the hydrolysis of lignocellulosic biomass into monomerics sugars, which can in turn be fermented to produce second-generation biofuels and bioproducts. Production performance improvement, which is essential to reduce production cost, relies on classical mutagenesis and genetic engineering techniques. Although sexual reproduction is a powerful tool for improving domesticated species, it is often difficult to apply to industrial fungi since most of them are considered asexual. In this study, we demonstrated that outbreeding is an efficient strategy to optimize <i>T. reesei</i>. Crossing between a natural isolate and a mutagenized strain generated a biodiverse progeny with some offspring displaying transgressive phenotype for cellulase activities.