T. reesei is an important commercial and industrial micro-organism due to its cellulase production ability. Many strains of T. reesei have been developed since its discovery, with heavy emphasis on increasing cellulase production. These "improvement programs" originally consisted of classical (ionising-radiation-based and chemical-based) mutagenesis, which led to strains capable of producing 20 times as much cellulase as the QM6a isolate.[6] The ultimate aim in the creation of hypercellulolytic strains was to obtain a carbon catabolite derepressed strain. This derepression would allow the T. reesei strain to produce cellulases under any set of growth conditions, even in the presence of glucose.
However, with the advent of modern genetic engineering tools such as targeted deletion, targeted knockout, and more, a new generation of strains dubbed "hyperproducers" has emerged. Some of the highest performing industrial strains produce up to 100 grams of cellulases per litre, more than 3 times as much as the RUT-C30 strain (which itself produces twice as much as the parent strain NG14 from which it was derived).