Development of Trichoderma reesei mutants by combined mutagenesis and induction of cellulase by low-cost corn starch hydrolysate

[Display omitted] •Trichoderma reesei mutants were obtained with chemical and irradiation treatment.•Mutant T. reesei D-7 showed 57% higher filter paper activity (FPA) than wild type.•Soluble inducer was prepared by hydrolysis of corn starch with α-amylase.•Mixture of corn starch hydrolysate and cellulose achieved higher FPA. The high cost of cellulase production is one of the key barriers to commercialization of cellulose-based biofuels. Screening high cellulase-producing strains and exploring low-cost inducers of cellulase are efficient strategies to address this issue. In this study, Trichoderma reesei Rut-C30 mutants were obtained by treatment with Ethyl Methyl Sulfonate (EMS) and plasma-irradiation. Mutant T. reesei D-7 was selected as the most promising cellulase producer based on screening through phosphoric acid-swollen cellulose plates. The filter paper activity (FPA) of T. reesei D-7 was 57.55% higher than that of the wild-type strain. Corn starch hydrolysate (CSH) prepared through hydrolysis of corn starch by α-amylase were used as soluble inducer for cellulase production with T. reesei D-7. FPA of 4.53 IU/ml was achieved at an optimal initial concentration of CSH (40g/l reducing sugar). Moreover, CSH and cellulose were proved to be the most effective soluble and insoluble inducers for cellulase production with T. reesei D-7. Mixture of CSH and cellulose further improved FPA up to 15.62 IU/ml, which was 3.45-fold or 1.52-fold as high as that achieved using CSH or cellulose as an inducer.