ABSTRACT
The possibility of inducing genetic variability in the fungus Trichoderma reesei which produces cellulases upon treatment with different mutagenesis was investigated. The fungal strain NRRL-12368 was treated with UV-light, NTG, and combined treatment with both of them or combined treatment with UV-lightNaNO2. The results indicated that the treatment with UV-light induced 183colonies, 48 of them are morphological variants and 6 are auxotrophic mutants. When the NTG mutagen was applied, 48 colonies were isolated, 20 of them are morphological variants and only one is auxotrophic mutant. Using the combination between UV and NTG, 64 colonies were obtained, 24 of them are morphological variants and only one is auxotrophic. The combination between UV and NaNO2 gave 49 colonies, 11 of them are morphological variants and one is auxotrophic mutant. These mutants were evaluated for their productivity concerning the three cellulase enzymes FPase, CMCase and beta-glucosidase. Some mutants overyielded the parental strain in the cellulases production. The mutant S26 produced 180%, 102% and 31.6% FPase, CMCase and beta-glucosidase more than the original strain, respectively. No relationship can be found between the requirements of auxotrophic mutants and their cellulase activities, since some mutants lost their enzymes activity, some others produced one or more of these enzymes, whereas two mutants produced the three enzymes more than their parental strain