Comparative effect of mutation of Aspergillus oryzae by gamma or ultraviolet irradiation

Mutation frequency of Aspergillus oryzae IAM2630 was studied compared with gamma and ultraviolet irradiation. In this study, mutation frequency of morphological changes on survived colonies was increased up to 50% by irradiation of gamma-rays at survival fraction of 10-3 to 10-4 on potato-dextrose agar. On the contrary, mutation frequency of ultraviolet was obtained less than 17% at survival fraction of 10-3. Mutants with improvement of three-to-five hold production of α-amylase were isolated by irradiation of gamma-rays at 1.2 kGy. However, we could not isolate any mutants of higher production of α-amylase by ultraviolet irradiation. (author)