Isolation of Highly Proteolytic Mutants from Aspergillus sojae

Mutational experiments were performed to improve the protease productivity of the mutant strain X-816 previously induced by X-ray irradiation from Asp. sojae K. S. as a high protease producer. The significant correlation was found between the protease production in wheat bran koji and the clear zone around a fungal colony formed on the special medium containing casein. Several mutants of high protease productivity were obtained by the use of the clear zone as a simple criterion for a primary screening test. In this paper, the composition of some other hydrolytic enzymes in wheat bran koji and the genetic stability of these mutants are also discussed.