Abstract
By making irradiation of ultraviolet ray on Asp. niger, 57 mutants were obtained and the proteolytic systems of these mutants were studied in comparison with that of the parent strain. The molds were grown on wheat bran and the culture extracts were made to act on milk casein for determining protease activities according to the modified Anson's method. The productivity of acid protease tended to decrease with mutation, and mutants were generally inferior to the parent in the acid protease activity. Most of the mutants were similar to the parent in that they had proteolytic systems that were principally composed of acid protease. But two of the mutants had considerably different proteolytic systems and consisted predominantly of alkaline protease. Both of these two mutants were belonging to Albino type.
