BREEDING OF STARCH-UTILIZING AND ITACONIC-ACID-PRODUCING KOJI MOLDS BY INTERSPECIFIC PROTOPLAST FUSION BETWEEN ASPERGILLUS-TERREUS AND ASPERGILLUS-USAMII

Interspecific protoplast fusion between Aspergillus ten eus, an itacon ic acid producer, and A. usamii, a glucoamylase producer, was done to breed new koji molds producing itaconic acid from starch. Protoplast f usion between auxotrophic mutant strains by poly(ethylene glycol) trea tment produced prototrophic fusants with a fusion frequency of 10(-5)- 10(-4). The stabilities of some fusants obtained were confirmed by suc cessive subcultures. Conidial analyses of DNA contents and the number of nuclei indicated that the fusants obtained were haploids like the p arental strains. One of the stable fusants, F-112, morphologically res embled A. terreus, and produced maximally 35.9 mg/ml itaconic acid fro m soluble starch (120 mg/ml) at day 6 of cultivation. This productivit y from soluble starch was five times as high as that of A. terreus and 70% of that of A. tel I eus from glucose (120 mg/ml).