Breeding by Protoplast Fusion of Koji Mold, Aspergillus sojae

Interspecific Electrofusion of Protoplasts betweenAspergillus oryzaeandAspergillus sojae

“…Selection of fusants appearing on the stabilizercontaining MM plates and induction of stable heterozygous diploids with green conidia from unstable heterokaryons were done as described previously. 4) glutaraldehyde solution containing 0.6 M KCl for 4 hr at room temperature. Samples were washed and resuspended in the buffer/0.6 M KCl· solution.…”

“…This method, however, has a number of disadvantages in comparison with the newly developed electrical fusion methods. 15 ) In previous papers, 4,5,16,17) we reported the intra-specific protoplast fusion of A. sojae and the inter-specific protoplast fusion between A. oryzae and A. sojae by PEG treatment, and reported that the frequency. of interspecific fusants was very much lower than that of intraspecific fusants obtained by PEG treatment.…”

“…Recently, protoplast fusion has become a valuable technique for strain improvement, i.e., in Aspergillus, [1][2][3][4][5][6][7][8][9] Penicillium,lo,ll) Mucor 12 ) and Trichoderma. 13 ,14) Polyethyleneglycol (PEG) has been used almost exclusively as the fusogenic agent for the fusion of these fungus protoplasts.…”

Improvement of enzyme productivities through mutation or haploidization of heterozygous diploids obtained by protoplast-fusion of Aspergillus sojae.

“…The DNAcontents per nucleus of the parents, heterozygous diploids and haploidized recombinants shownin strains. In the previous paper, 14) we reported that heterozygous diploids were obtained through protoplast fusion of two genealogically unrelated A. sojae strains with unbalanced or one-sided enzyme-productivities, and that the activities of both protease and glutaminase in these heterozygous diploids were distributed between those of the parents. The activities of the two each enzymes seerned to behave in such a manner that the sum of both activities in one strain did not exceed those in the parents.…”

“…In a previous paper, 14) we reported that fusants (heterokaryon) of Aspergillus sojae were obtained through protoplast fusion of a protease hyper-producer and a glutaminase hyper-producer, and that stable heterozygous diploids were induced from the heterokaryons on UVtreatment. Enzymeassaying of these diploids revealed that the productivities of either enzyme in most diploids were distributed around the meanvalue for the parents or below.…”