Non-foaming Mutants of Sake Yeasts

Abstract

Two selection methods of non-foaming mutants of sake yeasts (a kind of cell wall mutants lacking the ability to form froth head in sake mash) are described. The mutants, being different in both the affinity to gas bubble and in the agglutinability from the parent, were concentrated, by removing the wild type cells with froth in froth flotation method and by removing them by agglutination caused by lactobacillus cells in cell agglutination method. Spontaneous non-foaming mutants of Kyokai No. 7 strain were isolated from the concentrates after 9 successive trials of each selection procedure at the rates of 50% by the former and 81% by the latter. The UV-induced mutants were also isolated from the concentrates after the 7 successions at the rates of 80% and 100%, respectively, by the former and by the latter. There were two types among the non-foaming mutants with respect to the agglutinability; the one was non- or almost non-agglutinable type (type 1) and the other was weakly-agglutinable one (type 2). The ...