A novel killer yeast effective on Schizosaccharomyces pombe

To control the extent of deacidification in wine making, we screened Kluyveromyces strains by their activity to kill the fission yeast Schizosaccharomyces pombe. Among Kluyveromyces IFO strains tested, K. waltii IFO 1666T was shown to have the desired activity. The killer spectrum of this strain was different from those of the other known killer yeasts. The activity was found in the culture medium and was lost by protease treatment. The activity was associated with the precipitate obtained by an increase of ammonium sulfate concentration. The toxin was larger than 10,000 daltons as judged by ultrafiltration.