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This study was performed to construct killer wine yeasts which might suppress the growth of wild yeasts, reduce the consumption of starter and condense the fermentation period. Saccharomyces cerevisiae M524, a commercial wine yeast, was treated with N-methyl-N´-nitro-N-nitrosoguanidine to induce auxotrophic mutants, i.e., CHM 2(thr^-), CHM 3 (asp^-) and CHM 6 (tyr^-). These auxotrophs were fused successfully with a killer yeast, S. cerevisiae 1368R(α his 4 kar 1-1(kil-k) (k_0), respiratory deficient) using sphoroplast techniques and the fusants were designated as CHF 21(th^- kil^+), CHF 22(thr^- kil^+), CHF 31(asp^- kil^+) and GHF 61(tyr^- kil^+). Combined cultivation of CHF 31 with 1368R or S. cerevisiae 5×47 (killer sensitive) proved out that CHF 31 had the characteristic of killing and produced the same amount of ethanol as the prototroph, M524.
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