The electrofusion technique was applied to the breeding of
shochu yeast. An auxotrophic strain (lys) obtained from
Saccharomyces cerevisiae MK 021, a diploid strain used for
shochu making, and anauxotrophic strain (
ade) obtained from
Saccharomyces cerevisiae Kyokai No.9, a diploid strain, usedfor sake making, were fused by the electrofusion technique. The optimal parameters for the fusion of
Saccharomyces protoplasts were: 2 MHz AC frequency, 400 V/cm AC voltage, 6 kV/cm DC pulse voltage, 60 psec duration, and 2 pulses. Some of the fusants showed good growth and fermentation, and produced larger amounts of aroma components, when compared to the original strains. Spore segregation test was carried out to obtain more stable strains. Spores from a fusant strain, F-1 having the highest sporulation ability were isolated by micromanipulation, and their fermentation rate and formation of aroma components were investigated using rice or barley
koji. Of the selected segregants, F-1-2, was found to show especially good growth and to produce much aroma components such as
n-propyl alcohol, isobutyl alcohol, isoamyl alcohol and isoamyl acetate.
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