Mutants of bakers' yeasts producing a large amount of isobutyl alcohol or isoamyl alcohol,flavour components of bread

Summary Mutants resistant to 4-aza-dl-leucine were derived from strains of the bakers' yeast Saccharomyces cerevisiae and selected with respect to overproduction of isobutyl alcohol (i-BuOH) or isoamyl alcohol (i-AmOH). Many mutants that produced i-BuOH or i-AmOH more than the parent strains were obtained. In the evaluation of these mutants, bread containing more i-BuOH was evaluated as giving a favorable characteristic flavour, but bread with more i-AmOH was unfavorable. These mutants were able to ferment dough at similar rates to commercial bakers' yeasts. The mutants overproducing i-BuOH or i-AmOH were released from inhibition of the key enzymes, acetohydroxy acid synthase and -isopropylmalate synthase, respectively, in the pathway of branched-chain amino acids synthesis.Offprint requests to: M. Watanabe