In this study, we isolated the 2,4-dinitrophenol (DNP)-resistant
sake yeasts by UV mutagenesis, a useful mutagenesis method for
diploid sake yeast (8). Because DNP is a respiratory inhibitor that
blocks mitochondrial membrane potential (9), the resistant mutants
showing higher mitochondrial activity or no requirement for
growth without mitochondria would be obtained using DNP as a
selective pressure. As expected, we obtained the mutants whose
mitochondrial activity is modified and produced various compositions
of organic acids. In addition, the organic acid-producing
mechanisms of the DNP-resistant sake yeast were elucidated by
physiological and enzymatic analyses.