In conclusion, we identified Fis1p as the mitochondrial fragmentation factor during sake brewing, and elucidated that disruption of the FIS1 gene causes the production of a higher content of malate both in laboratory and industrial yeast strains. These findings show, for the first time, that mitochondrial morphology plays a role in the metabolism of constituents during alcohol fermentation and that inhibition of mitochondrial fragmentation causes higher malate production in sake yeast.