In sake production, what is one of the main uses of koji mold?

In sake production, koji mold plays a crucial role in converting rice starch into sugars through a process known as saccharification. This is vital because yeast requires sugar to produce alcohol during fermentation. The koji mold, specifically the species Aspergillus oryzae, is cultivated on steamed rice to break down the starches, effectively transforming them into fermentable sugars. This process is fundamental to sake brewing because without the action of the koji mold to create sugar from the starches, the yeast would not have the necessary food source to thrive and carry out fermentation, ultimately affecting the alcohol and flavor profiles of the finished sake. Thus, its primary role in converting starches into sugars highlights its central importance in successful sake production.