Glucose
Japanese: グルコース（ブドウ糖）
The most fundamental simple sugar. It serves as the starting material for fermentation, used by yeast and other microorganisms as an energy source.
Glucose is the most fundamental sugar serving as an energy source for living organisms. Named 'grape sugar' in Japanese for its abundance in grape juice.
In fermentation, glucose is the food for microorganisms. Yeast consumes glucose to produce alcohol and carbon dioxide; lactic acid bacteria convert it into lactic acid. The pathway varies by species, but the starting point is always this simple sugar.
In miso-making, amylase from koji mold first breaks rice starch down into glucose. Without this saccharification step, fermentation cannot begin.