Daqu is a special kind of yeast, which uses bacteria to ferment grain. The main component of grain is starch, which produces wine after fermentation.

Definition of catalyst: a substance that can significantly improve the reaction rate and keep its chemical properties and quantity unchanged before and after the reaction.

But koji is different. This is a kind of bacteria. How can it be said to be a catalyst? It eats grain and pulls out what we want. It is also growing and reproducing itself.

Examples in life: Enzymes are catalysts, which can speed up the reaction. Eating multi-enzyme tablets can speed up digestion. Saliva in the mouth is also an enzyme and can also help digestion. There are not many catalysts in our life, which are mainly used in chemical production and biological production.