Fermentation agent and Mainspring

Mainspring and fermentation agent are semantically related. In some cases you can use "Mainspring" instead a noun phrase "Fermentation agent".

Mainspring noun - The most important spring in a mechanical device (especially a clock or watch); as it uncoils it drives the mechanism.

Fermentation agent and mainspring are semantically related. Sometimes you can use "Fermentation agent" instead a noun "Mainspring".