WordNet sense 1 (a state of agitation or turbulent change or development):

agitation, fermentation, tempestuousness, unrest

WordNet sense 2 (a process in which an agent causes an organic substance to break down into simpler substances; especially, the anaerobic breakdown of sugar into alcohol):

zymosis, fermenting, zymolysis

WordNet sense 3 (cause to undergo fermentation):

work

WordNet sense 4 (go sour or spoil):

sour, turn