1. The promotion or process of changing food components into natural preservatives or to more easily digestible nutrients with the action of yeasts, fungi, or bacteria: Making bread, brewing beers, producing wine, and the manufacturing of yoghurts and cheeses are just a few examples of fermentogens.
2. The transformations of organic matter that have been brought about in nature and which have caused various forms of diseases by micro-organisms: In 1860, the Academy of Sciences awarded Louis Pasteur (1822-1895) its experimental physiology prize for his studies of fermentogens.

Pasteur's belief that micro-organisms were responsible for many diseases led others to also believe that there were fermentogens of diseases in animals and humans.