Fermentation is a generic process of producing a substance by cultivating a monad which produces (and usually exudes, either as waste or a secondary metabolite) the desired substance: the "product". The most common example is the fermentation of ethanol.
Many useful monads are nearly ubiquitous, and can be gathered without a lot of effort. Many of those produce useful materials. Yeasts that produce alcohol from sugars are one example. Molds which produce antibiotics are another. Bacteria that produce convert atmospheric nitrogen to organic nitrogen are a third. A substantial majority of monads cannot be easily cultivated, but some can. Those that can be cultivated and which produce useful materials are a boon.
- By definition, if the organism can produce the material, we could synthesize it. However many syntheses are so complex that the yield is infinitesimal. In these cases, it is often worthwhile to pay the additional thermodynamic costs of the growth and life of an organism to produce the material in question.
- Likewise, a monad which performs the desired synthesis can do it reliably and independently of the humans involved: it can be a set-and-forget operation. (Bread rising) which can mitigate the thermodynamic cost further by allowing the more expensive resource (the human) to perform other tasks instead.
Usually, the monads are collected in some way from the environment, and cultivated separately by species. Some, such as yeast, can even be stored in an inert form indefinitely once collected. They are grown either on a solid media (such as agar) or more preferentially in a liquid "broth". The growth media is maintained within the living conditions of the monad, and the media is supplemented with the nutrients required by the monad. Eventually, when the broth (or colony) contains a sufficient mass of the product the monad colony is either separated, culled, or exterminated, and the product is extracted.
- Liquid media are preferred over solid media
- Factors such as light, temperature, humidity, and other conditions are controlled as much as possible to favor monad growth and subsequent production of the desired metabolites.