After pulping 100kg of ripe Arabica cherries, there will be about 12kg of mucilage adhering to the beans. Once dry, this is about 2kg, with 1kg of that being sugars that will be broken down and consumed during the fermentation to loosen the mucilage from the beans for easy washing. Most fermentation cycles in Colombia are without water, first a yeast fermentation producing alcohol, then bacterial resulting in mainly inactive lactic acid. Almost always, no additives are used; rather the tiny life forms found everywhere.
Mucilage has a pH of about 6.5, and this drops to about 4.1 throughout fermentation, favouring different species as it does. Though a wide range of microbial flora started out in the raw material, ahem, as the environment becomes more acidic many species have a hard time and quickly face extinction. By the end of the fermentation cycle, the population distribution of the microorganisms has completely shifted, and the now dominant life form is a species that was present in only small populations in the original sticky fruity starting phase.