Bacteria are also important in rum fermentations and butyric acid bacteria, such as Clostridium and Cl. butyricum, Cl pasteurianum are important in production of volatile acids in saccharobutoricum relationships with yeast heavy rum. There may also be synergistic Butytic acid producing clostridia are most effective when added as pure cultures. The pitching rate is usually ca. 20% of that used for yeast, the clostridia being added to the fermentation when the the 100 ml wash. An alternative procedure is to preferment a portion(15-30% of the wash with pure cultures of clostridia.