Clostridium butyricum is a strictly anaerobic endospore-forming Gram-positive butyric acid–producing bacillus subsisting by means of fermentation using an intracellularly accumulated amylopectin-like α-polyglucan (granulose) as a substrate.

[1] C. butyricum is a soil inhabitant in various parts of the world, has been cultured from the stool of healthy children and adults, and is common in soured milk and cheeses.

[11] The standard preparation as marketed by Miyarisan Pharmaceutical (Tokyo, Japan) consists of white, marked tablets each containing 0.35 × 106 colony forming units (CFU) of C. butyricum MIYAIRI 588 (as active agent).

[12] Absence of neurotoxin production has been demonstrated by polymerase chain reaction (PCR) and Southern blot hybridisation for type E botulinum toxin gene.

Recent European Food Safety Authority opinions confirm the official strain nomenclature as Clostridium butyricum FERM BP-2789.