Introduction: Widespread medical usage of botulinum toxins has increased the need for the precise analysis of its biological activity. The aim of this study was production and crystallization of the botulinum type A toxins.

Methods: In this study, Clostridium botulinum was grown and inoculated into the Tripticase Soya Broth culture media, under anaerobic condition and toxin production was monitored. The maximum yield of toxin was obtained after 96 hours, then toxin was harvested by acidifying the whole culture and centrifugation. The period of bacterial growth was extensively checked for toxin activity by mouse assay and crystallization was done at the same time.

Results: The results of this study showed that Clostridium botulinum grew in the above condition and produced toxin after 96 hours. The toxin produced in the low pH range of 4– 5.8 was stored as cube- shaped crystals. The crystallized toxin preparation was stable over time and maintained its biological activity after 4 years of storage in a temperature of 4-6 ^{° C} .

Conclusion: Clostridium botulinum type A toxin rapidly becomes inactive in the laboratory environment. Therefore, it is important to find a way to keep its biological activity. According to the results of this study, biological activity of the crystallized toxin remained stable for a long period of time. Thus, this method is useful for both preventive and research applications of botulinum toxin .

Hakim Research Journal 2006 9(3): 25- 31.