Abstract: The microbial flora involved in the characteristic flavor formation of Chouguiyu, a traditional Chinese fermented fish product made of mandarin fish, is derived from the natural environment. Whether this microflora is safe for human health is arousing great concerns from customers and even the whole society. Nevertheless the toxicology of Bacillus thuringiensis 29.118, a dominant strain isolated from Chouguiyu, is yet unclear. Acute oral toxicity, genetic toxicology, and microscopic observation of colon after 30 days of feeding were applied to assess the toxicity of B. thuringiensis 29.118 to mice in this study. The results showed that the oral median lethal dose (LD50) for mice was higher than 4 000 mg/kg mb, and at a dose of 2 000 mg/kg mb no acute oral toxicity was observed. B. thuringiensis 29.118 had no distinct genetic toxicity to mice. All mice grew well after 30 days of feeding, and no significant difference existed in seven serum indexes and three liver indexes (P > 0.05); no distinct pathological symptoms were observed in liver and colon tissues. The tested dose of B. thuringiensis 29.118 was much higher than the actual one. Therefore, B. thuringiensis 29.118 was regarded to be safe based on our toxicological assessment.

Key words: Chouguiyu, Bacillus thuringiensis, toxicological assessment, safety evaluation, fermentation