Abstract：Cry protein is an insecticidal composition of Bacillus thuringiensis(Bt) microbial insecticides, it has been used as biological insecticides for over 50 years. Cry5B is one of a Cry protein, its food safety has yet to be evaluated. This article was focused on allergenicity assessment in vitro, the acute toxicity test and 30 d feeding study. The results of thermal stability and simulated gastrointestinal digestion experiment showed that Cry5B protein had stability after heating 60 min at 100 ℃ and was digested within 15 s in stimulated fluid, indicating that Cry5B protein had low allergenicity. The oral acute toxicity test indicated that the activities and physiological metabolism of mice(Mus musculus) were nomal and the Cry5B protein caused no adverse effects in mice by gavage at a high dose of 5 g/kg BW. The results of 30 d feeding study showed that all aspects of the SD rats(Rattus nargegicus) in weight , feed intake, blood biochemistry(lactate dehydrogenase,alkaline phosphatase, total protein, albumin, creatinine, blood urea nitrogen, aspartate aminotransferase, total cholesterol, gliucose, teramethy lathylenediamine, alanine aminotransferase), hematology(white blood cell count, red blood cell count, haemogliobin, blood platelet)were normal. Pathological results showed that the main internal organs such as liver and spleen and kidney of rats had phenomenon of mild edema, bleeding, but these lesions has nothing to do with the feeding transgenic cotton seed. The food safety evaluation of the Cry5B protein showed that Cry5B recombinant protein and transgenic Cry5B cottonseed did not have the allergenicity and toxicity, it can be considered safe for food,and it provide the data of further safety evaluation for transgenic Cry5B cotton.
