en 23408749 Cholera toxin B subunit (CTB) has been extensively studied as an immunogen, adjuvant, and inducer of oral tolerance in many investigations. Production of CTB has been carried out in the bacterial, plant, insect and yeast expression systems. In this study the expression of the CTB containing a 6XHis-tagged was performed by Escherichia coli (E.coli) M15. The yield of purified pentameric recombinant CTB was about 1 mg/l. Western blot analysis demonstrated that the recombinant CTB was antigenically active. In addition, GM1-ganglioside ELISA showed that recombinant CTB binds to GM1-gangelioside receptor, confirming disulfide bond formation and proper folding of the recombinant protein in E.coli. Overall, in regard to the vast applications of CTB in medicine, this bacterial expression system will be a fast, cost-effective and simple system for production of pentameric CTB and CTB conjugated proteins. Cholera toxin B Subunit, Enzyme-linked immunosorbent assay, Western blotting 89 94 https://www.ajmb.org/En/Article.aspx?id=85 https://www.ajmb.org/PDF/En/FullText/85.pdf FaridaDakterzadaDepartment of Bacteriology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran316AshrafMohabati MobarezDepartment of Bacteriology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran317MehryarHabibi RoudkenarResearch Center, Iranian Blood Transfusion Organization, Tehran, Iran318MehdiForouzandehDepartment of Biotechnology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran319