VERY EFFICIENT EXTRACELLULAR PRODUCTION OF CHOLERA-TOXIN B SUBUNIT USING BACILLUS-BREVIS

We have constructed a very efficient synthesis and secretion system fo r cholera toxin B subunit (CTB) of Vibrio cholerae 569B using Bacillus brevis. The constructed expression-secretion vector has the multiple promoters and the signal peptide coding region of the mwp gene, a stru ctural gene for one of the major cell wall proteins of B. brevis strai n 47, directly followed by the gene encoding the mature CTB. A large a mount of mature CTB (1.4 g per liter of culture) was secreted into the medium. It had the same amino terminal amino acid sequence as that of authentic CTB and was fully active in GM1 ganglioside binding assay.