IMPROVED PRODUCTION AND STABILITY OF ESCHERICHIA-COLI RECOMBINANTS EXPRESSING TRANSKETOLASE FOR LARGE-SCALE BIOTRANSFORMATION

The E. coli tkt gene has been subcloned into high copy number vectors. In fed batch fermentations up to 4gL(-1) of soluble intracellular tra nsketolase was produced representing 43% of the total cell protein. In creased plasmid stability during fed-batch fermentations was obtained by using kanamycin resistant pBGS vectors rather than the ampicillin r esistant pUC vectors. Plasmid stability was maintained throughout grow th in a complex medium without any selective pressure by incorporating the cer region from ColE1 into the expression construct.