Improved production and stability of E. 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 super(-1) of soluble intracellular transketolase was produced representing 43% of the total cell protein. Increased plasmid stability during fed-batch fermentations was obtained by using kanamycin resistant pBGS vectors rather than the ampicillin resistant pUC vectors. Plasmid stability was maintained throughout growth in a complex medium without any selective pressure by incorporating the cer region from ColE1 into the expression construct.