Introduction of the carbohydrate-activated promoter P_malK for recombinant protein production

Abstract.

A production protocol for the use of the malK promoter was established. The protocol includes two phases: an initial fed-batch phase on glucose to reach a high cell density and a fed-batch phase on maltose for production of the desired recombinant protein. It is suggested that this cultivation scheme could be used for all promoters that are catabolite repressed by glucose and where growth and production need to be separated. The specific feature of this system is shown by its ability to control the rate of synthesis of the product protein, ß-galactosidase. In the production phase with a constant feed or an exponential feeding of 0.1 h^–1 it took 4 h longer to reach the maximum specific production rate than with the higher dilution rates of 0.25 h^–1 and 0.4 h^–1, respectively. In the above experiments a dilution rate of 0.3 h^–1 in the growth phase was used. The volumetric production of this system could furthermore be extended to 40 h. All protocol procedures so far tested resulted in the same maximum production rate, but reached in different lengths of time. It is argued that this system is particularly well suited for the production of proteins that have a complex structure and/or need to be produced in a soluble form or to be exported to the periplasm.