Two Escherichia coli strains, widely used for the production of various recombinant proteins, were compared for their pre-induction growth and acetate accumulation patterns. The strains studied were €, coliBL21 (ADES), transformed with a plasmid encoding Pseudomonas exotoxin A, and an €. coli K12 derived strain, JM109, carrying a plasmid encoding maltose-binding protein fused with HIV protease. Cultures were grown in controlled bench-top fermentors to the optimal pre-induction density in both high glucose batch and low glucose fed batch strategies.
The results showed the superiority of f. coli BL21 (XDE3) as a host for a recombinant protein expression system. For example, JM109 responds differently to high glucose concentration and to low glucose concentration. Its acetate concentration was as high as 10 g/L in a batch mode and 5 g/L in a fed batch mode. In comparison, strain BL21 (XDES) reached 2 g/L acetate when grown in batch mode and not more than 1 g/L acetate when grown in a fed batch mode. f. coli BL21 (XDE3), most likely, possesses an acetate self-control mechanism which makes it possible to grow to the desired pre-induction density in a high glucose medium using simple batch propagation techniques. Such a technique is cost effective, reproducible, and easy to scale up. 0