Enhanced recombinant protein synthesis in batch and fed-batch Escherichia coli fermentation based on removal of inhibitory acetate by electrodialysis

BACKGROUND: The formation of acetate as a metabolic by-product in Escherichia coli fermentation is well known to have detrimental effects on cell growth and productivity. Various bioprocess and genetic approaches have previously been made to limit acetate accumulation, however, they tend to be conservative, limiting overall process productivity, or lead to other problems such as a decrease in maximum specific growth rate and decreased product yield on carbon. RESULTS: In this work, the utility of electrodialysis is examined as a potentially generic approach for in situ acetate removal and its impact on recombinant protein production. Using the induced synthesis of recombinant green fluorescent protein (GFP) in E. coli Tg1 (pGLO) as an example, it is shown that in situ removal of acetate to below inhibitory levels (similar to 1 g L-1) provides significant improvements in cell growth rate as well as specific biomass and recombinant protein yields. Experiments were performed in a 7.5 L stirred-tank bioreactor using an external single cell-pair electrodialysis module with an effective ion exchange membrane area of 0.01 m(2). For this system increases in specific recombinant protein yield of up to 4-fold have been observed dependent upon the time of induction, the mode of operation and the level to which acetate concentration is reduced in the fermentation broth. CONCLUSIONS: The implementation of ED can significantly increase the level of recombinant protein synthesis in batch and fed-batch fermentation. The approach is considered to be generic, readily implemented and has wide application for the production of recombinant enzymes and proteins. (c) 2009 Society of Chemical Industry