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

摘要

BACKGROUND: The formation of acetate as a metabolic by-product in Escherichia coli fermentation is well known to havedetrimental effects on cell growth and productivity. Various bioprocess and genetic approaches have previously been madeto limit acetate accumulation, however, they tend to be conservative, limiting overall process productivity, or lead to otherproblems 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 andits impact on recombinant protein production. Using the induced synthesis of recombinant green fluorescent protein (GFP) in E.coliTg1 (pGLO) as an example, it is shown that in situ removal of acetate to below inhibitory levels (~1 gL~(-1)) provides significantimprovements in cell growth rate as well as specific biomass and recombinant protein yields. Experiments were performed in a7.5 L stirred-tank bioreactor using an external single cell-pair electrodialysis module with an effective ion exchange membranearea of 0.01 m~2.For this system increases in specific recombinant protein yield of up to 4-fold have been observed dependentupon the time of induction, the mode of operation and the level to which acetate concentration is reduced in the fermentationbroth. CONCLUSIONS: The implementation of ED can significantly increase the level of recombinant protein synthesis in batch andfed-batch fermentation. The approach is considered to be generic, readily implemented and has wide application for theproduction of recombinant enzymes and proteins.