A high protein production rate using a high inducer concentration at a high temperature is a general strategy for recombinant protein production in inclusion bodies (IBs) by E. coli, which usually includes applications of strong promoter such as T7 and isopropyl-b-D-thiogalactopyranoside (IPTG) induction at 37°C in a complex medium. However, a new strategy that uses a slower protein production rate to improve recombinant protein titer and yield in IBs is reported in this study. This strategy using a lower feeding rate and a lower induction temperature at 29°C without adding any exogenous inducers increased the therapeutic protein (TP) volumetric titer by 84% and improved the specific production yield from 210 to 330 mg TP per g of dry cell weight. Furthermore, the new fermentation process significantly decreased an undesired variant, methionyl-TP, from 23.6% to 9.6%. The purified IB yield from the new process broth was also improved.
Keywords E. coli, therapeutic protein, inclusion body, fed batch fermentation, methionylation, and auto-induction