A Novel Induction Strategy Based on Temperature and pH Optimization to Improve the Yield of Recombinant Streptokinase in Escherichia coli

Introduction:Streptokinase (SK) is used for thrombolytic therapy of acute myocardial infarction. Recombinant fermentation is the most common and cost-effective procedure in the production SK. Nutrients composition, as well as such fermentation variables as temperature and pH, can affect the production level of protein-based drugs expressed in E. coli. In the present study, optimized recombinant streptokinase (r-SK) production in E. coli in the form of inclusion body (IB), the effect of induction temperature and extracellular pH were evaluated.Methods and Results:To maximize the expression level of r-SK three different induction temperatures were used to obtain the optimal temperature for r-SK production. The effect of extracellular pH on the level of r-SK production was also studied and the optimal pH was determined. To this purpose, 8 fermentation processes were applied and followed by: Cell disruption, Isolation of IBs, determination of target protein (SDS-PAGE, Western-blot). The biological activity of r-SK obtained from optimal conditions was determined in comparison with reference standard using gel clot method.The highest amount of expression level and IBs formation were performed by combining two temperatures: 42˚C for the first two hours of induction followed by 39˚C at pH 6. The expression level of r-SK under these conditions shows an 11.6% increase in comparison with the control. Conclusions:Choosing appropriate cultivation conditions can increase IB formation and use its advantages to produce higher quantities of r-SK with appropriate biological activity