Optimization of Auto-induction Conditions for the Heterologous Expression of a Maltogenic Amylase in Escherichia coli

Auto-induction is usually employed to achieve high cell density and overproduction of proteins with a simple and low-cost operation. The efficiency of heterologous protein expression in Escherichia coli is determined by different parameters. Interactions between these parameters usually complicate the identification of those that contribute more to the improvement of protein expression. As optimal implementation of the auto-induction considerably relies on both the composition of the auto-induction medium and induction conditions, the present study focused on the optimization of related culture parameters through response surface methodology.
In the first step, the optimum culture temperature and auto-induction duration were determined with the aim of achieving the highest specific activity. Then the culture composition was optimized through response surface methodology considering the concentration of carbon sources, glucose and lactose, as the variables for the simultaneous maximizing of the Maltogenic Amylase volumetric yield and specific activity.
Results and Expression of recombinant Maltogenic Amylase under optimum conditions in the shake-flask cultures of Escherichia coli harboring pET 28a increased by 1.7 folds in comparison with an un-optimized auto-induction culture. The Maltogenic Amylase specific activity and volumetric yield were found to be 34.93 U mg-1 and 390.78 U ml-1 at optimum conditions, respectively.