Culture optimization for protein expression in Escherichia coli

[Objective] We developed a new culture-complex auto-inducing media(CAI) for heterogenous protein expression in Escherichia coli.[Methods] To test expression efficiency in the CAI,we constructed seven different plasmids named p1,p-2,p-3,p-4,p-5,p-6 and p-7.These plasmids were transformed into E.coli BL21,then expressed in both Luria-Bertani madia LB and CAI.To improve the expression level even more,we analyzed the composition of the CAI and optimized the culture.[Results] The expression levels of seven fusion proteins in CAI were four times higher than those in Luria-Bertani.Through a series of changes we formed a new optimized culture(CAI-4).[Conclusion] Comparing to the expression levels of these fusion proteins(P-1,P-2,P-3) in CAI,the expression levels of fusion proteins in CAI-4 increased 2-fold.