Boosting Auto-Induction of Recombinant Proteins in Escherichia coli with Glucose and Lactose Additives
Background: Auto-induction is a convenient way to produce recombinant proteins without
inducer addition using lac operon-controlled Escherichia coli expression systems. Auto-induction
can occur unintentionally using a complex culture medium prepared by mixing culture substrates.
The differences in culture substrates sometimes lead to variations in the induction level.
Objectives: In this study, we investigated the feasibility of using glucose and lactose as boosters of
auto-induction with a complex culture medium.
Methods: First, auto-induction levels were assessed by quantifying recombinant GFPuv expression
under the control of the T7 lac promoter. Effectiveness of the additive-containing medium was examined
using ovine angiotensinogen (tac promoter-based expression) and Thermus thermophilus
manganese-catalase (T7 lac promoter-based expression).
Results: Auto-induced GFPuv expression was observed with the enzymatic protein digest Polypepton,
but not with another digest tryptone. Regardless of the type of protein digest, supplementing
Terrific Broth medium with glucose (at a final concentration of 2.9 g/L) and lactose (at a final concentration
of 7.6 g/L) was successful in obtaining an induction level similar to that achieved with a
commercially available auto-induction medium. The two recombinant proteins were produced in
milligram quantity of purified protein per liter of culture.
Conclusion: The medium composition shown in this study would be practically useful for attaining
reliable auto-induction for E. coli-based recombinant protein production.
Journal Title: Protein & Peptide Letters