Enhancing thermo-induced recombinant protein production in Escherichia coli by temperature oscillations and post-induction nutrient feeding strategies

•A novel thermal induction strategy for recombinant protein production by E. coli was developed.•Temperature oscillations between conditions adequate for optimal growth and full heterologous gene induction were applied.•The strategy allows, for the first time, the simultaneous expression of recombinant protein while maintaining cell growth.•A several-fold increase in biomass and recombinant protein concentration was achieved.•A decrease in the concentration of toxic organic acids was achieved.

Traditional strategies for production of thermo-induced recombinant protein in Escherichia coli consist of a two-phase culture, with an initial growth stage at low temperature (commonly 30 °C) followed by a production stage where temperature is increased stepwise (commonly up to 42 °C). A disadvantage of such strategies is that growth is inhibited upon temperature increase, limiting the duration of the production stage and consequently limiting recombinant protein production. In this work, a novel oscillatory thermo-induction strategy, consisting on temperature fluctuations between 37 and 42 °C or 30 and 42 °C, was tested for improving recombinant protein production. In addition, the induction schemes were combined with one of three different nutrient feeding strategies: two exponential and one linear. Recombinant human preproinsulin (HPPI), produced under control of the λPL-cI857 system in the E. coli BL21 strain, was used as the model protein. Compared to the conventional induction scheme at constant temperature (42 °C), longer productive times were attained under oscillatory induction, which resulted in a 1.3- to 1.7-fold increase in maximum HPPI concentration. Temperature oscillations led to a 2.3- to 4.0-fold increase in biomass accumulation and a decrease of 48–62% in the concentration of organic acids, compared to conventional induction. Under constant induction, growth ceased upon temperature increase and the maximum concentration of HPPI was 3.9 g/L, regardless of the post-induction feeding strategy used. In comparison, the combination of temperature oscillations and a high nutrient-feeding rate allowed sustained growth after induction and reaching up to 5.8 g/L of HPPI.