The optimization of the induction conditions for the highly efficient expression of soluble protein.

<p><i>E</i>. <i>coli</i> Rosetta2 (DE3) that contained <i>pGEM</i>::<i>ureOP</i> was grown at 37°C. When the OD₆₀₀ reached 0.6, protein expression was induced under 96 different conditions. The cells were grown for an additional 18 h, harvested, and disrupted via sonication, and analyzed using SDS-PAGE electrophorograms. Lane M: protein molecular weight marker (kDa). Lane M: protein molecular weight marker (kDa). Cell-free extracts obtained from cultures carried out at different steps of optimization. Line 1: 750 μM Ni ²⁺; Line 2: 750 μM IPTG, and 750 μM Ni²⁺; Lane 3: induction temperature 22°C, 750 μM IPTG and 750 μM Ni²⁺; Line 4: time of incubation 24 h, 22°C, 750 μM IPTG and 750 μM Ni²⁺.