Fig. 1

Experimental plan and BL21-pET expression systems. The production of GFP and ATX3-Q55 was carried out in two phases: (i) biomass growth and (ii) induction and recombinant production. During phase (i), the cells were grown at 37 °C without an inducer until reaching a cell density of OD₆₀₀: 0.8–1. In these conditions, the lac repressor (lac_rep) encoded by the lacI gene is bound to the lac operator (lacO) inhibiting the transcription of T7 RNA polymerase. The induction was carried out by adding IPTG (0.1 g/L), or lactose (10 g/L) or CWP (lactose: 10 g/L) and incubating the cells at 25 °C for 48 h. Adding the inducer to a growing culture of BL21 (DE3) cells induces the production of T7 RNA polymerase, which in turn transcribes the gene of interest (GOI) inserted into the plasmid