Fine-tuning of leaky expression delivers soluble and functional recombinant alphainterferon in the cytoplasm of Escherichia coli

Alphainterferons are cytokines that became famous in the treatment of certain infections and tumors due to their antiviral, antiproliferative, and immunomodulatory activities. While the production of these small proteins in Escherichia coli is well established, high-level overexpression typically results in the formation of insoluble and inactive inclusion bodies that need to be processed through costly and lengthy steps. Here we describe an optimized, inducer-free expression system using E. coli BL21(DE3) and a pET-based vector with the human IFN-α2a gene. By strategically transitioning the culture from high-temperature biomass accumulation (37°C) to mild conditions (16°C) during the early-midlog phase, we leveraged basal expression to favor folding over aggregation. This approach achieved a cytoplasmic solubility of up to 75%. The protein was recovered using a streamlined one- or two-step ion-exchange chromatography protocol, resulting in maximum purified yields of 23.5 mg/L. Characterization tests confirmed the protein’s identity, high purity, in vitro activity, and correct disulfide bonding pattern. This method provides a cost-effective alternative for the production of soluble alphainterferon by eliminating the need for chemical inducers and complex refolding processes. • Bioprocesses with E. coli mainly overexpress proteins as insoluble inclusion bodies • Such structures must undergo inconvenient steps for solubilization and renaturation • Cytoplasmic environment is so reducing that it prevents the correct protein folding • Lowering host’s basal expression was able to produce soluble and bioactive IFN-α2a