A Novel Strategy for Increasing Heterologous Protein Productıon in Escherichia coli

The utilization potential of corn steep liquor (CSL), an industrial byproduct, as an alternative culture medium for the heterologous production of a GST/Snakin-Z fusion peptide was investigated in Escherichia coli BL21, DH5α, and Mach1 strains by cultivating in Luria-Bertani (LB) and CSL at low incubation temperature (25°C) with and without Isopropyl-β-D-1-thiogalactoside (IPTG) induction. The highest OD600 values were measured as 1.25 and 1.26, respectively, in Mach1 cultured in CSL at 25 °C and 37 °C, while the highest wet biomass (6.33 mg/ml and 6.67 mg/ml, respectively) was obtained from BL21 grown under the same conditions. No significant difference was observed between OD600 values of CSL and LB cultures, nor between wet weights (p>0.05). Results indicated that CSL contained suitable nutrients for bacterial growth, and it could provide growth equivalent to the cell density obtained from LB cultures. The BL21, cultivated in LB at 25 °C, produced recombinant peptide, and IPTG induction enhanced expression but no peptide production was observed at 37 °C, even in the presence of IPTG. In contrast, high production levels were detected in BL21 cultivated in CSL at both temperatures, regardless of IPTG induction. DH5α also produced recombinant peptide in both media and at both temperatures, and IPTG enhanced production. Mach1 produced recombinant peptide in CSL, while it did not produce it in LB at both temperatures. The IPTG did not significantly affect protein expression at both temperatures. This study demonstrates that sole CSL can be nutrient-rich and an economical medium for inducer-free pilot and large-scale recombinant protein production in biotechnological processes.