Comparison of Genomic and Episomal Expression of Recombinant Human Growth Hormone in Escherichia coli

Background: The production of recombinant human growth hormone is usually problematic in Escherichia coli, and achieving higher functional protein yields is economically important. Objectives: In this study, the chromosomal expression of recombinant human growth hormone (hGH) in the araBAD operon was investigated using Rosetta-gami and BL21 (DE3) competent cells under the regulation of arabinose and T7 promoters using arabinose inducer and IPTG, respectively. Subsequently, the expression of the plasmid-based protein was examined using pET28 (a) + plasmid in Rosetta-gami under the T7 promoter, and the results were compared. Methods: The lambda red technique was used to integrate the desired gene into the host genome. The Fh8 tag was used to increase the protein’s expression, solubility, and thermal resistance. Results: The recombinant BL21 (DE3) under the T7 promoter and the recombinant Rosetta-gami containing pET28-Fh8-hGH plasmid showed significant expression among the chromosome-based and plasmid-based strains, respectively. Preliminary studies on the solubility and thermal resistance of the produced proteins indicated the efficacy of the Fh8 tag in increasing the expression, solubility, and thermal resistance of the product. Conclusions: One advantage of the genomic expression approach is the stability of the gene in the genome. Also, the lack of the need to use antibiotics in production systems can effectively reduce the production costs of this widely used hormone. In addition, the presence of the Fh8 tag can facilitate and accelerate its purification process by increasing the heat resistance thermostability of growth hormone.