Optimization of human interferon gamma production in Escherichia coli by response surface methodology

The Goldilocks Approach: A Review of Employing Design of Experiments in Prokaryotic Recombinant Protein Production

The production of high yields of soluble recombinant protein is one of the main objectives of protein biotechnology. Several factors, such as expression system, vector, host, media composition and induction conditions can influence recombinant protein yield. Identifying the most important factors for optimum protein expression may involve significant investment of time and considerable cost. To address this problem, statistical models such as Design of Experiments (DoE) have been used to optimise recombinant protein production. This review examines the application of DoE in the production of recombinant proteins in prokaryotic expression systems with specific emphasis on media composition and culture conditions. The review examines the most commonly used DoE screening and optimisation designs. It provides examples of DoE applied to optimisation of media and culture conditions.

Cloning and Expression of Recombinant Human Endostatin in Periplasm of Escherichia coli Expression System

PURPOSE

Recombinant human endostatin (rhEs) is an angiogenesis inhibitor which is used as a specific drug in the treatment of non-small-cell lung cancer. In the current research, we developed an efficient method for expressing soluble form of the rhEs protein in the periplasmic space of Escherichia coli via fusing with pelB signal peptide.

METHODS

The human endostatin (hEs) gene was amplified using synthetic (hEs) gene as a template; then, cloned and expressed under T7 lac promoter. IPTG was used as an inducer for rhEs expression. Next, the osmotic shock was used to extraction of protein from the periplasmic space. The presence of rhEs in the periplasmic space was approved by SDS-PAGE and Western blotting.

RESULTS

The results show the applicability of pelB fusion protein system usage for secreting rhEs in the periplasm of E. coli in the laboratory scale. The rhEs represents approximately 35 % (0.83mg/l) of the total cell protein.

CONCLUSION

The present study apparently is the first report of codon-optimized rhEs expression as a fusion with pelB signal peptide. The results presented the successful secretion of soluble rhEs to the periplasmic space.

Effect of Culture Condition Variables on Human Endostatin Gene Expression in Escherichia coli Using Response Surface Methodology

Background

Recombinant human endostatin (rhES) is an angiogenesis inhibitor used as a specific drug for the treatment of non-small-cell lung cancer. As mRNA concentration affects the recombinant protein expression level, any factor affecting mRNA concentration can alter the protein expression level. Response surface methodology (RSM) based on the Box-Behnken design (BBD) is a statistical tool for experimental design and for optimizing biotechnological processes.

Objectives

This investigation aimed to predict and develop the optimal culture conditions for mRNA expression of the synthetic human endostatin (hES) gene in Escherichia coli BL21 (DE3).

Materials and Methods

The hES gene was amplified, cloned, and expressed in the E. coli expression system. Three factors, including isopropyl β-D-1-thiogalactopyranoside (IPTG) concentration, post-induction time, and cell density before induction, were selected as important factors. The mRNA expression level was determined using real-time PCR. The expression levels of hES mRNA under the different growth conditions were analyzed. SDS-PAGE and western blot analyses were carried out for further confirmation of interest-gene expression.

Results

A maximum rhES mRNA level of 376.16% was obtained under the following conditions: 0.6 mM IPTG, 7 hours post-induction time, and 0.9 cell density before induction. The level of rhES mRNA was significantly correlated with post-induction time, IPTG concentration, and cell density before induction (P < 0.05). The expression of the hES gene was confirmed by western blot.

Conclusions

The obtained results indicate that RSM is an effective method for the optimization of culture conditions for hES gene expression in E. coli.

High-level Expression and Purification of Active Human FGF-2 in Escherichia coli by Codon and Culture Condition Optimization

BACKGROUND

Basic fibroblast growth factor (bFGF) is a member of a highly conserved superfamily of proteins that are involved in cell proliferation, differentiation, and migration.

OBJECTIVES

The objective of this study was to overexpress and purify the high-level active human bFGF in Escherichia coli (E. coli).

MATERIALS AND METHODS

This experimental study was conducted in the Islamic Republic of Iran. After codon optimization and gene synthesis, the optimized FGF-2 gene was subcloned into plasmid pET-32a. pET32-FGF-2 was transformed into E. coli BL21 for expression. The cultivation parameters were optimized to produce a high yield of FGF-2.

RESULTS

The optimal conditions were determined as follows: cultivation at 37°C in TB medium, with 1 mM isopropyl-β-D-thiogalactopyranoside (IPTG), followed by post-induction expression for 6 h. Under the abovementioned conditions, the expression volumetric productivity of FGF-2 reached 1.48 g/L.

CONCLUSIONS

A fusion tag from the pET32 expression plasmid permits the recovery of the recombinant fusion FGF-2 from E. coli, without affecting its biological activity.

Influence of induction conditions on the expression of carbazole dioxygenase components (CarAa, CarAc, and CarAd) from Pseudomonas stutzeri in recombinant Escherichia coli using experimental design

Carbazole 1,9a-dioxygenase (CarA), the first enzyme in the carbazole degradation pathway used by Pseudomonas sp., was expressed in E. coli under different conditions defined by experimental design. This enzyme depends on the coexistence of three components containing [2Fe-2S] clusters: CarAa, CarAc, and CarAd. The catalytic site is present in CarAa. The genes corresponding to components of carbazole 1,9a-dioxygenase from P. stutzeri were cloned and expressed by salt induction in E. coli BL21-SI (a host that allows the enhancement of overexpressed proteins in the soluble fraction), using the vector pDEST™14. The expression of these proteins was performed under different induction conditions (cell concentration, temperature, and time), with the help of two-level factorial design. Cell concentration at induction (measured by absorbance at 600 nm) was tested at 0.5 and 0.8. After salt induction, expression was performed at 30 and 37°C, for 4 h and 24 h. Protein expression was evaluated by densitometry analysis. Expression of CarAa was enhanced by induction at a lower cell concentration and temperature and over a longer time, according to the analysis of the experimental design results. The results were validated at Abs (ind) = 0.3, 25°C, and 24 h, at which CarAa expression was three times higher than under the standard condition. The behavior of CarAc and CarAd was the inverse, with the best co-expression condition tested being the standard one (Abs (ind) = 0.5, T = 37°C, and t = 4 h). The functionality of the proteins expressed in E. coli was confirmed by the degradation of 20 ppm carbazole.