Enhancement of human granulocyte-colony stimulating factor production in recombinant E. coli using batch cultivation

Process Intensification for Recombinant Protein Production in E. coli via Identification of Active Nodes in Cellular Metabolism and Dynamic Flux Balance Analysis

Complex media supplemented with a carbon source are commonly used in bioprocesses for recombinant protein production in Escherichia coli. Optimizing these processes is challenging and requires precise understanding of cellular metabolism and nutrient requirements. Compared to a design of experiments approach that necessitates extensive experimentation, metabolic modeling using a genome scale metabolic model (GEM) offers a more predictive and systematic approach to guide process optimization by identifying specific metabolic bottlenecks. In addition, spent media analysis (SMA) can unravel the preferential utilization of different media components during the bioprocess. Here, we integrated the updated E. coli GEM with time course SMA data from a fed-batch process and performed dynamic flux balance analysis (dFBA) to identify metabolites that function as active nodes and are vital for cellular function. These are potential target supplements to boost cellular activity and in turn the recombinant protein productivity. Using an iterative approach of performing fermentation, SMA, and metabolic modeling, we intensified the bioprocess in just five experimental trials, resulting in a six-fold increase in protein productivity. Our new feeding strategy involved yeast extract with amino acid supplementation (Ser, Thr, Asp, and Glu) and increased oxygen transfer rates. This approach demonstrates significant promise for application in bioprocess intensification.

Process Development for the Production and Purification of PEGylated RhG-CSF Expressed in Escherichia coli

Background and objective:

Recombinant human granulocyte-colony stimulating factor (rhG-CSF) and its PEGylated form (PEG-GCSF) are used in the cancer therapy. Thus the development of a more cost-effectively method for expressing rhG-CSF and the PEGylation optimization of rhG-CSF by reaction engineering and subsequent the purification strategy is necessary.

Methods:

RhG-CSF expression in Escherichia coli BL21 (DE3) was carried out by auto-induction batch fermentation and improved for maximizing rhG-CSF productivity. After that, purified rhG-CSF was PEGylated using methoxy polyethylene glycol propionaldehydes (mPEG20-ALD). The various conditions effect of extraction and purification of rhG-CSF and PEG-GCSF were assayed.

Results:

The assessment results revealed that auto-induction batch cultivation strategy had maximum productivity and rhG-CSF purity was more than 99%. The obtained Data of rhG-CSF PEGylation displayed that the optimized conditions of rhG-CSF PEGylation and purification enhanced hemogenisity PEG-GCSF and managed reaction toward optimal yield of PEG-GCSF (70%) and purity of 99.9%. Findings from FTIR, CD, and fluorescence spectroscopy and bioassay revealed that PEGylation was executed exactly in the rhG-CSF N-terminus, and products maintained their conformation properties.

Conclusion:

Overall, the developed approach expanded strategies for high yield rhG-CSF by simplified auto-induction batch fermentation system and rhG-CSF PEGylation, which are simple and time-saving, economical and high efficiency.

Molecular modeling and co-expression analysis of human stem cell factor as fusion partner to granulocyte colony stimulating factor for improving their bioactivity

Human granulocyte colony stimulating factor (hG-CSF) is an expensive hematopoietic growth factor that is clinically used in human for the treatment of neutropenia in diseases such as AIDS, aplastic anemia, myelodysplastic syndrome and congenital or chemotherapy-induced neutropenia. Here, through a computational biology approach, we show that human stem cell factor (hSCF) could be a better fusion partner than human thyroid peroxidase (hTPO), human erythropoietin (hEPO) and human interleukin-3 (hIL3) for co-expression with hG-CSF. Molecular modeling of hG-CSF-hSCF fusion protein with hG-CSF and hSCF receptors showed that binding of fusion protein with human granulocyte colony stimulating factor receptor (hG-CSFR) did not inhibit its binding to human stem cell factor receptor (hSCFR) and vice versa. To validate the results, coding sequences of hG-CSF and hSCF were cloned and co-expressed as fusion protein and their bioactivity was evaluated on hG-CSF responsive 3T3 cell line. The fused expression vector expressed recombinant hG-CSF-hSCF upon IPTG-induction, as revealed by real-time polymerase chain reaction (RT-PCR), sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot analysis. Bioactivity analysis confirmed that rhG-CSF-hSCF protein had higher bioactivity than hG-CSF. Thus, hSCF could be a good fusion partner for hG-CSF and its co-expression as hG-CSF-hSCF may offer an alternative to individual use of two hematopoietic factors in clinics. Future studies should determine the purification strategies, folding status and mechanism of action of the recombinant proteins. Communicated by Ramaswamy H. Sarma.

Batch production of a silk-elastin-like protein in E. coli BL21(DE3): key parameters for optimisation

Background

Silk-elastin-like proteins (SELPs) combining the physicochemical and biological properties of silk and elastin have a high potential for use in the pharmaceutical, regenerative medicine and materials fields. Their development for use is however restrained by their production levels. Here we describe the batch production optimisation for a novel recently described SELP in the pET-E. coli BL21(DE3) expression system. Both a comprehensive empirical approach examining all process variables (media, induction time and period, temperature, pH, aeration and agitation) and a detailed characterisation of the bioprocess were carried out in an attempt to maximise production with this system.

Results

This study shows that maximum SELP volumetric production is achieved at 37°C using terrific broth at pH 6–7.5, a shake flask volume to medium volume ratio of 10:1 and an agitation speed of 200 rpm. Maximum induction is attained at the beginning of the stationary phase with 0.5 mM IPTG and an induction period of at least 4 hours. We show that the selection agents ampicillin and carbenicillin are rapidly degraded early in the cultivation and that plasmid stability decreases dramatically on induction. Furthermore, acetate accumulates during the bioprocess to levels which are shown to be inhibitory to the host cells. Using our optimised conditions, 500 mg/L of purified SELP was obtained.

Conclusions

We have identified the optimal conditions for the shake flask production of a novel SELP with the final production levels obtained being the highest reported to date. While this study is focused on SELPs, we believe that it could also be of general interest to any study where the pET (ampicillin selective marker)-E. coli BL21(DE3) expression system is used. In particular, we show that induction time is critical in this system with, in contrast to that which is generally believed, optimal production being obtained by induction at the beginning of the stationary phase. Furthermore, we believe that we are at or near the maximum productivity for the system used, with rapid degradation of the selective agent by plasmid encoded β-lactamase, plasmid instability on induction and high acetate production levels being the principal limiting factors for further improved production.

Chemical synthesis and improved expression of recombinant human granulocyte colony-stimulating factor cDNA

Recently, granulocyte colony-stimulating factor (G-CSF) has been recognized as a useful molecule for the treatment of a wide range of complex ailments, such as cancer, AIDS, H1N1 influenza, cardiac and neurological diseases. The vast therapeutic potential of G-CSF has induced scientists to develop biotechnological approaches for the synthesis of this pharmacologically active agent. We used a synthetic G-CSF cDNA molecule to produce the target protein by a simple cloning protocol. We constructed the synthetic cDNA using a DNA synthesizer with the aim to increase its expression level by specific sequence modifications at the 5' end of the G-CSF-coding region, decreasing the GC content without altering the predicted amino acid sequences. The identity of the resulting protein was confirmed by a highly specific enzyme-linked immunosorbent assay. In conclusion, a synthetic G-CSF cDNA in combination with the recombinant DNA protocol offers a rapid and reliable strategy for synthesizing the target protein. However, commercial utilization of this methodology will require rigorous validation and quality control.

Increasing recombinant protein production in Escherichia coli through metabolic and genetic engineering

Different hosts have been used for recombinant protein production, ranging from simple bacteria, such as Escherichia coli and Bacillus subtilis, to more advanced eukaryotes as Saccharomyces cerevisiae and Pichia pastoris, to very complex insect and animal cells. All have their advantages and drawbacks and not one seems to be the perfect host for all purposes. In this review we compare the characteristics of all hosts used in commercial applications of recombinant protein production, both in the area of biopharmaceuticals and industrial enzymes. Although the bacterium E. coli remains a very often used organism, several drawbacks limit its possibility to be the first-choice host. Furthermore, we show what E. coli strains are typically used in high cell density cultivations and compare their genetic and physiological differences. In addition, we summarize the research efforts that have been done to improve yields of heterologous protein in E. coli, to reduce acetate formation, to secrete the recombinant protein into the periplasm or extracellular milieu, and to perform post-translational modifications. We conclude that great progress has been made in the incorporation of eukaryotic features into E. coli, which might allow the bacterium to regain its first-choice status, on the condition that these research efforts continue to gain momentum.