Cultivation of E. coli carrying a plasmid-based Measles vaccine construct (4.2 kbp pcDNA3F) employing medium optimisation and pH-temperature induction techniques

A Bioreactor-Based Yellow Fever Virus-like Particle Production Process with Integrated Process Analytical Technology Based on Transient Transfection

Yellow Fever (YF) is a severe disease that, while preventable through vaccination, lacks rapid intervention options for those already infected. There is an urgent need for passive immunization techniques using YF-virus-like particles (YF-VLPs). To address this, we successfully established a bioreactor-based production process for YF-VLPs, leveraging transient transfection and integrating Process Analytical Technology. A cornerstone of this approach was the optimization of plasmid DNA (pDNA) production to a yield of 11 mg/L using design of experiments. Glucose, NaCl, yeast extract, and a phosphate buffer showed significant influence on specific pDNA yield. The preliminary work for VLP-production in bioreactor showed adjustments to the HEK cell density, the polyplex formation duration, and medium exchanges effectively elevated transfection efficiencies. The additive Pluronic F-68 was neutral in its effects, and anti-clumping agents (ACA) adversely affected the transfection process. Finally, we established the stirred-tank bioreactor process with integrated dielectric spectroscopy, which gave real-time insight in relevant process steps, e.g., cell growth, polyplex uptake, and harvest time. We confirmed the presence and integrity of YF-VLP via Western blot, imaging flow cytometry measurement, and transmission electron microscopy. The YF-VLP production process can serve as a platform to produce VLPs as passive immunizing agents against other neglected tropical diseases.

Optimization of rPDT fusion protein expression by Escherichia coli in pilot scale fermentation: a statistical experimental design approach

High yield recombinant protein production is highly desirable for biotechnological purposes. In the design of recombinant expression conditions, a number of essential central elements such as expression strain, type of medium, bioprocess optimization, and mathematical modeling should be considered. Well-designed industrial scale production of one recombinant protein with optimized influential parameters and yield can address the cost and production reproducibility issues. In the present study, statistical experimental design methodology was used to investigate the effect of fermentation conditions (dissolved oxygen, IPTG, and temperature) on rPDT production by Escherichia coli. rPDT is a recombinant fusion protein consisting of three different protein domains including the N-terminal 179 amino acid fragment of the S1 subunit of pertussis toxin, the full-length genetically detoxified diphtheria toxin (CRM197), and the 50 kDa tetanus toxin fragment C. A 15 Box–Behnken design augmented with center points revealed that IPTG and DO at the center point and low temperature will result in high yield. The optimal condition for rPDT production were found to be 100 µM IPTG, DO 30% and temperature 20 °C.

Increasing plasmid-based DNA vaccine construct (16 kb pSVK-HBVA) production in Escherichia coli XL10-Gold through optimization of media component

At present, there are production processes to produce protein by Escherichia coli (E. coli) fermentation. Research on the design and optimization of the plasmid fermentation medium, however, is less advanced. The fermentation medium that is optimized for plasmid DNA production is different from the medium that is optimized for protein production. So, establishing a scientific and rational method to optimize the fermentation medium used for plasmid production is very important. Previously, our laboratory developed a novel therapeutic DNA vaccine (named pSVK-HBVA) for hepatitis B based on the alphavirus replicon, and found that E. coli XL10-Gold was the optimal host strain for the production of plasmid pSVK-HBVA. The aim of this study was to establish a scientific and rational method to optimize the fermentation medium used for plasmid production, and investigate the effect of growth medium composition on the production of plasmid pSVK-HBVA harboured in E. coli XL10-Gold, as well as to optimize the medium composition.

The one-factor-at-a-time experiments demonstrated that Luria-Bertani (LB) was the optimal basic medium. The optimal carbon source and nitrogen source were glycerol and home-made proteose peptone, respectively. Based on the Plackett–Burman (PB) design, proteose peptone, glycerol and NH₄Cl were identified as the significant variables, which were further optimized by the steepest ascent (descent) method and central composite design. Growth medium optimization in 500-mL shake flasks by response surface methodology resulted in a maximum volumetric yield of 13.61 mg/L, which was approximately 2.5 times higher than that obtained from the basic medium (LB).

Assessing the effects of exposure to environmental stress on some functional properties of Bifidobacterium animalis ssp. lactis

This study assessed the effects of exposing a strain of Bifidobacterium animalis ssp. lactis to acid, bile and osmotic stresses on antagonistic properties, biofilm formation and antibiotic susceptibility/resistance profile. Exposure to each stress factor appeared to have no significant effect on the antagonism against Escherichia coli NCTC 12900 and Salmonella enterica serovar Enteritidis PT4. No suppression in biofilm formation due to exposure to stress was observed. Bile and osmotic stresses resulted in significantly higher biofilm formation. Expression of an exopolysaccharide synthesis gene, gtf 01207, was significantly higher when the B. animalis ssp. lactis strain was exposed to osmotic stress. Susceptibility of the B. animalis ssp. lactis strain to chloramphenicol, erythromycin, ampicillin and vancomycin, and resistance to tetracycline remained unchanged when exposed to each stress. The expression of a tetracycline resistance gene, tet(W), was significantly higher when exposed to each stress. These results may suggest that the potential for the B. animalis ssp. lactis strain to provide probiotic benefit, after exposure to the stressful conditions of the gastrointestinal tract, remains intact.

Advances in host and vector development for the production of plasmid DNA vaccines

Recent developments in DNA vaccine research provide a new momentum for this rather young and potentially disruptive technology. Gene-based vaccines are capable of eliciting protective immunity in humans to persistent intracellular pathogens, such as HIV, malaria, and tuberculosis, for which the conventional vaccine technologies have failed so far. The recent identification and characterization of genes coding for tumor antigens has stimulated the development of DNA-based antigen-specific cancer vaccines. Although most academic researchers consider the production of reasonable amounts of plasmid DNA (pDNA) for immunological studies relatively easy to solve, problems often arise during this first phase of production. In this chapter we review the current state of the art of pDNA production at small (shake flasks) and mid-scales (lab-scale bioreactor fermentations) and address new trends in vector design and strain engineering. We will guide the reader through the different stages of process design starting from choosing the most appropriate plasmid backbone, choosing the right Escherichia coli (E. coli) strain for production, and cultivation media and scale-up issues. In addition, we will address some points concerning the safety and potency of the produced plasmids, with special focus on producing antibiotic resistance-free plasmids. The main goal of this chapter is to make immunologists aware of the fact that production of the pDNA vaccine has to be performed with as much as attention and care as the rest of their research.

Effects of temperature shifts and oscillations on recombinant protein production expressed in Escherichia coli

Escherichia coli is widely used host for the intracellular expression of many proteins. However, in some cases also secretion of protein from periplasm was observed. Improvement of both intracellular and extracellular production of recombinant protein in E. coli is an attractive goal in order to reduce production cost and increase process efficiency and economics. Since heat shock proteins in E. coli were reported to be helpful for protein refolding and hindering aggregation, in this work different types of single and periodic heat shocks were tested on lab scale to enhance intracellular and extracellular protein production. A single heat shock prior to induction and different oscillatory temperature variations during the induction phase were executed. The results showed that these variations influence protein production negatively. In other words, 45 and 50 % reduction in extracellular protein production were observed for the single heat shock and oscillated temperature between 35 and 40 °C, respectively. However, the oscillatory temperature approach introduced in this study is recommended as a tool to quantitatively analyze the effects of inhomogeneous temperature on cell physiology and productivity in large-scale bioreactors.

Improvement of antibiotic activity of Xenorhabdus bovienii by medium optimization using response surface methodology

BACKGROUND

The production of secondary metabolites with antibiotic properties is a common characteristic to entomopathogenic bacteria Xenorhabdus spp. These metabolites not only have diverse chemical structures but also have a wide range of bioactivities with medicinal and agricultural interests such as antibiotic, antimycotic and insecticidal, nematicidal and antiulcer, antineoplastic and antiviral. It has been known that cultivation parameters are critical to the secondary metabolites produced by microorganisms. Even small changes in the culture medium may not only impact the quantity of certain compounds but also the general metabolic profile of microorganisms. Manipulating nutritional or environmental factors can promote the biosynthesis of secondary metabolites and thus facilitate the discovery of new natural products. This work was conducted to evaluate the influence of nutrition on the antibiotic production of X. bovienii YL002 and to optimize the medium to maximize its antibiotic production.

RESULTS

Nutrition has high influence on the antibiotic production of X. bovienii YL002. Glycerol and soytone were identified as the best carbon and nitrogen sources that significantly affected the antibiotic production using one-factor-at-a-time approach. Response surface methodology (RSM) was applied to optimize the medium constituents (glycerol, soytone and minerals) for the antibiotic production of X. bovienii YL002. Higher antibiotic activity (337.5 U/mL) was obtained after optimization. The optimal levels of medium components were (g/L): glycerol 6.90, soytone 25.17, MgSO4·7H2O 1.57, (NH4)2SO4 2.55, KH2PO4 0.87, K2HPO4 1.11 and Na2SO4 1.81. An overall of 37.8% increase in the antibiotic activity of X. bovienii YL002 was obtained compared with that of the original medium.

CONCLUSIONS

To the best of our knowledge, there are no reports on antibiotic production of X. boviebii by medium optimization using RSM. The results strongly support the use of RSM for medium optimization. The optimized medium not only resulted in a 37.8% increase of antibiotic activity, but also reduced the numbers of experiments. The chosen method of medium optimization was efficient, simple and less time consuming. This work will be useful for the development of X. bovienii cultivation process for efficient antibiotic production on a large scale, and for the development of more advanced control strategies on plant diseases.