Parallel production and verification of protein products using a novel high-throughput screening method

The fed-batch principle for the molecular biology lab: controlled nutrient diets in ready-made media improve production of recombinant proteins in Escherichia coli

While the nutrient limited fed-batch technology is the standard of the cultivation of microorganisms and production of heterologous proteins in industry, despite its advantages in view of metabolic control and high cell density growth, shaken batch cultures are still the standard for protein production and expression screening in molecular biology and biochemistry laboratories. This is due to the difficulty and expenses to apply a controlled continuous glucose feed to shaken cultures. New ready-made growth media, e.g. by biocatalytic release of glucose from a polymer, offer a simple solution for the application of the fed-batch principle in shaken plate and flask cultures. Their wider use has shown that the controlled diet not only provides a solution to obtain significantly higher cell yields, but also in many cases folding of the target protein is improved by the applied lower growth rates; i.e. final volumetric yields for the active protein can be a multiple of what is obtained in complex medium cultures. The combination of the conventional optimization approaches with new and easy applicable growth systems has revolutionized recombinant protein production in Escherichia coli in view of product yield, culture robustness as well as significantly increased cell densities. This technical development establishes the basis for successful miniaturization and parallelization which is now an important tool for synthetic biology and protein engineering approaches. This review provides an overview of the recent developments, results and applications of advanced growth systems which use a controlled glucose release as substrate supply.

Escherichia coli as a cell factory for heterologous production of nonribosomal peptides and polyketides

Nonribosomal peptides (NRPs) and polyketides (PKs) are two classes of natural products with numerous bioactivities such as antiviral, antimicrobial and anticancer activity. However, pharmaceutical applications of these products are often impeded because many native producers are difficult to cultivate or show a low productivity. Over the last decade, with the development of synthetic biology and metabolic engineering, more and more bioactive natural products including NRPs and PKs have been heterologously produced using easy-to-handle surrogate microbes. In this process, the full biosynthetic pathway for the production of a target compound is first identified and isolated from the native producer, and then reconstituted in a well-characterized and easily culturable heterologous producer like Escherichia coli. Thereafter, the productivity could be rationally improved through multiple strategies from strain to bioprocess optimization. This review summarizes the endeavors and progresses made in the heterologous production of NRPs, PKs and NRP/PK hybrids using E. coli as a robust whole-cell factory in recent years.

High-yield production of biologically active recombinant protein in shake flask culture by combination of enzyme-based glucose delivery and increased oxygen transfer

This report describes the combined use of an enzyme-based glucose release system (EnBase^®) and high-aeration shake flask (Ultra Yield Flask™). The benefit of this combination is demonstrated by over 100-fold improvement in the active yield of recombinant alcohol dehydrogenase expressed in E. coli. Compared to Terrific Broth and ZYM-5052 autoinduction medium, the EnBase system improved yield mainly through increased productivity per cell. Four-fold increase in oxygen transfer by the Ultra Yield Flask contributed to higher cell density with EnBase but not with the other tested media, and consequently the product yield per ml of EnBase culture was further improved.

Enhanced growth and recombinant protein production of Escherichia coli by a perfluorinated oxygen carrier in miniaturized fed-batch cultures

Background

Liquid perfluorochemicals (PFCs) are interesting oxygen carriers in medicine and biotechnology with a high solubility for oxygen. They have been repeatedly used for improving oxygen transfer into prokaryotic and eukaryotic cell cultures, however their application is still limited. Here we show the great benefit of air/oxygen saturated perfluorodecalin (PFD) for high cell density cultivation of Escherichia coli in microwell plates and their positive effect on the soluble production of a correctly folded heterologously expressed alcohol dehydrogenase.

Results

In EnBase^® cultivations the best effect was seen with PFD saturated with oxygen enriched air (appr. 10 μM oxygen per ml) when PFD was added at the time of induction. In contrast the effect of PFD was negligible when it was added already at the time of inoculation. Optimisation of addition time and content of loaded oxygen into the PFD resulted in an increased the cell density by 40% compared to control cultures, and correspondingly also the product yield increased, demonstrated at the example of a recombinant alcohol dehydrogenase.

Conclusions

PFCs are a valuable additive in miniaturized cell culture formats. For production of recombinant proteins in low cell density shaken cultures the addition of oxygen-enriched PFD makes the process more robust, i.e. a high product yield is not any more limited to a very narrow cell density window during which the induction has to be done. The positive effect of PFD was even more obvious when it was added during high cell density cultures. The effect of the PFD phase depends on the amount of oxygen which is loaded into the PFD and which thus is a matter of optimisation.