The pitched-blade system is traditionally the choice for stirred tank bioreactors in large-scale production of animal cells in suspension culture. The packed-bed basket technology developed by New Brunswick Scientific provides a shear-free environment for large-scale (up to 100 L) production of animal cells. At present, little information is available on the utility of this system for the production of secreted proteins, especially in perfusion mode of operation. The perfusion process provides a homeostatic environment for optimal cell growth similar to that experienced by cells in vivo. In contrast, the batch culture approach does not appropriately model this homeostatic environment due to the depletion of nutrients and accumulation of waste products in the culture system. Thus, the objective of this study was to compare the growth and productivity of alkaline phosphatase (ALKP)-secreting Chinese hamster ovary (CHO) cells cultured in these two bioreactor types: pitched-blade bioreactors operated in batch mode versus packed-bed bioreactors operated in perfusion mode. CHO cells cultured in the packed-bed bioreactor, operated in perfusion mode, produced greater amounts of ALKP compared to cells cultured in the pitched-blade system run in batch mode. These observations suggest that continuous exposure of cells to fresh culture media and the shear-free culture environment provided by the Fibra-Cel growth matrix disks offered more favorable growth conditions for CHO cells, allowing for either greater cell proliferation (higher density) or greater protein production on a per-cell basis. Overall, the results of this comparison study suggest that packed-bed bioreactors provide significant advantages for moderate-scale production of cells. The benefits of this bioreactor system may translate to large-scale cell culture for generating secreted protein products useful in medical applications…
Tag: <span>protein expression</span>
Advances in industry and medicine have led to the engineering of complex “designer” proteins, such as antibodies in targeted therapeutics and enzymes in process development. The ability to easily generate an almost infinite number of variants at the DNA level has increased the demand for improved protein expression methodologies to fully capture what can be produced genetically. Often, the protein of interest is eukaryotic in origin and may require posttranslational modifications specific to its native host or may be toxic to the host cells expressing them. Cell-free protein expression systems have allowed us to step beyond the limits of traditional in vivo expression methodologies by decoupling protein expression from host cell viability. Furthermore, the ability to produce complex proteins using cell-free transcription/translation systems uniquely enables high-throughput directed evolution and protein engineering efforts. Several cell-free protein expression systems have been developed in the last decade with recent advances focusing on special folding or assembly environments. Equally as important is the capability to transition from the in vitro system to larger-scale in vivo expression, while maintaining activity of the target protein…
In general, yeasts offer advantages for recombinant protein expression because their intracellular environment is suitable for the correct folding of recombinant proteins and grow very high cell densities in defined fermentation media. Within the yeast kingdom, Pichia pastoris has been successfully used for expressing several recombinant proteins. The genome of this yeast contains two copies of the alcohol oxidase (AOX) gene, where the AOX1 promoter regulates 85% of the alcohol oxidase activity and drives the recombinant protein expression into the cell. One of the most successfully recombinant proteins expressed in Pichia pastoris is the hepatitis B surface antigen (HBsAg). The current manufacturing process of the active pharmaceutical ingredient (HBsAg) of the Cuban hepatitis B vaccine (HeberBiovac™ HB) starts with the expression of the HBsAg in Pichia pastoris….
Heterologous expression of membrane proteins remains a bottleneck for structural characterization by x-ray crystallography. Such proteins represent approximately 30% of the proteome and are not sufficiently represented in the Protein Data Bank (PDB). G-protein-coupled receptors (GPCRs) are an area of particular interest as it is estimated that one third of current FDA approved drugs act through this class of receptors. We have been studying rhodopsin with an interest in determining the conformational change that leads to signal transduction in this class of receptors. Although there has been some success in expressing select members of the large GPCR family in bacterial systems, the best characterized expression systems have generally been in mammalian tissue culture…
Incorporating a genomic regulatory sequence element can help to develop a robust expression vector, leading to improved recombinant protein expression in cultured cells. Such elements include the Expression Augmenting Sequence Element (EASE), scaffold- or matrix-attachment regions (S/MAR elements), Insulators, or the Universal Chromatin Opening Element (UCOE). However, generating a robust vector further requires having the relevant vector components in a context-optimized manner…
Expression vector and cell line engineering is the basis for expression and industrial production of biopharmaceuticals. The ultimate goal is to obtain clonal cell lines that secrete the protein of interest with high cell-specific productivity, and at consistently high levels over an extended number of cell generations, allowing for scale-up and cost-efficient large-scale manufacturing. Productivity and stability of expression are thus the prerequisites for developing commercially viable processes…
Membrane proteins such as hERG (human Ether-a-go-go Related Gene) and GPCRs (G-protein-coupled receptors) have been widely used as favorite targets for discovery of therapeutic drugs to treat cardiac arrhythmia, diabetes, epilepsy, cancer, glaucoma and many other indications. They are also widely used in cell-based assays to test new pharmaceuticals for safety in the early stages of drug discovery…
In order to unravel new protein activities and functions, we have expressed and purified a large number of human proteins. We have chosen to study secreted proteins and the extra-cellular domains of putative single transmembrane domain-containing proteins. In order to retain the natural protein characteristics as far as possible, we have used a mammalian expression system. Human embryonic kidney (HEK293) cells were chosen as they have been shown to possess a high protein-secretory potential. The secreted proteins were expressed with a carboxy-terminal tag and purified by affinity chromatography. Each protein was produced at a routine scale from 500 ml cell cultures, and the secreted protein was purified from the culture supernatant…
Baculovirus, particularly AcMNPV (Autographa californica multiple nucleocapsids polyhedrosis virus), is widely used for heterologous protein expression. There are several shortcomings in the current practice of preserving and scaling up baculovirus: 1) extracellular baculovirus stocks, routinely prepared in large volumes and stored at 4º C, are often unstable; 2) laborious and time-consuming steps to amplify and titer the baculovirus stocks are often necessary, and generally recommended, for achieving consistent viral infection and protein expression; 3) once prepared, the baculovirus is suspended and stored in conditioned medium. Given the complex, undefined, and unstable nature of the spent media components, including proteases and nucleases, protein expression tends to vary even when steps are taken to titer the virus stock and adjust the amount of stock used for infection. Here, we will report a new method for preserving and scaling up baculoviruses that: 1) provides a new form of viral stock more stable than the traditional, extracellular stock; 2) eliminates the need for virus amplification and retitering; 3) drastically reduces the turn-around time and resources required for scale-up; and 4) improves yield and consistency in protein expression.
The developing biotechnology community may offer solutions and hope for recent world events that have focused attention on the vulnerability of the world’s population. Concerns about new pandemics have been raised by the emergence of new influenza strains and the re-emergence of older and even more highly virulent strains. In addition, there are fears that bioterrorism could involve agents such as anthrax or smallpox, and these threats become even more of a concern when you consider the increased mobility of such organisms via today’s commercial aviation. The ability of the biomedical community to respond rapidly to these shifting threats is more important than ever…