Bioprocessing research - recombinant proteins

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Recombinant protein production (RPP) involves the heterologous overexpression, of a protein of interest, in a non-native host organism. In many instances, this host is E. coli. A gene encoding the protein of interest, is cloned onto an expression vector, with some form of inducible control at the transcriptional level. Construct expressing cells are cultured to high cell density in bioreactors, under environmentally controlled conditions, and directed to synthesise the recombinant protein. The overriding goal, is the eventual purification of a high yield of biologically active product. It has developed into a multi-billion-pound industry, responsible for the large-scale production of proteins used as biotherapeutics, those with commercial application, and in research. Synthesis of recombinant proteins in E. coli is not without caveats. Proteins that are large, multi-domained, require post-translational modification, or are membrane-bound, can be problematic. Overexpression of any protein can promote a number of undesirable cellular responses. In part, this is due to conflicting interests between the goal of RPP and the intrinsic nature of the E. coli host. In RPP, maximising yield is of critical importance. For proper growth, the intracellular environment is maintained in a state of homeostasis, any perturbation to this subverts the basic needs of the cell. Process design at the genetic level, attempts to direct synthesis of the recombinant protein to upwards of 50% of the total cellular protein. Depending on the sub-cellular localisation of the recombinant protein, a number of different host systems quickly become overwhelmed. Consequently, bioactivity and final yield are often less than desirable, and many recombinant proteins are still difficult to produce. This project will utilise a combination of microbiology, molecular biology and bioprocess engineering to optimise synthesis of recombinant proteins from the molecular to bioreactor scale.