Oral presentations O6.1 Plant bioreactors — in and ex situ production of recombinant proteins

In the past decade, accomplishments in biochemistry and molecular biology and genetics enabled scientists not only to gather a large amount of experimental data on structural and functional organization of genomes and metabolomes but also to develop tools for manipulation and highly specific modification of the gene expression in Eukaryota, including higher plant species. Development of genetic engineering resulted in creating technologies which enable the construction of plants characterized by novel, desirable traits. With the advent of biotechnology and gene transfer technology, a broad and extensive research brought about different expression systems for re-combinant/heterologous proteins of industrial and pharmaceutical value. In the past decade, plants have been actively considered as important expression systems of numerous recombinant proteins as they undergo acetyla-tion, phosphorylation, and glycosylation as well as other post-translational modifications required for the biological activity of many eukaryotic proteins. Today, the plant expression system is recognized as a new platform useful for the production of a large amount of proteins that can be either accumulated in plant tissues (in situ) or, after rhizosecretion, recovered from root exudates of hydroponic cultures (ex situ). Plants, as an alternative system for recombinant protein production, require specific methods of protein product isolation and purification. Currently, most of recombinant proteins are extracted from biochemically complex plant tissues using solvents, which makes downstream processing and purification of individual protein a laborious, difficult and costly process and a major obstacle to large-scale protein manufacturing. An alternative for this protein extraction and purification system is rhizosecretion of target protein–Elastin-Like Polypeptide fusion protein in the hydroponic medium and application of thermo-sensitive characteristics of ELP domain for its purification. ELPs are biopolymers consisting of the elastin-based repeat pentapeptide motif Val-Pro-Gly-Xaa-Gly (where the " guest residue " , Xaa, is any amino acid except Pro) which undergo a sharp inverse temperature phase transition (T t 2–3 o C). The T t depends on ELP molecular weight, amino acid substitution of Xaa, applied solvent, and ELP concentration as well as ionic strength of the solution. Reduced concentration of ELP results in a decrease of T t which can be balanced by an increase of salt concentration, a process which enables the recovery of the protein fused with ELP from the solutions of high dilution degree such as medium of hydroponi-cally grown plants or hairy root cultures. Recent developments and perspectives of the future application of in and ex situ production of recombinant …