**8. Purification and downstream processing of the recombinant proteins**

Recovery usually includes the process and breakdown of plant tissues, protein extraction, solid-liquid separation, and protein concentration while purification encompasses safety protection, liquid-liquid extraction, membrane filtration, chromatography, etc. The processing of leaves requires a particular attention; leaves should be processed immediately after the harvest or frozen to prevent protein degradation by proteases, whereas seeds can be stored for a long period of time due to the less probability of destruction of recombinant proteins expressed in seeds. Using the secretory systems of cells can also be beneficial since disinte‐ grating plant cells throughout recovery is not required; thus, the release of phenolic com‐ pounds can be avoided while the recombinant proteins can be unstable in culture mediums. Another way of facilitating the recovery of proteins is utilizing continuous labels. Protein labels must be removed after purification so that the structure of purified protein can change into its natural position. The technology of oleosin fusion, through which the gene sequence of recombinant proteins is fused to the sequence of a special internal oil protein called oleosin in safflower and canola, is separated after the digestion of internal protease following protein purification [1].
