Separation and purification of hGM-CSF expressed from genetically engineered rice cell

Abstract

Microbial and animal cells have been used as host organisms for recombinant protein production. However, they have contamination risks of mammalian viral contaminants and bacterial toxins. Compared to those, plant cell culture has some advantages: lower risks of infection from the bacterial toxins and mammalian viral contaminants, and production of correctly folded and post-translationally modified proteins. On the other hands, plant cell culture has some disadvantages including: low expression titer and difficulties in purification. We developed a purification process for rhGM-CSF from recombinant rice cell culture. First, acid precipitation process was conducted to remove α-amylase that was co-expressed with rhGM-CSF. The precipitation was done at a low pH(4.5), and 25% ammonium sulfate saturation. To concentrate and dialysis the supernatant from the precipitation process, diafiltration (MWCO 10 kDa) was adapted. To remove non-rhGM-CSF proteins, anion exchange chromatography was done. 30 kDa and 36 kDa impurities were effectively removed by Q-Sepharose XL. Gel filtration chromatography (Superdex G75) was followed. As the last purification step, SEC-HPLC was used. This step showed the potential of rhGM-CSF purification for over 95% purity. In addition, cation exchange chromatography step needs to be put between the anion chromatography step and gel filtration chromatography to improve the purity.