A
protein purification procedure is required to obtain high-value recombinant
injectable vaccine proteins produced in plants as a
bioreactor. However, existing purification procedures for plant-derived
recombinant proteins are often not optimized and are inefficient, with low recovery rates. In our previous study, we used 25-30%
ammonium sulfate to precipitate total soluble
proteins (TSPs) in purification process for
recombinant proteins from plant leaf biomass which has not been optimized. Thus, the objective in this study is to optimize the conditions for plant-derived
protein purification procedures. Various
ammonium sulfate concentrations (15-80%) were compared to determine their effects on TSPs yield. With 50%
ammonium sulfate, the yield of precipitated TSP was the highest, and that of the plant-derived
colorectal cancer-specific
surface glycoprotein GA733 fused to the
Fc fragment of human
IgG tagged with endoplasmic reticulum retention signal KDEL (GA733(P)-FcK)
protein significantly increased 1.8-fold. SDS-PAGE analysis showed that the purity of GA733(P)-FcK
protein band appeared to be similar to that of an equal dose of mammalian-derived GA733-Fc (GA733(M)-Fc). The binding activity of purified GA733(P)-FcK to anti-GA733 mAb was as efficient as the native GA733(M)-Fc. Thus, the purification process was effectively optimized for obtaining a high yield of plant-derived antigenic
protein with good quality. In conclusion, the purification recovery rate of large quantities of
recombinant protein from plant expression systems can be enhanced via optimization of
ammonium sulfate concentration during downstream processes, thereby offering a promising
solution for production of recombinant GA733-Fc
protein in plants.