Downstream process engineering evaluation of transgenic soybean seeds as host for recombinant protein production

The advantages of using seeds for the production of recombinant proteins with plant-based expression system has been demonstrated by several researchers. The high productivity makes soybean a potential system for large-scale recombinant protein production. However, there is a lack of detailed engineering studies of the downstream process (DSP) of recombinant proteins produced in transgenic soybean. In this work, we evaluated the use of transgenic soybean seeds as hosts for the production of recombinant proteins from a downstream process (DSP) engineering standpoint. Recombinant β-glucuronidase (rGUS), was used as a model for extraction and purification studies. This study showed, that even a protein with acidic pI (rGUS) can be successfully separated from native soybean proteins, which also have acidic pI. Maximum GUS specific activity (9.5 × 103 U/mg) with high total activity recovery (8.9 × 104 U/mL) was obtained using a simple extraction solution composed of 50 mmol/L citrate buffer at pH 5.25. Purification of rGUS was evaluated by a two-step chromatographic procedure – anion-exchange followed by hydrophobic interaction chromatography – which was compared to the purification of rGUS from transgenic corn and canola. Overall purification factor and activity recovery obtained were 97.3 and 110% (a value higher than 100% probably due to removal of an inhibitor). Comparison of this study with similar ones made with corn and canola seeds indicates that in terms of DSP soybean seeds can be considered a potentially viable plant system for the production of recombinant proteins.