Recent use of transgenic plants as an alternative protein expression system offers the potential to recover native plant enzymes as byproducts from recombinant protein purification processes. Due to the nature of the native proteins, canola and com are suitable hosts for acidic recombinant proteins, and soybean for the basic ones. Ion-exchange chromatography and polyelectrolyte precipitation as established techniques in recombinant protein downstream processing were applied to non-transgenic plant extracts to assess the feasibility of enzyme byproduct recovery. Cation exchange chromatography of canola and soy extracts completely recovered the native α-galactosidase and urease activities in the extract. α-Gal-actosidase and β-glucosidase activities were fully recovered in anion exchange chromatography of corn germ proteins with enrichment factors of about 3. Simple anion exchange chromatography for canola extracts recovered α-galactosidase activity with 59% yield and 11 times enrichment. Polyelectrolyte precipitation using polyethyleneimine at a dosage of 38 mg/g total protein recovered 47% of α-galactosidase from canola with an enrichment factor of about 3. Several recommendations on the use of the byproduct fractions are proposed. Additional processing of byproduct fractions to concentrate form is economically feasible.
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