Direct immobilization and recovery of recombinant proteins from cell lysates by using EctP1-peptide as a short fusion tag for silica and titania supports

Immobilization of protein, compared to the use of free protein, offers improved stability, easy separation and continuous reusability. However, the classic routes for protein immobilization, based on non-specific adsorption, often negatively affect protein functionality. In this study, EctP1 peptide was explored as a novel short fusion tag for non-covalent adsorption on unmodified solid surfaces, silica and titania. A fusion of EctP1 with bovine carbonic anhydrase (BCA) was employed to investigate the optimal binding conditions that could diminish the nonspecific adsorption of Escherichia coli proteins. The stable binding of BCA-EctP1 on titania was observed in the pH range of 2–9, while the stable binding on silica was in the pH range 6–9. Moreover, the immobilized BCA-EctP1 on silica and titania particles showed enhanced thermal and storage stability and retained 95% of its residual activity after 5 uses. We further demonstrated the merits of the noncovalent immobilization of EctP1 fusion proteins to silica and titania in the recovery of the bound proteins. Interestingly, monomeric arginine showed better recovery yield of EctP1 fusion proteins (about 78–84%), compared to the recovery yield by the salts, NaCl and MgCl₂ (about 30–51%). Using BCA and monomeric red fluorescent protein (mRFP) as model proteins, the EctP1 fusion proteins were released in a biologically active form with approximately 80% recovery and 93% purity. Our approach is a simple and reproducible technique for direct immobilization of recombinant proteins from E. coli lysates on solid supports, with the potential high-purity recovery of recombinant proteins.