Bioprocessing technologies utilizing ‘biorecogniton’ between a solid matrix and a protein is being widely experimented as a means to replacing conventional, solution-phase technology. The matrices are frequently chromatographic resins with specific functional groups exposed outside. Since the reactions and interactions of the proteins occur as attached to the solid matrix, this solid-phase processing has distinct advantages over the solution-phase technology.
      Besides the “solid-phase refolding” of inclusion body proteins, another application of the solid-phase technology is the site-specific, mono-PEGylation of proteins. The major problems associated with the solution-phase PEGylation would be the uncontrollability of the random, multiple PEGylation, and the difficulties associated with the subsequent purification of the desired PEGylate.  We developed “solid-phase PEGylation” process, in which a target protein (rhIFN-α-2a) was first adsorbed to ion exchange resin and then N-terminally PEGylated by reductive alkylation. After the PEGylation, the conventional salt gradient elution efficiently removed unwanted species. As a result, we could consistently obtain the mono-PEGylate.
      In addition, we are attempting to extend the concept to develop an integrated process of the mono-PEGylation and the in-vitro refolding, in which a solubilized inclusion body protein could be first mono-PEGylated and then refolded into the correct conformation.  By this way, we can obtain a purified and correctly refolded mono-PEGylate directly from inclusion body.
      In this presentation, the background and the processing details will be discussed.