Chapter 13 - Recovery of Bioactive Molecules and Recombinant Proteins from Heterogeneous Culture Media

Abstract

Recovery of biosynthetically derived products from the various culture broths is a complex engineering problem. Conventional broth processing involves a multistep scheme of non-specific unit operations which leads to significant loss of the desired bioproduct in the first few steps. We have been investigating the use of affinity adsorbents immobilized in reversible hydrogel beads or capsules for whole broth processing ( 1,2 ). The potential advantages of using immobilized affinity adsorbents include higher yield compared to the conventional bioseparation methods due to greater specificity. The reversible gel matrix may also render greater protection to the affinity ligand from fouling or enzymatic degradation. Earlier we reported the development of a mathematical model that describes antibiotic adsorption on immobilized affinity adsorbent beads ( 3 ). We are now interested in using similar immobilized affinity adsorbents for the recovery of recombinant proteins. In this study we examined whole broth extraction of a recombinant β-lactamase (M.W.-23,000) produced by Bacillus stearothermophilus . The applicability of the modeling approach developed earlier for small molecules ( 3 ), is now extended to describe macromolecule adsorption. Preliminary results indicate that this new approach to recover polypeptides and small protein products is feasible. However, bioproduct adsorption within these beads was found to be hindered by restricted diffusion and pore blockage effects. Elucidation of the complex interrelated mechanism of these effects and development of strategies to minimize their effect are required.