Rotating bed reactor packed with heterofunctional structured silica-supported lipase. Developing an effective system for the organic solvent and aqueous phase reactions

The authors describe their work on highly porous silica-based enzyme carriers. This research was motivated by the fact that polymeric enzyme carriers are sensitivity to extended use in many organic solvents. Novozyme 435, used as a reference material, is a commonly used immobilized lipase based on CalB loaded on a polymeric carrier bead. Millimeter-sized siliceous pellets were used by the authors and functionalized with octyl, amine, or amine+octyl (MH-O, MH-A, and MH-OA respectively) and subsequently charged with CalB. An RBR was used as testbed for comparing the performance of the three variants of CalB on siliceous pellets and commerical, polymeric N435 in organic and aqueous media. N435 appeared most active, likely due to the high catalyst load. The MH-O, however, showed the highest specific activity and also the highest activity in a test reaction in organic media, while the MH-OA performed best in a hydrolytic test reaction in aqueous media. The author’s expressed that the high mass-transfer and mechanic protection of the immobilized enzymes due to the RBR was very advantageous.

Highlights:

• “A rational engineering solution may be the use of rotating bed reactors (RBRs), that allow for a simultaneous mixing and percolation of reactants through the bed of heterogeneous catalysts placed in a cylindrical basket, mounted at the end of the shaft. The problems of catalysts damage and separation are removed, and the tortuous interconnected channels between the particles can induce intensive lateral mixing and much enhanced mass transfer, which boost the overall reaction rate.”
• “Moreover, similarly as in PBRs the catalysts load can be high, and it translates into high values of STY, without compromising process safety. For these reasons, the RBRs attract increasing attention and were recently applied in a number of practical situations: hydrogenation of D-xylose to D-xylitol, using ruthenium decorated carbon foam, lipase catalyzed regioselective lactamization, selective fractionation of hemicellulose and lignin or hardwood, and (S)-naproxen synthesis using immobilized decarboxylase.” [references in publication]
• “All experiments were carried out using a commercial RBR (SpinChem) with 100 mL working volume.”
• “The rotating bed reactors, while protecting catalysts integrity, allow for a very intensive mass transfer, and therefore, expression very high activity and specificity featured by most enzymes. Thus, the system developed paves the way to a new platform for a high yield production of various specialty chemicals in a multi-kilogram scale in a safe and sustained way.”