Characterisation of a novel support for biocatalysis in supercritical carbon dioxide

The work presents a characterisation study of Accurel EP100 (polypropylene based hydrophobic granules) as support material for lipase (Lypozyme 10,000 l, from native Rhizomucor miehei) operating as biocatalyst in supercritical CO₂ as solvent. The study involved assay of biocatalytic activity and operational stability as functions of system pressure and temperature. Furthermore, the presence of diffusion limitations was tested, by varying the bed diameter and support particle size. In addition, SEM and Gas Absorption were employed to test the mechanical stability. Results were compared with the commercially available biocatalyst Lipozyme™ IM60.

Pressure did not have a significant effect on the activity or the stability, while temperature had a positive effect on the activity and negative effect on the stability. As expected, an ‘optimum’ value of system water content gave maximum catalytic activity for each biocatalyst. External- and internal-diffusion limitations were both found negligible. The mechanical stability analysis demonstrated little (if any) effect of supercritical carbon dioxide (scCO₂) on the structural integrity of Accurel EP100, although subtle increases in pore volume and surface area were observed.