Amphiphilic conetworks as activating carriers for the enhancement of enzymatic activity in supercritical CO₂

Enzymatic reactions in supercritical carbon dioxide (scCO₂) represent a way of combining the advantages of biocatalysis with the environmental benign nature of scCO₂ as a solvent. Here we demonstrate that activities of enzymes in scCO₂ can be greatly enhanced by incorporating them into amphiphilic conetworks (APCNs), a novel type of enzyme support. Two sets of hydrophilic/scCO₂-philic APCNs, poly(2-hydroxyethyl acrylate)-linked by-poly(dimethyl siloxane) (PHEA-l-PDMS) and poly(2-hydroxyethyl acrylate)-linked by-perfluoropolyether (PHEA-l-PFPE), were prepared and loaded with the synthetically relevant lipase from Rhizomucor miehei. The effect of the APCNs' composition on the amount of the absorbed lipase was studied. It is observed that both sets of lipase-loaded APCNs enhance the catalytic activity of the enzyme in scCO₂. The chemical nature of the scCO₂-philic phase as well as the conetworks composition greatly influences the activity of the lipase in the conetworks. Activities obtained with PFPE-based APCNS were up to 10-fold higher than those obtained with PDMS-based conetworks. The highest specific activity measured corresponds to a 2,000-fold activation compared to the lyophilized enzyme powder. This activity is 10 times higher than the specific activity of the lipase immobilized on an optimized commercial carrier.