Bioreactors based on monolith-supported ionic liquid phase for enzyme catalysis in supercritical carbon dioxide

Bioreactors with covalently supported ionic liquid phases (SILP) were prepared as polymeric monoliths based on styrene-divinylbenzene or 2-hydroxyethyl methacrylate-ethylene dimethacrylate, and with imidazolium units loadings ranging from 54.7 to 39.8 % wt IL per gram of polymer. The SILPs were able to absorb Candida antarctica lipase B (CALB), leading to highly efficient and robust heterogeneous biocatalysts. The bioreactors were prepared as macroporous monolithic mini-flow systems and tested for the continuous flow synthesis of citronellyl propionate in supercritical carbon dioxide (scCO(2)) by transesterification. The catalytic activity of these mini-flow-bioreactors remained practically unchanged for seven operational cycles of 5 h each in different supercritical conditions. The best results were obtained when the most hydrophobic monolith, M-SILP-8-CALB, was assayed at 80 degrees C and 10MPa, reaching a total turnover number (TON) of 35.8 x 10(4) mol product/mol enzyme. The results substantially exceeded those obtained for packed-bed reactors with supported silica-CALB-Si-4 catalyst under the same experimental conditions.