Supercritical fluids are superior media for catalysis by cross-linked enzyme microcrystals of subtilisin Carlsberg

We report on the performance of cross-linked enzyme microcrystals (CLECs) o f subtilisin Carlsberg in supercritical fluids (SC-fluids). The catalytic a ctivity of CLECs in SC-ethane was found to be 2- to 10-fold greater than in hexane under the same conditions, using CLECs dried by propanol washing. A ir-dried CLECs and lyophilized powders showed much lower activities, reflec ting the same hydration hysteresis effects as in organic solvents. Reaction rates were much lower in SC-CO2, especially at higher water activity, prob ably as a result of acid-base effects of carbonic acid on the enzyme.