Effects of supercritical CO2 exposure and depressurization on immobilized lipase activity

Lipozyme IM20 from Novo Nordisk (Denmark) was examined after various treatments. Conditions were chosen to reflect those that would be considered in the design of an industrial process. A two-level factorial design was employed to assess the effects of pressurization/depressurization cycles, rate of depressurization and exposure length. A significant three-factor interaction was observed. Lowest residual activity was observed for runs in which the depressurization rate was 86-89 bar min(-1). Incubation for 12 h also yielded low residual activity but only when exposing the immobilized enzyme to one cycle. The highest residual activity was obtained for immobilized enzymes repeatedly exposed for periods of 12 h (5 times) with a depressurization rate of 4.3 to 4.45 bar min(-1). This effect may be due to the extraction of an inhibiting compound. Tuning process parameters can lead to a seven-fold change in residual activity.