Inactivation of enzymes in an aqueous solution by micro-bubbles of supercritical carbon dioxide

Enzyme solutions of glucoamylase, acid protease, alkaline protease and lipase were treated with micro-bubbles of supercritical carbon dioxide (SC CO₂) fed from a cylindrical filter nozzle. The micro-bubbles of SC CO₂ could increase the CO₂ concentration in the sample solution from 0.4 to 0.92 mol/l at 25 MPa and 35°C, and hence could improve the efficiency of inactivation by about 3 times compared to treating without the filter nozzle. Alkaline protease and lipase in the solution could be completely inactivated by the treatment at 35°C and 15 MPa for 30 min. With the inactivation of glucoamylase and acid protease, their residual activity-CO₂ density profiles consisted of two straight lines with intersections at density values of 0.82 and 0.60 g/cm³, respectively. These enzymes showed an abrupt decrease in activation in regions above the CO₂ density of their intersections.