Inactivation of Enzymes and Decomposition of α-Helix Structure by Supercritical Carbon Dioxide Microbubble Method

The conformational changes of enzymes inactivated by the supercritical CO₂ (SC CO₂) microbubble method were investigated by measuring the circular dichroic (CD) spectra at far ultraviolet (UV) range. The decay of negative ellipticity of lipase, alkaline protease, acid protease, and glucoamylase was observed after the SC CO₂ treatment at 35 °C and 25 MPa for 30 min. The residual α-helix contents of these enzymes were 62.9, 31.3, 37.6, and 12.4%, respectively. On the other hand, the α-helix structure of glucoamylase remained 85.7% after the heat treatment at 80 °C for 30 min. Furthermore, residual α-helix content of glucoamylase treated with SC CO₂ decreased from 12.4 to 5.1% during 10 days at 20 °C, and the residual enzyme activity also decreased from 17.5 to 0%. The plots of the residual activities against the residual α-helix contents gave a linear relationship both for glucoamylase and acid protease.