Treatment of immobilized α-amylase under supercritical CO2 conditions: Can activity be enhanced after consecutive enzymatic reactions?

• Supercritical CO2 treated α-amylase was immobilized in Ca-alginate beads and on NaY zeolite.
• Subsequently assayed several times for the hydrolysis of soluble starch.
• Retreated with supercritical CO2.
• Four retreatment loops and seventeen reactions were realized with NaY zeolite immobilized samples.
• Activity was successfully enhanced after consecutive enzymatic reactions.

Various approaches have been applied in order to enhance enzyme stability and activity. In this study, the aim was to investigate the capability of supercritical carbon dioxide (SC-CO2) to alter the activity of α-amylase after consecutive enzymatic reactions. Therefore, α-amylase from Aspergillus oryzae initially treated with SC-CO2 (29.7 mmol ml−1 min−1) was immobilized in Ca-alginate beads and NaY zeolite, subsequently assayed several times for the hydrolysis of soluble starch and when a lower activity value was recorded compared to the initial activity of the untreated enzyme (17.7 mmol ml−1 min−1), the immobilized samples were retreated with SC-CO2. These consecutive reactions and treatment loops were repeated till the activity cannot be increased with SC-CO2 retreatment in comparison to the initial activity of the untreated enzyme. The best results were achieved with NaY zeolite immobilized samples where four successful loops and seventeen reactions were realized till the residual activity.

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