Ultrasound-Assisted Intensification of Activity of Free and Immobilized Enzymes: A Review

Ultrasound has shown considerable promise for various applications in food science and biotechnology. In the past, ultrasound has been used intensively to inactivate the enzyme, but today, ultrasound is also considered efficient to activate the enzyme by altering structural conformation under mild controlled conditions. The present review analyzes the governing mechanisms for intensification along with elucidating the effects of ultrasound parameters on enzyme activity. Different ultrasound parameters considered in the analysis include duty cycle, ultrasonic frequency, intensity/power, amplitude, and treatment time, whereas additional process parameters considered include temperature, pH, and enzyme concentration/nature of the medium. The review also provides a discussion on the effect of ultrasound on thermodynamic (activation energy, enthalpy, entropy, and free energy) and kinetic (V max, K m, and catalytic efficiency) parameters to highlight the changes in the design parameters. Results for the different spectroscopic techniques such as circular dichroism and fluorescence spectroscopy have also been described to examine the alteration in structural configuration for free and immobilized enzymes after treatment with ultrasound. Overall, this review has conclusively demonstrated that ultrasonic treatment shows an increase in enzymatic activity under an optimized set of treatment conditions also leading to beneficial processing in enzyme-based applications.