Measurement of Ultrasonic Velocity and Attenuation Coefficient on Cell Density and Disruption of Aspergillus Niger

Abstract

The present study envisaged the measurement of ultrasonic velocity and attenuation coefficient on cell density of A.niger by using novel Pulse Echo Overlap (PEO) technique. The author reported parameters like acoustic impedance, adiabatic compressibility and free length were computed by applying Jacobson’s Free Length Theory (FLT). The cell density was carried out by using hemocytometer. The ultrasound transducer of 10 mm gap between transmitting and reflecting surfaces was immersed into the sonication vessels which were filled with varied cell density of 101 to 108 per ml to measure ultrasonic parameters for 2 and 10 MHz ultrasound. The sonication vessel kept inside the water bath to maintain constant environmental temperature of 303K by using automatic temperature controlled bath. In addition, the cell disruptions were carried out at 2 and 10 MHz high power ultrasound of output power of 600 watts by using ultrasonic processor. The ultrasonic velocity and attenuation coefficient were measured simultaneously with disruption of cell density as a function of sonication time. The uncertainty in measuring of ultrasonic velocity (v) is ± 0.02% and the attenuation coefficient (α) is ± 0.0015%. It was observed that both ultrasonic velocity and attenuation coefficient linearly increased with increasing concentration of cells. It was reported that the increased ultrasonic velocity was due to decreased adiabatic compressibility and free length with increased cell density. It was investigated that the attenuation coefficient was high at 10 MHz than 2 MHz high absorption losses occurred at 10 MHz. It was concluded that ultrasound waves propagated through culture of A.niger
disturb the equilibrium between cells presented in the suspension and this retarded equilibrium shifts between the number of cells and their sizes and shapes, in turn, the ultrasound velocity and absorption.