In this study, the disruption and protein release kinetics of Acetobacter peroxydans by ultrasonication was examined. The effects of acoustic power and the medium pH on the survival percent was investigated. An increase in the cell disruption with increasing acoustic power was observed. The most effective disruption was achieved for 100 W acoustic power. When the pH of ultrasonication medium was increased, the rate of disruption decreased. Within the pH range of 3-10, the most effective value for the cell disruption was determined to be 3. The effects of acoustic power and medium pH on the kinetic constant, beta, which determines the pattern of failures according to the equation proposed by Doulah were investigated. The value of rate constant of the protein release was found to be 0.022 min(-1) using the first order protein release kinetic equation proposed by Doulah. (C) 2000 Elsevier Science S.A. All rights reserved.