The ability of carbon dioxide microbubbles (MB-CO 2) to inactivate Lactobacillus fructivorans suspended in physiological saline and unpasteurised sake at ambient temperature and a pressure lower than 2.0MPa was investigated. The number of L. fructivorans cells in physiological saline solution containing 15% ethanol showed a 6-log reduction following MB-CO 2 treatment at 40°C and 2.0MPa for 50min. The effectiveness of the treatment increased concomitantly with temperature, pressure and ethanol concentration of the sample solution but was unaffected by the glucose concentration in the sample solution. Furthermore, the number of L. fructivorans cells showed a 5-log reduction in sake after MB-CO 2 treatment at 40°C and 2.0MPa for 60min. Sensory evaluation revealed no significant difference between MB-CO 2-treated sake and unpasteurised sake. These results indicated that MB-CO 2 treatment was highly effective for the inactivation of L. fructivorans and might become a practical method for pasteurising sake at ambient temperature. © 2012 The Authors. International Journal of Food Science and Technology © 2012 Institute of Food Science and Technology.