The inactivation of Lactobacillus fructivorans suspended in various buffer solutions by low-pressure CO 2 microbubbles (MB-CO 2) was investigated. The number of surviving L. fructivorans cells suspended in 0.1 mol/L acetic acid/0.1 mol/L sodium acetate buffer at pH 4 was decreased by 4-log cycles by MB-CO 2 at 40 °C and 2.0 MPa for 60 min, whereas there were no reductions in the numbers of L. fructivorans cells suspended in 0.1 mol/L citric acid (CA)/0.1 mol/L sodium citrate (NaC) buffer at pH 4, 0.1 mol/L CA/0.2 mol/L disodium hydrogen phosphate (NaP) buffer at pH 4, or 0.1 mol/L CA/0.2 mol/L dipotassium hydrogen phosphate buffer at pH 4 by MB-CO 2 under the same conditions. However, the inactivation of L. fructivorans cells by MB-CO 2 was similar in 0.01 mol/L CA/0.01 mol/L NaC buffer, 0.001 mol/L CA/0.002 mol/L NaP buffer, and deionized water. Furthermore, the inactivating effect of MB-CO 2 tended to increase with decreasing buffer pH. © 2012 Elsevier Ltd.