LAUSR

The effect of ethanol on the inactivation of Saccharomyces pastorianus by a two‐stage system with low‐pressure carbon dioxide microbubbles (two‐stage MBCO2) was investigated. Zero and >5 log reductions of S. pastorianus populations suspended in physiological saline (PS) containing 0% and 10% ethanol, respectively, occurred by the two‐stage MBCO2 at a mixing vessel pressure of 1 MPa and a heating coil temperature of 40°C. Conversely, the detected number of surviving S. pastorianus cells in PS containing 5% ethanol was higher in yeast and mold agar (YMA, an optimum agar) than YMA with 2.5% sodium chloride, followed by yeast nitrogen base agar (YNBA, a minimum agar). The fluorescence polarization of S. pastorianus in PS containing 5% and 10% ethanol increased similarly with exposure time in the heating coil of two‐stage MBCO2 and was correlated with the surviving cell number measured in YNBA. The intracellular pH (pHin) of S. pastorianus in PS containing 5% ethanol decreased linearly with exposure time in the heating coil of two‐stage MBCO2. Also, the pHin‐lowering of S. pastorianus in PS containing 10% ethanol was drastically caused by two‐stage MBCO2 at 1 min exposure time in the heating coil but then stayed constant until 5 min, agreeing with the inactivation efficiency. Therefore, ethanol in S. pastorianus suspension was suggested to accelerate the cell membrane injury caused by two‐stage MBCO2. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 34:282–286, 2018