Determination of the Lethal Injury on the Inactivation of Saccharomyces pastorianus Cells by Low-pressure Carbon Dioxide Microbubbles.

Abstract

To clarify the lethal injury related to the inactivation of Saccharomyces pastorianus cells by low-pressure carbon dioxide microbubble (CO2MB) treatment, surviving number, leakage of nucleic acids and proteins, fluorescence polarisation (FP) of the cell membrane, activity of alkaline phosphatase (AP), intracellular pH (pHin), mitochondrial membrane potential (MMP), cell surface hydrophobicity (CSH) and oxidative stress of S. pastorianus treated with CO2MB at various temperatures were measured. The number of surviving S. pastorianus cells decreased below the detection limit after CO2MB treatment at temperatures of 40, 45 and 50℃, inducing a 2-log reduction at 35℃. The S. pastorianus cells treated with CO2MB at temperatures above 40℃ showed an increase in FP and leakage of nucleic acids and proteins. The AP in S. pastorianus cells treated with CO2MB at a temperature of 35℃ was also activated but inactivated at temperatures above 40℃. Furthermore, the decrease in pHin and MMP and the increase in CSH of S. pastorianus were caused by CO2MB treatment at temperatures above 35℃. Oxidative stress in S. pastorianus cells was also increased by CO2MB treatment without warming but decreased at temperatures above 35℃. Our results lead us to infer that the type of cell injury in S. pastorianus induced by CO2MB treatment differed from that caused by the treatment temperature and that the lethal injury was enzyme inactivation.