Effects of High-pressure Gas on the Growth Thermograms of Yeast

Abstract

Using a microcalorimeter the heat evolved during incubation of yeast cultures at 30^oC was detected in the form of growth thermogram (metabolic heat — incubation time curve). Correlation of the heat evolution curves with the number of cells and the turbidity of the culture was found to be very good. In this study, the effects of high-pressure gas in open system on the growth curve of yeast were investigated and the inhibition action of the gases (nitrogen, air, nitrous oxide and argon) on the growth was quantitatively assayed using Biothermo Analyzer. The growth thermograms were used to estimate microbial activity of yeast under compressed gases and to determine minimum inhibitory pressure (MIP) that is regarded as an index of toxic potency of dissolved gases. It was found that the increase of pressure induced clear inhibitory action on yeast cells, especially for air. The order of the action was as follows: air > N₂O > Ar > N₂.