Abstract
In a previous work 1 it has been shown that yeast cells suspended in tap water are killed in various lengths of time by pressures extending from 4000 to 7000 atmospheres. The present investigation was undertaken to determine the effect, if any, of the kinetic conditions resulting when high pressure is exerted on salt solutions of various concentrations.
The yeast, Saccharomyces cerevisiae, strain “Levure Royale”, was obtained from the Anheuser-Busch Brewing Co. of St. Louis, in starch-free cakes. Two percent suspensions of the yeast in distilled water solutions of NaCl, varying in concentration from .005M to .4M, were put into glass vials of about one cc. capacity, stoppered with rubber corks. The pressure chamber consisted of a cylindrical cavity, 1.2 inch in diameter, bored in a steel block, and fitted with a hardened steel plunger. A rubber disc served as packing for the plunger. Four vials containing yeast in solutions of different concentrations could be compressed in the chamber at the same time. Care was taken to exclude air from the solutions in the vials and from the water which filled the chamber. A motor-driven hydraulic press supplied the pressure. From the readings of a previously tested gauge, mounted on the press, we calculated the effective pressures inside the chamber. After a 2-minute compression and a sudden decompression the yeast cells were stained with methylene blue and the number of dead (stained) cells was counted. The temperature of the room varied from 18° to 22°C.
The results are plotted in the accompanying graph. Each point represents the percentage obtained in a count on 800 cells.
Get full access to this article
View all access options for this article.