Observations on the growth of yeasts in pure nutrient solutions.

The multiplication of yeasts in pure nutrient solutions has already received much study; as a result there are many discrepancies in conclusions which have been reached. This brief report deals with two phases of the question: 1, the effect of concentration of an accessory containing substance, and 2, the effect of aeration on the multiplication of yeasts in pure nutrient solutions.

In both of these studies, Fulmer and Nelson's Medium E 1 was used. To study the first part of the problem Fred, Peterson and Davenport's yeast water medium 2 was added to medium E in different dilutions, as follows: 1, 100 cc. medium E + 10 cc. sterile water; 2, 100 cc. medium E + 10 cc. yeast water medium; 3, 100 cc. medium E + 10 cc. of a 1-10,000 dilution of yeast medium, and 5, 100 cc. of a medium E + 10 cc. of a 1-1,000,000 dilution of yeast medium. These cultures after sterilization and inoculation were incubated under the same conditions. Saccharomyces anomolous, Torula colliculosae, Willia satunus, Zygosaccharomyces mandschuricus and Pichia farinosus were used.

The results showed that when the yeast water medium was present in greatest amounts there was an acceleration in multiplication, but when it was added only in minute traces, there was little difference between these flasks ad the control. There was no alteration in multiplication accelerating effect by “hating the yeast medium for 60 hours at I 5 lbs. pressure (121 .5° C). It is believed that the acceleration in multiplication observed when large amounts of yeast water were added was due to chemically definite food substances and that one need not place the explanation on the presence of “bios.”