Date of Award

Spring 1959

Document Type



Life & Environmental Sciences

First Advisor

Donald Waldhalm


The process of freeze drying has been successfully used to preserve bacterial cultures over long periods of time. This process assures no alteration of the biological characteristics, either physical or chemical, of the material frozen. The viability of the organism is determined by the affect which the media has on the organism during the process. The biological characteristics remain unaltered after drying is completed due to the fact that the metabolic processes stop almost completely. These metabolic processes are dependent largely upon osmosis, diffusion, ionization and the colloidal state, all of which are in turn dependent upon hydration.

The purpose of t his experiment is to determine the comparative viability of Streptococcus lactis after freeze drying from two different media: blood serum and skim Milk. Since blood serum is considered an optimal medium for the freeze drying of any material, and skim milk is an optimum medium for the cultivation of the Streptococcus lactis organism, the two media are beneficial to the organism in that they both promote good growth. The media used in this experiment are unique for such a purpose. However, they will not necessarily be equally beneficial when used for the purpose of freeze drying.

Included in

Bacteriology Commons