Centennial Honors College
Western Illinois University
Undergraduate Research Day 2012
Poster Presentation
Comparative Growth and Sucrase Production of Leuconostoc mesenteroides on
Defined and Complex Media
Jordan Liles
Faculty Mentor: Scott M. Holt
Biology
Leuconostoc mesenteroides is a bacterial genus that converts sucrose, or common
table sugar, into the bipolymers dextran, alternan, and levan. Sucrase is an enzyme
made by Leuconostoc that turns sugar into natural biopolymers. The biopolymers have
a variety of commercial applications related to food, cosmetics, and health products.
Leuconostocs have very intricate nutritional needs, and must be grown in a medium that
has a large amount of amino acids. For most industrial uses, Leuconostoc
mesenteroides is grown on an undefined, or complex, medium that contains an
unknown ratio of ingredients. Complex medium used to grow bacteria often produces
inconsistent results in different experiments because it contains unknown
concentrations of specific amino acids and other compounds. Defined medium,
however, consists of a known ratio of amino acids and other nutrients. Thus, using a
defined medium will offer more consistent results of enzyme production and
physiological growth rates because the starting materials from which the bacteria grow
will always be the same.
The goal of this research was to compare growth rates of Leuconostoc mesenteroides
when it is grown on a complex growth medium containing sucrose and a chemically
defined growth medium containing sucrose.
Growth rates for Leuconostoc 512F were higher using the complex media, however, the
cell counts (CFU/ml) were higher when grown on the defined media. These data
indicated that the defined growth media may be a suitable alternative to the complex
media but more growth trials are needed to determine statistical significance.