LACTOBACILLUS: YEAST INTERRELATIONSHIPS

Abstract

The effects of medium (sucrose broth vs. sucrose-flour broth), incubation temperature (22, 27, 32, and 37[degree]C), and initial pH (4, 5, 6, and 7) of the medium on Lactobacillus plantarum, L. casei, and Saccharomyces carlsbergensis were examined. Maximal population densities of each lactobacillus and yeast were determined in pure and mixed, lactobacillus-yeast, cultures. In each case in which microbial interaction was noted, it was the yeast which was affected. At an incubation temperature of 37[degree]C, yeast growth was markedly reduced in mixed culture on sucrose-flour broth when grown with L. plantarum and on sucrose broth when grown with L. casei. On the other hand, yeast growth was increased in mixed culture on sucrose broth when grown with L. plantarum and on sue rose-flour broth when grown with L. casei. Effects of temperature and medium composition could not be separated from interactions between the requirements of the organisms. It was demonstrated, however, that dissimilarities in the behavior of microorganisms in pure and mixed cultures are manifest only under certain conditions.