THE TIPICITY AND SELECTIVITY OF PROBIOTIC BACTERIA FROM ACID DAIRY PRODUCTS

Abstract

The determination of total bifidobacteria number from yogurts and the determination of total germ number from the pure culture of Bifidobacterium essensis and Lactobacillus acidophilus was made on solid culture medium MRS and broth MRS, GL, B1. In the case of solid media we the anaerob culture was practiced, for 5 days and aerob incubation in the case of broth media. The selectivity of culture media was tested with bacterial flora of L. bulgaricus, S. termophilus and Bifidobacterium essensis from Activia yogurt (Danone), from sale. After the microscopic examination, the selectivity of culture media was proved to be the same, the associated flora to the lactobacilli didn’t develop. In the case of culture on solid media, B1 and GL media had the best results, but the colonies on MRS-dicloxacillin presented a slower growth, the colonies being smaller at the end of the incubation period. We examined the development of pure culture of Lactobacillus acidophilus on solid MRS, B1 and that of Bifidobacterium essensis on broth B1, MRS and GL media. As a final result of the comparative experiment it can be said that in the case of use for the incubation of bifidobacteria of broth media with a diminished redox potential, the selective determination of bifidobacteria number was possible after 2 days of aerobic incubation, while the usual incubation method necessitates 5 days. The development of L acidophilus on solid B1 media was satisfactory and of the same value with MRS usual agar.