In previous research three strains of lactic acid bacteria with probiotic properties have been defined in the context of probiotic concept: Lactobacillus acidophilus M92, Lactobacillus plantarum L4, and Enterococcus faecium L3. In this research, there have been explored many possibilities of appliances to these probiotic strains in combination with various prebiotic substrates for the purpose of attaining enhanced, synbiotic effect. The assimilation of probiotic substrates with selected lactic acid bacteria has been realized in vivo, with experimental Swiss Albino mice. The best synbiotic preparations, so far, have been: Lactobacillus acidophilus M92 in combination with inulin, Lactobacillus plantarum L4, and Enterococcus faecium L3 in combination with lactulose. The immunomodulatory effect on tested probiotic strains and prebiotic substrates on immunity system of mice was explored by ELISA method. Immunizing mice orally with synbiotic preparations has caused stronger immune response than individual probiotic strains and prebiotic substrates. Only synbiotic L. acidophilus M92, L. plantarum L4 and E. faecium L3 preparations using various prebiotic substrates have shown positive influence on intestinal microflora in mice due to the competitive exclusion of undesirable members of intestinal microflora, enterobacteria and sulphite reducing clostridia. The a adhesive function of tested probiotic strains in the small and large intestine of experimental mice has been confirmed by inducing the resistance of these strains on rimfampicin, and by identification of bacterial strains isolated from mice intestine by using RAPD-PCR method. The possible application of the probiotic strains Lactobacillus acidophilus M92 and Lactobacillus plantarum L4 in the production of fermented probiotic drink from milk permeate has been explored in this research, as this byproduct of milk ultrafiltration has no commercial use for time beeing. In addition, during spontaneous fermentation of milk permeate some naturally present bacterial strains have been isolated and their suitability as future potential starter cultures has been tested.