In this study, lactic acid production was determined of a total of 32 strains of lactobacilli and streptococci. Different amounts of lactic acid were produced by strains studies; however, lactic acid levels were 13.4 to 18.6 mg/mL for Lactobacillus delbrueckii subsp. bulgaricus strains and 0.6 to 11.5 mg/mL for Streptococcus thermophilus strains. Antimicrobial activity was tested against Helicobacter pylori ATCC 43504. The some strains were able to inhibit H. pylori. Bacteriocin-like substances (BLS) producing strains were determined under conditions eliminating the effects of organic acids. As a result, it was observed that inhibitory activities of only ten strains were due to bacteriocin-like substances.