Inhibition of Yogurt Starter Cultures by Jenseniin G, a Propionibacterium Bacteriocin

Abstract

Jenseniin G, a heat-stable bacteriocin that is produced by Propionibacterium jensenii P126 (ATCC 4872), inhibits Lactobacillus delbrueckii ssp. bulgaricus NCDO 1489. The purpose of this investigation was to examine effects of jenseniin G on growth and acid production by additional yogurt starter cultures including strains of L. delbrueckii ssp. bulgaricus and Streptococcus thermophilus. Yogurt starters were examined for inhibition by jenseniin G in agar and broth culture media and in skim milk. Jenseniin G inhibited all 12 yogurt starter cultures. Lactobacilli were 2 to 16 times more sensitive than were streptococci. Addition of jenseniin G to broth and milk cultures of starters prevented growth. Addition of jenseniin G (20 to 60 AU/ml) to stationary phase cultures of lactobacilli and streptococci in simulated yogurt limited acid formation and maintained acidity at pH 4.15 to 4.42 for 30 d at 5°C. The yogurt contained more than 107 viable organisms/ml, which met the requirements for the Live and Active Cultures seal of the National Yogurt Association. These data suggest the usefulness of jenseniin G in preventing overacidification or postacidification of yogurt.