Stimulation by Formate of Antimicrobial Activity of Lactobacillus bulgaricus in Milk

When sodium formate was added to skim milk at concentrations of 0.15 mM prior to fermentation by Lactobacillus bulgaricus, the antimicrobial activity of the milk fermented for 5 hr increased by 66% over control samples. Maximum stimulation was attained at 0.45 mM concentration and further increase was less stimulatory. The stimulatory effect of formate was neutralized in the samples incubated for 24 hr. Formate addition did not affect the pH of the fermented milk.