Effect of Low pH on the Ability of <i>Lactobacillus acidophilus</i> to Survive and Adhere to Human Intestinal Cells

Abstract

ABSTRACT Lactobacillus acidophilus was suspended in broth and buffer at pH 2, 3 and 4 and incubated at 37°C for 2 hr. In both broth and buffer pH 2, viable cell numbers decreased rapidly, and none were recovered after 45 min. At pH 4 in broth and buffer, the number of cells was not significantly reduced in 2 hr. In potassium phthalate buffer at p 3, no viable cells were recovered after 30 min, while in KCl buff and broth at pH 3, no significant reduction was seen. Cells subjected to low pH for up to 5 h were able to adhere to human intestinal cells in vitro. Exposure to low pH did not appear to disrupt the ruthenium red staining layer exterior to the cell wall.