Enhancing acid tolerance of the probiotic bacterium Lactobacillus acidophilus NCFM with trehalose

Enhancing the acid tolerance of the probiotic bacterial strain Lactobacillus acidophilus NCFM (L. acidophilus NCFM) is critical for improving its viability during transiting through gastrointestinal tract, which is the basis of eliciting beneficial effects as an intestinal probiotic. In this study, the role of trehalose and the glutamateγ-aminobutyric acid antiporter gene gadC in enhancing the acid tolerance of L. acidophilus NCFM was investigated. Trehalose at a concentration of 0.5% (w/v) was sufficient to significantly increase bacterial viability at pH 2.0, and trehalose of 2.0% can preserve more than 80% of bacterial viability both at pH 2.0 and 3.0. The inactivation of gadC gene in L. acidophilus NCFM significantly reduced bacterial viability at pH 2.0, and diminished the protective effect of trehalose against acid stress. In conclusion, exogeneous trehalose conferred L. acidophilus NCFM enhanced viability at extreme low pH values, an effect that appeared to depend on its endogenous glutamate-depenent acid resistance system.