Leuconostoc mesenteroides is a commercially important lactic acid bacterium currently used as a starter for kimchi and kefir. However, its sensitivity to acid stress limits its performance. L. mesenteroides was grown in a medium supplemented with 3.2 or 6.4 mM glutathione (GSH), and cell survival rates were measured during a long-term mild acid challenge (pH 4.0). As a result, GSH was imported by the cells and protected against acid stress; thereafter it was consumed as a nutrient. Acid stress resistance of starter cultures of this bacterium can thus be improved by cultivating it in media supplemented with GSH.