Relationship between gastric acid tolerance and capsule formation in plant origin lactic acid bacteria, Lactobacillus plantarum FSCM2-12

Using gastric juice tolerant Lactobacillus plantarum FSCM2-12, NBRC 109604 and NBRC 101975, and gastric juice sensitive Lactobacillus brevis FSCT-2, the relationship between the gastric acid tolerance and the morphologic characteristics were examined. Survival ratio of L. plantarum FSCM2-12 cultured in the medium supplemented with glucose, fructose, or sucrose as a carbon source, was more than 70% after treatment with the artificial gastric juice. However, the survival ratio of the strain cultured in the medium supplemented with glycerol or no carbon source, was drastically decreased. L. plantarum FSCM2-12 did not form the biofilm, but clear capsule was observed under the microscope after Hiss staining and by transmission electron microscopic observation. Furthermore, thickness of the capsule showed correlation with gastric juice tolerance. The capsules were thick and the survival ratio after treatment with artificial gastric juice was more than 70% when the strain was cultured in the medium supplemented with glucose, fructose, and sucrose as a carbon sources. Similar phenomena were observed in L. plantarum NBRC 109604 and NBRC 101975, therefore, the high gastric acid tolerance might be provided by