Isolation, Characterization and Acid/Alkaline Tolerance of Lactic Acid Bacteria Present in Fermented Rye, Wheat, Oat and Barley

Objective: This study determined the lactic acid bacteria (LAB) present in fermented rye, wheat, oat and barley grains, and evaluated their survival in simulated gastric juice and pancreatic juice.

Methods: Samples of rye, wheat, oat and barley grains were fermented for 72 hours at room temperature. Lactic acid bacteria (LAB) strains were isolated using MRS agar and were enumerated. Isolated LAB strains were cultured with MRS broth and the fermentation patterns of the isolated strains were characterized using API 50 CH kit (Biomerieux, France). Each isolated LAB strain was exposed to simulated gastric juice at pH of 2.0 for 80 minutes at 370C, followed by exposure to simulated pancreatic juice at pH of 8.0 for 120 minutes at 370C. Aliquots were taken at 0 minute and 80 minutes at pH of 2.0 and 0 minutes and 120 minutes at pH of 8.0 for enumeration of LAB strains.

Results: The total LAB cell count ranged from 6.6 * 108 ± 11 cfu/ml in the rye sample to 9.5*109 ± 7 cfu/ml in the oat sample. 13 LAB strains were isolated from the four selected cereal grains and were characterized as six strains of Lactobacillus plantarum1, five strains of L. brevis 1 and one strain each of L. collinoides and Leuconostoc citreum. All the isolated LAB strains from the four selected cereals survived in the simulated gastric juice at pH of 2.0 (before and after incubation at 0min and 80a min) and after addition of simulated pancreatic juice at pH of 8.0 (before and after incubation at 80b min and 200 min respectively). The mean viable counts of all the strains ranged from 2.0 *108 in R3 at 80b min to 1.54 * 1010 in B4 at 80b minutes.

Conclusion: LAB associated with fermentation of rye, wheat, oat and barley grains are likely to survive transport through the harsh acidic and alkaline conditions of the GIT.