The Effect of Biofilm-like Structure , Sublethal Acid Stress , and Plant Gums on Culturability of Entrapped Lactobacillus Plantarum

Introduction: To increase lactobacillus cells stability, different methods based on entrapment used and their effect on the culturability of entrapped cells was studied. Materials and methods In the present study, sub-lethal acid stress, biofilm-like structure, and the combination of plant gums were used to assess the culturability of entrapped Lactobacillus plantarum during different production phases. Results: Based on the obtained results, incubation of alginate entrapped cells in MRS broth containing acetic acid increased the survival rate by 29% compared to beads treated in MRS broth. In addition, incubation of alginate entrapped cells in acidic medium resulted in 5% higher survival of biofilm-like cells after the freeze-drying process. To increase the stability of cells during storage, cells were entrapped in alginate plus different plant gums. Incorporation of tragacanth gum and salep gum to alginate showed higher culturability of cells (4.6 and 3.1 folds, respectively) in comparison to alginate treated beads. Additionally, the lowest inactivation constant rate (k value), 0.09, and highest D value, 25 days, obtained for tragacanth gum at 4°C during storage indicating that treatment with tragacanth gum could preserve the cells better in comparison to other treatments under storage condition. Discussion and conclusion: The incubation of Lactobacillus plantarum beads in acidic MRS medium can result in increased culturability especially after freeze-drying. This can be due to cross-protection effect. Additionally, due to tragacanth gum traits, this plant gum could protect the entrapped cells better compared to other plant gums in the storage condition. In conclusion, we can use tragacanth gum as a second material for increasing the stability of entrapped L. plantarum cells.